SoarCerer - 2008/03

March 2008 33
SoarCerer
by Jean “JG” Pailet
The internal air pressure can rise
dramatically and erratically, potentially
causing the surfaces to warp. Another small
hole through the covering at the tip, or
through the tip itself, will vent any excess
pressure to the outside.
Begin assembling the flat central wing
panel by pinning the LE and TE to the
building board. The TE’s forward edge must
be elevated 1/8 inch along its full length so it
will conform to the ribs’ contour when they
are inserted into their notches.
Initially place the central-area ribs from
the W-3 plywood ribs inward into their TE
notches and insert the 3/16-inch aluminum
tubing through them. Place the remaining
W-2 ribs and the W-1 dihedral ribs. The W-
1 ribs should be set at an approximate 10°
angle to accommodate the required outerpanel
dihedral.
Insert the full-length 3/16-inch carbonfiber
tube/spar through all the central panel
ribs, from dihedral rib to dihedral rib. Also
install the three 1/16 square hardwood spars.
They should extend 1/4 inch beyond the
dihedral ribs and are not glued to the
dihedral ribs until later, when the three wing
panels are joined.
Secure all other joints with the glue of
your choice. (Mine has been odorless
cyanoacrylate since I developed an allergic
reaction to regular cyanoacrylate.) When
you are satisfied that all the glue joints have
cured properly, remove the assembled
structure from the workbench.
Construct/assemble the two outer wing
panels in a similar manner, and make sure to
build in the required 3/32-inch tip washout.
Note, too, that the 1/8-inch tip plates are set
at a 45° angle and the dihedral ribs are again
set at a 10° angle. As with the center wing
panel, the outer wing panel’s 1/16 hardwood
spars should extend 1/4 inch beyond the
dihedral ribs.
The three wing panels are ready for
assembly to each other. Cut/carve a short
This FAI-legal Towline model
can also compete in the
NFFS Classic Glider event
O’Reilly for creating a great set of
computer-generated plans), let’s
build the SoarCerer.
CONSTRUCTION
Wing: The 1/8 x 1 TE is
manufactured (carved) from mediumhard
sheet-balsa stock. Use a razor plane,
sandpaper, and a great deal of elbow grease to
create the cross-sectional taper from 1/8 inch at
the wing’s forward edge to 1/32 inch at its aft
edge. Then cut the notches required to mate it
with the ribs.
Notice that the TE is one piece from outer
dihedral rib to outer dihedral rib. The LE and
all the spars are also one piece for their full
28-inch lengths. The shorter central aluminum
spar is also one piece from end to end. This
assures that the flat central wing section is a
strong, one-piece, integrated structure.
As does the TE, the LE requires a
manufacturing process before beginning the
wing assembly. This involves cutting a groove
in the 1/8 x 3/16 LE strip to accept the .040-
inch-diameter carbon-fiber rod, which is
inserted later. The groove should
be 1/32 inch above the LE’s
lower surface to provide
the correct Phillips entry
shape to the airfoil when
the LE is later carved and sanded to
conform to the rib airfoil contour.
Each rib should have a small (1/16 inch
in diameter is enough) vent hole through
it. These holes equalize pressure
buildup throughout the wing
and stabilizer
spans
when the
model is sitting out on a
field and is exposed directly to the sun on a
hot summer day.
Eastern
FF
Champs, the
Inter-City, the
Hoosier Cup, the King
Orange, and the Fiesta of Five
Flags contests. In FAI
competition these airplanes have
placed as high as third overall in
the annual America’s Cup series.
So with an apology for plagiarism and a
“thank you” for many great design ideas to
Bill Dunwoody, Bob Hatschek, and Stan
Buddenbohm (and appreciation to Jim
THE SOARCERER’S
ancestry dates back to
1967, when fellow Brooklyn
Skyscraper, Bill Dunwoody, had
plans for his Soar Sam A-1 Towline
Glider published in the July Flying
Models magazine. Both of my sons
competed successfully with Soar Sams for
many years.
Eventually I decided to design a Glider
of my own. I tried to incorporate some of the
Soar Sam’s best features with characteristics
of the Circulator, which another Skyscraper,
Bob Hatschek, designed. The result was the
Tow Soar. Experience with that model led to
the Tow Soar Two, which was published in
the October 2000 MA.
The current SoarCerer is a blend of these
earlier designs and a number of Stan
Buddenbohm’s MiniMaster’s outstanding
construction features. Even without the
benefit of circle tow, the SoarCerer and its
predecessors have proven to be extremely
competitive.
After a couple second-place finishes at
the Nats, they have accumulated wins at the
The SoarCerer is a blend of several
popular FF Towline Gliders,
such as the Skyscraper and
the Tow Soar.
03sig2.QXD 1/24/08 1:30 PM Page 3334 MODEL AVIATION
Photos by the author
The full-length 3/16-inch carbon-fiber tube/spar is located at the
center of pressure through all the central-panel ribs, from dihedral
rib to dihedral rib.
While the bottom sheeting extends outward one rib bay from the
centerline, the top sheeting extends outward two rib bays.
The horizontal stabilizer’s construction is conventional, aside from the groove required in the LE for the .030-inch-diameter carbon-fiber rod.
Add ballast to the cavities and
compartments at the front of the
fuselage to locate the balance point at
the designated 56% mark.
Inventive applications of colored tissue can yield interesting and
colorful results with practically no weight penalty.
Insert a dummy release pin to lock the timer, DT, and rudder
lines while doing the initial hand-launched glide tests.
Short lengths of aluminum tubing are glued to the fuselage side
to provide guide tubes for the timer-actuating, auto-rudder, and
DT lines.
The towhook fits inside a shallow cavity on the fuselage bottom.
The sliding 4-40 machine screw within the towhook provides an
almost infinite range of adjustment.
03sig2.QXD 1/24/08 2:15 PM Page 3436 MODEL AVIATION
Type: F1H Towline Glider
Builder skill level: Intermediate
Wingspan: 55.375 inches
Flying weight: 220 grams
Wing area: 230.51 square inches
Stabilizer area: 43.04 square inches
Total area: 273.55 square inches
Length: 33.25 inches
Construction: Balsa, dowel rod, carbon fiber,
aluminum tubing
Covering/finish: Polyspan, dope, Japanese tissue
length of hardwood dowel to form a dihedral brace within the
carbon fiber and aluminum main spars where they mate at the
dihedral joint. Cut mating angles on the 1/4-inch overhang of the three
hardwood spars so they will form a lap joint where they meet at the
dihedral ribs.
Secure the internal dowel dihedral brace to the inside of the
respective carbon fiber and aluminum spars with a slow-drying epoxy
glue. I use 3M Scotch-Weld (product DP460).
Similarly, use a slow-drying epoxy on the dihedral ribs’ mating
faces. This will allow you time to tack-glue the other dihedral joints
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(ribs, spars, LE, and TE) as you set the proper alignment and dihedral
angle.
After the three wing panels are assembled to each other, glue the
.040 carbon-fiber rods into the grooves in their respective LEs. Carve
and sand the LEs to provide the desired airfoil contour. The final step
in the wing construction is installing the center-area 1/20 balsa sheeting
over and under the LE, TE, and ribs.
Although the bottom sheeting extends outward one rib bay from the
centerline, the top sheeting extends outward two rib bays. Some final
carving and sanding will properly contour the sheeting where it
overlaps the LE.
Horizontal Stabilizer: This component’s construction is conventional,
aside from the groove required in the LE for the .030-inch-diameter
carbon-fiber rod. You must cut a slot in the forward part of the 3/16-
inch center rib to accept the 1/32 plywood DT horn/alignment key.
After assembling the LE, TE, ribs, and spars, insert the carbon-fiber
rod into the LE. Carve and sand the LE to the appropriate airfoil shape
in conformance with the rib contours.
Fin/Vertical Tail and Rudder: The fin and rudder are simple sheetbalsa
flat surfaces. The fin LE is sanded to a rounded cross-section,
and the aft portion of the rudder is tapered to a 1/32-inch TE thickness.
Since the grain of these surfaces is vertical, I add a small piece of
1/64 plywood to each side of the upper portion of the rudder to provide
stiffness and a bearing surface for the rudder angle-adjustment screws.
The actual rudder-adjusting mechanism can be homemade or
purchased from FAI Model Supply.
The rudder hinge is a length of 1/16-inch-outside-diameter
aluminum tubing glued to the forward edge of the rudder and a length
of 1/32-inch-diameter music wire bent to form the hinge and tail skid.
The wire should extend up into the fuselage. The auto-rudder actuating
horn is bent from 1/32-inch music wire.
Fuselage: The lower portion of the fuselage, from nose to tail, is
essentially a sheet-balsa box with .050-inch-diameter carbon-fiber rods
laid into each corner. The upper forward fuselage is a balsa box
forming the wing mount. The fuselage top, bottom, and sides are cut
from 1/16 sheet balsa, as are all formers.
I recommend that the formers for the lower fuselage box have a
grain that is diagonal in alternating directions. Before assembling the
box, you must glue a 1/16 plywood towhook attachment floor with 4-40
T-nuts installed to the inside of the fuselage bottom. All four corners of
SoarCerer
03sig2.QXD 1/24/08 2:00 PM Page 36the lower fuselage box are open to allow for
installing the corner carbon-fiber rods once
the basic balsa box has been constructed.
Build the upper forward fuselage/wing
mount onto the lower fuselage box. This wing
mount/platform should provide 1° positive
wing-incidence angle, and its hard-balsa upper
surface’s grain must be crossways (at 90°) to
the fuselage centerline.
A balsa block forms the nose of the
fuselage, and a smaller balsa block fills in the
aft end of the fuselage. Holes drilled into the
nose block will provide cavities for ballast
when performing final balancing.
Installing a false wall behind the timer, in
the timer bay, will provide an additional area
for ballast, if required. The 1/16 hard-balsa
stabilizer platform, with a slot to accept the
stabilizer key, is installed on the aft fuselage,
as is a 1/16 pad at the stabilizer TE. Hardwood
dowels that are 1/8 inch in diameter provide
tie-downs for the wing and stabilizer.
The towhook and nose skid are formed
from 1/16-inch music wire. The timer/rudder
release pin and the stabilizer DT hold-down
are made from 1/32-inch music wire. The
release pin slides into two short lengths of
1/16-inch-diameter aluminum tubing glued to a
1/32 plywood pad, which, in turn, is glued to
the fuselage side.
Attaching the towhook to the fuselage
within a shallow cavity on the fuselage
bottom and the sliding 4-40 machine screw
within the towhook provide an almost infinite
range of adjustment for the proper positioning
of the towline to accommodate varying
balance, trim, and wind conditions.
Cut an opening for the DT timer into the
fuselage side. Short lengths of aluminum
tubing are glued to the fuselage side to
provide guide tubes for the timer-actuating,
auto-rudder, and DT lines. The accompanying
photos, coupled with the plans, will provide
clear insight into how to rig the required lines
and rubber bands.
A short length of light plastic or cardboard
tubing installed just aft of the wing provides a
housing for a locator transmitter (and I
strongly urge you not to fly without one).
Covering and Finishing: Polyspan is the
only covering material I use on wing and tail
surfaces. It provides all the best characteristics
of Japanese tissue (particularly enhancing a
structure’s torsional rigidity) for a small
weight penalty.
Most importantly, Polyspan is durable and
puncture-resistant. In addition, unwanted
warps can be removed and desired trim
adjustments can be made with a heat gun; the
surface retains the set you want.
Polyspan’s only shortcoming is that it
comes in only one not-so-vivid color: washedout
white. The accompanying photos illustrate
inventive applications of colored tissue (at
effectively no weight penalty) that can yield
interesting and colorful results.
All surfaces to which Polyspan will be
adhered must be given at least two coats of
clear dope, thinned 50%, with a light sanding
after each coat. I prefer to use nitrate dope
since there is no need to worry about fuelproofing
on a nonpowered model such as this.
Apply a third coat of unthinned dope to the
underside of all the ribs. This will help assure
that the covering will adhere properly to the
significant undercamber when heat-shrunk
later.
Apply/glue the Polyspan to the respective
surfaces with either thinner or heavily diluted
dope. A hot (approximately 300°) covering
iron will help bend the Polyspan around any
small radii, such as the wing and stabilizer
LEs and tips, as it is being applied.
After covering, use a similarly hot iron to
remove any wrinkles and tighten the skin over
all the surfaces. Apply two coats of 50%-
thinned clear nitrate dope to all the surfaces.
Now is the time to get inventive and
artistic with colorful trimming. As I
mentioned, the simple application, with
thinner, of colored Japanese tissue can
accomplish wonders in making your model
beautiful and, more importantly, visible
against the backgrounds of sky and earth.
Apply two more coats of 50%-thinned
nitrate dope to all covered and decorated
surfaces. Then you can apply any desired
decals, logos, and the required AMA license
numbers.
I do not use Polyspan on the all-wood
surfaces of the fuselage, fin, and rudder.
Japanese tissue, in your choice of color(s),
will do the job fine.
Give all the exposed wood surfaces two
coats of 50%-thinned nitrate dope with the
requisite sanding afterward. Then apply the
tissue using either thinned dope or only
38 MODEL AVIATION
03sig2.QXD 1/24/08 2:04 PM Page 38thinner. Finish the job with four coats of the
thinned dope.
Final Assembly: Install the nose skid using
epoxy cement. (3M Scotch-Weld is fine too.)
Glue the fin to the bottom of the fuselage
(Ambroid or cyanaocrylate are okay here as
well), making certain that it is aligned
perfectly on the fuselage centerline.
Properly align the wing and tail with
respect to the fuselage centerline. They must
be “square” (at right angles) to the fuselage
centerline and retain that relationship every
time they are installed.
Short (1/4 to 1/2 inch) lengths of 1/16-inchdiameter
dowels, split lengthwise and glued
to the undersides of the wing LE and TE and
stabilizer TE, will serve this purpose. (The
DT horn’s alignment key will do the job at
the stabilizer LE.) Positioned on the wing and
stabilizer so they rest against the fuselage
sides assures the proper alignment.
With the wing, stabilizer, timer, and
tracker/transmitter installed, add ballast to the
cavities/compartments at the front of the
fuselage to locate the balance point at the
designated 56% of the wing’s root chord.
Trimming and Testing: If you have a
locator/transmitter, install it now!
As shown on the plans, my models have
flown best when ballasted to balance at 56%
of the wing root chord. Insert a dummy
release pin to lock the timer, DT, and rudder
lines while doing the initial hand-launched
glide tests. These are aimed at achieving a
straight-ahead glide path using rudder trim
only.
Simultaneously adjust for a flat, nostall/
no-dive glide path by shimming the
stabilizer LE or TE as required. Ballasting the
nose or tail to shift the CG fore or aft a bit can
also be helpful during this tow-mode stage of
trimming.
During glide-mode trimming, keep the
timer locked with the dummy release pin, but
release the rudder line. Right-hand glide
circles are basically the norm, and repetitive
hand glides and rudder adjustments will yield
the desired flat, wide turn. Now begin the tow
testing.
Wind is both your friend and your foe
during the tow. With too much wind you risk
damaging the model, and with too little wind
you may not be able to run fast enough or far
enough (like me at my advanced age) to
maintain airspeed and gain altitude.
Assuming there is a moderate breeze (5-
10 mph), begin the tow tests with the
towhook screw set 3/8 inch ahead of the
balance point and the timer set for 30
seconds. Secure the timer and rudder lines
with the release pin, and secure the DT line to
the timer.
With the towline ring in place against the
towhook screw, have your helper hold the
SoarCerer at a nose-high 45° angle facing
directly into the wind. He/she should take a
step or two with you as you begin to run into
the wind and release the model gently in an
upward direction.
In a strong wind, you may find it
necessary to run toward the model as it rises
rather than away from it, to avoid imposing
possibly damaging excessive loads on it.
Move the towhook screw forward for windy
conditions and aft for calmer weather. The
difference of 1/8-1/4 inch either way should be
enough to make a noticeable change. The
Glider should tow straight ahead without
veering appreciably to either side.
When released (you have to slack off
abruptly on the towline), the SoarCerer
should settle into a flat and wide glide circle.
These two desired flight paths will be
achieved only through repetitive testing and
trimming. Practice, practice, practice!
The SoarCerer has been designed to meet
the FAI requirement of a maximum 279
square inches of projected wing and stabilizer
area for the F1H event. It can compete in the
National Free Flight Society’s Classic Glider
event too.
The F1H rules specify a minimum weight
of 220 grams. If you have to add ballast to
meet that requirement, be certain to locate the
extra weight/ballast at the balance point to
avoid disrupting your carefully achieved
flight trim and remove it when flying in
Classic Glider.
We need to acknowledge those unsung
heroes and heroines of Towline Glider
flying—those who wait patiently with us for
the wind and lift to be just right before
launching the darn things. We could not do it
without you! MA
Jean “JG” Pailet
April-September: 456 Florencia Pl.
Melville NY 11747
(631) 549-1485
October-March: 1326 Santa Rosa Ct.
Lady Lake FL 32159
(352) 259-3963
Sources:
Carbon fiber, epoxy:
Aerospace Composite Products
(800) 811-2009
www.acp-composites.com
CST—The Composites Store
(800) 338-1278
www.cstsales.com
Towline supplies, carbon fiber:
Bradley Model Products
(407) 277-9132
www.members.aol.com/bmp4carbon
Timers, gizmos, gadgets:
Campbell’s Custom Kits
(765) 683-1749
www.campbellscustomkits.com
FAI Model Supply
(570) 882-9873
www.faimodelsupply.com
Polyspan:
Campbell’s Custom Kits
Larry Davidson
(540) 721-4563
[email protected]
FAI Model Supply
Retrieval systems:
Walston Retrieval Systems
(770) 434-4905
www.walstonretrieval.com
40 MODEL AVIATION
03sig2.QXD 1/24/08 1:31 PM Page 40

March 2008 33
SoarCerer
by Jean “JG” Pailet
The internal air pressure can rise
dramatically and erratically, potentially
causing the surfaces to warp. Another small
hole through the covering at the tip, or
through the tip itself, will vent any excess
pressure to the outside.
Begin assembling the flat central wing
panel by pinning the LE and TE to the
building board. The TE’s forward edge must
be elevated 1/8 inch along its full length so it
will conform to the ribs’ contour when they
are inserted into their notches.
Initially place the central-area ribs from
the W-3 plywood ribs inward into their TE
notches and insert the 3/16-inch aluminum
tubing through them. Place the remaining
W-2 ribs and the W-1 dihedral ribs. The W-
1 ribs should be set at an approximate 10°
angle to accommodate the required outerpanel
dihedral.
Insert the full-length 3/16-inch carbonfiber
tube/spar through all the central panel
ribs, from dihedral rib to dihedral rib. Also
install the three 1/16 square hardwood spars.
They should extend 1/4 inch beyond the
dihedral ribs and are not glued to the
dihedral ribs until later, when the three wing
panels are joined.
Secure all other joints with the glue of
your choice. (Mine has been odorless
cyanoacrylate since I developed an allergic
reaction to regular cyanoacrylate.) When
you are satisfied that all the glue joints have
cured properly, remove the assembled
structure from the workbench.
Construct/assemble the two outer wing
panels in a similar manner, and make sure to
build in the required 3/32-inch tip washout.
Note, too, that the 1/8-inch tip plates are set
at a 45° angle and the dihedral ribs are again
set at a 10° angle. As with the center wing
panel, the outer wing panel’s 1/16 hardwood
spars should extend 1/4 inch beyond the
dihedral ribs.
The three wing panels are ready for
assembly to each other. Cut/carve a short
This FAI-legal Towline model
can also compete in the
NFFS Classic Glider event
O’Reilly for creating a great set of
computer-generated plans), let’s
build the SoarCerer.
CONSTRUCTION
Wing: The 1/8 x 1 TE is
manufactured (carved) from mediumhard
sheet-balsa stock. Use a razor plane,
sandpaper, and a great deal of elbow grease to
create the cross-sectional taper from 1/8 inch at
the wing’s forward edge to 1/32 inch at its aft
edge. Then cut the notches required to mate it
with the ribs.
Notice that the TE is one piece from outer
dihedral rib to outer dihedral rib. The LE and
all the spars are also one piece for their full
28-inch lengths. The shorter central aluminum
spar is also one piece from end to end. This
assures that the flat central wing section is a
strong, one-piece, integrated structure.
As does the TE, the LE requires a
manufacturing process before beginning the
wing assembly. This involves cutting a groove
in the 1/8 x 3/16 LE strip to accept the .040-
inch-diameter carbon-fiber rod, which is
inserted later. The groove should
be 1/32 inch above the LE’s
lower surface to provide
the correct Phillips entry
shape to the airfoil when
the LE is later carved and sanded to
conform to the rib airfoil contour.
Each rib should have a small (1/16 inch
in diameter is enough) vent hole through
it. These holes equalize pressure
buildup throughout the wing
and stabilizer
spans
when the
model is sitting out on a
field and is exposed directly to the sun on a
hot summer day.
Eastern
FF
Champs, the
Inter-City, the
Hoosier Cup, the King
Orange, and the Fiesta of Five
Flags contests. In FAI
competition these airplanes have
placed as high as third overall in
the annual America’s Cup series.
So with an apology for plagiarism and a
“thank you” for many great design ideas to
Bill Dunwoody, Bob Hatschek, and Stan
Buddenbohm (and appreciation to Jim
THE SOARCERER’S
ancestry dates back to
1967, when fellow Brooklyn
Skyscraper, Bill Dunwoody, had
plans for his Soar Sam A-1 Towline
Glider published in the July Flying
Models magazine. Both of my sons
competed successfully with Soar Sams for
many years.
Eventually I decided to design a Glider
of my own. I tried to incorporate some of the
Soar Sam’s best features with characteristics
of the Circulator, which another Skyscraper,
Bob Hatschek, designed. The result was the
Tow Soar. Experience with that model led to
the Tow Soar Two, which was published in
the October 2000 MA.
The current SoarCerer is a blend of these
earlier designs and a number of Stan
Buddenbohm’s MiniMaster’s outstanding
construction features. Even without the
benefit of circle tow, the SoarCerer and its
predecessors have proven to be extremely
competitive.
After a couple second-place finishes at
the Nats, they have accumulated wins at the
The SoarCerer is a blend of several
popular FF Towline Gliders,
such as the Skyscraper and
the Tow Soar.
03sig2.QXD 1/24/08 1:30 PM Page 3334 MODEL AVIATION
Photos by the author
The full-length 3/16-inch carbon-fiber tube/spar is located at the
center of pressure through all the central-panel ribs, from dihedral
rib to dihedral rib.
While the bottom sheeting extends outward one rib bay from the
centerline, the top sheeting extends outward two rib bays.
The horizontal stabilizer’s construction is conventional, aside from the groove required in the LE for the .030-inch-diameter carbon-fiber rod.
Add ballast to the cavities and
compartments at the front of the
fuselage to locate the balance point at
the designated 56% mark.
Inventive applications of colored tissue can yield interesting and
colorful results with practically no weight penalty.
Insert a dummy release pin to lock the timer, DT, and rudder
lines while doing the initial hand-launched glide tests.
Short lengths of aluminum tubing are glued to the fuselage side
to provide guide tubes for the timer-actuating, auto-rudder, and
DT lines.
The towhook fits inside a shallow cavity on the fuselage bottom.
The sliding 4-40 machine screw within the towhook provides an
almost infinite range of adjustment.
03sig2.QXD 1/24/08 2:15 PM Page 3436 MODEL AVIATION
Type: F1H Towline Glider
Builder skill level: Intermediate
Wingspan: 55.375 inches
Flying weight: 220 grams
Wing area: 230.51 square inches
Stabilizer area: 43.04 square inches
Total area: 273.55 square inches
Length: 33.25 inches
Construction: Balsa, dowel rod, carbon fiber,
aluminum tubing
Covering/finish: Polyspan, dope, Japanese tissue
length of hardwood dowel to form a dihedral brace within the
carbon fiber and aluminum main spars where they mate at the
dihedral joint. Cut mating angles on the 1/4-inch overhang of the three
hardwood spars so they will form a lap joint where they meet at the
dihedral ribs.
Secure the internal dowel dihedral brace to the inside of the
respective carbon fiber and aluminum spars with a slow-drying epoxy
glue. I use 3M Scotch-Weld (product DP460).
Similarly, use a slow-drying epoxy on the dihedral ribs’ mating
faces. This will allow you time to tack-glue the other dihedral joints
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(ribs, spars, LE, and TE) as you set the proper alignment and dihedral
angle.
After the three wing panels are assembled to each other, glue the
.040 carbon-fiber rods into the grooves in their respective LEs. Carve
and sand the LEs to provide the desired airfoil contour. The final step
in the wing construction is installing the center-area 1/20 balsa sheeting
over and under the LE, TE, and ribs.
Although the bottom sheeting extends outward one rib bay from the
centerline, the top sheeting extends outward two rib bays. Some final
carving and sanding will properly contour the sheeting where it
overlaps the LE.
Horizontal Stabilizer: This component’s construction is conventional,
aside from the groove required in the LE for the .030-inch-diameter
carbon-fiber rod. You must cut a slot in the forward part of the 3/16-
inch center rib to accept the 1/32 plywood DT horn/alignment key.
After assembling the LE, TE, ribs, and spars, insert the carbon-fiber
rod into the LE. Carve and sand the LE to the appropriate airfoil shape
in conformance with the rib contours.
Fin/Vertical Tail and Rudder: The fin and rudder are simple sheetbalsa
flat surfaces. The fin LE is sanded to a rounded cross-section,
and the aft portion of the rudder is tapered to a 1/32-inch TE thickness.
Since the grain of these surfaces is vertical, I add a small piece of
1/64 plywood to each side of the upper portion of the rudder to provide
stiffness and a bearing surface for the rudder angle-adjustment screws.
The actual rudder-adjusting mechanism can be homemade or
purchased from FAI Model Supply.
The rudder hinge is a length of 1/16-inch-outside-diameter
aluminum tubing glued to the forward edge of the rudder and a length
of 1/32-inch-diameter music wire bent to form the hinge and tail skid.
The wire should extend up into the fuselage. The auto-rudder actuating
horn is bent from 1/32-inch music wire.
Fuselage: The lower portion of the fuselage, from nose to tail, is
essentially a sheet-balsa box with .050-inch-diameter carbon-fiber rods
laid into each corner. The upper forward fuselage is a balsa box
forming the wing mount. The fuselage top, bottom, and sides are cut
from 1/16 sheet balsa, as are all formers.
I recommend that the formers for the lower fuselage box have a
grain that is diagonal in alternating directions. Before assembling the
box, you must glue a 1/16 plywood towhook attachment floor with 4-40
T-nuts installed to the inside of the fuselage bottom. All four corners of
SoarCerer
03sig2.QXD 1/24/08 2:00 PM Page 36the lower fuselage box are open to allow for
installing the corner carbon-fiber rods once
the basic balsa box has been constructed.
Build the upper forward fuselage/wing
mount onto the lower fuselage box. This wing
mount/platform should provide 1° positive
wing-incidence angle, and its hard-balsa upper
surface’s grain must be crossways (at 90°) to
the fuselage centerline.
A balsa block forms the nose of the
fuselage, and a smaller balsa block fills in the
aft end of the fuselage. Holes drilled into the
nose block will provide cavities for ballast
when performing final balancing.
Installing a false wall behind the timer, in
the timer bay, will provide an additional area
for ballast, if required. The 1/16 hard-balsa
stabilizer platform, with a slot to accept the
stabilizer key, is installed on the aft fuselage,
as is a 1/16 pad at the stabilizer TE. Hardwood
dowels that are 1/8 inch in diameter provide
tie-downs for the wing and stabilizer.
The towhook and nose skid are formed
from 1/16-inch music wire. The timer/rudder
release pin and the stabilizer DT hold-down
are made from 1/32-inch music wire. The
release pin slides into two short lengths of
1/16-inch-diameter aluminum tubing glued to a
1/32 plywood pad, which, in turn, is glued to
the fuselage side.
Attaching the towhook to the fuselage
within a shallow cavity on the fuselage
bottom and the sliding 4-40 machine screw
within the towhook provide an almost infinite
range of adjustment for the proper positioning
of the towline to accommodate varying
balance, trim, and wind conditions.
Cut an opening for the DT timer into the
fuselage side. Short lengths of aluminum
tubing are glued to the fuselage side to
provide guide tubes for the timer-actuating,
auto-rudder, and DT lines. The accompanying
photos, coupled with the plans, will provide
clear insight into how to rig the required lines
and rubber bands.
A short length of light plastic or cardboard
tubing installed just aft of the wing provides a
housing for a locator transmitter (and I
strongly urge you not to fly without one).
Covering and Finishing: Polyspan is the
only covering material I use on wing and tail
surfaces. It provides all the best characteristics
of Japanese tissue (particularly enhancing a
structure’s torsional rigidity) for a small
weight penalty.
Most importantly, Polyspan is durable and
puncture-resistant. In addition, unwanted
warps can be removed and desired trim
adjustments can be made with a heat gun; the
surface retains the set you want.
Polyspan’s only shortcoming is that it
comes in only one not-so-vivid color: washedout
white. The accompanying photos illustrate
inventive applications of colored tissue (at
effectively no weight penalty) that can yield
interesting and colorful results.
All surfaces to which Polyspan will be
adhered must be given at least two coats of
clear dope, thinned 50%, with a light sanding
after each coat. I prefer to use nitrate dope
since there is no need to worry about fuelproofing
on a nonpowered model such as this.
Apply a third coat of unthinned dope to the
underside of all the ribs. This will help assure
that the covering will adhere properly to the
significant undercamber when heat-shrunk
later.
Apply/glue the Polyspan to the respective
surfaces with either thinner or heavily diluted
dope. A hot (approximately 300°) covering
iron will help bend the Polyspan around any
small radii, such as the wing and stabilizer
LEs and tips, as it is being applied.
After covering, use a similarly hot iron to
remove any wrinkles and tighten the skin over
all the surfaces. Apply two coats of 50%-
thinned clear nitrate dope to all the surfaces.
Now is the time to get inventive and
artistic with colorful trimming. As I
mentioned, the simple application, with
thinner, of colored Japanese tissue can
accomplish wonders in making your model
beautiful and, more importantly, visible
against the backgrounds of sky and earth.
Apply two more coats of 50%-thinned
nitrate dope to all covered and decorated
surfaces. Then you can apply any desired
decals, logos, and the required AMA license
numbers.
I do not use Polyspan on the all-wood
surfaces of the fuselage, fin, and rudder.
Japanese tissue, in your choice of color(s),
will do the job fine.
Give all the exposed wood surfaces two
coats of 50%-thinned nitrate dope with the
requisite sanding afterward. Then apply the
tissue using either thinned dope or only
38 MODEL AVIATION
03sig2.QXD 1/24/08 2:04 PM Page 38thinner. Finish the job with four coats of the
thinned dope.
Final Assembly: Install the nose skid using
epoxy cement. (3M Scotch-Weld is fine too.)
Glue the fin to the bottom of the fuselage
(Ambroid or cyanaocrylate are okay here as
well), making certain that it is aligned
perfectly on the fuselage centerline.
Properly align the wing and tail with
respect to the fuselage centerline. They must
be “square” (at right angles) to the fuselage
centerline and retain that relationship every
time they are installed.
Short (1/4 to 1/2 inch) lengths of 1/16-inchdiameter
dowels, split lengthwise and glued
to the undersides of the wing LE and TE and
stabilizer TE, will serve this purpose. (The
DT horn’s alignment key will do the job at
the stabilizer LE.) Positioned on the wing and
stabilizer so they rest against the fuselage
sides assures the proper alignment.
With the wing, stabilizer, timer, and
tracker/transmitter installed, add ballast to the
cavities/compartments at the front of the
fuselage to locate the balance point at the
designated 56% of the wing’s root chord.
Trimming and Testing: If you have a
locator/transmitter, install it now!
As shown on the plans, my models have
flown best when ballasted to balance at 56%
of the wing root chord. Insert a dummy
release pin to lock the timer, DT, and rudder
lines while doing the initial hand-launched
glide tests. These are aimed at achieving a
straight-ahead glide path using rudder trim
only.
Simultaneously adjust for a flat, nostall/
no-dive glide path by shimming the
stabilizer LE or TE as required. Ballasting the
nose or tail to shift the CG fore or aft a bit can
also be helpful during this tow-mode stage of
trimming.
During glide-mode trimming, keep the
timer locked with the dummy release pin, but
release the rudder line. Right-hand glide
circles are basically the norm, and repetitive
hand glides and rudder adjustments will yield
the desired flat, wide turn. Now begin the tow
testing.
Wind is both your friend and your foe
during the tow. With too much wind you risk
damaging the model, and with too little wind
you may not be able to run fast enough or far
enough (like me at my advanced age) to
maintain airspeed and gain altitude.
Assuming there is a moderate breeze (5-
10 mph), begin the tow tests with the
towhook screw set 3/8 inch ahead of the
balance point and the timer set for 30
seconds. Secure the timer and rudder lines
with the release pin, and secure the DT line to
the timer.
With the towline ring in place against the
towhook screw, have your helper hold the
SoarCerer at a nose-high 45° angle facing
directly into the wind. He/she should take a
step or two with you as you begin to run into
the wind and release the model gently in an
upward direction.
In a strong wind, you may find it
necessary to run toward the model as it rises
rather than away from it, to avoid imposing
possibly damaging excessive loads on it.
Move the towhook screw forward for windy
conditions and aft for calmer weather. The
difference of 1/8-1/4 inch either way should be
enough to make a noticeable change. The
Glider should tow straight ahead without
veering appreciably to either side.
When released (you have to slack off
abruptly on the towline), the SoarCerer
should settle into a flat and wide glide circle.
These two desired flight paths will be
achieved only through repetitive testing and
trimming. Practice, practice, practice!
The SoarCerer has been designed to meet
the FAI requirement of a maximum 279
square inches of projected wing and stabilizer
area for the F1H event. It can compete in the
National Free Flight Society’s Classic Glider
event too.
The F1H rules specify a minimum weight
of 220 grams. If you have to add ballast to
meet that requirement, be certain to locate the
extra weight/ballast at the balance point to
avoid disrupting your carefully achieved
flight trim and remove it when flying in
Classic Glider.
We need to acknowledge those unsung
heroes and heroines of Towline Glider
flying—those who wait patiently with us for
the wind and lift to be just right before
launching the darn things. We could not do it
without you! MA
Jean “JG” Pailet
April-September: 456 Florencia Pl.
Melville NY 11747
(631) 549-1485
October-March: 1326 Santa Rosa Ct.
Lady Lake FL 32159
(352) 259-3963
Sources:
Carbon fiber, epoxy:
Aerospace Composite Products
(800) 811-2009
www.acp-composites.com
CST—The Composites Store
(800) 338-1278
www.cstsales.com
Towline supplies, carbon fiber:
Bradley Model Products
(407) 277-9132
www.members.aol.com/bmp4carbon
Timers, gizmos, gadgets:
Campbell’s Custom Kits
(765) 683-1749
www.campbellscustomkits.com
FAI Model Supply
(570) 882-9873
www.faimodelsupply.com
Polyspan:
Campbell’s Custom Kits
Larry Davidson
(540) 721-4563
[email protected]
FAI Model Supply
Retrieval systems:
Walston Retrieval Systems
(770) 434-4905
www.walstonretrieval.com
40 MODEL AVIATION
03sig2.QXD 1/24/08 1:31 PM Page 40