SEVERAL YEARS AGO, in one of the aircraft magazines I saw
pictures of a unique-looking home-built biplane called the “Der Jager
D-IX.” I was attracted to it because of its shape and color scheme.
Marshall Wright designed and built the airplane.
Sometime later, I stumbled across a three-view drawing for
the design. I kept it with the intention of building a scale
model of the D-IX at some point in the future. In addition to the
three-views, I found some photos on the Internet of the original
biplane.
I designed the model for an AXi 2826/10 brushless motor using a
Jeti Advance 40 PLUS speed controller and 3S Li-Poly batteries. I
made sure that the battery’s installation is easy; the top half of the
cowl comes off, and the battery is placed on the battery floor.
Four Blue Bird BMS-380 servos are used for control. They
are half the size of a standard servo, half the weight, and have the
same torque rating: approximately 50 inch-ounces. If you do not
want to fly this model as an electric, any .40-.45 glow engine can
be used.
I drew the plans and then proceeded to build the Der Jager model.
The test flight was a nonevent; the model tracked straight on takeoffs
and has excellent flying characteristics. It is fully aerobatic with no
bad habits, and the landings are straightforward. Even with the wheel
pants, the D-IX doesn’t nose over when flown off the grass.
April 2009 25
by Laddie Mikulasko
The author designed his airplane to be similar to the full-scale aircraft
that was designed by the Stolp-White Aircraft Company in 1969. The
model includes almost every charming aspect of the biplane lineage.
The Der Jager’s light wing loading allows it to climb quickly.
Sport aerobatics are comfortable.
A WW1-looking home-built,
fresh from the 1970s
04sig1.QXD 2/24/09 11:16 AM Page 25
26 MODEL AVIATION
Photos by the author
Wing panels join the center-sections with stacked dowel rods
at the apex of the rib shape. Center-area ribs are made from
light plywood.
The ribs are organized over the top wing plans as they are cut
from blank material. Holes in the inner ribs are for the aileron
servo wire and dowel supports.
The wide sheeting near the TE is centered over the hinge line.
Once the aileron is cut away, cap the open areas with balsa.
TE scallops add distinctive character to the Der Jager. After
drawing the outline, sand away the excess with a rasp or round
dowel covered with sandpaper.
The cabane struts and N struts have an aluminum-sheet core that
is laminated with wood on both sides. The material is sanded to a
streamlined shape later.
The center-section of the upper wing secures the dowel-rod wing
joiners inside plywood ribs. The completed sheeting is sanded
flush with the outer panels.
04sig1.QXD 2/24/09 11:33 AM Page 26
April 2009 27
The primary fuselage sides are marked left and right, as are the
forward 1/4-inch sheets that will be sanded to shape later.
The cabane struts mount inside tabs in the top wing’s centersection
and are secured with #4 socket-head servo screws.
The wooden sections of the wheel pants are laminated with
wood glue, which is easy to sand later. Plywood buried inside
acts as a mounting point.
The piano-wire landing gear is stitched to the former with
thread, Kevlar, or copper wire. The lower wing’s center-section
is built into the forward framework.
The cabane struts are securely mounted into hardwood areas.
Sheeting is wrapped around the forward turtledeck, forming the
cockpit area.
Once the fuselage sides are pulled together, the lower sheeting
and longerons can be added. Watch out for twisting and keep
the tail post square.
04sig1.QXD 2/24/09 11:18 AM Page 27
28 MODEL AVIATION
Cowling halves are framed separately. The lower half (shown) is
permanently attached to the fuselage and houses the motor.
A channel is carved in the right cabane strut to hide the aileronservo
extension wire. Covering material is applied over the woodskinned
aluminum supports later.
The stabilizer and fin are framed to simulate steel-tube
framework, so they are rounded on all outside edges.
Each control surface of the tail must have cardboard templates
made to form the laminations of the curved outer-framework
material.
An AXi Gold 2826/10 motor and Jeti 40 Advance ESC are
powered with a 3300 mAh 3S Li-Poly battery from FlightPower.
Temporary foam fixtures are placed to align and set the struts’ final
locations. Double-stick tape and pins hold the fixtures in place.
04sig1.QXD 2/24/09 11:35 AM Page 28
April 2009 29
Pushrods from upper to lower aileron are linked to aluminum angle
brackets located in hard points near the LE of the control surface.
Access to rudder and elevator servos is through the cockpit
opening, which is later covered with a pilot figure.
The simulated engine is made from scrap balsa that is covered
and painted to match the IO-235 four-cylinder engine used in
the full-scale aircraft.
Simulated bullet-hole decorations, as on the full-scale aircraft.
Support wires add support but are mostly for appearance.
Type: RC Sport Scale
Skill level: Intermediate
builder, intermediate pilot
Wingspan: Top, 50 inches; bottom,
42 inches
Wing area: Approximately 750 square inches
Length: 42 inches
Weight: 4 pounds (depending on battery)
Power: 300- to 500-watt system, 40- to 54-amp ESC,
3S 3300 mAh Li-Poly battery
Construction: Balsa, light plywood, hardwood-dowel wing joiners
Covering/finish: UltraCote heat-shrink film
Radio: Four miniservos (40 inch-ounces output), receiver,
custom servo extensions
Other: 21/4-inch spinner, 3-inch wheels, APC 10 x 8E propeller, 11/4-inch tail
wheel, 5/32-inch music-wire landing gear, 1/32-inch aluminum-sheet strut material
04sig1.QXD 2/24/09 11:20 AM Page 29
30 MODEL AVIATION
The four wing panels plug into the structure and are secured with an aluminum main strut that attaches from the lower
fuselage to the top outer panel.
The AXi power system is equivalent to a .32
cu. in. glow engine that offers better-thanscale
performance. The Der Jager flies
predictably and has a distinctive appearance.
I tried to make building this airplane as
simple as possible. The outer wing panels are
removable; however, if transporting a 50-
inch-wingspan model is not a problem, you
have the option of building the wings in one
piece and permanently attaching them to the
fuselage.
The two aileron servos are mounted inside
the top wing. The connecting rods join the
top aileron to the bottom aileron. The elevator
and rudder servos are located inside the
cockpit.
To build this model, you will need light
balsa, light plywood, 5/32-inch-diameter music
wire, and 1/32-inch-thick aluminum sheeting.
Build the wing center-section. Pin the
bottom main spar to the building board.
Glue ribs W1, W2, and W3 to the spar.
Adhere the top main spar to the ribs.
Take hold of the two outside wing panels
and slide the joiners all the way into ribs W2
and W3. Glue the sub-LE to ribs W1, W2,
and W3. Adhere the top LE sheet (51) to
these ribs. Glue on the rest of the top
sheeting (62).
Flip the wing over. In the center-section,
install the Y harness for the ailerons. Glue
the bottom sheeting (61) to ribs W1, W2,
and W3. Glue the plywood strips (67) to ribs
W8 and W9; you must use the five-ply
plywood. The plywood strips will be
holding the brackets for N struts and the
main struts (75).
Glue on the bottom LE sheeting (52).
Adhere the aileron strip (58) to ribs W5 to
W10. Glue on the sheeting (63) over ribs
W4 and W5 and the sheeting (59) and (60)
over ribs W7 and W9. Glue on the capstrips.
Attach the LE spar (54).
Separate the ailerons from the wing
panels. Glue the hinge spar (57) to the wing
and the aileron LE to the aileron. Sand the
wing. Glue in the plywood mounting frame
for the aileron servo.
In the bottom of the center-section, cut
the slots for the cabane struts to go into and
one larger hole for the extension cable.
Build the bottom wing in a similar
fashion. The difference is having the joiners
(47) and (48) glued to the two identical root
ribs W11, which will become part of the
fuselage; the outside wing panels will slide
onto them.
Once the wing panels are built, line up
the halves of the bottom wing and place 1/2-
inch shims under the wingtips to get the
proper dihedral. Glue the left joiners to the
right joiners.
Tail Surfaces: Before building the elevators
and the rudder, cut the templates from
CONSTRUCTION
Wing: The individual wing panels plug into
the fuselage using 1/4-inch-diameter dowel
as joiners. The dowels are not strong enough
by themselves to hold the wing panels; the
main strut (75) will hold everything in place
once the panels are plugged in. It’s
unnecessary, but you can replace the
hardwood dowels with carbon-fiber tubes.
To get started, transfer the ribs’ outlines
and mark the location of the holes on the
plywood and the balsa. Cut out the ribs and
drill all the holes.
Cut 1/4-inch hardwood dowels (69) (70)
and (47) (48) to the proper lengths. Adhere
two (69) dowels to create a double-width
joiner for the top wing, and then glue two
dowels (47) together for the bottom wing
joiner.
Build the top wing first. It includes three
sections: two outside panels and the center
panel.
Begin constructing the outside panels.
Pin the bottom main spar (49) to the board
directly over the plans. Pin the 1/4 square
balsa to the building board, to be used as a
shim under the ribs at the TE. Position and
glue all ribs to this spar. Glue the top main
spar (50) to the ribs.
Cut out the TE sheets (55) and (56) that
include the scallops. Slide the TE sheet (56)
between the shim and the ribs. Adhere the
ribs to the TE sheet. Glue the sub-LE (53) to
the ribs. Sand the sub-LE so that it follows
the contour of the ribs.
Glue the wingtip sheet (66) to rib W10.
Adhere the top TE sheet (55) to the ribs.
Glue the top LE sheet (51) to the ribs and to
the sub-LE. Glue on 1-inch-wide aileronhinge
balsa strip (58) to ribs W5 to W10.
Adhere the top capstrips to the ribs. Slide in
and glue joiner dowels (69) and (70) to ribs
W4 and W5.
Do not go any further with this wing
half. Construct the other half of the top wing
to the same stage.
04sig1.QXD 2/24/09 11:21 AM Page 30
corrugated cardboard. Slice four 1/4-inch-wide
strips from the 1/16 balsa sheet. Smear glue onto
the strips and form them around the templates.
Use pins to hold the strips against the templates
until the glue dries.
When the glue is dry, adhere the rest of the
frame and the 1/4-inch sheets. Build the
stabilizer and the fin, and then sand all the
surfaces.
Bend a 1/16-inch-diameter piano wire to
form the tail-wheel strut. Insert the end of the
strut into the balsa sheet in the rudder, and then
glue in the wire with thin cyanoacrylate. Wrap
the whole sheet with fiberglass. You can use
thin cyanoacrylate to saturate the cloth.
Cabane and Wing N Struts: Cut four identical
cabane struts (72) and four N struts (74) from 1/8
light plywood. Cut two cabane struts (71) and
two N struts (73) from 1/32 aluminum sheet.
Drill the 1/16-inch-diameter holes in N struts, as
shown on the drawing.
Sand the surface of the aluminum with
sandpaper. Using cyanoacrylate or GOOP-type
adhesive, adhere the plywood pieces to both
sides of the aluminum struts. Sand the edges of
the plywood to streamline their shape. Cut a slot
in one of the front cabane struts, and insert and
glue in the aileron-servo extension cable.
Wrap all the struts with fiberglass and
saturate them with thin cyanoacrylate. Sand
lightly and bend the exposed aluminum ends of
the struts as shown on the drawing.
Fuselage: Cut out as many parts as possible.
The fuselage is built upside-down in three
sections: the cowl, the center-section, and the
tail section.
Cut and bend 5/32-inch-diameter piano wire
to form the main landing-gear legs. Attach them
to former F5 with thread (canvas thread, Kevlar,
or copper wire).
Glue the hardwood block (17) to former
F4B, and adhere hardwood blocks (18) to
formers F3D and F6B. Pin formers F3D, F5,
F6B, and F8B to the building board. Pin and
glue the fuselage sides (1) to these formers.
Insert and glue in the battery floor (13). Insert
and glue in formers F4B and F7.
Pin formers F9B, F10B, F11, and F12 to the
building board. Adhere the rear fuselage sides
(2) to these formers and to the fuselage side (1).
Glue 3/8-inch triangle stock between the
fuselage side (2) and former F8B.
On the outside of the fuselage, glue the balsa
doublers (3) between formers F3D and F6B.
Between F6B and F8B, adhere the doublers (4)
to the fuselage sides.
Glue the bottom wing to the fuselage. Slide
the joiners (47) and (48) into the slots in the
fuselage sides (1). Check the alignment and
adhere the joiners to formers F6B and F7. Glue
the balsa strip (12) to the bottom of all the
formers. Complete the sheeting of the bottom
between formers F3B and F8B.
Turn the fuselage right-side up. Glue the
firewall (20) and firewall support sides (19) to
the battery floor (13) and to former F3D.
The cowl is built in top and bottom halves.
Cut four identical plywood pieces (21). Drill a
1/4-inch hole for the magnets and a 1/16-inch hole
for the guide pins.
Pin two of the four plywood pieces (21) to
the building board. Pin and glue formers F1B,
F2B, and F3B to them. Insert and glue 1/4
square balsa into these formers. Adhere the
sheeting (9) and (10).
Remove the bottom of the cowl from the
building board and glue the scoop (24) to it. The
bottom of the cowl can be glued to former F3D.
Build the removable top of the cowl the same
way, but don’t adhere it to anything. Glue the
magnets and guide pins into the plywood pieces
(21).
Mount the cabane to the hardwood blocks
(18) using self-tapping screws. Insert the
cabane’s top tabs into the slots in the bottom of
the top wing’s center-section. Line up the holes
on cabane struts with the holes in W3 ribs.
Attach the cabane to the W3 ribs with selftapping
screws. At the same time, feed the plug
from the aileron extension into the cavity
between ribs W2 and W3.
Plug in all the wing panels and check the
alignment. If any adjustments are required, now
is the time to do it. Install the wing N struts. Use
self-tapping screws to hold them to the wings.
It’s time to install the most important strut
(75). Cut the 1/2-inch K&S streamlined
aluminum tube to the proper length. Flatten the
ends. Drill a 3/32-inch hole at each end, and bend
the ends so that the flat end is flush with the
plywood (67) behind the main spar of the top
wing. The same goes for the other end, but it
has to follow the contour of the hardwood block
(17) in the fuselage. Drill the hole in the
hardwood block and the plywood for selftapping
screws.
Remove the wings from the fuselage,
including the center-section. In the top wing,
install the servo extension for the aileron servo.
Glue the stabilizer to the fuselage. Adhere
all top fuselage formers. Glue the top sheeting
(5) to the front fuselage formers and the
sheeting (6) to the back formers. Cut out the
cockpit opening. Glue on the headrest (25).
Adhere the longeron (14) to the side of the
fuselage. Glue the fin to the fuselage.
Make the wheel pants and the streamline
covers for the main gear legs from the balsa
materials cited on the plans.
Finishing: Use your own method to apply the
finish; I used UltraCote. After completing the
covering, I installed the hinges and the servos. I
mounted a threaded connecting rod between the
top and bottom aileron with a clevis at each end.
The small “L”-shaped aluminum bracket is
attached to the plywood plate on each aileron
with self-tapping screws.
The dummy engine is made from scrap
balsa pieces and then glued to the top half of the
cowl.
After installing the radio and motor, remove
the top half of the cowl and slide the motor
battery onto the battery floor. Check the CG.
Move the battery as needed to get the D-IX to
balance on the CG spot. Mark the battery
location. I used hook-and-loop fastener to hold
it in place.
Install the servos and check the control
surfaces’ operation. The elevator should travel
3/4 inch up and down. The rudder 11/4 inches left
and right at the widest point. The top ailerons
should travel 1/2 inch up and down at the widest
point.
You’re finished with the construction. Have
fun flying this unique-looking scale model. MA
Laddie Mikulasko
[email protected]
Sources:
AXi 2826/10 motor, Jeti 40 Advance ESC:
MS Composit
(317) 578-1955
www.mscompositusa.com
UltraCote covering:
Hangar 9
(800) 338-4639
www.hangar-9.com
3200 mAh EVO LITE V2 3S battery:
FlightPower
(919) 741-6310
www.flightpowerusa.com
Edition: Model Aviation - 2009/04
Page Numbers: 25,26,27,28,29,30,31,32,33
Edition: Model Aviation - 2009/04
Page Numbers: 25,26,27,28,29,30,31,32,33
SEVERAL YEARS AGO, in one of the aircraft magazines I saw
pictures of a unique-looking home-built biplane called the “Der Jager
D-IX.” I was attracted to it because of its shape and color scheme.
Marshall Wright designed and built the airplane.
Sometime later, I stumbled across a three-view drawing for
the design. I kept it with the intention of building a scale
model of the D-IX at some point in the future. In addition to the
three-views, I found some photos on the Internet of the original
biplane.
I designed the model for an AXi 2826/10 brushless motor using a
Jeti Advance 40 PLUS speed controller and 3S Li-Poly batteries. I
made sure that the battery’s installation is easy; the top half of the
cowl comes off, and the battery is placed on the battery floor.
Four Blue Bird BMS-380 servos are used for control. They
are half the size of a standard servo, half the weight, and have the
same torque rating: approximately 50 inch-ounces. If you do not
want to fly this model as an electric, any .40-.45 glow engine can
be used.
I drew the plans and then proceeded to build the Der Jager model.
The test flight was a nonevent; the model tracked straight on takeoffs
and has excellent flying characteristics. It is fully aerobatic with no
bad habits, and the landings are straightforward. Even with the wheel
pants, the D-IX doesn’t nose over when flown off the grass.
April 2009 25
by Laddie Mikulasko
The author designed his airplane to be similar to the full-scale aircraft
that was designed by the Stolp-White Aircraft Company in 1969. The
model includes almost every charming aspect of the biplane lineage.
The Der Jager’s light wing loading allows it to climb quickly.
Sport aerobatics are comfortable.
A WW1-looking home-built,
fresh from the 1970s
04sig1.QXD 2/24/09 11:16 AM Page 25
26 MODEL AVIATION
Photos by the author
Wing panels join the center-sections with stacked dowel rods
at the apex of the rib shape. Center-area ribs are made from
light plywood.
The ribs are organized over the top wing plans as they are cut
from blank material. Holes in the inner ribs are for the aileron
servo wire and dowel supports.
The wide sheeting near the TE is centered over the hinge line.
Once the aileron is cut away, cap the open areas with balsa.
TE scallops add distinctive character to the Der Jager. After
drawing the outline, sand away the excess with a rasp or round
dowel covered with sandpaper.
The cabane struts and N struts have an aluminum-sheet core that
is laminated with wood on both sides. The material is sanded to a
streamlined shape later.
The center-section of the upper wing secures the dowel-rod wing
joiners inside plywood ribs. The completed sheeting is sanded
flush with the outer panels.
04sig1.QXD 2/24/09 11:33 AM Page 26
April 2009 27
The primary fuselage sides are marked left and right, as are the
forward 1/4-inch sheets that will be sanded to shape later.
The cabane struts mount inside tabs in the top wing’s centersection
and are secured with #4 socket-head servo screws.
The wooden sections of the wheel pants are laminated with
wood glue, which is easy to sand later. Plywood buried inside
acts as a mounting point.
The piano-wire landing gear is stitched to the former with
thread, Kevlar, or copper wire. The lower wing’s center-section
is built into the forward framework.
The cabane struts are securely mounted into hardwood areas.
Sheeting is wrapped around the forward turtledeck, forming the
cockpit area.
Once the fuselage sides are pulled together, the lower sheeting
and longerons can be added. Watch out for twisting and keep
the tail post square.
04sig1.QXD 2/24/09 11:18 AM Page 27
28 MODEL AVIATION
Cowling halves are framed separately. The lower half (shown) is
permanently attached to the fuselage and houses the motor.
A channel is carved in the right cabane strut to hide the aileronservo
extension wire. Covering material is applied over the woodskinned
aluminum supports later.
The stabilizer and fin are framed to simulate steel-tube
framework, so they are rounded on all outside edges.
Each control surface of the tail must have cardboard templates
made to form the laminations of the curved outer-framework
material.
An AXi Gold 2826/10 motor and Jeti 40 Advance ESC are
powered with a 3300 mAh 3S Li-Poly battery from FlightPower.
Temporary foam fixtures are placed to align and set the struts’ final
locations. Double-stick tape and pins hold the fixtures in place.
04sig1.QXD 2/24/09 11:35 AM Page 28
April 2009 29
Pushrods from upper to lower aileron are linked to aluminum angle
brackets located in hard points near the LE of the control surface.
Access to rudder and elevator servos is through the cockpit
opening, which is later covered with a pilot figure.
The simulated engine is made from scrap balsa that is covered
and painted to match the IO-235 four-cylinder engine used in
the full-scale aircraft.
Simulated bullet-hole decorations, as on the full-scale aircraft.
Support wires add support but are mostly for appearance.
Type: RC Sport Scale
Skill level: Intermediate
builder, intermediate pilot
Wingspan: Top, 50 inches; bottom,
42 inches
Wing area: Approximately 750 square inches
Length: 42 inches
Weight: 4 pounds (depending on battery)
Power: 300- to 500-watt system, 40- to 54-amp ESC,
3S 3300 mAh Li-Poly battery
Construction: Balsa, light plywood, hardwood-dowel wing joiners
Covering/finish: UltraCote heat-shrink film
Radio: Four miniservos (40 inch-ounces output), receiver,
custom servo extensions
Other: 21/4-inch spinner, 3-inch wheels, APC 10 x 8E propeller, 11/4-inch tail
wheel, 5/32-inch music-wire landing gear, 1/32-inch aluminum-sheet strut material
04sig1.QXD 2/24/09 11:20 AM Page 29
30 MODEL AVIATION
The four wing panels plug into the structure and are secured with an aluminum main strut that attaches from the lower
fuselage to the top outer panel.
The AXi power system is equivalent to a .32
cu. in. glow engine that offers better-thanscale
performance. The Der Jager flies
predictably and has a distinctive appearance.
I tried to make building this airplane as
simple as possible. The outer wing panels are
removable; however, if transporting a 50-
inch-wingspan model is not a problem, you
have the option of building the wings in one
piece and permanently attaching them to the
fuselage.
The two aileron servos are mounted inside
the top wing. The connecting rods join the
top aileron to the bottom aileron. The elevator
and rudder servos are located inside the
cockpit.
To build this model, you will need light
balsa, light plywood, 5/32-inch-diameter music
wire, and 1/32-inch-thick aluminum sheeting.
Build the wing center-section. Pin the
bottom main spar to the building board.
Glue ribs W1, W2, and W3 to the spar.
Adhere the top main spar to the ribs.
Take hold of the two outside wing panels
and slide the joiners all the way into ribs W2
and W3. Glue the sub-LE to ribs W1, W2,
and W3. Adhere the top LE sheet (51) to
these ribs. Glue on the rest of the top
sheeting (62).
Flip the wing over. In the center-section,
install the Y harness for the ailerons. Glue
the bottom sheeting (61) to ribs W1, W2,
and W3. Glue the plywood strips (67) to ribs
W8 and W9; you must use the five-ply
plywood. The plywood strips will be
holding the brackets for N struts and the
main struts (75).
Glue on the bottom LE sheeting (52).
Adhere the aileron strip (58) to ribs W5 to
W10. Glue on the sheeting (63) over ribs
W4 and W5 and the sheeting (59) and (60)
over ribs W7 and W9. Glue on the capstrips.
Attach the LE spar (54).
Separate the ailerons from the wing
panels. Glue the hinge spar (57) to the wing
and the aileron LE to the aileron. Sand the
wing. Glue in the plywood mounting frame
for the aileron servo.
In the bottom of the center-section, cut
the slots for the cabane struts to go into and
one larger hole for the extension cable.
Build the bottom wing in a similar
fashion. The difference is having the joiners
(47) and (48) glued to the two identical root
ribs W11, which will become part of the
fuselage; the outside wing panels will slide
onto them.
Once the wing panels are built, line up
the halves of the bottom wing and place 1/2-
inch shims under the wingtips to get the
proper dihedral. Glue the left joiners to the
right joiners.
Tail Surfaces: Before building the elevators
and the rudder, cut the templates from
CONSTRUCTION
Wing: The individual wing panels plug into
the fuselage using 1/4-inch-diameter dowel
as joiners. The dowels are not strong enough
by themselves to hold the wing panels; the
main strut (75) will hold everything in place
once the panels are plugged in. It’s
unnecessary, but you can replace the
hardwood dowels with carbon-fiber tubes.
To get started, transfer the ribs’ outlines
and mark the location of the holes on the
plywood and the balsa. Cut out the ribs and
drill all the holes.
Cut 1/4-inch hardwood dowels (69) (70)
and (47) (48) to the proper lengths. Adhere
two (69) dowels to create a double-width
joiner for the top wing, and then glue two
dowels (47) together for the bottom wing
joiner.
Build the top wing first. It includes three
sections: two outside panels and the center
panel.
Begin constructing the outside panels.
Pin the bottom main spar (49) to the board
directly over the plans. Pin the 1/4 square
balsa to the building board, to be used as a
shim under the ribs at the TE. Position and
glue all ribs to this spar. Glue the top main
spar (50) to the ribs.
Cut out the TE sheets (55) and (56) that
include the scallops. Slide the TE sheet (56)
between the shim and the ribs. Adhere the
ribs to the TE sheet. Glue the sub-LE (53) to
the ribs. Sand the sub-LE so that it follows
the contour of the ribs.
Glue the wingtip sheet (66) to rib W10.
Adhere the top TE sheet (55) to the ribs.
Glue the top LE sheet (51) to the ribs and to
the sub-LE. Glue on 1-inch-wide aileronhinge
balsa strip (58) to ribs W5 to W10.
Adhere the top capstrips to the ribs. Slide in
and glue joiner dowels (69) and (70) to ribs
W4 and W5.
Do not go any further with this wing
half. Construct the other half of the top wing
to the same stage.
04sig1.QXD 2/24/09 11:21 AM Page 30
corrugated cardboard. Slice four 1/4-inch-wide
strips from the 1/16 balsa sheet. Smear glue onto
the strips and form them around the templates.
Use pins to hold the strips against the templates
until the glue dries.
When the glue is dry, adhere the rest of the
frame and the 1/4-inch sheets. Build the
stabilizer and the fin, and then sand all the
surfaces.
Bend a 1/16-inch-diameter piano wire to
form the tail-wheel strut. Insert the end of the
strut into the balsa sheet in the rudder, and then
glue in the wire with thin cyanoacrylate. Wrap
the whole sheet with fiberglass. You can use
thin cyanoacrylate to saturate the cloth.
Cabane and Wing N Struts: Cut four identical
cabane struts (72) and four N struts (74) from 1/8
light plywood. Cut two cabane struts (71) and
two N struts (73) from 1/32 aluminum sheet.
Drill the 1/16-inch-diameter holes in N struts, as
shown on the drawing.
Sand the surface of the aluminum with
sandpaper. Using cyanoacrylate or GOOP-type
adhesive, adhere the plywood pieces to both
sides of the aluminum struts. Sand the edges of
the plywood to streamline their shape. Cut a slot
in one of the front cabane struts, and insert and
glue in the aileron-servo extension cable.
Wrap all the struts with fiberglass and
saturate them with thin cyanoacrylate. Sand
lightly and bend the exposed aluminum ends of
the struts as shown on the drawing.
Fuselage: Cut out as many parts as possible.
The fuselage is built upside-down in three
sections: the cowl, the center-section, and the
tail section.
Cut and bend 5/32-inch-diameter piano wire
to form the main landing-gear legs. Attach them
to former F5 with thread (canvas thread, Kevlar,
or copper wire).
Glue the hardwood block (17) to former
F4B, and adhere hardwood blocks (18) to
formers F3D and F6B. Pin formers F3D, F5,
F6B, and F8B to the building board. Pin and
glue the fuselage sides (1) to these formers.
Insert and glue in the battery floor (13). Insert
and glue in formers F4B and F7.
Pin formers F9B, F10B, F11, and F12 to the
building board. Adhere the rear fuselage sides
(2) to these formers and to the fuselage side (1).
Glue 3/8-inch triangle stock between the
fuselage side (2) and former F8B.
On the outside of the fuselage, glue the balsa
doublers (3) between formers F3D and F6B.
Between F6B and F8B, adhere the doublers (4)
to the fuselage sides.
Glue the bottom wing to the fuselage. Slide
the joiners (47) and (48) into the slots in the
fuselage sides (1). Check the alignment and
adhere the joiners to formers F6B and F7. Glue
the balsa strip (12) to the bottom of all the
formers. Complete the sheeting of the bottom
between formers F3B and F8B.
Turn the fuselage right-side up. Glue the
firewall (20) and firewall support sides (19) to
the battery floor (13) and to former F3D.
The cowl is built in top and bottom halves.
Cut four identical plywood pieces (21). Drill a
1/4-inch hole for the magnets and a 1/16-inch hole
for the guide pins.
Pin two of the four plywood pieces (21) to
the building board. Pin and glue formers F1B,
F2B, and F3B to them. Insert and glue 1/4
square balsa into these formers. Adhere the
sheeting (9) and (10).
Remove the bottom of the cowl from the
building board and glue the scoop (24) to it. The
bottom of the cowl can be glued to former F3D.
Build the removable top of the cowl the same
way, but don’t adhere it to anything. Glue the
magnets and guide pins into the plywood pieces
(21).
Mount the cabane to the hardwood blocks
(18) using self-tapping screws. Insert the
cabane’s top tabs into the slots in the bottom of
the top wing’s center-section. Line up the holes
on cabane struts with the holes in W3 ribs.
Attach the cabane to the W3 ribs with selftapping
screws. At the same time, feed the plug
from the aileron extension into the cavity
between ribs W2 and W3.
Plug in all the wing panels and check the
alignment. If any adjustments are required, now
is the time to do it. Install the wing N struts. Use
self-tapping screws to hold them to the wings.
It’s time to install the most important strut
(75). Cut the 1/2-inch K&S streamlined
aluminum tube to the proper length. Flatten the
ends. Drill a 3/32-inch hole at each end, and bend
the ends so that the flat end is flush with the
plywood (67) behind the main spar of the top
wing. The same goes for the other end, but it
has to follow the contour of the hardwood block
(17) in the fuselage. Drill the hole in the
hardwood block and the plywood for selftapping
screws.
Remove the wings from the fuselage,
including the center-section. In the top wing,
install the servo extension for the aileron servo.
Glue the stabilizer to the fuselage. Adhere
all top fuselage formers. Glue the top sheeting
(5) to the front fuselage formers and the
sheeting (6) to the back formers. Cut out the
cockpit opening. Glue on the headrest (25).
Adhere the longeron (14) to the side of the
fuselage. Glue the fin to the fuselage.
Make the wheel pants and the streamline
covers for the main gear legs from the balsa
materials cited on the plans.
Finishing: Use your own method to apply the
finish; I used UltraCote. After completing the
covering, I installed the hinges and the servos. I
mounted a threaded connecting rod between the
top and bottom aileron with a clevis at each end.
The small “L”-shaped aluminum bracket is
attached to the plywood plate on each aileron
with self-tapping screws.
The dummy engine is made from scrap
balsa pieces and then glued to the top half of the
cowl.
After installing the radio and motor, remove
the top half of the cowl and slide the motor
battery onto the battery floor. Check the CG.
Move the battery as needed to get the D-IX to
balance on the CG spot. Mark the battery
location. I used hook-and-loop fastener to hold
it in place.
Install the servos and check the control
surfaces’ operation. The elevator should travel
3/4 inch up and down. The rudder 11/4 inches left
and right at the widest point. The top ailerons
should travel 1/2 inch up and down at the widest
point.
You’re finished with the construction. Have
fun flying this unique-looking scale model. MA
Laddie Mikulasko
[email protected]
Sources:
AXi 2826/10 motor, Jeti 40 Advance ESC:
MS Composit
(317) 578-1955
www.mscompositusa.com
UltraCote covering:
Hangar 9
(800) 338-4639
www.hangar-9.com
3200 mAh EVO LITE V2 3S battery:
FlightPower
(919) 741-6310
www.flightpowerusa.com
Edition: Model Aviation - 2009/04
Page Numbers: 25,26,27,28,29,30,31,32,33
SEVERAL YEARS AGO, in one of the aircraft magazines I saw
pictures of a unique-looking home-built biplane called the “Der Jager
D-IX.” I was attracted to it because of its shape and color scheme.
Marshall Wright designed and built the airplane.
Sometime later, I stumbled across a three-view drawing for
the design. I kept it with the intention of building a scale
model of the D-IX at some point in the future. In addition to the
three-views, I found some photos on the Internet of the original
biplane.
I designed the model for an AXi 2826/10 brushless motor using a
Jeti Advance 40 PLUS speed controller and 3S Li-Poly batteries. I
made sure that the battery’s installation is easy; the top half of the
cowl comes off, and the battery is placed on the battery floor.
Four Blue Bird BMS-380 servos are used for control. They
are half the size of a standard servo, half the weight, and have the
same torque rating: approximately 50 inch-ounces. If you do not
want to fly this model as an electric, any .40-.45 glow engine can
be used.
I drew the plans and then proceeded to build the Der Jager model.
The test flight was a nonevent; the model tracked straight on takeoffs
and has excellent flying characteristics. It is fully aerobatic with no
bad habits, and the landings are straightforward. Even with the wheel
pants, the D-IX doesn’t nose over when flown off the grass.
April 2009 25
by Laddie Mikulasko
The author designed his airplane to be similar to the full-scale aircraft
that was designed by the Stolp-White Aircraft Company in 1969. The
model includes almost every charming aspect of the biplane lineage.
The Der Jager’s light wing loading allows it to climb quickly.
Sport aerobatics are comfortable.
A WW1-looking home-built,
fresh from the 1970s
04sig1.QXD 2/24/09 11:16 AM Page 25
26 MODEL AVIATION
Photos by the author
Wing panels join the center-sections with stacked dowel rods
at the apex of the rib shape. Center-area ribs are made from
light plywood.
The ribs are organized over the top wing plans as they are cut
from blank material. Holes in the inner ribs are for the aileron
servo wire and dowel supports.
The wide sheeting near the TE is centered over the hinge line.
Once the aileron is cut away, cap the open areas with balsa.
TE scallops add distinctive character to the Der Jager. After
drawing the outline, sand away the excess with a rasp or round
dowel covered with sandpaper.
The cabane struts and N struts have an aluminum-sheet core that
is laminated with wood on both sides. The material is sanded to a
streamlined shape later.
The center-section of the upper wing secures the dowel-rod wing
joiners inside plywood ribs. The completed sheeting is sanded
flush with the outer panels.
04sig1.QXD 2/24/09 11:33 AM Page 26
April 2009 27
The primary fuselage sides are marked left and right, as are the
forward 1/4-inch sheets that will be sanded to shape later.
The cabane struts mount inside tabs in the top wing’s centersection
and are secured with #4 socket-head servo screws.
The wooden sections of the wheel pants are laminated with
wood glue, which is easy to sand later. Plywood buried inside
acts as a mounting point.
The piano-wire landing gear is stitched to the former with
thread, Kevlar, or copper wire. The lower wing’s center-section
is built into the forward framework.
The cabane struts are securely mounted into hardwood areas.
Sheeting is wrapped around the forward turtledeck, forming the
cockpit area.
Once the fuselage sides are pulled together, the lower sheeting
and longerons can be added. Watch out for twisting and keep
the tail post square.
04sig1.QXD 2/24/09 11:18 AM Page 27
28 MODEL AVIATION
Cowling halves are framed separately. The lower half (shown) is
permanently attached to the fuselage and houses the motor.
A channel is carved in the right cabane strut to hide the aileronservo
extension wire. Covering material is applied over the woodskinned
aluminum supports later.
The stabilizer and fin are framed to simulate steel-tube
framework, so they are rounded on all outside edges.
Each control surface of the tail must have cardboard templates
made to form the laminations of the curved outer-framework
material.
An AXi Gold 2826/10 motor and Jeti 40 Advance ESC are
powered with a 3300 mAh 3S Li-Poly battery from FlightPower.
Temporary foam fixtures are placed to align and set the struts’ final
locations. Double-stick tape and pins hold the fixtures in place.
04sig1.QXD 2/24/09 11:35 AM Page 28
April 2009 29
Pushrods from upper to lower aileron are linked to aluminum angle
brackets located in hard points near the LE of the control surface.
Access to rudder and elevator servos is through the cockpit
opening, which is later covered with a pilot figure.
The simulated engine is made from scrap balsa that is covered
and painted to match the IO-235 four-cylinder engine used in
the full-scale aircraft.
Simulated bullet-hole decorations, as on the full-scale aircraft.
Support wires add support but are mostly for appearance.
Type: RC Sport Scale
Skill level: Intermediate
builder, intermediate pilot
Wingspan: Top, 50 inches; bottom,
42 inches
Wing area: Approximately 750 square inches
Length: 42 inches
Weight: 4 pounds (depending on battery)
Power: 300- to 500-watt system, 40- to 54-amp ESC,
3S 3300 mAh Li-Poly battery
Construction: Balsa, light plywood, hardwood-dowel wing joiners
Covering/finish: UltraCote heat-shrink film
Radio: Four miniservos (40 inch-ounces output), receiver,
custom servo extensions
Other: 21/4-inch spinner, 3-inch wheels, APC 10 x 8E propeller, 11/4-inch tail
wheel, 5/32-inch music-wire landing gear, 1/32-inch aluminum-sheet strut material
04sig1.QXD 2/24/09 11:20 AM Page 29
30 MODEL AVIATION
The four wing panels plug into the structure and are secured with an aluminum main strut that attaches from the lower
fuselage to the top outer panel.
The AXi power system is equivalent to a .32
cu. in. glow engine that offers better-thanscale
performance. The Der Jager flies
predictably and has a distinctive appearance.
I tried to make building this airplane as
simple as possible. The outer wing panels are
removable; however, if transporting a 50-
inch-wingspan model is not a problem, you
have the option of building the wings in one
piece and permanently attaching them to the
fuselage.
The two aileron servos are mounted inside
the top wing. The connecting rods join the
top aileron to the bottom aileron. The elevator
and rudder servos are located inside the
cockpit.
To build this model, you will need light
balsa, light plywood, 5/32-inch-diameter music
wire, and 1/32-inch-thick aluminum sheeting.
Build the wing center-section. Pin the
bottom main spar to the building board.
Glue ribs W1, W2, and W3 to the spar.
Adhere the top main spar to the ribs.
Take hold of the two outside wing panels
and slide the joiners all the way into ribs W2
and W3. Glue the sub-LE to ribs W1, W2,
and W3. Adhere the top LE sheet (51) to
these ribs. Glue on the rest of the top
sheeting (62).
Flip the wing over. In the center-section,
install the Y harness for the ailerons. Glue
the bottom sheeting (61) to ribs W1, W2,
and W3. Glue the plywood strips (67) to ribs
W8 and W9; you must use the five-ply
plywood. The plywood strips will be
holding the brackets for N struts and the
main struts (75).
Glue on the bottom LE sheeting (52).
Adhere the aileron strip (58) to ribs W5 to
W10. Glue on the sheeting (63) over ribs
W4 and W5 and the sheeting (59) and (60)
over ribs W7 and W9. Glue on the capstrips.
Attach the LE spar (54).
Separate the ailerons from the wing
panels. Glue the hinge spar (57) to the wing
and the aileron LE to the aileron. Sand the
wing. Glue in the plywood mounting frame
for the aileron servo.
In the bottom of the center-section, cut
the slots for the cabane struts to go into and
one larger hole for the extension cable.
Build the bottom wing in a similar
fashion. The difference is having the joiners
(47) and (48) glued to the two identical root
ribs W11, which will become part of the
fuselage; the outside wing panels will slide
onto them.
Once the wing panels are built, line up
the halves of the bottom wing and place 1/2-
inch shims under the wingtips to get the
proper dihedral. Glue the left joiners to the
right joiners.
Tail Surfaces: Before building the elevators
and the rudder, cut the templates from
CONSTRUCTION
Wing: The individual wing panels plug into
the fuselage using 1/4-inch-diameter dowel
as joiners. The dowels are not strong enough
by themselves to hold the wing panels; the
main strut (75) will hold everything in place
once the panels are plugged in. It’s
unnecessary, but you can replace the
hardwood dowels with carbon-fiber tubes.
To get started, transfer the ribs’ outlines
and mark the location of the holes on the
plywood and the balsa. Cut out the ribs and
drill all the holes.
Cut 1/4-inch hardwood dowels (69) (70)
and (47) (48) to the proper lengths. Adhere
two (69) dowels to create a double-width
joiner for the top wing, and then glue two
dowels (47) together for the bottom wing
joiner.
Build the top wing first. It includes three
sections: two outside panels and the center
panel.
Begin constructing the outside panels.
Pin the bottom main spar (49) to the board
directly over the plans. Pin the 1/4 square
balsa to the building board, to be used as a
shim under the ribs at the TE. Position and
glue all ribs to this spar. Glue the top main
spar (50) to the ribs.
Cut out the TE sheets (55) and (56) that
include the scallops. Slide the TE sheet (56)
between the shim and the ribs. Adhere the
ribs to the TE sheet. Glue the sub-LE (53) to
the ribs. Sand the sub-LE so that it follows
the contour of the ribs.
Glue the wingtip sheet (66) to rib W10.
Adhere the top TE sheet (55) to the ribs.
Glue the top LE sheet (51) to the ribs and to
the sub-LE. Glue on 1-inch-wide aileronhinge
balsa strip (58) to ribs W5 to W10.
Adhere the top capstrips to the ribs. Slide in
and glue joiner dowels (69) and (70) to ribs
W4 and W5.
Do not go any further with this wing
half. Construct the other half of the top wing
to the same stage.
04sig1.QXD 2/24/09 11:21 AM Page 30
corrugated cardboard. Slice four 1/4-inch-wide
strips from the 1/16 balsa sheet. Smear glue onto
the strips and form them around the templates.
Use pins to hold the strips against the templates
until the glue dries.
When the glue is dry, adhere the rest of the
frame and the 1/4-inch sheets. Build the
stabilizer and the fin, and then sand all the
surfaces.
Bend a 1/16-inch-diameter piano wire to
form the tail-wheel strut. Insert the end of the
strut into the balsa sheet in the rudder, and then
glue in the wire with thin cyanoacrylate. Wrap
the whole sheet with fiberglass. You can use
thin cyanoacrylate to saturate the cloth.
Cabane and Wing N Struts: Cut four identical
cabane struts (72) and four N struts (74) from 1/8
light plywood. Cut two cabane struts (71) and
two N struts (73) from 1/32 aluminum sheet.
Drill the 1/16-inch-diameter holes in N struts, as
shown on the drawing.
Sand the surface of the aluminum with
sandpaper. Using cyanoacrylate or GOOP-type
adhesive, adhere the plywood pieces to both
sides of the aluminum struts. Sand the edges of
the plywood to streamline their shape. Cut a slot
in one of the front cabane struts, and insert and
glue in the aileron-servo extension cable.
Wrap all the struts with fiberglass and
saturate them with thin cyanoacrylate. Sand
lightly and bend the exposed aluminum ends of
the struts as shown on the drawing.
Fuselage: Cut out as many parts as possible.
The fuselage is built upside-down in three
sections: the cowl, the center-section, and the
tail section.
Cut and bend 5/32-inch-diameter piano wire
to form the main landing-gear legs. Attach them
to former F5 with thread (canvas thread, Kevlar,
or copper wire).
Glue the hardwood block (17) to former
F4B, and adhere hardwood blocks (18) to
formers F3D and F6B. Pin formers F3D, F5,
F6B, and F8B to the building board. Pin and
glue the fuselage sides (1) to these formers.
Insert and glue in the battery floor (13). Insert
and glue in formers F4B and F7.
Pin formers F9B, F10B, F11, and F12 to the
building board. Adhere the rear fuselage sides
(2) to these formers and to the fuselage side (1).
Glue 3/8-inch triangle stock between the
fuselage side (2) and former F8B.
On the outside of the fuselage, glue the balsa
doublers (3) between formers F3D and F6B.
Between F6B and F8B, adhere the doublers (4)
to the fuselage sides.
Glue the bottom wing to the fuselage. Slide
the joiners (47) and (48) into the slots in the
fuselage sides (1). Check the alignment and
adhere the joiners to formers F6B and F7. Glue
the balsa strip (12) to the bottom of all the
formers. Complete the sheeting of the bottom
between formers F3B and F8B.
Turn the fuselage right-side up. Glue the
firewall (20) and firewall support sides (19) to
the battery floor (13) and to former F3D.
The cowl is built in top and bottom halves.
Cut four identical plywood pieces (21). Drill a
1/4-inch hole for the magnets and a 1/16-inch hole
for the guide pins.
Pin two of the four plywood pieces (21) to
the building board. Pin and glue formers F1B,
F2B, and F3B to them. Insert and glue 1/4
square balsa into these formers. Adhere the
sheeting (9) and (10).
Remove the bottom of the cowl from the
building board and glue the scoop (24) to it. The
bottom of the cowl can be glued to former F3D.
Build the removable top of the cowl the same
way, but don’t adhere it to anything. Glue the
magnets and guide pins into the plywood pieces
(21).
Mount the cabane to the hardwood blocks
(18) using self-tapping screws. Insert the
cabane’s top tabs into the slots in the bottom of
the top wing’s center-section. Line up the holes
on cabane struts with the holes in W3 ribs.
Attach the cabane to the W3 ribs with selftapping
screws. At the same time, feed the plug
from the aileron extension into the cavity
between ribs W2 and W3.
Plug in all the wing panels and check the
alignment. If any adjustments are required, now
is the time to do it. Install the wing N struts. Use
self-tapping screws to hold them to the wings.
It’s time to install the most important strut
(75). Cut the 1/2-inch K&S streamlined
aluminum tube to the proper length. Flatten the
ends. Drill a 3/32-inch hole at each end, and bend
the ends so that the flat end is flush with the
plywood (67) behind the main spar of the top
wing. The same goes for the other end, but it
has to follow the contour of the hardwood block
(17) in the fuselage. Drill the hole in the
hardwood block and the plywood for selftapping
screws.
Remove the wings from the fuselage,
including the center-section. In the top wing,
install the servo extension for the aileron servo.
Glue the stabilizer to the fuselage. Adhere
all top fuselage formers. Glue the top sheeting
(5) to the front fuselage formers and the
sheeting (6) to the back formers. Cut out the
cockpit opening. Glue on the headrest (25).
Adhere the longeron (14) to the side of the
fuselage. Glue the fin to the fuselage.
Make the wheel pants and the streamline
covers for the main gear legs from the balsa
materials cited on the plans.
Finishing: Use your own method to apply the
finish; I used UltraCote. After completing the
covering, I installed the hinges and the servos. I
mounted a threaded connecting rod between the
top and bottom aileron with a clevis at each end.
The small “L”-shaped aluminum bracket is
attached to the plywood plate on each aileron
with self-tapping screws.
The dummy engine is made from scrap
balsa pieces and then glued to the top half of the
cowl.
After installing the radio and motor, remove
the top half of the cowl and slide the motor
battery onto the battery floor. Check the CG.
Move the battery as needed to get the D-IX to
balance on the CG spot. Mark the battery
location. I used hook-and-loop fastener to hold
it in place.
Install the servos and check the control
surfaces’ operation. The elevator should travel
3/4 inch up and down. The rudder 11/4 inches left
and right at the widest point. The top ailerons
should travel 1/2 inch up and down at the widest
point.
You’re finished with the construction. Have
fun flying this unique-looking scale model. MA
Laddie Mikulasko
[email protected]
Sources:
AXi 2826/10 motor, Jeti 40 Advance ESC:
MS Composit
(317) 578-1955
www.mscompositusa.com
UltraCote covering:
Hangar 9
(800) 338-4639
www.hangar-9.com
3200 mAh EVO LITE V2 3S battery:
FlightPower
(919) 741-6310
www.flightpowerusa.com
Edition: Model Aviation - 2009/04
Page Numbers: 25,26,27,28,29,30,31,32,33
SEVERAL YEARS AGO, in one of the aircraft magazines I saw
pictures of a unique-looking home-built biplane called the “Der Jager
D-IX.” I was attracted to it because of its shape and color scheme.
Marshall Wright designed and built the airplane.
Sometime later, I stumbled across a three-view drawing for
the design. I kept it with the intention of building a scale
model of the D-IX at some point in the future. In addition to the
three-views, I found some photos on the Internet of the original
biplane.
I designed the model for an AXi 2826/10 brushless motor using a
Jeti Advance 40 PLUS speed controller and 3S Li-Poly batteries. I
made sure that the battery’s installation is easy; the top half of the
cowl comes off, and the battery is placed on the battery floor.
Four Blue Bird BMS-380 servos are used for control. They
are half the size of a standard servo, half the weight, and have the
same torque rating: approximately 50 inch-ounces. If you do not
want to fly this model as an electric, any .40-.45 glow engine can
be used.
I drew the plans and then proceeded to build the Der Jager model.
The test flight was a nonevent; the model tracked straight on takeoffs
and has excellent flying characteristics. It is fully aerobatic with no
bad habits, and the landings are straightforward. Even with the wheel
pants, the D-IX doesn’t nose over when flown off the grass.
April 2009 25
by Laddie Mikulasko
The author designed his airplane to be similar to the full-scale aircraft
that was designed by the Stolp-White Aircraft Company in 1969. The
model includes almost every charming aspect of the biplane lineage.
The Der Jager’s light wing loading allows it to climb quickly.
Sport aerobatics are comfortable.
A WW1-looking home-built,
fresh from the 1970s
04sig1.QXD 2/24/09 11:16 AM Page 25
26 MODEL AVIATION
Photos by the author
Wing panels join the center-sections with stacked dowel rods
at the apex of the rib shape. Center-area ribs are made from
light plywood.
The ribs are organized over the top wing plans as they are cut
from blank material. Holes in the inner ribs are for the aileron
servo wire and dowel supports.
The wide sheeting near the TE is centered over the hinge line.
Once the aileron is cut away, cap the open areas with balsa.
TE scallops add distinctive character to the Der Jager. After
drawing the outline, sand away the excess with a rasp or round
dowel covered with sandpaper.
The cabane struts and N struts have an aluminum-sheet core that
is laminated with wood on both sides. The material is sanded to a
streamlined shape later.
The center-section of the upper wing secures the dowel-rod wing
joiners inside plywood ribs. The completed sheeting is sanded
flush with the outer panels.
04sig1.QXD 2/24/09 11:33 AM Page 26
April 2009 27
The primary fuselage sides are marked left and right, as are the
forward 1/4-inch sheets that will be sanded to shape later.
The cabane struts mount inside tabs in the top wing’s centersection
and are secured with #4 socket-head servo screws.
The wooden sections of the wheel pants are laminated with
wood glue, which is easy to sand later. Plywood buried inside
acts as a mounting point.
The piano-wire landing gear is stitched to the former with
thread, Kevlar, or copper wire. The lower wing’s center-section
is built into the forward framework.
The cabane struts are securely mounted into hardwood areas.
Sheeting is wrapped around the forward turtledeck, forming the
cockpit area.
Once the fuselage sides are pulled together, the lower sheeting
and longerons can be added. Watch out for twisting and keep
the tail post square.
04sig1.QXD 2/24/09 11:18 AM Page 27
28 MODEL AVIATION
Cowling halves are framed separately. The lower half (shown) is
permanently attached to the fuselage and houses the motor.
A channel is carved in the right cabane strut to hide the aileronservo
extension wire. Covering material is applied over the woodskinned
aluminum supports later.
The stabilizer and fin are framed to simulate steel-tube
framework, so they are rounded on all outside edges.
Each control surface of the tail must have cardboard templates
made to form the laminations of the curved outer-framework
material.
An AXi Gold 2826/10 motor and Jeti 40 Advance ESC are
powered with a 3300 mAh 3S Li-Poly battery from FlightPower.
Temporary foam fixtures are placed to align and set the struts’ final
locations. Double-stick tape and pins hold the fixtures in place.
04sig1.QXD 2/24/09 11:35 AM Page 28
April 2009 29
Pushrods from upper to lower aileron are linked to aluminum angle
brackets located in hard points near the LE of the control surface.
Access to rudder and elevator servos is through the cockpit
opening, which is later covered with a pilot figure.
The simulated engine is made from scrap balsa that is covered
and painted to match the IO-235 four-cylinder engine used in
the full-scale aircraft.
Simulated bullet-hole decorations, as on the full-scale aircraft.
Support wires add support but are mostly for appearance.
Type: RC Sport Scale
Skill level: Intermediate
builder, intermediate pilot
Wingspan: Top, 50 inches; bottom,
42 inches
Wing area: Approximately 750 square inches
Length: 42 inches
Weight: 4 pounds (depending on battery)
Power: 300- to 500-watt system, 40- to 54-amp ESC,
3S 3300 mAh Li-Poly battery
Construction: Balsa, light plywood, hardwood-dowel wing joiners
Covering/finish: UltraCote heat-shrink film
Radio: Four miniservos (40 inch-ounces output), receiver,
custom servo extensions
Other: 21/4-inch spinner, 3-inch wheels, APC 10 x 8E propeller, 11/4-inch tail
wheel, 5/32-inch music-wire landing gear, 1/32-inch aluminum-sheet strut material
04sig1.QXD 2/24/09 11:20 AM Page 29
30 MODEL AVIATION
The four wing panels plug into the structure and are secured with an aluminum main strut that attaches from the lower
fuselage to the top outer panel.
The AXi power system is equivalent to a .32
cu. in. glow engine that offers better-thanscale
performance. The Der Jager flies
predictably and has a distinctive appearance.
I tried to make building this airplane as
simple as possible. The outer wing panels are
removable; however, if transporting a 50-
inch-wingspan model is not a problem, you
have the option of building the wings in one
piece and permanently attaching them to the
fuselage.
The two aileron servos are mounted inside
the top wing. The connecting rods join the
top aileron to the bottom aileron. The elevator
and rudder servos are located inside the
cockpit.
To build this model, you will need light
balsa, light plywood, 5/32-inch-diameter music
wire, and 1/32-inch-thick aluminum sheeting.
Build the wing center-section. Pin the
bottom main spar to the building board.
Glue ribs W1, W2, and W3 to the spar.
Adhere the top main spar to the ribs.
Take hold of the two outside wing panels
and slide the joiners all the way into ribs W2
and W3. Glue the sub-LE to ribs W1, W2,
and W3. Adhere the top LE sheet (51) to
these ribs. Glue on the rest of the top
sheeting (62).
Flip the wing over. In the center-section,
install the Y harness for the ailerons. Glue
the bottom sheeting (61) to ribs W1, W2,
and W3. Glue the plywood strips (67) to ribs
W8 and W9; you must use the five-ply
plywood. The plywood strips will be
holding the brackets for N struts and the
main struts (75).
Glue on the bottom LE sheeting (52).
Adhere the aileron strip (58) to ribs W5 to
W10. Glue on the sheeting (63) over ribs
W4 and W5 and the sheeting (59) and (60)
over ribs W7 and W9. Glue on the capstrips.
Attach the LE spar (54).
Separate the ailerons from the wing
panels. Glue the hinge spar (57) to the wing
and the aileron LE to the aileron. Sand the
wing. Glue in the plywood mounting frame
for the aileron servo.
In the bottom of the center-section, cut
the slots for the cabane struts to go into and
one larger hole for the extension cable.
Build the bottom wing in a similar
fashion. The difference is having the joiners
(47) and (48) glued to the two identical root
ribs W11, which will become part of the
fuselage; the outside wing panels will slide
onto them.
Once the wing panels are built, line up
the halves of the bottom wing and place 1/2-
inch shims under the wingtips to get the
proper dihedral. Glue the left joiners to the
right joiners.
Tail Surfaces: Before building the elevators
and the rudder, cut the templates from
CONSTRUCTION
Wing: The individual wing panels plug into
the fuselage using 1/4-inch-diameter dowel
as joiners. The dowels are not strong enough
by themselves to hold the wing panels; the
main strut (75) will hold everything in place
once the panels are plugged in. It’s
unnecessary, but you can replace the
hardwood dowels with carbon-fiber tubes.
To get started, transfer the ribs’ outlines
and mark the location of the holes on the
plywood and the balsa. Cut out the ribs and
drill all the holes.
Cut 1/4-inch hardwood dowels (69) (70)
and (47) (48) to the proper lengths. Adhere
two (69) dowels to create a double-width
joiner for the top wing, and then glue two
dowels (47) together for the bottom wing
joiner.
Build the top wing first. It includes three
sections: two outside panels and the center
panel.
Begin constructing the outside panels.
Pin the bottom main spar (49) to the board
directly over the plans. Pin the 1/4 square
balsa to the building board, to be used as a
shim under the ribs at the TE. Position and
glue all ribs to this spar. Glue the top main
spar (50) to the ribs.
Cut out the TE sheets (55) and (56) that
include the scallops. Slide the TE sheet (56)
between the shim and the ribs. Adhere the
ribs to the TE sheet. Glue the sub-LE (53) to
the ribs. Sand the sub-LE so that it follows
the contour of the ribs.
Glue the wingtip sheet (66) to rib W10.
Adhere the top TE sheet (55) to the ribs.
Glue the top LE sheet (51) to the ribs and to
the sub-LE. Glue on 1-inch-wide aileronhinge
balsa strip (58) to ribs W5 to W10.
Adhere the top capstrips to the ribs. Slide in
and glue joiner dowels (69) and (70) to ribs
W4 and W5.
Do not go any further with this wing
half. Construct the other half of the top wing
to the same stage.
04sig1.QXD 2/24/09 11:21 AM Page 30
corrugated cardboard. Slice four 1/4-inch-wide
strips from the 1/16 balsa sheet. Smear glue onto
the strips and form them around the templates.
Use pins to hold the strips against the templates
until the glue dries.
When the glue is dry, adhere the rest of the
frame and the 1/4-inch sheets. Build the
stabilizer and the fin, and then sand all the
surfaces.
Bend a 1/16-inch-diameter piano wire to
form the tail-wheel strut. Insert the end of the
strut into the balsa sheet in the rudder, and then
glue in the wire with thin cyanoacrylate. Wrap
the whole sheet with fiberglass. You can use
thin cyanoacrylate to saturate the cloth.
Cabane and Wing N Struts: Cut four identical
cabane struts (72) and four N struts (74) from 1/8
light plywood. Cut two cabane struts (71) and
two N struts (73) from 1/32 aluminum sheet.
Drill the 1/16-inch-diameter holes in N struts, as
shown on the drawing.
Sand the surface of the aluminum with
sandpaper. Using cyanoacrylate or GOOP-type
adhesive, adhere the plywood pieces to both
sides of the aluminum struts. Sand the edges of
the plywood to streamline their shape. Cut a slot
in one of the front cabane struts, and insert and
glue in the aileron-servo extension cable.
Wrap all the struts with fiberglass and
saturate them with thin cyanoacrylate. Sand
lightly and bend the exposed aluminum ends of
the struts as shown on the drawing.
Fuselage: Cut out as many parts as possible.
The fuselage is built upside-down in three
sections: the cowl, the center-section, and the
tail section.
Cut and bend 5/32-inch-diameter piano wire
to form the main landing-gear legs. Attach them
to former F5 with thread (canvas thread, Kevlar,
or copper wire).
Glue the hardwood block (17) to former
F4B, and adhere hardwood blocks (18) to
formers F3D and F6B. Pin formers F3D, F5,
F6B, and F8B to the building board. Pin and
glue the fuselage sides (1) to these formers.
Insert and glue in the battery floor (13). Insert
and glue in formers F4B and F7.
Pin formers F9B, F10B, F11, and F12 to the
building board. Adhere the rear fuselage sides
(2) to these formers and to the fuselage side (1).
Glue 3/8-inch triangle stock between the
fuselage side (2) and former F8B.
On the outside of the fuselage, glue the balsa
doublers (3) between formers F3D and F6B.
Between F6B and F8B, adhere the doublers (4)
to the fuselage sides.
Glue the bottom wing to the fuselage. Slide
the joiners (47) and (48) into the slots in the
fuselage sides (1). Check the alignment and
adhere the joiners to formers F6B and F7. Glue
the balsa strip (12) to the bottom of all the
formers. Complete the sheeting of the bottom
between formers F3B and F8B.
Turn the fuselage right-side up. Glue the
firewall (20) and firewall support sides (19) to
the battery floor (13) and to former F3D.
The cowl is built in top and bottom halves.
Cut four identical plywood pieces (21). Drill a
1/4-inch hole for the magnets and a 1/16-inch hole
for the guide pins.
Pin two of the four plywood pieces (21) to
the building board. Pin and glue formers F1B,
F2B, and F3B to them. Insert and glue 1/4
square balsa into these formers. Adhere the
sheeting (9) and (10).
Remove the bottom of the cowl from the
building board and glue the scoop (24) to it. The
bottom of the cowl can be glued to former F3D.
Build the removable top of the cowl the same
way, but don’t adhere it to anything. Glue the
magnets and guide pins into the plywood pieces
(21).
Mount the cabane to the hardwood blocks
(18) using self-tapping screws. Insert the
cabane’s top tabs into the slots in the bottom of
the top wing’s center-section. Line up the holes
on cabane struts with the holes in W3 ribs.
Attach the cabane to the W3 ribs with selftapping
screws. At the same time, feed the plug
from the aileron extension into the cavity
between ribs W2 and W3.
Plug in all the wing panels and check the
alignment. If any adjustments are required, now
is the time to do it. Install the wing N struts. Use
self-tapping screws to hold them to the wings.
It’s time to install the most important strut
(75). Cut the 1/2-inch K&S streamlined
aluminum tube to the proper length. Flatten the
ends. Drill a 3/32-inch hole at each end, and bend
the ends so that the flat end is flush with the
plywood (67) behind the main spar of the top
wing. The same goes for the other end, but it
has to follow the contour of the hardwood block
(17) in the fuselage. Drill the hole in the
hardwood block and the plywood for selftapping
screws.
Remove the wings from the fuselage,
including the center-section. In the top wing,
install the servo extension for the aileron servo.
Glue the stabilizer to the fuselage. Adhere
all top fuselage formers. Glue the top sheeting
(5) to the front fuselage formers and the
sheeting (6) to the back formers. Cut out the
cockpit opening. Glue on the headrest (25).
Adhere the longeron (14) to the side of the
fuselage. Glue the fin to the fuselage.
Make the wheel pants and the streamline
covers for the main gear legs from the balsa
materials cited on the plans.
Finishing: Use your own method to apply the
finish; I used UltraCote. After completing the
covering, I installed the hinges and the servos. I
mounted a threaded connecting rod between the
top and bottom aileron with a clevis at each end.
The small “L”-shaped aluminum bracket is
attached to the plywood plate on each aileron
with self-tapping screws.
The dummy engine is made from scrap
balsa pieces and then glued to the top half of the
cowl.
After installing the radio and motor, remove
the top half of the cowl and slide the motor
battery onto the battery floor. Check the CG.
Move the battery as needed to get the D-IX to
balance on the CG spot. Mark the battery
location. I used hook-and-loop fastener to hold
it in place.
Install the servos and check the control
surfaces’ operation. The elevator should travel
3/4 inch up and down. The rudder 11/4 inches left
and right at the widest point. The top ailerons
should travel 1/2 inch up and down at the widest
point.
You’re finished with the construction. Have
fun flying this unique-looking scale model. MA
Laddie Mikulasko
[email protected]
Sources:
AXi 2826/10 motor, Jeti 40 Advance ESC:
MS Composit
(317) 578-1955
www.mscompositusa.com
UltraCote covering:
Hangar 9
(800) 338-4639
www.hangar-9.com
3200 mAh EVO LITE V2 3S battery:
FlightPower
(919) 741-6310
www.flightpowerusa.com
Edition: Model Aviation - 2009/04
Page Numbers: 25,26,27,28,29,30,31,32,33
SEVERAL YEARS AGO, in one of the aircraft magazines I saw
pictures of a unique-looking home-built biplane called the “Der Jager
D-IX.” I was attracted to it because of its shape and color scheme.
Marshall Wright designed and built the airplane.
Sometime later, I stumbled across a three-view drawing for
the design. I kept it with the intention of building a scale
model of the D-IX at some point in the future. In addition to the
three-views, I found some photos on the Internet of the original
biplane.
I designed the model for an AXi 2826/10 brushless motor using a
Jeti Advance 40 PLUS speed controller and 3S Li-Poly batteries. I
made sure that the battery’s installation is easy; the top half of the
cowl comes off, and the battery is placed on the battery floor.
Four Blue Bird BMS-380 servos are used for control. They
are half the size of a standard servo, half the weight, and have the
same torque rating: approximately 50 inch-ounces. If you do not
want to fly this model as an electric, any .40-.45 glow engine can
be used.
I drew the plans and then proceeded to build the Der Jager model.
The test flight was a nonevent; the model tracked straight on takeoffs
and has excellent flying characteristics. It is fully aerobatic with no
bad habits, and the landings are straightforward. Even with the wheel
pants, the D-IX doesn’t nose over when flown off the grass.
April 2009 25
by Laddie Mikulasko
The author designed his airplane to be similar to the full-scale aircraft
that was designed by the Stolp-White Aircraft Company in 1969. The
model includes almost every charming aspect of the biplane lineage.
The Der Jager’s light wing loading allows it to climb quickly.
Sport aerobatics are comfortable.
A WW1-looking home-built,
fresh from the 1970s
04sig1.QXD 2/24/09 11:16 AM Page 25
26 MODEL AVIATION
Photos by the author
Wing panels join the center-sections with stacked dowel rods
at the apex of the rib shape. Center-area ribs are made from
light plywood.
The ribs are organized over the top wing plans as they are cut
from blank material. Holes in the inner ribs are for the aileron
servo wire and dowel supports.
The wide sheeting near the TE is centered over the hinge line.
Once the aileron is cut away, cap the open areas with balsa.
TE scallops add distinctive character to the Der Jager. After
drawing the outline, sand away the excess with a rasp or round
dowel covered with sandpaper.
The cabane struts and N struts have an aluminum-sheet core that
is laminated with wood on both sides. The material is sanded to a
streamlined shape later.
The center-section of the upper wing secures the dowel-rod wing
joiners inside plywood ribs. The completed sheeting is sanded
flush with the outer panels.
04sig1.QXD 2/24/09 11:33 AM Page 26
April 2009 27
The primary fuselage sides are marked left and right, as are the
forward 1/4-inch sheets that will be sanded to shape later.
The cabane struts mount inside tabs in the top wing’s centersection
and are secured with #4 socket-head servo screws.
The wooden sections of the wheel pants are laminated with
wood glue, which is easy to sand later. Plywood buried inside
acts as a mounting point.
The piano-wire landing gear is stitched to the former with
thread, Kevlar, or copper wire. The lower wing’s center-section
is built into the forward framework.
The cabane struts are securely mounted into hardwood areas.
Sheeting is wrapped around the forward turtledeck, forming the
cockpit area.
Once the fuselage sides are pulled together, the lower sheeting
and longerons can be added. Watch out for twisting and keep
the tail post square.
04sig1.QXD 2/24/09 11:18 AM Page 27
28 MODEL AVIATION
Cowling halves are framed separately. The lower half (shown) is
permanently attached to the fuselage and houses the motor.
A channel is carved in the right cabane strut to hide the aileronservo
extension wire. Covering material is applied over the woodskinned
aluminum supports later.
The stabilizer and fin are framed to simulate steel-tube
framework, so they are rounded on all outside edges.
Each control surface of the tail must have cardboard templates
made to form the laminations of the curved outer-framework
material.
An AXi Gold 2826/10 motor and Jeti 40 Advance ESC are
powered with a 3300 mAh 3S Li-Poly battery from FlightPower.
Temporary foam fixtures are placed to align and set the struts’ final
locations. Double-stick tape and pins hold the fixtures in place.
04sig1.QXD 2/24/09 11:35 AM Page 28
April 2009 29
Pushrods from upper to lower aileron are linked to aluminum angle
brackets located in hard points near the LE of the control surface.
Access to rudder and elevator servos is through the cockpit
opening, which is later covered with a pilot figure.
The simulated engine is made from scrap balsa that is covered
and painted to match the IO-235 four-cylinder engine used in
the full-scale aircraft.
Simulated bullet-hole decorations, as on the full-scale aircraft.
Support wires add support but are mostly for appearance.
Type: RC Sport Scale
Skill level: Intermediate
builder, intermediate pilot
Wingspan: Top, 50 inches; bottom,
42 inches
Wing area: Approximately 750 square inches
Length: 42 inches
Weight: 4 pounds (depending on battery)
Power: 300- to 500-watt system, 40- to 54-amp ESC,
3S 3300 mAh Li-Poly battery
Construction: Balsa, light plywood, hardwood-dowel wing joiners
Covering/finish: UltraCote heat-shrink film
Radio: Four miniservos (40 inch-ounces output), receiver,
custom servo extensions
Other: 21/4-inch spinner, 3-inch wheels, APC 10 x 8E propeller, 11/4-inch tail
wheel, 5/32-inch music-wire landing gear, 1/32-inch aluminum-sheet strut material
04sig1.QXD 2/24/09 11:20 AM Page 29
30 MODEL AVIATION
The four wing panels plug into the structure and are secured with an aluminum main strut that attaches from the lower
fuselage to the top outer panel.
The AXi power system is equivalent to a .32
cu. in. glow engine that offers better-thanscale
performance. The Der Jager flies
predictably and has a distinctive appearance.
I tried to make building this airplane as
simple as possible. The outer wing panels are
removable; however, if transporting a 50-
inch-wingspan model is not a problem, you
have the option of building the wings in one
piece and permanently attaching them to the
fuselage.
The two aileron servos are mounted inside
the top wing. The connecting rods join the
top aileron to the bottom aileron. The elevator
and rudder servos are located inside the
cockpit.
To build this model, you will need light
balsa, light plywood, 5/32-inch-diameter music
wire, and 1/32-inch-thick aluminum sheeting.
Build the wing center-section. Pin the
bottom main spar to the building board.
Glue ribs W1, W2, and W3 to the spar.
Adhere the top main spar to the ribs.
Take hold of the two outside wing panels
and slide the joiners all the way into ribs W2
and W3. Glue the sub-LE to ribs W1, W2,
and W3. Adhere the top LE sheet (51) to
these ribs. Glue on the rest of the top
sheeting (62).
Flip the wing over. In the center-section,
install the Y harness for the ailerons. Glue
the bottom sheeting (61) to ribs W1, W2,
and W3. Glue the plywood strips (67) to ribs
W8 and W9; you must use the five-ply
plywood. The plywood strips will be
holding the brackets for N struts and the
main struts (75).
Glue on the bottom LE sheeting (52).
Adhere the aileron strip (58) to ribs W5 to
W10. Glue on the sheeting (63) over ribs
W4 and W5 and the sheeting (59) and (60)
over ribs W7 and W9. Glue on the capstrips.
Attach the LE spar (54).
Separate the ailerons from the wing
panels. Glue the hinge spar (57) to the wing
and the aileron LE to the aileron. Sand the
wing. Glue in the plywood mounting frame
for the aileron servo.
In the bottom of the center-section, cut
the slots for the cabane struts to go into and
one larger hole for the extension cable.
Build the bottom wing in a similar
fashion. The difference is having the joiners
(47) and (48) glued to the two identical root
ribs W11, which will become part of the
fuselage; the outside wing panels will slide
onto them.
Once the wing panels are built, line up
the halves of the bottom wing and place 1/2-
inch shims under the wingtips to get the
proper dihedral. Glue the left joiners to the
right joiners.
Tail Surfaces: Before building the elevators
and the rudder, cut the templates from
CONSTRUCTION
Wing: The individual wing panels plug into
the fuselage using 1/4-inch-diameter dowel
as joiners. The dowels are not strong enough
by themselves to hold the wing panels; the
main strut (75) will hold everything in place
once the panels are plugged in. It’s
unnecessary, but you can replace the
hardwood dowels with carbon-fiber tubes.
To get started, transfer the ribs’ outlines
and mark the location of the holes on the
plywood and the balsa. Cut out the ribs and
drill all the holes.
Cut 1/4-inch hardwood dowels (69) (70)
and (47) (48) to the proper lengths. Adhere
two (69) dowels to create a double-width
joiner for the top wing, and then glue two
dowels (47) together for the bottom wing
joiner.
Build the top wing first. It includes three
sections: two outside panels and the center
panel.
Begin constructing the outside panels.
Pin the bottom main spar (49) to the board
directly over the plans. Pin the 1/4 square
balsa to the building board, to be used as a
shim under the ribs at the TE. Position and
glue all ribs to this spar. Glue the top main
spar (50) to the ribs.
Cut out the TE sheets (55) and (56) that
include the scallops. Slide the TE sheet (56)
between the shim and the ribs. Adhere the
ribs to the TE sheet. Glue the sub-LE (53) to
the ribs. Sand the sub-LE so that it follows
the contour of the ribs.
Glue the wingtip sheet (66) to rib W10.
Adhere the top TE sheet (55) to the ribs.
Glue the top LE sheet (51) to the ribs and to
the sub-LE. Glue on 1-inch-wide aileronhinge
balsa strip (58) to ribs W5 to W10.
Adhere the top capstrips to the ribs. Slide in
and glue joiner dowels (69) and (70) to ribs
W4 and W5.
Do not go any further with this wing
half. Construct the other half of the top wing
to the same stage.
04sig1.QXD 2/24/09 11:21 AM Page 30
corrugated cardboard. Slice four 1/4-inch-wide
strips from the 1/16 balsa sheet. Smear glue onto
the strips and form them around the templates.
Use pins to hold the strips against the templates
until the glue dries.
When the glue is dry, adhere the rest of the
frame and the 1/4-inch sheets. Build the
stabilizer and the fin, and then sand all the
surfaces.
Bend a 1/16-inch-diameter piano wire to
form the tail-wheel strut. Insert the end of the
strut into the balsa sheet in the rudder, and then
glue in the wire with thin cyanoacrylate. Wrap
the whole sheet with fiberglass. You can use
thin cyanoacrylate to saturate the cloth.
Cabane and Wing N Struts: Cut four identical
cabane struts (72) and four N struts (74) from 1/8
light plywood. Cut two cabane struts (71) and
two N struts (73) from 1/32 aluminum sheet.
Drill the 1/16-inch-diameter holes in N struts, as
shown on the drawing.
Sand the surface of the aluminum with
sandpaper. Using cyanoacrylate or GOOP-type
adhesive, adhere the plywood pieces to both
sides of the aluminum struts. Sand the edges of
the plywood to streamline their shape. Cut a slot
in one of the front cabane struts, and insert and
glue in the aileron-servo extension cable.
Wrap all the struts with fiberglass and
saturate them with thin cyanoacrylate. Sand
lightly and bend the exposed aluminum ends of
the struts as shown on the drawing.
Fuselage: Cut out as many parts as possible.
The fuselage is built upside-down in three
sections: the cowl, the center-section, and the
tail section.
Cut and bend 5/32-inch-diameter piano wire
to form the main landing-gear legs. Attach them
to former F5 with thread (canvas thread, Kevlar,
or copper wire).
Glue the hardwood block (17) to former
F4B, and adhere hardwood blocks (18) to
formers F3D and F6B. Pin formers F3D, F5,
F6B, and F8B to the building board. Pin and
glue the fuselage sides (1) to these formers.
Insert and glue in the battery floor (13). Insert
and glue in formers F4B and F7.
Pin formers F9B, F10B, F11, and F12 to the
building board. Adhere the rear fuselage sides
(2) to these formers and to the fuselage side (1).
Glue 3/8-inch triangle stock between the
fuselage side (2) and former F8B.
On the outside of the fuselage, glue the balsa
doublers (3) between formers F3D and F6B.
Between F6B and F8B, adhere the doublers (4)
to the fuselage sides.
Glue the bottom wing to the fuselage. Slide
the joiners (47) and (48) into the slots in the
fuselage sides (1). Check the alignment and
adhere the joiners to formers F6B and F7. Glue
the balsa strip (12) to the bottom of all the
formers. Complete the sheeting of the bottom
between formers F3B and F8B.
Turn the fuselage right-side up. Glue the
firewall (20) and firewall support sides (19) to
the battery floor (13) and to former F3D.
The cowl is built in top and bottom halves.
Cut four identical plywood pieces (21). Drill a
1/4-inch hole for the magnets and a 1/16-inch hole
for the guide pins.
Pin two of the four plywood pieces (21) to
the building board. Pin and glue formers F1B,
F2B, and F3B to them. Insert and glue 1/4
square balsa into these formers. Adhere the
sheeting (9) and (10).
Remove the bottom of the cowl from the
building board and glue the scoop (24) to it. The
bottom of the cowl can be glued to former F3D.
Build the removable top of the cowl the same
way, but don’t adhere it to anything. Glue the
magnets and guide pins into the plywood pieces
(21).
Mount the cabane to the hardwood blocks
(18) using self-tapping screws. Insert the
cabane’s top tabs into the slots in the bottom of
the top wing’s center-section. Line up the holes
on cabane struts with the holes in W3 ribs.
Attach the cabane to the W3 ribs with selftapping
screws. At the same time, feed the plug
from the aileron extension into the cavity
between ribs W2 and W3.
Plug in all the wing panels and check the
alignment. If any adjustments are required, now
is the time to do it. Install the wing N struts. Use
self-tapping screws to hold them to the wings.
It’s time to install the most important strut
(75). Cut the 1/2-inch K&S streamlined
aluminum tube to the proper length. Flatten the
ends. Drill a 3/32-inch hole at each end, and bend
the ends so that the flat end is flush with the
plywood (67) behind the main spar of the top
wing. The same goes for the other end, but it
has to follow the contour of the hardwood block
(17) in the fuselage. Drill the hole in the
hardwood block and the plywood for selftapping
screws.
Remove the wings from the fuselage,
including the center-section. In the top wing,
install the servo extension for the aileron servo.
Glue the stabilizer to the fuselage. Adhere
all top fuselage formers. Glue the top sheeting
(5) to the front fuselage formers and the
sheeting (6) to the back formers. Cut out the
cockpit opening. Glue on the headrest (25).
Adhere the longeron (14) to the side of the
fuselage. Glue the fin to the fuselage.
Make the wheel pants and the streamline
covers for the main gear legs from the balsa
materials cited on the plans.
Finishing: Use your own method to apply the
finish; I used UltraCote. After completing the
covering, I installed the hinges and the servos. I
mounted a threaded connecting rod between the
top and bottom aileron with a clevis at each end.
The small “L”-shaped aluminum bracket is
attached to the plywood plate on each aileron
with self-tapping screws.
The dummy engine is made from scrap
balsa pieces and then glued to the top half of the
cowl.
After installing the radio and motor, remove
the top half of the cowl and slide the motor
battery onto the battery floor. Check the CG.
Move the battery as needed to get the D-IX to
balance on the CG spot. Mark the battery
location. I used hook-and-loop fastener to hold
it in place.
Install the servos and check the control
surfaces’ operation. The elevator should travel
3/4 inch up and down. The rudder 11/4 inches left
and right at the widest point. The top ailerons
should travel 1/2 inch up and down at the widest
point.
You’re finished with the construction. Have
fun flying this unique-looking scale model. MA
Laddie Mikulasko
[email protected]
Sources:
AXi 2826/10 motor, Jeti 40 Advance ESC:
MS Composit
(317) 578-1955
www.mscompositusa.com
UltraCote covering:
Hangar 9
(800) 338-4639
www.hangar-9.com
3200 mAh EVO LITE V2 3S battery:
FlightPower
(919) 741-6310
www.flightpowerusa.com
Edition: Model Aviation - 2009/04
Page Numbers: 25,26,27,28,29,30,31,32,33
SEVERAL YEARS AGO, in one of the aircraft magazines I saw
pictures of a unique-looking home-built biplane called the “Der Jager
D-IX.” I was attracted to it because of its shape and color scheme.
Marshall Wright designed and built the airplane.
Sometime later, I stumbled across a three-view drawing for
the design. I kept it with the intention of building a scale
model of the D-IX at some point in the future. In addition to the
three-views, I found some photos on the Internet of the original
biplane.
I designed the model for an AXi 2826/10 brushless motor using a
Jeti Advance 40 PLUS speed controller and 3S Li-Poly batteries. I
made sure that the battery’s installation is easy; the top half of the
cowl comes off, and the battery is placed on the battery floor.
Four Blue Bird BMS-380 servos are used for control. They
are half the size of a standard servo, half the weight, and have the
same torque rating: approximately 50 inch-ounces. If you do not
want to fly this model as an electric, any .40-.45 glow engine can
be used.
I drew the plans and then proceeded to build the Der Jager model.
The test flight was a nonevent; the model tracked straight on takeoffs
and has excellent flying characteristics. It is fully aerobatic with no
bad habits, and the landings are straightforward. Even with the wheel
pants, the D-IX doesn’t nose over when flown off the grass.
April 2009 25
by Laddie Mikulasko
The author designed his airplane to be similar to the full-scale aircraft
that was designed by the Stolp-White Aircraft Company in 1969. The
model includes almost every charming aspect of the biplane lineage.
The Der Jager’s light wing loading allows it to climb quickly.
Sport aerobatics are comfortable.
A WW1-looking home-built,
fresh from the 1970s
04sig1.QXD 2/24/09 11:16 AM Page 25
26 MODEL AVIATION
Photos by the author
Wing panels join the center-sections with stacked dowel rods
at the apex of the rib shape. Center-area ribs are made from
light plywood.
The ribs are organized over the top wing plans as they are cut
from blank material. Holes in the inner ribs are for the aileron
servo wire and dowel supports.
The wide sheeting near the TE is centered over the hinge line.
Once the aileron is cut away, cap the open areas with balsa.
TE scallops add distinctive character to the Der Jager. After
drawing the outline, sand away the excess with a rasp or round
dowel covered with sandpaper.
The cabane struts and N struts have an aluminum-sheet core that
is laminated with wood on both sides. The material is sanded to a
streamlined shape later.
The center-section of the upper wing secures the dowel-rod wing
joiners inside plywood ribs. The completed sheeting is sanded
flush with the outer panels.
04sig1.QXD 2/24/09 11:33 AM Page 26
April 2009 27
The primary fuselage sides are marked left and right, as are the
forward 1/4-inch sheets that will be sanded to shape later.
The cabane struts mount inside tabs in the top wing’s centersection
and are secured with #4 socket-head servo screws.
The wooden sections of the wheel pants are laminated with
wood glue, which is easy to sand later. Plywood buried inside
acts as a mounting point.
The piano-wire landing gear is stitched to the former with
thread, Kevlar, or copper wire. The lower wing’s center-section
is built into the forward framework.
The cabane struts are securely mounted into hardwood areas.
Sheeting is wrapped around the forward turtledeck, forming the
cockpit area.
Once the fuselage sides are pulled together, the lower sheeting
and longerons can be added. Watch out for twisting and keep
the tail post square.
04sig1.QXD 2/24/09 11:18 AM Page 27
28 MODEL AVIATION
Cowling halves are framed separately. The lower half (shown) is
permanently attached to the fuselage and houses the motor.
A channel is carved in the right cabane strut to hide the aileronservo
extension wire. Covering material is applied over the woodskinned
aluminum supports later.
The stabilizer and fin are framed to simulate steel-tube
framework, so they are rounded on all outside edges.
Each control surface of the tail must have cardboard templates
made to form the laminations of the curved outer-framework
material.
An AXi Gold 2826/10 motor and Jeti 40 Advance ESC are
powered with a 3300 mAh 3S Li-Poly battery from FlightPower.
Temporary foam fixtures are placed to align and set the struts’ final
locations. Double-stick tape and pins hold the fixtures in place.
04sig1.QXD 2/24/09 11:35 AM Page 28
April 2009 29
Pushrods from upper to lower aileron are linked to aluminum angle
brackets located in hard points near the LE of the control surface.
Access to rudder and elevator servos is through the cockpit
opening, which is later covered with a pilot figure.
The simulated engine is made from scrap balsa that is covered
and painted to match the IO-235 four-cylinder engine used in
the full-scale aircraft.
Simulated bullet-hole decorations, as on the full-scale aircraft.
Support wires add support but are mostly for appearance.
Type: RC Sport Scale
Skill level: Intermediate
builder, intermediate pilot
Wingspan: Top, 50 inches; bottom,
42 inches
Wing area: Approximately 750 square inches
Length: 42 inches
Weight: 4 pounds (depending on battery)
Power: 300- to 500-watt system, 40- to 54-amp ESC,
3S 3300 mAh Li-Poly battery
Construction: Balsa, light plywood, hardwood-dowel wing joiners
Covering/finish: UltraCote heat-shrink film
Radio: Four miniservos (40 inch-ounces output), receiver,
custom servo extensions
Other: 21/4-inch spinner, 3-inch wheels, APC 10 x 8E propeller, 11/4-inch tail
wheel, 5/32-inch music-wire landing gear, 1/32-inch aluminum-sheet strut material
04sig1.QXD 2/24/09 11:20 AM Page 29
30 MODEL AVIATION
The four wing panels plug into the structure and are secured with an aluminum main strut that attaches from the lower
fuselage to the top outer panel.
The AXi power system is equivalent to a .32
cu. in. glow engine that offers better-thanscale
performance. The Der Jager flies
predictably and has a distinctive appearance.
I tried to make building this airplane as
simple as possible. The outer wing panels are
removable; however, if transporting a 50-
inch-wingspan model is not a problem, you
have the option of building the wings in one
piece and permanently attaching them to the
fuselage.
The two aileron servos are mounted inside
the top wing. The connecting rods join the
top aileron to the bottom aileron. The elevator
and rudder servos are located inside the
cockpit.
To build this model, you will need light
balsa, light plywood, 5/32-inch-diameter music
wire, and 1/32-inch-thick aluminum sheeting.
Build the wing center-section. Pin the
bottom main spar to the building board.
Glue ribs W1, W2, and W3 to the spar.
Adhere the top main spar to the ribs.
Take hold of the two outside wing panels
and slide the joiners all the way into ribs W2
and W3. Glue the sub-LE to ribs W1, W2,
and W3. Adhere the top LE sheet (51) to
these ribs. Glue on the rest of the top
sheeting (62).
Flip the wing over. In the center-section,
install the Y harness for the ailerons. Glue
the bottom sheeting (61) to ribs W1, W2,
and W3. Glue the plywood strips (67) to ribs
W8 and W9; you must use the five-ply
plywood. The plywood strips will be
holding the brackets for N struts and the
main struts (75).
Glue on the bottom LE sheeting (52).
Adhere the aileron strip (58) to ribs W5 to
W10. Glue on the sheeting (63) over ribs
W4 and W5 and the sheeting (59) and (60)
over ribs W7 and W9. Glue on the capstrips.
Attach the LE spar (54).
Separate the ailerons from the wing
panels. Glue the hinge spar (57) to the wing
and the aileron LE to the aileron. Sand the
wing. Glue in the plywood mounting frame
for the aileron servo.
In the bottom of the center-section, cut
the slots for the cabane struts to go into and
one larger hole for the extension cable.
Build the bottom wing in a similar
fashion. The difference is having the joiners
(47) and (48) glued to the two identical root
ribs W11, which will become part of the
fuselage; the outside wing panels will slide
onto them.
Once the wing panels are built, line up
the halves of the bottom wing and place 1/2-
inch shims under the wingtips to get the
proper dihedral. Glue the left joiners to the
right joiners.
Tail Surfaces: Before building the elevators
and the rudder, cut the templates from
CONSTRUCTION
Wing: The individual wing panels plug into
the fuselage using 1/4-inch-diameter dowel
as joiners. The dowels are not strong enough
by themselves to hold the wing panels; the
main strut (75) will hold everything in place
once the panels are plugged in. It’s
unnecessary, but you can replace the
hardwood dowels with carbon-fiber tubes.
To get started, transfer the ribs’ outlines
and mark the location of the holes on the
plywood and the balsa. Cut out the ribs and
drill all the holes.
Cut 1/4-inch hardwood dowels (69) (70)
and (47) (48) to the proper lengths. Adhere
two (69) dowels to create a double-width
joiner for the top wing, and then glue two
dowels (47) together for the bottom wing
joiner.
Build the top wing first. It includes three
sections: two outside panels and the center
panel.
Begin constructing the outside panels.
Pin the bottom main spar (49) to the board
directly over the plans. Pin the 1/4 square
balsa to the building board, to be used as a
shim under the ribs at the TE. Position and
glue all ribs to this spar. Glue the top main
spar (50) to the ribs.
Cut out the TE sheets (55) and (56) that
include the scallops. Slide the TE sheet (56)
between the shim and the ribs. Adhere the
ribs to the TE sheet. Glue the sub-LE (53) to
the ribs. Sand the sub-LE so that it follows
the contour of the ribs.
Glue the wingtip sheet (66) to rib W10.
Adhere the top TE sheet (55) to the ribs.
Glue the top LE sheet (51) to the ribs and to
the sub-LE. Glue on 1-inch-wide aileronhinge
balsa strip (58) to ribs W5 to W10.
Adhere the top capstrips to the ribs. Slide in
and glue joiner dowels (69) and (70) to ribs
W4 and W5.
Do not go any further with this wing
half. Construct the other half of the top wing
to the same stage.
04sig1.QXD 2/24/09 11:21 AM Page 30
corrugated cardboard. Slice four 1/4-inch-wide
strips from the 1/16 balsa sheet. Smear glue onto
the strips and form them around the templates.
Use pins to hold the strips against the templates
until the glue dries.
When the glue is dry, adhere the rest of the
frame and the 1/4-inch sheets. Build the
stabilizer and the fin, and then sand all the
surfaces.
Bend a 1/16-inch-diameter piano wire to
form the tail-wheel strut. Insert the end of the
strut into the balsa sheet in the rudder, and then
glue in the wire with thin cyanoacrylate. Wrap
the whole sheet with fiberglass. You can use
thin cyanoacrylate to saturate the cloth.
Cabane and Wing N Struts: Cut four identical
cabane struts (72) and four N struts (74) from 1/8
light plywood. Cut two cabane struts (71) and
two N struts (73) from 1/32 aluminum sheet.
Drill the 1/16-inch-diameter holes in N struts, as
shown on the drawing.
Sand the surface of the aluminum with
sandpaper. Using cyanoacrylate or GOOP-type
adhesive, adhere the plywood pieces to both
sides of the aluminum struts. Sand the edges of
the plywood to streamline their shape. Cut a slot
in one of the front cabane struts, and insert and
glue in the aileron-servo extension cable.
Wrap all the struts with fiberglass and
saturate them with thin cyanoacrylate. Sand
lightly and bend the exposed aluminum ends of
the struts as shown on the drawing.
Fuselage: Cut out as many parts as possible.
The fuselage is built upside-down in three
sections: the cowl, the center-section, and the
tail section.
Cut and bend 5/32-inch-diameter piano wire
to form the main landing-gear legs. Attach them
to former F5 with thread (canvas thread, Kevlar,
or copper wire).
Glue the hardwood block (17) to former
F4B, and adhere hardwood blocks (18) to
formers F3D and F6B. Pin formers F3D, F5,
F6B, and F8B to the building board. Pin and
glue the fuselage sides (1) to these formers.
Insert and glue in the battery floor (13). Insert
and glue in formers F4B and F7.
Pin formers F9B, F10B, F11, and F12 to the
building board. Adhere the rear fuselage sides
(2) to these formers and to the fuselage side (1).
Glue 3/8-inch triangle stock between the
fuselage side (2) and former F8B.
On the outside of the fuselage, glue the balsa
doublers (3) between formers F3D and F6B.
Between F6B and F8B, adhere the doublers (4)
to the fuselage sides.
Glue the bottom wing to the fuselage. Slide
the joiners (47) and (48) into the slots in the
fuselage sides (1). Check the alignment and
adhere the joiners to formers F6B and F7. Glue
the balsa strip (12) to the bottom of all the
formers. Complete the sheeting of the bottom
between formers F3B and F8B.
Turn the fuselage right-side up. Glue the
firewall (20) and firewall support sides (19) to
the battery floor (13) and to former F3D.
The cowl is built in top and bottom halves.
Cut four identical plywood pieces (21). Drill a
1/4-inch hole for the magnets and a 1/16-inch hole
for the guide pins.
Pin two of the four plywood pieces (21) to
the building board. Pin and glue formers F1B,
F2B, and F3B to them. Insert and glue 1/4
square balsa into these formers. Adhere the
sheeting (9) and (10).
Remove the bottom of the cowl from the
building board and glue the scoop (24) to it. The
bottom of the cowl can be glued to former F3D.
Build the removable top of the cowl the same
way, but don’t adhere it to anything. Glue the
magnets and guide pins into the plywood pieces
(21).
Mount the cabane to the hardwood blocks
(18) using self-tapping screws. Insert the
cabane’s top tabs into the slots in the bottom of
the top wing’s center-section. Line up the holes
on cabane struts with the holes in W3 ribs.
Attach the cabane to the W3 ribs with selftapping
screws. At the same time, feed the plug
from the aileron extension into the cavity
between ribs W2 and W3.
Plug in all the wing panels and check the
alignment. If any adjustments are required, now
is the time to do it. Install the wing N struts. Use
self-tapping screws to hold them to the wings.
It’s time to install the most important strut
(75). Cut the 1/2-inch K&S streamlined
aluminum tube to the proper length. Flatten the
ends. Drill a 3/32-inch hole at each end, and bend
the ends so that the flat end is flush with the
plywood (67) behind the main spar of the top
wing. The same goes for the other end, but it
has to follow the contour of the hardwood block
(17) in the fuselage. Drill the hole in the
hardwood block and the plywood for selftapping
screws.
Remove the wings from the fuselage,
including the center-section. In the top wing,
install the servo extension for the aileron servo.
Glue the stabilizer to the fuselage. Adhere
all top fuselage formers. Glue the top sheeting
(5) to the front fuselage formers and the
sheeting (6) to the back formers. Cut out the
cockpit opening. Glue on the headrest (25).
Adhere the longeron (14) to the side of the
fuselage. Glue the fin to the fuselage.
Make the wheel pants and the streamline
covers for the main gear legs from the balsa
materials cited on the plans.
Finishing: Use your own method to apply the
finish; I used UltraCote. After completing the
covering, I installed the hinges and the servos. I
mounted a threaded connecting rod between the
top and bottom aileron with a clevis at each end.
The small “L”-shaped aluminum bracket is
attached to the plywood plate on each aileron
with self-tapping screws.
The dummy engine is made from scrap
balsa pieces and then glued to the top half of the
cowl.
After installing the radio and motor, remove
the top half of the cowl and slide the motor
battery onto the battery floor. Check the CG.
Move the battery as needed to get the D-IX to
balance on the CG spot. Mark the battery
location. I used hook-and-loop fastener to hold
it in place.
Install the servos and check the control
surfaces’ operation. The elevator should travel
3/4 inch up and down. The rudder 11/4 inches left
and right at the widest point. The top ailerons
should travel 1/2 inch up and down at the widest
point.
You’re finished with the construction. Have
fun flying this unique-looking scale model. MA
Laddie Mikulasko
[email protected]
Sources:
AXi 2826/10 motor, Jeti 40 Advance ESC:
MS Composit
(317) 578-1955
www.mscompositusa.com
UltraCote covering:
Hangar 9
(800) 338-4639
www.hangar-9.com
3200 mAh EVO LITE V2 3S battery:
FlightPower
(919) 741-6310
www.flightpowerusa.com
Edition: Model Aviation - 2009/04
Page Numbers: 25,26,27,28,29,30,31,32,33
SEVERAL YEARS AGO, in one of the aircraft magazines I saw
pictures of a unique-looking home-built biplane called the “Der Jager
D-IX.” I was attracted to it because of its shape and color scheme.
Marshall Wright designed and built the airplane.
Sometime later, I stumbled across a three-view drawing for
the design. I kept it with the intention of building a scale
model of the D-IX at some point in the future. In addition to the
three-views, I found some photos on the Internet of the original
biplane.
I designed the model for an AXi 2826/10 brushless motor using a
Jeti Advance 40 PLUS speed controller and 3S Li-Poly batteries. I
made sure that the battery’s installation is easy; the top half of the
cowl comes off, and the battery is placed on the battery floor.
Four Blue Bird BMS-380 servos are used for control. They
are half the size of a standard servo, half the weight, and have the
same torque rating: approximately 50 inch-ounces. If you do not
want to fly this model as an electric, any .40-.45 glow engine can
be used.
I drew the plans and then proceeded to build the Der Jager model.
The test flight was a nonevent; the model tracked straight on takeoffs
and has excellent flying characteristics. It is fully aerobatic with no
bad habits, and the landings are straightforward. Even with the wheel
pants, the D-IX doesn’t nose over when flown off the grass.
April 2009 25
by Laddie Mikulasko
The author designed his airplane to be similar to the full-scale aircraft
that was designed by the Stolp-White Aircraft Company in 1969. The
model includes almost every charming aspect of the biplane lineage.
The Der Jager’s light wing loading allows it to climb quickly.
Sport aerobatics are comfortable.
A WW1-looking home-built,
fresh from the 1970s
04sig1.QXD 2/24/09 11:16 AM Page 25
26 MODEL AVIATION
Photos by the author
Wing panels join the center-sections with stacked dowel rods
at the apex of the rib shape. Center-area ribs are made from
light plywood.
The ribs are organized over the top wing plans as they are cut
from blank material. Holes in the inner ribs are for the aileron
servo wire and dowel supports.
The wide sheeting near the TE is centered over the hinge line.
Once the aileron is cut away, cap the open areas with balsa.
TE scallops add distinctive character to the Der Jager. After
drawing the outline, sand away the excess with a rasp or round
dowel covered with sandpaper.
The cabane struts and N struts have an aluminum-sheet core that
is laminated with wood on both sides. The material is sanded to a
streamlined shape later.
The center-section of the upper wing secures the dowel-rod wing
joiners inside plywood ribs. The completed sheeting is sanded
flush with the outer panels.
04sig1.QXD 2/24/09 11:33 AM Page 26
April 2009 27
The primary fuselage sides are marked left and right, as are the
forward 1/4-inch sheets that will be sanded to shape later.
The cabane struts mount inside tabs in the top wing’s centersection
and are secured with #4 socket-head servo screws.
The wooden sections of the wheel pants are laminated with
wood glue, which is easy to sand later. Plywood buried inside
acts as a mounting point.
The piano-wire landing gear is stitched to the former with
thread, Kevlar, or copper wire. The lower wing’s center-section
is built into the forward framework.
The cabane struts are securely mounted into hardwood areas.
Sheeting is wrapped around the forward turtledeck, forming the
cockpit area.
Once the fuselage sides are pulled together, the lower sheeting
and longerons can be added. Watch out for twisting and keep
the tail post square.
04sig1.QXD 2/24/09 11:18 AM Page 27
28 MODEL AVIATION
Cowling halves are framed separately. The lower half (shown) is
permanently attached to the fuselage and houses the motor.
A channel is carved in the right cabane strut to hide the aileronservo
extension wire. Covering material is applied over the woodskinned
aluminum supports later.
The stabilizer and fin are framed to simulate steel-tube
framework, so they are rounded on all outside edges.
Each control surface of the tail must have cardboard templates
made to form the laminations of the curved outer-framework
material.
An AXi Gold 2826/10 motor and Jeti 40 Advance ESC are
powered with a 3300 mAh 3S Li-Poly battery from FlightPower.
Temporary foam fixtures are placed to align and set the struts’ final
locations. Double-stick tape and pins hold the fixtures in place.
04sig1.QXD 2/24/09 11:35 AM Page 28
April 2009 29
Pushrods from upper to lower aileron are linked to aluminum angle
brackets located in hard points near the LE of the control surface.
Access to rudder and elevator servos is through the cockpit
opening, which is later covered with a pilot figure.
The simulated engine is made from scrap balsa that is covered
and painted to match the IO-235 four-cylinder engine used in
the full-scale aircraft.
Simulated bullet-hole decorations, as on the full-scale aircraft.
Support wires add support but are mostly for appearance.
Type: RC Sport Scale
Skill level: Intermediate
builder, intermediate pilot
Wingspan: Top, 50 inches; bottom,
42 inches
Wing area: Approximately 750 square inches
Length: 42 inches
Weight: 4 pounds (depending on battery)
Power: 300- to 500-watt system, 40- to 54-amp ESC,
3S 3300 mAh Li-Poly battery
Construction: Balsa, light plywood, hardwood-dowel wing joiners
Covering/finish: UltraCote heat-shrink film
Radio: Four miniservos (40 inch-ounces output), receiver,
custom servo extensions
Other: 21/4-inch spinner, 3-inch wheels, APC 10 x 8E propeller, 11/4-inch tail
wheel, 5/32-inch music-wire landing gear, 1/32-inch aluminum-sheet strut material
04sig1.QXD 2/24/09 11:20 AM Page 29
30 MODEL AVIATION
The four wing panels plug into the structure and are secured with an aluminum main strut that attaches from the lower
fuselage to the top outer panel.
The AXi power system is equivalent to a .32
cu. in. glow engine that offers better-thanscale
performance. The Der Jager flies
predictably and has a distinctive appearance.
I tried to make building this airplane as
simple as possible. The outer wing panels are
removable; however, if transporting a 50-
inch-wingspan model is not a problem, you
have the option of building the wings in one
piece and permanently attaching them to the
fuselage.
The two aileron servos are mounted inside
the top wing. The connecting rods join the
top aileron to the bottom aileron. The elevator
and rudder servos are located inside the
cockpit.
To build this model, you will need light
balsa, light plywood, 5/32-inch-diameter music
wire, and 1/32-inch-thick aluminum sheeting.
Build the wing center-section. Pin the
bottom main spar to the building board.
Glue ribs W1, W2, and W3 to the spar.
Adhere the top main spar to the ribs.
Take hold of the two outside wing panels
and slide the joiners all the way into ribs W2
and W3. Glue the sub-LE to ribs W1, W2,
and W3. Adhere the top LE sheet (51) to
these ribs. Glue on the rest of the top
sheeting (62).
Flip the wing over. In the center-section,
install the Y harness for the ailerons. Glue
the bottom sheeting (61) to ribs W1, W2,
and W3. Glue the plywood strips (67) to ribs
W8 and W9; you must use the five-ply
plywood. The plywood strips will be
holding the brackets for N struts and the
main struts (75).
Glue on the bottom LE sheeting (52).
Adhere the aileron strip (58) to ribs W5 to
W10. Glue on the sheeting (63) over ribs
W4 and W5 and the sheeting (59) and (60)
over ribs W7 and W9. Glue on the capstrips.
Attach the LE spar (54).
Separate the ailerons from the wing
panels. Glue the hinge spar (57) to the wing
and the aileron LE to the aileron. Sand the
wing. Glue in the plywood mounting frame
for the aileron servo.
In the bottom of the center-section, cut
the slots for the cabane struts to go into and
one larger hole for the extension cable.
Build the bottom wing in a similar
fashion. The difference is having the joiners
(47) and (48) glued to the two identical root
ribs W11, which will become part of the
fuselage; the outside wing panels will slide
onto them.
Once the wing panels are built, line up
the halves of the bottom wing and place 1/2-
inch shims under the wingtips to get the
proper dihedral. Glue the left joiners to the
right joiners.
Tail Surfaces: Before building the elevators
and the rudder, cut the templates from
CONSTRUCTION
Wing: The individual wing panels plug into
the fuselage using 1/4-inch-diameter dowel
as joiners. The dowels are not strong enough
by themselves to hold the wing panels; the
main strut (75) will hold everything in place
once the panels are plugged in. It’s
unnecessary, but you can replace the
hardwood dowels with carbon-fiber tubes.
To get started, transfer the ribs’ outlines
and mark the location of the holes on the
plywood and the balsa. Cut out the ribs and
drill all the holes.
Cut 1/4-inch hardwood dowels (69) (70)
and (47) (48) to the proper lengths. Adhere
two (69) dowels to create a double-width
joiner for the top wing, and then glue two
dowels (47) together for the bottom wing
joiner.
Build the top wing first. It includes three
sections: two outside panels and the center
panel.
Begin constructing the outside panels.
Pin the bottom main spar (49) to the board
directly over the plans. Pin the 1/4 square
balsa to the building board, to be used as a
shim under the ribs at the TE. Position and
glue all ribs to this spar. Glue the top main
spar (50) to the ribs.
Cut out the TE sheets (55) and (56) that
include the scallops. Slide the TE sheet (56)
between the shim and the ribs. Adhere the
ribs to the TE sheet. Glue the sub-LE (53) to
the ribs. Sand the sub-LE so that it follows
the contour of the ribs.
Glue the wingtip sheet (66) to rib W10.
Adhere the top TE sheet (55) to the ribs.
Glue the top LE sheet (51) to the ribs and to
the sub-LE. Glue on 1-inch-wide aileronhinge
balsa strip (58) to ribs W5 to W10.
Adhere the top capstrips to the ribs. Slide in
and glue joiner dowels (69) and (70) to ribs
W4 and W5.
Do not go any further with this wing
half. Construct the other half of the top wing
to the same stage.
04sig1.QXD 2/24/09 11:21 AM Page 30
corrugated cardboard. Slice four 1/4-inch-wide
strips from the 1/16 balsa sheet. Smear glue onto
the strips and form them around the templates.
Use pins to hold the strips against the templates
until the glue dries.
When the glue is dry, adhere the rest of the
frame and the 1/4-inch sheets. Build the
stabilizer and the fin, and then sand all the
surfaces.
Bend a 1/16-inch-diameter piano wire to
form the tail-wheel strut. Insert the end of the
strut into the balsa sheet in the rudder, and then
glue in the wire with thin cyanoacrylate. Wrap
the whole sheet with fiberglass. You can use
thin cyanoacrylate to saturate the cloth.
Cabane and Wing N Struts: Cut four identical
cabane struts (72) and four N struts (74) from 1/8
light plywood. Cut two cabane struts (71) and
two N struts (73) from 1/32 aluminum sheet.
Drill the 1/16-inch-diameter holes in N struts, as
shown on the drawing.
Sand the surface of the aluminum with
sandpaper. Using cyanoacrylate or GOOP-type
adhesive, adhere the plywood pieces to both
sides of the aluminum struts. Sand the edges of
the plywood to streamline their shape. Cut a slot
in one of the front cabane struts, and insert and
glue in the aileron-servo extension cable.
Wrap all the struts with fiberglass and
saturate them with thin cyanoacrylate. Sand
lightly and bend the exposed aluminum ends of
the struts as shown on the drawing.
Fuselage: Cut out as many parts as possible.
The fuselage is built upside-down in three
sections: the cowl, the center-section, and the
tail section.
Cut and bend 5/32-inch-diameter piano wire
to form the main landing-gear legs. Attach them
to former F5 with thread (canvas thread, Kevlar,
or copper wire).
Glue the hardwood block (17) to former
F4B, and adhere hardwood blocks (18) to
formers F3D and F6B. Pin formers F3D, F5,
F6B, and F8B to the building board. Pin and
glue the fuselage sides (1) to these formers.
Insert and glue in the battery floor (13). Insert
and glue in formers F4B and F7.
Pin formers F9B, F10B, F11, and F12 to the
building board. Adhere the rear fuselage sides
(2) to these formers and to the fuselage side (1).
Glue 3/8-inch triangle stock between the
fuselage side (2) and former F8B.
On the outside of the fuselage, glue the balsa
doublers (3) between formers F3D and F6B.
Between F6B and F8B, adhere the doublers (4)
to the fuselage sides.
Glue the bottom wing to the fuselage. Slide
the joiners (47) and (48) into the slots in the
fuselage sides (1). Check the alignment and
adhere the joiners to formers F6B and F7. Glue
the balsa strip (12) to the bottom of all the
formers. Complete the sheeting of the bottom
between formers F3B and F8B.
Turn the fuselage right-side up. Glue the
firewall (20) and firewall support sides (19) to
the battery floor (13) and to former F3D.
The cowl is built in top and bottom halves.
Cut four identical plywood pieces (21). Drill a
1/4-inch hole for the magnets and a 1/16-inch hole
for the guide pins.
Pin two of the four plywood pieces (21) to
the building board. Pin and glue formers F1B,
F2B, and F3B to them. Insert and glue 1/4
square balsa into these formers. Adhere the
sheeting (9) and (10).
Remove the bottom of the cowl from the
building board and glue the scoop (24) to it. The
bottom of the cowl can be glued to former F3D.
Build the removable top of the cowl the same
way, but don’t adhere it to anything. Glue the
magnets and guide pins into the plywood pieces
(21).
Mount the cabane to the hardwood blocks
(18) using self-tapping screws. Insert the
cabane’s top tabs into the slots in the bottom of
the top wing’s center-section. Line up the holes
on cabane struts with the holes in W3 ribs.
Attach the cabane to the W3 ribs with selftapping
screws. At the same time, feed the plug
from the aileron extension into the cavity
between ribs W2 and W3.
Plug in all the wing panels and check the
alignment. If any adjustments are required, now
is the time to do it. Install the wing N struts. Use
self-tapping screws to hold them to the wings.
It’s time to install the most important strut
(75). Cut the 1/2-inch K&S streamlined
aluminum tube to the proper length. Flatten the
ends. Drill a 3/32-inch hole at each end, and bend
the ends so that the flat end is flush with the
plywood (67) behind the main spar of the top
wing. The same goes for the other end, but it
has to follow the contour of the hardwood block
(17) in the fuselage. Drill the hole in the
hardwood block and the plywood for selftapping
screws.
Remove the wings from the fuselage,
including the center-section. In the top wing,
install the servo extension for the aileron servo.
Glue the stabilizer to the fuselage. Adhere
all top fuselage formers. Glue the top sheeting
(5) to the front fuselage formers and the
sheeting (6) to the back formers. Cut out the
cockpit opening. Glue on the headrest (25).
Adhere the longeron (14) to the side of the
fuselage. Glue the fin to the fuselage.
Make the wheel pants and the streamline
covers for the main gear legs from the balsa
materials cited on the plans.
Finishing: Use your own method to apply the
finish; I used UltraCote. After completing the
covering, I installed the hinges and the servos. I
mounted a threaded connecting rod between the
top and bottom aileron with a clevis at each end.
The small “L”-shaped aluminum bracket is
attached to the plywood plate on each aileron
with self-tapping screws.
The dummy engine is made from scrap
balsa pieces and then glued to the top half of the
cowl.
After installing the radio and motor, remove
the top half of the cowl and slide the motor
battery onto the battery floor. Check the CG.
Move the battery as needed to get the D-IX to
balance on the CG spot. Mark the battery
location. I used hook-and-loop fastener to hold
it in place.
Install the servos and check the control
surfaces’ operation. The elevator should travel
3/4 inch up and down. The rudder 11/4 inches left
and right at the widest point. The top ailerons
should travel 1/2 inch up and down at the widest
point.
You’re finished with the construction. Have
fun flying this unique-looking scale model. MA
Laddie Mikulasko
[email protected]
Sources:
AXi 2826/10 motor, Jeti 40 Advance ESC:
MS Composit
(317) 578-1955
www.mscompositusa.com
UltraCote covering:
Hangar 9
(800) 338-4639
www.hangar-9.com
3200 mAh EVO LITE V2 3S battery:
FlightPower
(919) 741-6310
www.flightpowerusa.com
Edition: Model Aviation - 2009/04
Page Numbers: 25,26,27,28,29,30,31,32,33
SEVERAL YEARS AGO, in one of the aircraft magazines I saw
pictures of a unique-looking home-built biplane called the “Der Jager
D-IX.” I was attracted to it because of its shape and color scheme.
Marshall Wright designed and built the airplane.
Sometime later, I stumbled across a three-view drawing for
the design. I kept it with the intention of building a scale
model of the D-IX at some point in the future. In addition to the
three-views, I found some photos on the Internet of the original
biplane.
I designed the model for an AXi 2826/10 brushless motor using a
Jeti Advance 40 PLUS speed controller and 3S Li-Poly batteries. I
made sure that the battery’s installation is easy; the top half of the
cowl comes off, and the battery is placed on the battery floor.
Four Blue Bird BMS-380 servos are used for control. They
are half the size of a standard servo, half the weight, and have the
same torque rating: approximately 50 inch-ounces. If you do not
want to fly this model as an electric, any .40-.45 glow engine can
be used.
I drew the plans and then proceeded to build the Der Jager model.
The test flight was a nonevent; the model tracked straight on takeoffs
and has excellent flying characteristics. It is fully aerobatic with no
bad habits, and the landings are straightforward. Even with the wheel
pants, the D-IX doesn’t nose over when flown off the grass.
April 2009 25
by Laddie Mikulasko
The author designed his airplane to be similar to the full-scale aircraft
that was designed by the Stolp-White Aircraft Company in 1969. The
model includes almost every charming aspect of the biplane lineage.
The Der Jager’s light wing loading allows it to climb quickly.
Sport aerobatics are comfortable.
A WW1-looking home-built,
fresh from the 1970s
04sig1.QXD 2/24/09 11:16 AM Page 25
26 MODEL AVIATION
Photos by the author
Wing panels join the center-sections with stacked dowel rods
at the apex of the rib shape. Center-area ribs are made from
light plywood.
The ribs are organized over the top wing plans as they are cut
from blank material. Holes in the inner ribs are for the aileron
servo wire and dowel supports.
The wide sheeting near the TE is centered over the hinge line.
Once the aileron is cut away, cap the open areas with balsa.
TE scallops add distinctive character to the Der Jager. After
drawing the outline, sand away the excess with a rasp or round
dowel covered with sandpaper.
The cabane struts and N struts have an aluminum-sheet core that
is laminated with wood on both sides. The material is sanded to a
streamlined shape later.
The center-section of the upper wing secures the dowel-rod wing
joiners inside plywood ribs. The completed sheeting is sanded
flush with the outer panels.
04sig1.QXD 2/24/09 11:33 AM Page 26
April 2009 27
The primary fuselage sides are marked left and right, as are the
forward 1/4-inch sheets that will be sanded to shape later.
The cabane struts mount inside tabs in the top wing’s centersection
and are secured with #4 socket-head servo screws.
The wooden sections of the wheel pants are laminated with
wood glue, which is easy to sand later. Plywood buried inside
acts as a mounting point.
The piano-wire landing gear is stitched to the former with
thread, Kevlar, or copper wire. The lower wing’s center-section
is built into the forward framework.
The cabane struts are securely mounted into hardwood areas.
Sheeting is wrapped around the forward turtledeck, forming the
cockpit area.
Once the fuselage sides are pulled together, the lower sheeting
and longerons can be added. Watch out for twisting and keep
the tail post square.
04sig1.QXD 2/24/09 11:18 AM Page 27
28 MODEL AVIATION
Cowling halves are framed separately. The lower half (shown) is
permanently attached to the fuselage and houses the motor.
A channel is carved in the right cabane strut to hide the aileronservo
extension wire. Covering material is applied over the woodskinned
aluminum supports later.
The stabilizer and fin are framed to simulate steel-tube
framework, so they are rounded on all outside edges.
Each control surface of the tail must have cardboard templates
made to form the laminations of the curved outer-framework
material.
An AXi Gold 2826/10 motor and Jeti 40 Advance ESC are
powered with a 3300 mAh 3S Li-Poly battery from FlightPower.
Temporary foam fixtures are placed to align and set the struts’ final
locations. Double-stick tape and pins hold the fixtures in place.
04sig1.QXD 2/24/09 11:35 AM Page 28
April 2009 29
Pushrods from upper to lower aileron are linked to aluminum angle
brackets located in hard points near the LE of the control surface.
Access to rudder and elevator servos is through the cockpit
opening, which is later covered with a pilot figure.
The simulated engine is made from scrap balsa that is covered
and painted to match the IO-235 four-cylinder engine used in
the full-scale aircraft.
Simulated bullet-hole decorations, as on the full-scale aircraft.
Support wires add support but are mostly for appearance.
Type: RC Sport Scale
Skill level: Intermediate
builder, intermediate pilot
Wingspan: Top, 50 inches; bottom,
42 inches
Wing area: Approximately 750 square inches
Length: 42 inches
Weight: 4 pounds (depending on battery)
Power: 300- to 500-watt system, 40- to 54-amp ESC,
3S 3300 mAh Li-Poly battery
Construction: Balsa, light plywood, hardwood-dowel wing joiners
Covering/finish: UltraCote heat-shrink film
Radio: Four miniservos (40 inch-ounces output), receiver,
custom servo extensions
Other: 21/4-inch spinner, 3-inch wheels, APC 10 x 8E propeller, 11/4-inch tail
wheel, 5/32-inch music-wire landing gear, 1/32-inch aluminum-sheet strut material
04sig1.QXD 2/24/09 11:20 AM Page 29
30 MODEL AVIATION
The four wing panels plug into the structure and are secured with an aluminum main strut that attaches from the lower
fuselage to the top outer panel.
The AXi power system is equivalent to a .32
cu. in. glow engine that offers better-thanscale
performance. The Der Jager flies
predictably and has a distinctive appearance.
I tried to make building this airplane as
simple as possible. The outer wing panels are
removable; however, if transporting a 50-
inch-wingspan model is not a problem, you
have the option of building the wings in one
piece and permanently attaching them to the
fuselage.
The two aileron servos are mounted inside
the top wing. The connecting rods join the
top aileron to the bottom aileron. The elevator
and rudder servos are located inside the
cockpit.
To build this model, you will need light
balsa, light plywood, 5/32-inch-diameter music
wire, and 1/32-inch-thick aluminum sheeting.
Build the wing center-section. Pin the
bottom main spar to the building board.
Glue ribs W1, W2, and W3 to the spar.
Adhere the top main spar to the ribs.
Take hold of the two outside wing panels
and slide the joiners all the way into ribs W2
and W3. Glue the sub-LE to ribs W1, W2,
and W3. Adhere the top LE sheet (51) to
these ribs. Glue on the rest of the top
sheeting (62).
Flip the wing over. In the center-section,
install the Y harness for the ailerons. Glue
the bottom sheeting (61) to ribs W1, W2,
and W3. Glue the plywood strips (67) to ribs
W8 and W9; you must use the five-ply
plywood. The plywood strips will be
holding the brackets for N struts and the
main struts (75).
Glue on the bottom LE sheeting (52).
Adhere the aileron strip (58) to ribs W5 to
W10. Glue on the sheeting (63) over ribs
W4 and W5 and the sheeting (59) and (60)
over ribs W7 and W9. Glue on the capstrips.
Attach the LE spar (54).
Separate the ailerons from the wing
panels. Glue the hinge spar (57) to the wing
and the aileron LE to the aileron. Sand the
wing. Glue in the plywood mounting frame
for the aileron servo.
In the bottom of the center-section, cut
the slots for the cabane struts to go into and
one larger hole for the extension cable.
Build the bottom wing in a similar
fashion. The difference is having the joiners
(47) and (48) glued to the two identical root
ribs W11, which will become part of the
fuselage; the outside wing panels will slide
onto them.
Once the wing panels are built, line up
the halves of the bottom wing and place 1/2-
inch shims under the wingtips to get the
proper dihedral. Glue the left joiners to the
right joiners.
Tail Surfaces: Before building the elevators
and the rudder, cut the templates from
CONSTRUCTION
Wing: The individual wing panels plug into
the fuselage using 1/4-inch-diameter dowel
as joiners. The dowels are not strong enough
by themselves to hold the wing panels; the
main strut (75) will hold everything in place
once the panels are plugged in. It’s
unnecessary, but you can replace the
hardwood dowels with carbon-fiber tubes.
To get started, transfer the ribs’ outlines
and mark the location of the holes on the
plywood and the balsa. Cut out the ribs and
drill all the holes.
Cut 1/4-inch hardwood dowels (69) (70)
and (47) (48) to the proper lengths. Adhere
two (69) dowels to create a double-width
joiner for the top wing, and then glue two
dowels (47) together for the bottom wing
joiner.
Build the top wing first. It includes three
sections: two outside panels and the center
panel.
Begin constructing the outside panels.
Pin the bottom main spar (49) to the board
directly over the plans. Pin the 1/4 square
balsa to the building board, to be used as a
shim under the ribs at the TE. Position and
glue all ribs to this spar. Glue the top main
spar (50) to the ribs.
Cut out the TE sheets (55) and (56) that
include the scallops. Slide the TE sheet (56)
between the shim and the ribs. Adhere the
ribs to the TE sheet. Glue the sub-LE (53) to
the ribs. Sand the sub-LE so that it follows
the contour of the ribs.
Glue the wingtip sheet (66) to rib W10.
Adhere the top TE sheet (55) to the ribs.
Glue the top LE sheet (51) to the ribs and to
the sub-LE. Glue on 1-inch-wide aileronhinge
balsa strip (58) to ribs W5 to W10.
Adhere the top capstrips to the ribs. Slide in
and glue joiner dowels (69) and (70) to ribs
W4 and W5.
Do not go any further with this wing
half. Construct the other half of the top wing
to the same stage.
04sig1.QXD 2/24/09 11:21 AM Page 30
corrugated cardboard. Slice four 1/4-inch-wide
strips from the 1/16 balsa sheet. Smear glue onto
the strips and form them around the templates.
Use pins to hold the strips against the templates
until the glue dries.
When the glue is dry, adhere the rest of the
frame and the 1/4-inch sheets. Build the
stabilizer and the fin, and then sand all the
surfaces.
Bend a 1/16-inch-diameter piano wire to
form the tail-wheel strut. Insert the end of the
strut into the balsa sheet in the rudder, and then
glue in the wire with thin cyanoacrylate. Wrap
the whole sheet with fiberglass. You can use
thin cyanoacrylate to saturate the cloth.
Cabane and Wing N Struts: Cut four identical
cabane struts (72) and four N struts (74) from 1/8
light plywood. Cut two cabane struts (71) and
two N struts (73) from 1/32 aluminum sheet.
Drill the 1/16-inch-diameter holes in N struts, as
shown on the drawing.
Sand the surface of the aluminum with
sandpaper. Using cyanoacrylate or GOOP-type
adhesive, adhere the plywood pieces to both
sides of the aluminum struts. Sand the edges of
the plywood to streamline their shape. Cut a slot
in one of the front cabane struts, and insert and
glue in the aileron-servo extension cable.
Wrap all the struts with fiberglass and
saturate them with thin cyanoacrylate. Sand
lightly and bend the exposed aluminum ends of
the struts as shown on the drawing.
Fuselage: Cut out as many parts as possible.
The fuselage is built upside-down in three
sections: the cowl, the center-section, and the
tail section.
Cut and bend 5/32-inch-diameter piano wire
to form the main landing-gear legs. Attach them
to former F5 with thread (canvas thread, Kevlar,
or copper wire).
Glue the hardwood block (17) to former
F4B, and adhere hardwood blocks (18) to
formers F3D and F6B. Pin formers F3D, F5,
F6B, and F8B to the building board. Pin and
glue the fuselage sides (1) to these formers.
Insert and glue in the battery floor (13). Insert
and glue in formers F4B and F7.
Pin formers F9B, F10B, F11, and F12 to the
building board. Adhere the rear fuselage sides
(2) to these formers and to the fuselage side (1).
Glue 3/8-inch triangle stock between the
fuselage side (2) and former F8B.
On the outside of the fuselage, glue the balsa
doublers (3) between formers F3D and F6B.
Between F6B and F8B, adhere the doublers (4)
to the fuselage sides.
Glue the bottom wing to the fuselage. Slide
the joiners (47) and (48) into the slots in the
fuselage sides (1). Check the alignment and
adhere the joiners to formers F6B and F7. Glue
the balsa strip (12) to the bottom of all the
formers. Complete the sheeting of the bottom
between formers F3B and F8B.
Turn the fuselage right-side up. Glue the
firewall (20) and firewall support sides (19) to
the battery floor (13) and to former F3D.
The cowl is built in top and bottom halves.
Cut four identical plywood pieces (21). Drill a
1/4-inch hole for the magnets and a 1/16-inch hole
for the guide pins.
Pin two of the four plywood pieces (21) to
the building board. Pin and glue formers F1B,
F2B, and F3B to them. Insert and glue 1/4
square balsa into these formers. Adhere the
sheeting (9) and (10).
Remove the bottom of the cowl from the
building board and glue the scoop (24) to it. The
bottom of the cowl can be glued to former F3D.
Build the removable top of the cowl the same
way, but don’t adhere it to anything. Glue the
magnets and guide pins into the plywood pieces
(21).
Mount the cabane to the hardwood blocks
(18) using self-tapping screws. Insert the
cabane’s top tabs into the slots in the bottom of
the top wing’s center-section. Line up the holes
on cabane struts with the holes in W3 ribs.
Attach the cabane to the W3 ribs with selftapping
screws. At the same time, feed the plug
from the aileron extension into the cavity
between ribs W2 and W3.
Plug in all the wing panels and check the
alignment. If any adjustments are required, now
is the time to do it. Install the wing N struts. Use
self-tapping screws to hold them to the wings.
It’s time to install the most important strut
(75). Cut the 1/2-inch K&S streamlined
aluminum tube to the proper length. Flatten the
ends. Drill a 3/32-inch hole at each end, and bend
the ends so that the flat end is flush with the
plywood (67) behind the main spar of the top
wing. The same goes for the other end, but it
has to follow the contour of the hardwood block
(17) in the fuselage. Drill the hole in the
hardwood block and the plywood for selftapping
screws.
Remove the wings from the fuselage,
including the center-section. In the top wing,
install the servo extension for the aileron servo.
Glue the stabilizer to the fuselage. Adhere
all top fuselage formers. Glue the top sheeting
(5) to the front fuselage formers and the
sheeting (6) to the back formers. Cut out the
cockpit opening. Glue on the headrest (25).
Adhere the longeron (14) to the side of the
fuselage. Glue the fin to the fuselage.
Make the wheel pants and the streamline
covers for the main gear legs from the balsa
materials cited on the plans.
Finishing: Use your own method to apply the
finish; I used UltraCote. After completing the
covering, I installed the hinges and the servos. I
mounted a threaded connecting rod between the
top and bottom aileron with a clevis at each end.
The small “L”-shaped aluminum bracket is
attached to the plywood plate on each aileron
with self-tapping screws.
The dummy engine is made from scrap
balsa pieces and then glued to the top half of the
cowl.
After installing the radio and motor, remove
the top half of the cowl and slide the motor
battery onto the battery floor. Check the CG.
Move the battery as needed to get the D-IX to
balance on the CG spot. Mark the battery
location. I used hook-and-loop fastener to hold
it in place.
Install the servos and check the control
surfaces’ operation. The elevator should travel
3/4 inch up and down. The rudder 11/4 inches left
and right at the widest point. The top ailerons
should travel 1/2 inch up and down at the widest
point.
You’re finished with the construction. Have
fun flying this unique-looking scale model. MA
Laddie Mikulasko
[email protected]
Sources:
AXi 2826/10 motor, Jeti 40 Advance ESC:
MS Composit
(317) 578-1955
www.mscompositusa.com
UltraCote covering:
Hangar 9
(800) 338-4639
www.hangar-9.com
3200 mAh EVO LITE V2 3S battery:
FlightPower
(919) 741-6310
www.flightpowerusa.com
Edition: Model Aviation - 2009/04
Page Numbers: 25,26,27,28,29,30,31,32,33
SEVERAL YEARS AGO, in one of the aircraft magazines I saw
pictures of a unique-looking home-built biplane called the “Der Jager
D-IX.” I was attracted to it because of its shape and color scheme.
Marshall Wright designed and built the airplane.
Sometime later, I stumbled across a three-view drawing for
the design. I kept it with the intention of building a scale
model of the D-IX at some point in the future. In addition to the
three-views, I found some photos on the Internet of the original
biplane.
I designed the model for an AXi 2826/10 brushless motor using a
Jeti Advance 40 PLUS speed controller and 3S Li-Poly batteries. I
made sure that the battery’s installation is easy; the top half of the
cowl comes off, and the battery is placed on the battery floor.
Four Blue Bird BMS-380 servos are used for control. They
are half the size of a standard servo, half the weight, and have the
same torque rating: approximately 50 inch-ounces. If you do not
want to fly this model as an electric, any .40-.45 glow engine can
be used.
I drew the plans and then proceeded to build the Der Jager model.
The test flight was a nonevent; the model tracked straight on takeoffs
and has excellent flying characteristics. It is fully aerobatic with no
bad habits, and the landings are straightforward. Even with the wheel
pants, the D-IX doesn’t nose over when flown off the grass.
April 2009 25
by Laddie Mikulasko
The author designed his airplane to be similar to the full-scale aircraft
that was designed by the Stolp-White Aircraft Company in 1969. The
model includes almost every charming aspect of the biplane lineage.
The Der Jager’s light wing loading allows it to climb quickly.
Sport aerobatics are comfortable.
A WW1-looking home-built,
fresh from the 1970s
04sig1.QXD 2/24/09 11:16 AM Page 25
26 MODEL AVIATION
Photos by the author
Wing panels join the center-sections with stacked dowel rods
at the apex of the rib shape. Center-area ribs are made from
light plywood.
The ribs are organized over the top wing plans as they are cut
from blank material. Holes in the inner ribs are for the aileron
servo wire and dowel supports.
The wide sheeting near the TE is centered over the hinge line.
Once the aileron is cut away, cap the open areas with balsa.
TE scallops add distinctive character to the Der Jager. After
drawing the outline, sand away the excess with a rasp or round
dowel covered with sandpaper.
The cabane struts and N struts have an aluminum-sheet core that
is laminated with wood on both sides. The material is sanded to a
streamlined shape later.
The center-section of the upper wing secures the dowel-rod wing
joiners inside plywood ribs. The completed sheeting is sanded
flush with the outer panels.
04sig1.QXD 2/24/09 11:33 AM Page 26
April 2009 27
The primary fuselage sides are marked left and right, as are the
forward 1/4-inch sheets that will be sanded to shape later.
The cabane struts mount inside tabs in the top wing’s centersection
and are secured with #4 socket-head servo screws.
The wooden sections of the wheel pants are laminated with
wood glue, which is easy to sand later. Plywood buried inside
acts as a mounting point.
The piano-wire landing gear is stitched to the former with
thread, Kevlar, or copper wire. The lower wing’s center-section
is built into the forward framework.
The cabane struts are securely mounted into hardwood areas.
Sheeting is wrapped around the forward turtledeck, forming the
cockpit area.
Once the fuselage sides are pulled together, the lower sheeting
and longerons can be added. Watch out for twisting and keep
the tail post square.
04sig1.QXD 2/24/09 11:18 AM Page 27
28 MODEL AVIATION
Cowling halves are framed separately. The lower half (shown) is
permanently attached to the fuselage and houses the motor.
A channel is carved in the right cabane strut to hide the aileronservo
extension wire. Covering material is applied over the woodskinned
aluminum supports later.
The stabilizer and fin are framed to simulate steel-tube
framework, so they are rounded on all outside edges.
Each control surface of the tail must have cardboard templates
made to form the laminations of the curved outer-framework
material.
An AXi Gold 2826/10 motor and Jeti 40 Advance ESC are
powered with a 3300 mAh 3S Li-Poly battery from FlightPower.
Temporary foam fixtures are placed to align and set the struts’ final
locations. Double-stick tape and pins hold the fixtures in place.
04sig1.QXD 2/24/09 11:35 AM Page 28
April 2009 29
Pushrods from upper to lower aileron are linked to aluminum angle
brackets located in hard points near the LE of the control surface.
Access to rudder and elevator servos is through the cockpit
opening, which is later covered with a pilot figure.
The simulated engine is made from scrap balsa that is covered
and painted to match the IO-235 four-cylinder engine used in
the full-scale aircraft.
Simulated bullet-hole decorations, as on the full-scale aircraft.
Support wires add support but are mostly for appearance.
Type: RC Sport Scale
Skill level: Intermediate
builder, intermediate pilot
Wingspan: Top, 50 inches; bottom,
42 inches
Wing area: Approximately 750 square inches
Length: 42 inches
Weight: 4 pounds (depending on battery)
Power: 300- to 500-watt system, 40- to 54-amp ESC,
3S 3300 mAh Li-Poly battery
Construction: Balsa, light plywood, hardwood-dowel wing joiners
Covering/finish: UltraCote heat-shrink film
Radio: Four miniservos (40 inch-ounces output), receiver,
custom servo extensions
Other: 21/4-inch spinner, 3-inch wheels, APC 10 x 8E propeller, 11/4-inch tail
wheel, 5/32-inch music-wire landing gear, 1/32-inch aluminum-sheet strut material
04sig1.QXD 2/24/09 11:20 AM Page 29
30 MODEL AVIATION
The four wing panels plug into the structure and are secured with an aluminum main strut that attaches from the lower
fuselage to the top outer panel.
The AXi power system is equivalent to a .32
cu. in. glow engine that offers better-thanscale
performance. The Der Jager flies
predictably and has a distinctive appearance.
I tried to make building this airplane as
simple as possible. The outer wing panels are
removable; however, if transporting a 50-
inch-wingspan model is not a problem, you
have the option of building the wings in one
piece and permanently attaching them to the
fuselage.
The two aileron servos are mounted inside
the top wing. The connecting rods join the
top aileron to the bottom aileron. The elevator
and rudder servos are located inside the
cockpit.
To build this model, you will need light
balsa, light plywood, 5/32-inch-diameter music
wire, and 1/32-inch-thick aluminum sheeting.
Build the wing center-section. Pin the
bottom main spar to the building board.
Glue ribs W1, W2, and W3 to the spar.
Adhere the top main spar to the ribs.
Take hold of the two outside wing panels
and slide the joiners all the way into ribs W2
and W3. Glue the sub-LE to ribs W1, W2,
and W3. Adhere the top LE sheet (51) to
these ribs. Glue on the rest of the top
sheeting (62).
Flip the wing over. In the center-section,
install the Y harness for the ailerons. Glue
the bottom sheeting (61) to ribs W1, W2,
and W3. Glue the plywood strips (67) to ribs
W8 and W9; you must use the five-ply
plywood. The plywood strips will be
holding the brackets for N struts and the
main struts (75).
Glue on the bottom LE sheeting (52).
Adhere the aileron strip (58) to ribs W5 to
W10. Glue on the sheeting (63) over ribs
W4 and W5 and the sheeting (59) and (60)
over ribs W7 and W9. Glue on the capstrips.
Attach the LE spar (54).
Separate the ailerons from the wing
panels. Glue the hinge spar (57) to the wing
and the aileron LE to the aileron. Sand the
wing. Glue in the plywood mounting frame
for the aileron servo.
In the bottom of the center-section, cut
the slots for the cabane struts to go into and
one larger hole for the extension cable.
Build the bottom wing in a similar
fashion. The difference is having the joiners
(47) and (48) glued to the two identical root
ribs W11, which will become part of the
fuselage; the outside wing panels will slide
onto them.
Once the wing panels are built, line up
the halves of the bottom wing and place 1/2-
inch shims under the wingtips to get the
proper dihedral. Glue the left joiners to the
right joiners.
Tail Surfaces: Before building the elevators
and the rudder, cut the templates from
CONSTRUCTION
Wing: The individual wing panels plug into
the fuselage using 1/4-inch-diameter dowel
as joiners. The dowels are not strong enough
by themselves to hold the wing panels; the
main strut (75) will hold everything in place
once the panels are plugged in. It’s
unnecessary, but you can replace the
hardwood dowels with carbon-fiber tubes.
To get started, transfer the ribs’ outlines
and mark the location of the holes on the
plywood and the balsa. Cut out the ribs and
drill all the holes.
Cut 1/4-inch hardwood dowels (69) (70)
and (47) (48) to the proper lengths. Adhere
two (69) dowels to create a double-width
joiner for the top wing, and then glue two
dowels (47) together for the bottom wing
joiner.
Build the top wing first. It includes three
sections: two outside panels and the center
panel.
Begin constructing the outside panels.
Pin the bottom main spar (49) to the board
directly over the plans. Pin the 1/4 square
balsa to the building board, to be used as a
shim under the ribs at the TE. Position and
glue all ribs to this spar. Glue the top main
spar (50) to the ribs.
Cut out the TE sheets (55) and (56) that
include the scallops. Slide the TE sheet (56)
between the shim and the ribs. Adhere the
ribs to the TE sheet. Glue the sub-LE (53) to
the ribs. Sand the sub-LE so that it follows
the contour of the ribs.
Glue the wingtip sheet (66) to rib W10.
Adhere the top TE sheet (55) to the ribs.
Glue the top LE sheet (51) to the ribs and to
the sub-LE. Glue on 1-inch-wide aileronhinge
balsa strip (58) to ribs W5 to W10.
Adhere the top capstrips to the ribs. Slide in
and glue joiner dowels (69) and (70) to ribs
W4 and W5.
Do not go any further with this wing
half. Construct the other half of the top wing
to the same stage.
04sig1.QXD 2/24/09 11:21 AM Page 30
corrugated cardboard. Slice four 1/4-inch-wide
strips from the 1/16 balsa sheet. Smear glue onto
the strips and form them around the templates.
Use pins to hold the strips against the templates
until the glue dries.
When the glue is dry, adhere the rest of the
frame and the 1/4-inch sheets. Build the
stabilizer and the fin, and then sand all the
surfaces.
Bend a 1/16-inch-diameter piano wire to
form the tail-wheel strut. Insert the end of the
strut into the balsa sheet in the rudder, and then
glue in the wire with thin cyanoacrylate. Wrap
the whole sheet with fiberglass. You can use
thin cyanoacrylate to saturate the cloth.
Cabane and Wing N Struts: Cut four identical
cabane struts (72) and four N struts (74) from 1/8
light plywood. Cut two cabane struts (71) and
two N struts (73) from 1/32 aluminum sheet.
Drill the 1/16-inch-diameter holes in N struts, as
shown on the drawing.
Sand the surface of the aluminum with
sandpaper. Using cyanoacrylate or GOOP-type
adhesive, adhere the plywood pieces to both
sides of the aluminum struts. Sand the edges of
the plywood to streamline their shape. Cut a slot
in one of the front cabane struts, and insert and
glue in the aileron-servo extension cable.
Wrap all the struts with fiberglass and
saturate them with thin cyanoacrylate. Sand
lightly and bend the exposed aluminum ends of
the struts as shown on the drawing.
Fuselage: Cut out as many parts as possible.
The fuselage is built upside-down in three
sections: the cowl, the center-section, and the
tail section.
Cut and bend 5/32-inch-diameter piano wire
to form the main landing-gear legs. Attach them
to former F5 with thread (canvas thread, Kevlar,
or copper wire).
Glue the hardwood block (17) to former
F4B, and adhere hardwood blocks (18) to
formers F3D and F6B. Pin formers F3D, F5,
F6B, and F8B to the building board. Pin and
glue the fuselage sides (1) to these formers.
Insert and glue in the battery floor (13). Insert
and glue in formers F4B and F7.
Pin formers F9B, F10B, F11, and F12 to the
building board. Adhere the rear fuselage sides
(2) to these formers and to the fuselage side (1).
Glue 3/8-inch triangle stock between the
fuselage side (2) and former F8B.
On the outside of the fuselage, glue the balsa
doublers (3) between formers F3D and F6B.
Between F6B and F8B, adhere the doublers (4)
to the fuselage sides.
Glue the bottom wing to the fuselage. Slide
the joiners (47) and (48) into the slots in the
fuselage sides (1). Check the alignment and
adhere the joiners to formers F6B and F7. Glue
the balsa strip (12) to the bottom of all the
formers. Complete the sheeting of the bottom
between formers F3B and F8B.
Turn the fuselage right-side up. Glue the
firewall (20) and firewall support sides (19) to
the battery floor (13) and to former F3D.
The cowl is built in top and bottom halves.
Cut four identical plywood pieces (21). Drill a
1/4-inch hole for the magnets and a 1/16-inch hole
for the guide pins.
Pin two of the four plywood pieces (21) to
the building board. Pin and glue formers F1B,
F2B, and F3B to them. Insert and glue 1/4
square balsa into these formers. Adhere the
sheeting (9) and (10).
Remove the bottom of the cowl from the
building board and glue the scoop (24) to it. The
bottom of the cowl can be glued to former F3D.
Build the removable top of the cowl the same
way, but don’t adhere it to anything. Glue the
magnets and guide pins into the plywood pieces
(21).
Mount the cabane to the hardwood blocks
(18) using self-tapping screws. Insert the
cabane’s top tabs into the slots in the bottom of
the top wing’s center-section. Line up the holes
on cabane struts with the holes in W3 ribs.
Attach the cabane to the W3 ribs with selftapping
screws. At the same time, feed the plug
from the aileron extension into the cavity
between ribs W2 and W3.
Plug in all the wing panels and check the
alignment. If any adjustments are required, now
is the time to do it. Install the wing N struts. Use
self-tapping screws to hold them to the wings.
It’s time to install the most important strut
(75). Cut the 1/2-inch K&S streamlined
aluminum tube to the proper length. Flatten the
ends. Drill a 3/32-inch hole at each end, and bend
the ends so that the flat end is flush with the
plywood (67) behind the main spar of the top
wing. The same goes for the other end, but it
has to follow the contour of the hardwood block
(17) in the fuselage. Drill the hole in the
hardwood block and the plywood for selftapping
screws.
Remove the wings from the fuselage,
including the center-section. In the top wing,
install the servo extension for the aileron servo.
Glue the stabilizer to the fuselage. Adhere
all top fuselage formers. Glue the top sheeting
(5) to the front fuselage formers and the
sheeting (6) to the back formers. Cut out the
cockpit opening. Glue on the headrest (25).
Adhere the longeron (14) to the side of the
fuselage. Glue the fin to the fuselage.
Make the wheel pants and the streamline
covers for the main gear legs from the balsa
materials cited on the plans.
Finishing: Use your own method to apply the
finish; I used UltraCote. After completing the
covering, I installed the hinges and the servos. I
mounted a threaded connecting rod between the
top and bottom aileron with a clevis at each end.
The small “L”-shaped aluminum bracket is
attached to the plywood plate on each aileron
with self-tapping screws.
The dummy engine is made from scrap
balsa pieces and then glued to the top half of the
cowl.
After installing the radio and motor, remove
the top half of the cowl and slide the motor
battery onto the battery floor. Check the CG.
Move the battery as needed to get the D-IX to
balance on the CG spot. Mark the battery
location. I used hook-and-loop fastener to hold
it in place.
Install the servos and check the control
surfaces’ operation. The elevator should travel
3/4 inch up and down. The rudder 11/4 inches left
and right at the widest point. The top ailerons
should travel 1/2 inch up and down at the widest
point.
You’re finished with the construction. Have
fun flying this unique-looking scale model. MA
Laddie Mikulasko
[email protected]
Sources:
AXi 2826/10 motor, Jeti 40 Advance ESC:
MS Composit
(317) 578-1955
www.mscompositusa.com
UltraCote covering:
Hangar 9
(800) 338-4639
www.hangar-9.com
3200 mAh EVO LITE V2 3S battery:
FlightPower
(919) 741-6310
www.flightpowerusa.com