Genie Redux - 2012/03

Nearly every time I rub the old lamp I found years ago,
another Genie pops out! The last Genie was in 2001, and
was also known as the Classic 320 (September 2002 MA).
The Genie Redux made its fi rst appearance in 2004. Previous
incarnations were in 1999, 1998, 1997 (July 1997 MA), and 1995.
Progress in design is usually the result of inspiration
(the pylon and high thrustline concepts) or innovation
(incremental improvements in existing concepts). The
Genie Redux design history falls into the latter category.
It is an evolution extending through more than 15
years. Each incremental change was an attempt to
improve—aerodynamically and/or structurally—
on the predecessor. There were no giant leaps
forward. Progressive steps of improvement and
refi nement were the intent and result.
The airplanes were simple, straightforward
designs with no auto-surfaces! All proved
to be competitive with their high-tech
contemporaries. Technology played a
part only in the use of carbon and
Kevlar materials for some structural
components.
Genie
Redux
An award-winning design
several years in the making
by J.G. Pailet
[email protected]
The author sends the Genie into fl ight in Pensacola FL.
www.ModelAviation.com MARCH 2012 Model Aviation 4142 Model Aviation MARCH 2012 www.ModelAviation.com
the lack of sheeting and to relocate
the turbulator spars accordingly. The
following text assumes you choose the
D-box structure.
The main spar is a balsa/carbon fi ber/
balsa “sandwich,” using epoxy glue as
the bonding agent. Bond the sandwich
under pressure, ideally using a vacuumbag
process.
The inboard end of the main spar
should extend ¼ inch past the centerline
to allow for the required angular lap
joint when the main wing panels are
later joined together.
For the inboard/main wing panels,
the spar and aft end of the forward rib
sections must be elevated 3/32 inch above
the plans during construction to provide
for the desired undercamber and bottom
sheeting thickness. Because the tip airfoil
has no undercamber, the outer wing
panel spars, while elevated the full 3/32
inch at the polyhedral joint, are raised
only enough to accommodate the lower
sheeting at the outboard ends.
The front end of the forward ribs must
be elevated to allow for the sheeting,
and the front ends of the aft ribs must
be raised to provide undercamber and to
mate properly with the lower sheeting.
Before assembly, cut grooves in the
LEs to accept the .040 carbon-fi ber rods
which will be inserted later. The grooves
should be 1/32 inch above the lower
surface of the LE to provide the correct
Phillips entry shape to the LE when it is
later carved and sanded to conform to
the rib airfoil contour.
Notches should be cut into the TEs to
accept the aft ends of the ribs. Build the
four wing panels independently, using
your favorite adhesive. I use odorless
CA, because of a personal allergic
reaction to regular CA.
Note: the inboard dihedral and
outboard polyhedral ribs should be set
at a slight angle to accommodate the
required dihedral and polyhedral when
Genie Redux
Rick Crosslin created a wind
tunnel which allows children
to test fl ying objects they have
created.
The carbon-fi ber brace on the main spar of the wing and dihedral joint
provides for a rigid structure with little weight penalty.
The stabilizer structure shows the carbon-fi ber cap strips installed.
The front of the fuselage has an opening
for the timer.
I must share credit for the success of
these models with my regular design and
engineering consultants: Don Broggini,
John Carbone, Bob Hatscheck, and
Joe Mollendorf. Thanks, guys! Another
thank-you goes to Jim O’Reilly for the
excellent computer-generated plans.
The Genie Redux was one of the
National Free Flight Society’s 2010
Models of the Year.
The Wing
As depicted on the plans, the
wing features a sheet balsa-covered
forward portion to form a standard
D-box structure. However, the
underlying turbulator-spar structure has
demonstrated its strength adequacy in
earlier designs.
I prefer the sheeted version for its
cleaner aerodynamic characteristics. You
will save some weight by eliminating
the sheeting, but be sure to alter the
forward rib profi le to compensate for
Photos by the authorwww.ModelAviation.com MARCH 2012 Model Aviation 43
joined together. Also note that the wing
tips are set at a 45° angle.
As the drawing indicates, the wing and
stabilizer ribs have vent holes in them
to equalize the pressure throughout
the wing. When the model is sitting
out on a fi eld exposed to the sun on
a hot day, the internal air pressure
within the various rib bays can increase
dramatically and erratically, potentially
causing the surfaces to warp. Vent holes
help alleviate that problem.
I make a small, 1/32-inch diameter
hole at each wing and stabilizer tip,
either through the covering or through
the tip itself, to vent any excess pressure
to the outside.
After all of the half ribs, full ribs, and
diagonal ribs are in place, install the 1/16
x 1/8 hard balsa spars. As with the main
spar, these two spars should extend ¼
inch inboard past the centerline.
All outer panel spars—main and
turbulator—should extend inward
past the polyhedral joint far enough to
contact the main panels’ outermost half
rib. The four wing panels are now ready
to be joined together.
The centerline dihedral joint is the
most critical because it sustains the
highest loads, so it is reinforced on its
front face with a 1/16-plywood gusset
and two .050 carbon-fi ber rods on its
rear face.
It is important that the gusset and
rods taper and vary in length as shown
to avoid a localized area of stress
concentration. Join the two panels by
gluing together the mating surfaces of
the two centerline ribs and the mating
angular surfaces of the main and
turbulator spars to form scarf joints. Use
Another shot of David Wigley’s Westland Wyvern. This model photographs great!
The F1J Genie Redux is in the foreground and the 1/2A version is in the rear.
slow-drying epoxy to ensure that you
have time to properly align the wing
panels before the glue sets.
After the glue sets, install the plywood
gusset by cutting 1/16 inch off the aft ends
of the forward central area ribs to create
a slot to accommodate the gusset and
allow it to rest against the forward face
of the main spar.
Similarly, 1/16-inch diameter holes
must be made in the forward ends of
the rear ribs to permit you to insert .050
carbon-fi ber rods against the rear face
of the main spar. When the gusset and
rods are glued into place, reinforcing the
center dihedral joint is complete.
The polyhedral joints primarily
depend upon the angular-cut scarf joints
of the main and turbulator spars for
strength, coupled with the face-to-face
mating of the two W1A ribs. Again, I44 Model Aviation MARCH 2012 www.ModelAviation.com
Genie Redux
recommend using slow-drying epoxy
to allow time to align the respective
inboard and outboard wing panels.
Additional strengthening is achieved
by gluing the inward-extended ends of
the spars to the most-outboard half ribs
of the main wing panels. You should
now have a one-piece, assembled wing,
ready for the LE .040 carbon-fi ber rod
and the D-box sheeting.
The carbon-fi ber rod is installed as
one piece from polyhedral joint to
polyhedral joint, because the relatively
shallow dihedral angle allows it to be
bent without breaking at the centerline,
affording extra strength at the
centerline joint.
The outboard wing panels use
separate lengths of carbon-fi ber rod. The
LE is not yet carved to its fi nal crosssectional
shape; it is still a rectangle in
cross section. The D-box sheeting uses
a simple butt joint at the dihedral and
polyhedral joints.
It is best to install the sheeting on the
inboard wing panels fi rst. I recommend
that the top sheeting be installed fi rst
because its curvature makes it more
diffi cult to ensure proper adhesion to
all the LE, rib, and spar surfaces and
edges. After the top sheeting is tackglued
in place, turn the wing over and
thoroughly apply glue to the mating
edges and joints.
The bottom sheeting is slightly easier
to install because it is fl at and has no
curvature. However, once it is installed,
the D-box is a closed entity and you
can’t get back inside to touch up any
glue joints.
Slow-drying epoxy glue will allow
you time to be certain that you have
properly applied the glue to mating
edges of the ribs, sheeting, and main
spar. After installing the sheeting on the
wing panels, carve and sand the LE to its
fi nished shape so that it blends into the
full airfoil contour.
All aft ribs—particularly the
diagonals—should now be capped with
carbon-fi ber strips. As noted on the
plans, these cap strips (except for the
diagonals) should extend forward onto
the D-box sheeting and aft onto the TE.
An optional step in the wing
construction can be adding a length of
.020 carbon-fi ber rod along the upper
edge of each wingtip, affording damage
protection from nicks and bruises that
occur during normal fl ying activities.
Horizontal Stabilizer
The horizontal stabilizer utilizes a
balsa/carbon fi ber/balsa sandwich-type
spar similar to the wing and a .030
carbon-fi ber rod imbedded into the
LE. Otherwise its construction is fairly
conventional.
As with the wing, the tips are set at a
45° angle and all of the ribs (except the
1/32-inch half ribs) have carbon-fi ber cap
strips. Except for the diagonals, the cap
strips extend onto both the LE and TE.
Installation of the DT-horn/stabilizer
key completes the construction. The 1/64
plywood DT hold-down pad is added
after the stabilizer is covered.
Fin, Vertical Tail, Sub Fin, and Rudder
These are all simple 3/16 sheet balsa
fl at surfaces. The LE of the fi n, sub
fi n, and rudder should be sanded to
a rounded cross section and their aft
portions symmetrically tapered to a 1/32-
inch thickness.
Add a 1/64 plywood reinforcement strip
to the bottom portion of the rudder.
This also serves as a hard pad for the
rudder-adjusting screws. The adjusting
mechanism can be
homemade or purchased
from FAI Model Supply.
Use any type of simple
hinges to attach the
rudder to the fi n.
The vertical tail
assembly is supported
in its attachment to the
fuselage by a length of
1/8-diameter hardwood
dowel extending through
the fuselage. A hole drilled
through the length of this
dowel also serves as the
mount for the tail skid.
The .045-diameter tail
skid is imbedded into the
LE of the sub fi n to help
secure to it the fuselage.
The polyhedral wing
joint has carbon-fi ber
cap strips on the ribs for
added strength.
Carbon fi ber is used on the LE and tip
contour. This shows the framed-up wing’s
outer panel.www.ModelAviation.com MARCH 2012 Model Aviation 45
Pylon and Wing Mount
As are the vertical tail surfaces, the
pylon is a simple, fl at-sided, 3/16 sheetbalsa
structure. It incorporates hardwood
LEs and TEs extending into the fuselage
to secure and stabilize it and to anchor
the wing attachment hooks, which are
bent from 1/16-diameter music wire. The
LEs and TEs are rounded and tapered.
The bottom of the pylon attaches directly
to the top of the fuselage (which serves
as the 0° reference line for the engine
downthrust and wing and stabilizer
incidence angles).
The top of the pylon should be at
1° positive incidence. The wing-mount
platform is pieced together with short
lengths of 1/16 hard sheet balsa with the
grain running laterally. Carbon-fi ber
rods at the LE, TE, and under the wing’s
main spar help stiffen it laterally.
Soft balsa fi llets stabilize its
attachment to the pylon, and 1/16-square
hard balsa rails stiffen it longitudinally.
The rails also serve to stabilize the
wing laterally by matching its dihedral
angle. The pylon is not mounted on the
fuselage until the model is completely
fi nished because its fore and aft position
ultimately determines the model’s
balance point location.
Fuselage
The fuselage top, bottom, and both
sides are identical in shape, yielding an
elongated box of square cross sections,
diminishing in size from nose to tail. The
internal formers are 1/16 sheet balsa with
grain alternating in diagonal directions.
The fuselage box is built with the
corners open to allow installation of
carbon-fi ber rods in each of the corners.
A small balsa plug with an internal
2-56 T-nut fi lls the open aft end of the
fuselage, affording a simple means of
adding ballast if needed.
Completing the forward end of the
fuselage is more complex. My engine
choice is the Cyclon. If you opt for
another, you’ll have to adapt the
engine-mounting arrangement to suit
your own needs.
Cut a soft balsa block with its grain
running fore and aft (longitudinally)
to fi t inside the open front end of the
fuselage. Sand its front face to provide the
specifi ed 3° of downthrust and 3° of left
thrust for a right-power fl ight pattern.
Cut a round disc of 1/8 fi ve-ply
plywood with a diameter to match
the inside width of the front end of
the fuselage. Install 2-56 T-nuts in the
plywood disc/fi rewall to mate with the
engine’s mounting-hole pattern.
Drill a 1/16-inch diameter hole vertically
through this plywood fi rewall to allow
you to install the music-wire forward
skid. Recess the angled front face of the
balsa block to accept the heads of the
T-nuts and glue the fi rewall fl ush against
the face of the square balsa block using
epoxy cement. I recommend 3M Scotch-
Weld Epoxy Adhesive DP-460.
Install the fi rewall/block assembly
inside the front end of the fuselage
box with the front face of the fi rewall
fl ush with the front edges. (Because of
the downthrust and side thrust angles,
they will require slight trimming.) The
fuselage’s front portion must be carved
and sanded to create the transition from
the square cross section of the fuselage
box to the round disc of the fi rewall.
The next step is installing the four
.050 carbon-fi ber rods in the open
corners of the fuselage box. These rods
should initially extend forward an inch or
two beyond the front face of the fi rewall.
Glue the rods in place in all four
corners of the fuselage box from the aft
end of the fuselage to the forward area
of the timer location. Make grooves in
the balsa block and fi rewall so that the
carbon-fi ber rods can be bent inward
to set in the grooves and blend into
the transition from a square to a round
fuselage cross section.
Wrapping a rubber band tightly around
the protruding ends of the rods will hold
them in place while you glue them into
the grooves. This is another good place to
use the DP-460 epoxy glue.
After the glue has set, the carbonfi
ber rods can be cut off fl ush with the
front face of the fi rewall. For additional
security, you can also run a ½-inch or
longer #4 fl at-head wood screw through
the center of the fi rewall and epoxy it
into the balsa block.
Complete the engine mount
construction by applying a layer of
1-ounce fi berglass cloth over the fi rewall
and running aft at least to the timerlocation
area.
Reinforce the side of the fuselage
where you will mount the timer with
a layer of 1/32 plywood. A simple, twofunction
(engine run and dethermalizer)
mechanical timer, such as those available
from Texas Timers, will do the job
because this is a locked-up, non-autofunction
model. I emphasize mechanical
because I don’t think burning-wick/fusetype
timers are accurate or safe.
Covering and Finishing
Polyspan is the only covering material
I use on wing and tail surfaces. It
provides the best characteristics of
Japanese tissue (enhancing a structure’s
torsional rigidity) with only a small
weight penalty. It is durable and
puncture resistant.
The Cyclon engine is mounted with 3° of downthrust and 3° of left thrust, for a right-power
fl ight pattern.46 Model Aviation MARCH 2012 www.ModelAviation.com
Genie Redux
Unwanted warps can be removed
and trim adjustments made using a
heat gun; the surface retains the set you
want. Polyspan’s only shortcoming is
that it only comes in one not-so-vivid
color: washed-out white. However,
inventive applications of colored tissue,
with scarcely any weight penalty, can
yield some colorful results.
Apply at least two coats of clear
dope, thinned 50%, to all surfaces
and edges of the structures that will
contact the covering material. Sand
lightly after each coat. I prefer to use
nitrate dope throughout the entire
covering process, with a coat of fuel
proofer as the fi nal step.
Polyspan can now be applied and
glued to the respective structures’
surfaces and edges with thinned dope.
The Polyspan does not need to extend
forward onto the D-box sheeting
more than ½ inch. A covering iron set
at roughly 300° will help bend the
Polyspan around any small radii such
as the wingtips, stabilizer tips, and the
stabilizer LE as you apply it.
When complete, heat shrink the
Polyspan with a hot iron to remove
wrinkles and tighten the skin. Give all
the covered surfaces two coats of 50%
thinned, clear nitrate dope.
Now, get artistic with colorful
trimming. Applied with thinner, adding
colorful Japanese tissue can make your
model beautiful and visible against
the sky and earth. Apply two coats of
50% thinned dope to all covered and
decorated surfaces followed by a fi nal
coat of your favorite fuel proofer.
I don’t use Polyspan on the all-wood
surfaces of the fuselage, pylon and wing
mount, fi n and rudder, and sub fi n.
Japanese tissue in your choice of colors
and design will do the job. Give the
exposed wood surfaces at least two coats
of 50% thinned dope with the requisite
light sanding afterwards, then apply the
tissue using thinned dope. Finish with
four more coats of thinned dope and a
coat of fuel proofer.
Final Assembly
The fi nal steps include attaching the
nose skid, vertical tail and rudder, sub
fi n, stabilizer platforms, and pylon/
wing platform.
Glue the nose skid into the hole in
the fi rewall with DP-460 epoxy after
roughening the upper portion’s surface
with a fi le or grinding wheel to ensure
good glue adhesion. Roughen the upper
portion of the tailskid wire and glue
it into the hole in the dowel that will
support the vertical tail and rudder.
When gluing the sub fi n and dowel
to the fuselage, take care to ensure that
they are vertical and perfectly aligned
with its centerline. Position the stabilizer
platform as shown on the plans and glue
it directly to the top of the fuselage.
Glue a small, hard balsa pad to support
the stabilizer’s TE onto the fuselage top.
After drilling a hole into the vertical
tail to accept the protruding support
dowel, it can be glued to the top of
the fuselage. Proper alignment along
the fuselage centerline is critical. The
rudder-adjusting mechanism is also
installed during this process.
Mount the timer in its fuselage bay
and glue short lengths (roughly 2 inches)
of 1/16 OD aluminum tubing onto the
fuselage to act as guides for the DT line.
I glue a short length of large-diameter,
carbon-fi ber tubing under the front of
the fuselage to hold my bladder-type
pressure fuel tank.
Mount the engine to the fi rewall and
the remote fuel cut-off to the engine.
Now comes the tricky part—correctly
locating the pylon on the fuselage to
obtain the desired balance-point location.
The pylon position shown on the
plans is intended for heavier, ball-bearing
engines such as the Cyclon, A.D.,
Shuriken, and CS. For lighter, plainbearing
engines (TDs, Stels, VAs, and
AMEs), the pylon goes farther aft to
attain the desired 85% to 90% balancepoint
location.
To obtain the correct pylon position,
the model must be fully assembled
in ready-to-fl y condition. In addition
to engine, propeller, tank, and timer,
you should simulate the weight of the
airborne tracker/locater transmitter by
taping roughly 4 grams of weight to the
Completed wing structures for the 345 (F1J) and 325 (1/2A) models.www.ModelAviation.com MARCH 2012 Model Aviation 47
TE of the pylon (where the transmitter
will be when fl ying). With the stabilizer
in place, you can begin the trial-anderror
process of locating the proper
pylon position.
Begin by attaching the wing to the top
of the fuselage directly behind the engine
with rubber bands. Lay the inverted
pylon/wing mount (with dummy locater
transmitter weight attached) on top of
the wing so the forward edge of the wing
mount is aligned with the wing’s LE.
Support the whole works under
each side of the wing at a point threequarters
forward of the wing TE (which
will be within the 85% to 90% range).
Shifting the wing fore and/or aft,
balance the model so that the fuselage
is horizontal, determining the correct
pylon position.
Measure and mark that place on the
top of the fuselage, disassemble all of
the components (wing, stabilizer, engine,
etc.), and permanently install the pylon
on the fuselage in its correct location.
The pylon’s hardwood LE and TE are
intended to extend into the fuselage and
attach to the balsa block in the front and
the fuselage bottom in the back. Cut
openings in the fuselage top with the
forward one extending down into the
balsa block.
Install a 1/16 plywood pad ½-inch wide
inside the fuselage across its width to
provide a secure attachment for the
pylon’s TE. Cut a slot in one side of the
fuselage at the proper location and slide
the plywood pad in and glue it in place.
Anchor the pylon’s TF with a small
wood screw through the pad.
As with the vertical tail and sub fi n,
aligning the pylon on the fuselage’s
centerline is critical. Mount a small
tube at the pylon’s TE to hold your
transmitter and a couple of small soft
balsa blocks to fair/blend its forward end
into the pylon-fuselage joint.
Align the wing and stabilizer at right
angles to the fuselage centerline each
time they are mounted. Short (¼- to
½-inch) lengths of 1/16-inch dowels,
split lengthwise and glued to the
undersides of the wing LE and TE and
the stabilizer TE will serve this purpose.
(The stabilizer DT horn’s alignment
key will do the job at the stabilizer’s
LE.) Positioning them on the wing and
stabilizer so that they rest against the
fuselage sides ensures proper alignment.
Trimming and Testing
Perform all hand-glide and power
testing with the airplane in its fi nal
fl ight confi guration (propeller, tank, and
transmitter installed). I use my owndesign
propellers, which are available
from Mike Hazel (see “Sources”).
Constructed from carbon fi ber, they
come in fi xed- and folding-blade
versions (blades for the folders are from
Mike; hubs for the folders are from me).
Their basic size is 63/8 x 2 for F1J/.061
use. For ½A/.049 use, I cut the diameter
to 55/8. For more readily available
commercial propellers, most fl iers use
the APC 6 x 2 or 5.7 x 3 or 5.5 x 2.
The Genie Redux is intended to fl y
a right/right-power/glide fl ight pattern.
Initial hand gliding should ensure a
moderate turn with no severe dive or
stall tendencies. Adjust the glide turn
using stabilizer tilt (right tip up for
right turn).
Add ballast to the nose or tail to
correct for a stall or dive, respectively.
These preliminary adjustments should
be considered just that: preliminary.
Fine-tune the Genie after the proper
power pattern is established.
Engine runs on the fi rst few powered
fl ights should not exceed 3 seconds.
Use a short DT setting. The launch
angle should be nearly vertical and its
direction should be slightly to the right
of the wind.
Adjust the power pattern during
these initial, short-engine-run test fl ights
by varying the incidence angle of the
stabilizer: LE up to correct looping
tendencies; TE up to correct diving
tendencies.
Experimenting with washin and/or
washout on the inboard wing panels
is the usual way to correct or induce
rolling tendencies. I prefer washout to
washin because the drag created by any
signifi cant amount of washin can induce
a turning effect that overpowers the
intended rolling effect.
Conversely, any drag and turning
effects from washout tend to work in
concert with the intended rolling effect.
Progressively increase the engine-run
duration by 1-second increments to
the maximum (generally 7 seconds at
most fi elds in the East and Midwest).
Make concurrent trim adjustments as
necessary to attain the desired power
pattern of a nearly vertical climb with
a three-fourths to full turn spiral from
launch to engine cutoff.
As you become more secure in the
power pattern’s safety and perfection,
increase the glide duration and observe
the glide pattern. The goal is a clockwise
circle with a slow, fl at, nearly stalled
glide attitude. Adjustments to the
stabilizer tilt and ballasting to vary the
CG are the means to the desired end.
Wing washout and/or washin can be
used to control the glide’s lateral fl atness.
Make adjustments in small increments.
Adjusting for glide trim will likely
affect power trim. Stabilizer tilt
changes may affect decalage, which
will probably affect the power pattern.
Begin the fi ne-tuning, tweaking, and
compromising to obtain the optimum
balance between the powered and
gliding fl ight cycles.
I hope that you will be as satisfi ed
with your Genie Redux as I have been
with mine.
—J.G. Pailet
[email protected]
SOURCES:
Aerospace Composite Products
(800) 811-2009
www.acpsales.com
The Composites Store
(800) 338-1278
www.cstsales.com
Larry Davidson
(540) 721-4563
[email protected]
Walston Retrieval Systems
(770) 434-4905
www.walstonretrieval.com
Mike Hazel
(503) 364-8593
[email protected]
Cyclon Engines
(530) 757-6058
[email protected]
Texas Timers
(423) 282-6423
www.texastimers.com
Campbell’s Custom Kits
(765) 683-1749
[email protected]
FAI Model Supply
(570) 882-9873
www.faimodelsupply.com

Nearly every time I rub the old lamp I found years ago,
another Genie pops out! The last Genie was in 2001, and
was also known as the Classic 320 (September 2002 MA).
The Genie Redux made its fi rst appearance in 2004. Previous
incarnations were in 1999, 1998, 1997 (July 1997 MA), and 1995.
Progress in design is usually the result of inspiration
(the pylon and high thrustline concepts) or innovation
(incremental improvements in existing concepts). The
Genie Redux design history falls into the latter category.
It is an evolution extending through more than 15
years. Each incremental change was an attempt to
improve—aerodynamically and/or structurally—
on the predecessor. There were no giant leaps
forward. Progressive steps of improvement and
refi nement were the intent and result.
The airplanes were simple, straightforward
designs with no auto-surfaces! All proved
to be competitive with their high-tech
contemporaries. Technology played a
part only in the use of carbon and
Kevlar materials for some structural
components.
Genie
Redux
An award-winning design
several years in the making
by J.G. Pailet
[email protected]
The author sends the Genie into fl ight in Pensacola FL.
www.ModelAviation.com MARCH 2012 Model Aviation 4142 Model Aviation MARCH 2012 www.ModelAviation.com
the lack of sheeting and to relocate
the turbulator spars accordingly. The
following text assumes you choose the
D-box structure.
The main spar is a balsa/carbon fi ber/
balsa “sandwich,” using epoxy glue as
the bonding agent. Bond the sandwich
under pressure, ideally using a vacuumbag
process.
The inboard end of the main spar
should extend ¼ inch past the centerline
to allow for the required angular lap
joint when the main wing panels are
later joined together.
For the inboard/main wing panels,
the spar and aft end of the forward rib
sections must be elevated 3/32 inch above
the plans during construction to provide
for the desired undercamber and bottom
sheeting thickness. Because the tip airfoil
has no undercamber, the outer wing
panel spars, while elevated the full 3/32
inch at the polyhedral joint, are raised
only enough to accommodate the lower
sheeting at the outboard ends.
The front end of the forward ribs must
be elevated to allow for the sheeting,
and the front ends of the aft ribs must
be raised to provide undercamber and to
mate properly with the lower sheeting.
Before assembly, cut grooves in the
LEs to accept the .040 carbon-fi ber rods
which will be inserted later. The grooves
should be 1/32 inch above the lower
surface of the LE to provide the correct
Phillips entry shape to the LE when it is
later carved and sanded to conform to
the rib airfoil contour.
Notches should be cut into the TEs to
accept the aft ends of the ribs. Build the
four wing panels independently, using
your favorite adhesive. I use odorless
CA, because of a personal allergic
reaction to regular CA.
Note: the inboard dihedral and
outboard polyhedral ribs should be set
at a slight angle to accommodate the
required dihedral and polyhedral when
Genie Redux
Rick Crosslin created a wind
tunnel which allows children
to test fl ying objects they have
created.
The carbon-fi ber brace on the main spar of the wing and dihedral joint
provides for a rigid structure with little weight penalty.
The stabilizer structure shows the carbon-fi ber cap strips installed.
The front of the fuselage has an opening
for the timer.
I must share credit for the success of
these models with my regular design and
engineering consultants: Don Broggini,
John Carbone, Bob Hatscheck, and
Joe Mollendorf. Thanks, guys! Another
thank-you goes to Jim O’Reilly for the
excellent computer-generated plans.
The Genie Redux was one of the
National Free Flight Society’s 2010
Models of the Year.
The Wing
As depicted on the plans, the
wing features a sheet balsa-covered
forward portion to form a standard
D-box structure. However, the
underlying turbulator-spar structure has
demonstrated its strength adequacy in
earlier designs.
I prefer the sheeted version for its
cleaner aerodynamic characteristics. You
will save some weight by eliminating
the sheeting, but be sure to alter the
forward rib profi le to compensate for
Photos by the authorwww.ModelAviation.com MARCH 2012 Model Aviation 43
joined together. Also note that the wing
tips are set at a 45° angle.
As the drawing indicates, the wing and
stabilizer ribs have vent holes in them
to equalize the pressure throughout
the wing. When the model is sitting
out on a fi eld exposed to the sun on
a hot day, the internal air pressure
within the various rib bays can increase
dramatically and erratically, potentially
causing the surfaces to warp. Vent holes
help alleviate that problem.
I make a small, 1/32-inch diameter
hole at each wing and stabilizer tip,
either through the covering or through
the tip itself, to vent any excess pressure
to the outside.
After all of the half ribs, full ribs, and
diagonal ribs are in place, install the 1/16
x 1/8 hard balsa spars. As with the main
spar, these two spars should extend ¼
inch inboard past the centerline.
All outer panel spars—main and
turbulator—should extend inward
past the polyhedral joint far enough to
contact the main panels’ outermost half
rib. The four wing panels are now ready
to be joined together.
The centerline dihedral joint is the
most critical because it sustains the
highest loads, so it is reinforced on its
front face with a 1/16-plywood gusset
and two .050 carbon-fi ber rods on its
rear face.
It is important that the gusset and
rods taper and vary in length as shown
to avoid a localized area of stress
concentration. Join the two panels by
gluing together the mating surfaces of
the two centerline ribs and the mating
angular surfaces of the main and
turbulator spars to form scarf joints. Use
Another shot of David Wigley’s Westland Wyvern. This model photographs great!
The F1J Genie Redux is in the foreground and the 1/2A version is in the rear.
slow-drying epoxy to ensure that you
have time to properly align the wing
panels before the glue sets.
After the glue sets, install the plywood
gusset by cutting 1/16 inch off the aft ends
of the forward central area ribs to create
a slot to accommodate the gusset and
allow it to rest against the forward face
of the main spar.
Similarly, 1/16-inch diameter holes
must be made in the forward ends of
the rear ribs to permit you to insert .050
carbon-fi ber rods against the rear face
of the main spar. When the gusset and
rods are glued into place, reinforcing the
center dihedral joint is complete.
The polyhedral joints primarily
depend upon the angular-cut scarf joints
of the main and turbulator spars for
strength, coupled with the face-to-face
mating of the two W1A ribs. Again, I44 Model Aviation MARCH 2012 www.ModelAviation.com
Genie Redux
recommend using slow-drying epoxy
to allow time to align the respective
inboard and outboard wing panels.
Additional strengthening is achieved
by gluing the inward-extended ends of
the spars to the most-outboard half ribs
of the main wing panels. You should
now have a one-piece, assembled wing,
ready for the LE .040 carbon-fi ber rod
and the D-box sheeting.
The carbon-fi ber rod is installed as
one piece from polyhedral joint to
polyhedral joint, because the relatively
shallow dihedral angle allows it to be
bent without breaking at the centerline,
affording extra strength at the
centerline joint.
The outboard wing panels use
separate lengths of carbon-fi ber rod. The
LE is not yet carved to its fi nal crosssectional
shape; it is still a rectangle in
cross section. The D-box sheeting uses
a simple butt joint at the dihedral and
polyhedral joints.
It is best to install the sheeting on the
inboard wing panels fi rst. I recommend
that the top sheeting be installed fi rst
because its curvature makes it more
diffi cult to ensure proper adhesion to
all the LE, rib, and spar surfaces and
edges. After the top sheeting is tackglued
in place, turn the wing over and
thoroughly apply glue to the mating
edges and joints.
The bottom sheeting is slightly easier
to install because it is fl at and has no
curvature. However, once it is installed,
the D-box is a closed entity and you
can’t get back inside to touch up any
glue joints.
Slow-drying epoxy glue will allow
you time to be certain that you have
properly applied the glue to mating
edges of the ribs, sheeting, and main
spar. After installing the sheeting on the
wing panels, carve and sand the LE to its
fi nished shape so that it blends into the
full airfoil contour.
All aft ribs—particularly the
diagonals—should now be capped with
carbon-fi ber strips. As noted on the
plans, these cap strips (except for the
diagonals) should extend forward onto
the D-box sheeting and aft onto the TE.
An optional step in the wing
construction can be adding a length of
.020 carbon-fi ber rod along the upper
edge of each wingtip, affording damage
protection from nicks and bruises that
occur during normal fl ying activities.
Horizontal Stabilizer
The horizontal stabilizer utilizes a
balsa/carbon fi ber/balsa sandwich-type
spar similar to the wing and a .030
carbon-fi ber rod imbedded into the
LE. Otherwise its construction is fairly
conventional.
As with the wing, the tips are set at a
45° angle and all of the ribs (except the
1/32-inch half ribs) have carbon-fi ber cap
strips. Except for the diagonals, the cap
strips extend onto both the LE and TE.
Installation of the DT-horn/stabilizer
key completes the construction. The 1/64
plywood DT hold-down pad is added
after the stabilizer is covered.
Fin, Vertical Tail, Sub Fin, and Rudder
These are all simple 3/16 sheet balsa
fl at surfaces. The LE of the fi n, sub
fi n, and rudder should be sanded to
a rounded cross section and their aft
portions symmetrically tapered to a 1/32-
inch thickness.
Add a 1/64 plywood reinforcement strip
to the bottom portion of the rudder.
This also serves as a hard pad for the
rudder-adjusting screws. The adjusting
mechanism can be
homemade or purchased
from FAI Model Supply.
Use any type of simple
hinges to attach the
rudder to the fi n.
The vertical tail
assembly is supported
in its attachment to the
fuselage by a length of
1/8-diameter hardwood
dowel extending through
the fuselage. A hole drilled
through the length of this
dowel also serves as the
mount for the tail skid.
The .045-diameter tail
skid is imbedded into the
LE of the sub fi n to help
secure to it the fuselage.
The polyhedral wing
joint has carbon-fi ber
cap strips on the ribs for
added strength.
Carbon fi ber is used on the LE and tip
contour. This shows the framed-up wing’s
outer panel.www.ModelAviation.com MARCH 2012 Model Aviation 45
Pylon and Wing Mount
As are the vertical tail surfaces, the
pylon is a simple, fl at-sided, 3/16 sheetbalsa
structure. It incorporates hardwood
LEs and TEs extending into the fuselage
to secure and stabilize it and to anchor
the wing attachment hooks, which are
bent from 1/16-diameter music wire. The
LEs and TEs are rounded and tapered.
The bottom of the pylon attaches directly
to the top of the fuselage (which serves
as the 0° reference line for the engine
downthrust and wing and stabilizer
incidence angles).
The top of the pylon should be at
1° positive incidence. The wing-mount
platform is pieced together with short
lengths of 1/16 hard sheet balsa with the
grain running laterally. Carbon-fi ber
rods at the LE, TE, and under the wing’s
main spar help stiffen it laterally.
Soft balsa fi llets stabilize its
attachment to the pylon, and 1/16-square
hard balsa rails stiffen it longitudinally.
The rails also serve to stabilize the
wing laterally by matching its dihedral
angle. The pylon is not mounted on the
fuselage until the model is completely
fi nished because its fore and aft position
ultimately determines the model’s
balance point location.
Fuselage
The fuselage top, bottom, and both
sides are identical in shape, yielding an
elongated box of square cross sections,
diminishing in size from nose to tail. The
internal formers are 1/16 sheet balsa with
grain alternating in diagonal directions.
The fuselage box is built with the
corners open to allow installation of
carbon-fi ber rods in each of the corners.
A small balsa plug with an internal
2-56 T-nut fi lls the open aft end of the
fuselage, affording a simple means of
adding ballast if needed.
Completing the forward end of the
fuselage is more complex. My engine
choice is the Cyclon. If you opt for
another, you’ll have to adapt the
engine-mounting arrangement to suit
your own needs.
Cut a soft balsa block with its grain
running fore and aft (longitudinally)
to fi t inside the open front end of the
fuselage. Sand its front face to provide the
specifi ed 3° of downthrust and 3° of left
thrust for a right-power fl ight pattern.
Cut a round disc of 1/8 fi ve-ply
plywood with a diameter to match
the inside width of the front end of
the fuselage. Install 2-56 T-nuts in the
plywood disc/fi rewall to mate with the
engine’s mounting-hole pattern.
Drill a 1/16-inch diameter hole vertically
through this plywood fi rewall to allow
you to install the music-wire forward
skid. Recess the angled front face of the
balsa block to accept the heads of the
T-nuts and glue the fi rewall fl ush against
the face of the square balsa block using
epoxy cement. I recommend 3M Scotch-
Weld Epoxy Adhesive DP-460.
Install the fi rewall/block assembly
inside the front end of the fuselage
box with the front face of the fi rewall
fl ush with the front edges. (Because of
the downthrust and side thrust angles,
they will require slight trimming.) The
fuselage’s front portion must be carved
and sanded to create the transition from
the square cross section of the fuselage
box to the round disc of the fi rewall.
The next step is installing the four
.050 carbon-fi ber rods in the open
corners of the fuselage box. These rods
should initially extend forward an inch or
two beyond the front face of the fi rewall.
Glue the rods in place in all four
corners of the fuselage box from the aft
end of the fuselage to the forward area
of the timer location. Make grooves in
the balsa block and fi rewall so that the
carbon-fi ber rods can be bent inward
to set in the grooves and blend into
the transition from a square to a round
fuselage cross section.
Wrapping a rubber band tightly around
the protruding ends of the rods will hold
them in place while you glue them into
the grooves. This is another good place to
use the DP-460 epoxy glue.
After the glue has set, the carbonfi
ber rods can be cut off fl ush with the
front face of the fi rewall. For additional
security, you can also run a ½-inch or
longer #4 fl at-head wood screw through
the center of the fi rewall and epoxy it
into the balsa block.
Complete the engine mount
construction by applying a layer of
1-ounce fi berglass cloth over the fi rewall
and running aft at least to the timerlocation
area.
Reinforce the side of the fuselage
where you will mount the timer with
a layer of 1/32 plywood. A simple, twofunction
(engine run and dethermalizer)
mechanical timer, such as those available
from Texas Timers, will do the job
because this is a locked-up, non-autofunction
model. I emphasize mechanical
because I don’t think burning-wick/fusetype
timers are accurate or safe.
Covering and Finishing
Polyspan is the only covering material
I use on wing and tail surfaces. It
provides the best characteristics of
Japanese tissue (enhancing a structure’s
torsional rigidity) with only a small
weight penalty. It is durable and
puncture resistant.
The Cyclon engine is mounted with 3° of downthrust and 3° of left thrust, for a right-power
fl ight pattern.46 Model Aviation MARCH 2012 www.ModelAviation.com
Genie Redux
Unwanted warps can be removed
and trim adjustments made using a
heat gun; the surface retains the set you
want. Polyspan’s only shortcoming is
that it only comes in one not-so-vivid
color: washed-out white. However,
inventive applications of colored tissue,
with scarcely any weight penalty, can
yield some colorful results.
Apply at least two coats of clear
dope, thinned 50%, to all surfaces
and edges of the structures that will
contact the covering material. Sand
lightly after each coat. I prefer to use
nitrate dope throughout the entire
covering process, with a coat of fuel
proofer as the fi nal step.
Polyspan can now be applied and
glued to the respective structures’
surfaces and edges with thinned dope.
The Polyspan does not need to extend
forward onto the D-box sheeting
more than ½ inch. A covering iron set
at roughly 300° will help bend the
Polyspan around any small radii such
as the wingtips, stabilizer tips, and the
stabilizer LE as you apply it.
When complete, heat shrink the
Polyspan with a hot iron to remove
wrinkles and tighten the skin. Give all
the covered surfaces two coats of 50%
thinned, clear nitrate dope.
Now, get artistic with colorful
trimming. Applied with thinner, adding
colorful Japanese tissue can make your
model beautiful and visible against
the sky and earth. Apply two coats of
50% thinned dope to all covered and
decorated surfaces followed by a fi nal
coat of your favorite fuel proofer.
I don’t use Polyspan on the all-wood
surfaces of the fuselage, pylon and wing
mount, fi n and rudder, and sub fi n.
Japanese tissue in your choice of colors
and design will do the job. Give the
exposed wood surfaces at least two coats
of 50% thinned dope with the requisite
light sanding afterwards, then apply the
tissue using thinned dope. Finish with
four more coats of thinned dope and a
coat of fuel proofer.
Final Assembly
The fi nal steps include attaching the
nose skid, vertical tail and rudder, sub
fi n, stabilizer platforms, and pylon/
wing platform.
Glue the nose skid into the hole in
the fi rewall with DP-460 epoxy after
roughening the upper portion’s surface
with a fi le or grinding wheel to ensure
good glue adhesion. Roughen the upper
portion of the tailskid wire and glue
it into the hole in the dowel that will
support the vertical tail and rudder.
When gluing the sub fi n and dowel
to the fuselage, take care to ensure that
they are vertical and perfectly aligned
with its centerline. Position the stabilizer
platform as shown on the plans and glue
it directly to the top of the fuselage.
Glue a small, hard balsa pad to support
the stabilizer’s TE onto the fuselage top.
After drilling a hole into the vertical
tail to accept the protruding support
dowel, it can be glued to the top of
the fuselage. Proper alignment along
the fuselage centerline is critical. The
rudder-adjusting mechanism is also
installed during this process.
Mount the timer in its fuselage bay
and glue short lengths (roughly 2 inches)
of 1/16 OD aluminum tubing onto the
fuselage to act as guides for the DT line.
I glue a short length of large-diameter,
carbon-fi ber tubing under the front of
the fuselage to hold my bladder-type
pressure fuel tank.
Mount the engine to the fi rewall and
the remote fuel cut-off to the engine.
Now comes the tricky part—correctly
locating the pylon on the fuselage to
obtain the desired balance-point location.
The pylon position shown on the
plans is intended for heavier, ball-bearing
engines such as the Cyclon, A.D.,
Shuriken, and CS. For lighter, plainbearing
engines (TDs, Stels, VAs, and
AMEs), the pylon goes farther aft to
attain the desired 85% to 90% balancepoint
location.
To obtain the correct pylon position,
the model must be fully assembled
in ready-to-fl y condition. In addition
to engine, propeller, tank, and timer,
you should simulate the weight of the
airborne tracker/locater transmitter by
taping roughly 4 grams of weight to the
Completed wing structures for the 345 (F1J) and 325 (1/2A) models.www.ModelAviation.com MARCH 2012 Model Aviation 47
TE of the pylon (where the transmitter
will be when fl ying). With the stabilizer
in place, you can begin the trial-anderror
process of locating the proper
pylon position.
Begin by attaching the wing to the top
of the fuselage directly behind the engine
with rubber bands. Lay the inverted
pylon/wing mount (with dummy locater
transmitter weight attached) on top of
the wing so the forward edge of the wing
mount is aligned with the wing’s LE.
Support the whole works under
each side of the wing at a point threequarters
forward of the wing TE (which
will be within the 85% to 90% range).
Shifting the wing fore and/or aft,
balance the model so that the fuselage
is horizontal, determining the correct
pylon position.
Measure and mark that place on the
top of the fuselage, disassemble all of
the components (wing, stabilizer, engine,
etc.), and permanently install the pylon
on the fuselage in its correct location.
The pylon’s hardwood LE and TE are
intended to extend into the fuselage and
attach to the balsa block in the front and
the fuselage bottom in the back. Cut
openings in the fuselage top with the
forward one extending down into the
balsa block.
Install a 1/16 plywood pad ½-inch wide
inside the fuselage across its width to
provide a secure attachment for the
pylon’s TE. Cut a slot in one side of the
fuselage at the proper location and slide
the plywood pad in and glue it in place.
Anchor the pylon’s TF with a small
wood screw through the pad.
As with the vertical tail and sub fi n,
aligning the pylon on the fuselage’s
centerline is critical. Mount a small
tube at the pylon’s TE to hold your
transmitter and a couple of small soft
balsa blocks to fair/blend its forward end
into the pylon-fuselage joint.
Align the wing and stabilizer at right
angles to the fuselage centerline each
time they are mounted. Short (¼- to
½-inch) lengths of 1/16-inch dowels,
split lengthwise and glued to the
undersides of the wing LE and TE and
the stabilizer TE will serve this purpose.
(The stabilizer DT horn’s alignment
key will do the job at the stabilizer’s
LE.) Positioning them on the wing and
stabilizer so that they rest against the
fuselage sides ensures proper alignment.
Trimming and Testing
Perform all hand-glide and power
testing with the airplane in its fi nal
fl ight confi guration (propeller, tank, and
transmitter installed). I use my owndesign
propellers, which are available
from Mike Hazel (see “Sources”).
Constructed from carbon fi ber, they
come in fi xed- and folding-blade
versions (blades for the folders are from
Mike; hubs for the folders are from me).
Their basic size is 63/8 x 2 for F1J/.061
use. For ½A/.049 use, I cut the diameter
to 55/8. For more readily available
commercial propellers, most fl iers use
the APC 6 x 2 or 5.7 x 3 or 5.5 x 2.
The Genie Redux is intended to fl y
a right/right-power/glide fl ight pattern.
Initial hand gliding should ensure a
moderate turn with no severe dive or
stall tendencies. Adjust the glide turn
using stabilizer tilt (right tip up for
right turn).
Add ballast to the nose or tail to
correct for a stall or dive, respectively.
These preliminary adjustments should
be considered just that: preliminary.
Fine-tune the Genie after the proper
power pattern is established.
Engine runs on the fi rst few powered
fl ights should not exceed 3 seconds.
Use a short DT setting. The launch
angle should be nearly vertical and its
direction should be slightly to the right
of the wind.
Adjust the power pattern during
these initial, short-engine-run test fl ights
by varying the incidence angle of the
stabilizer: LE up to correct looping
tendencies; TE up to correct diving
tendencies.
Experimenting with washin and/or
washout on the inboard wing panels
is the usual way to correct or induce
rolling tendencies. I prefer washout to
washin because the drag created by any
signifi cant amount of washin can induce
a turning effect that overpowers the
intended rolling effect.
Conversely, any drag and turning
effects from washout tend to work in
concert with the intended rolling effect.
Progressively increase the engine-run
duration by 1-second increments to
the maximum (generally 7 seconds at
most fi elds in the East and Midwest).
Make concurrent trim adjustments as
necessary to attain the desired power
pattern of a nearly vertical climb with
a three-fourths to full turn spiral from
launch to engine cutoff.
As you become more secure in the
power pattern’s safety and perfection,
increase the glide duration and observe
the glide pattern. The goal is a clockwise
circle with a slow, fl at, nearly stalled
glide attitude. Adjustments to the
stabilizer tilt and ballasting to vary the
CG are the means to the desired end.
Wing washout and/or washin can be
used to control the glide’s lateral fl atness.
Make adjustments in small increments.
Adjusting for glide trim will likely
affect power trim. Stabilizer tilt
changes may affect decalage, which
will probably affect the power pattern.
Begin the fi ne-tuning, tweaking, and
compromising to obtain the optimum
balance between the powered and
gliding fl ight cycles.
I hope that you will be as satisfi ed
with your Genie Redux as I have been
with mine.
—J.G. Pailet
[email protected]
SOURCES:
Aerospace Composite Products
(800) 811-2009
www.acpsales.com
The Composites Store
(800) 338-1278
www.cstsales.com
Larry Davidson
(540) 721-4563
[email protected]
Walston Retrieval Systems
(770) 434-4905
www.walstonretrieval.com
Mike Hazel
(503) 364-8593
[email protected]
Cyclon Engines
(530) 757-6058
[email protected]
Texas Timers
(423) 282-6423
www.texastimers.com
Campbell’s Custom Kits
(765) 683-1749
[email protected]
FAI Model Supply
(570) 882-9873
www.faimodelsupply.com

Nearly every time I rub the old lamp I found years ago,
another Genie pops out! The last Genie was in 2001, and
was also known as the Classic 320 (September 2002 MA).
The Genie Redux made its fi rst appearance in 2004. Previous
incarnations were in 1999, 1998, 1997 (July 1997 MA), and 1995.
Progress in design is usually the result of inspiration
(the pylon and high thrustline concepts) or innovation
(incremental improvements in existing concepts). The
Genie Redux design history falls into the latter category.
It is an evolution extending through more than 15
years. Each incremental change was an attempt to
improve—aerodynamically and/or structurally—
on the predecessor. There were no giant leaps
forward. Progressive steps of improvement and
refi nement were the intent and result.
The airplanes were simple, straightforward
designs with no auto-surfaces! All proved
to be competitive with their high-tech
contemporaries. Technology played a
part only in the use of carbon and
Kevlar materials for some structural
components.
Genie
Redux
An award-winning design
several years in the making
by J.G. Pailet
[email protected]
The author sends the Genie into fl ight in Pensacola FL.
www.ModelAviation.com MARCH 2012 Model Aviation 4142 Model Aviation MARCH 2012 www.ModelAviation.com
the lack of sheeting and to relocate
the turbulator spars accordingly. The
following text assumes you choose the
D-box structure.
The main spar is a balsa/carbon fi ber/
balsa “sandwich,” using epoxy glue as
the bonding agent. Bond the sandwich
under pressure, ideally using a vacuumbag
process.
The inboard end of the main spar
should extend ¼ inch past the centerline
to allow for the required angular lap
joint when the main wing panels are
later joined together.
For the inboard/main wing panels,
the spar and aft end of the forward rib
sections must be elevated 3/32 inch above
the plans during construction to provide
for the desired undercamber and bottom
sheeting thickness. Because the tip airfoil
has no undercamber, the outer wing
panel spars, while elevated the full 3/32
inch at the polyhedral joint, are raised
only enough to accommodate the lower
sheeting at the outboard ends.
The front end of the forward ribs must
be elevated to allow for the sheeting,
and the front ends of the aft ribs must
be raised to provide undercamber and to
mate properly with the lower sheeting.
Before assembly, cut grooves in the
LEs to accept the .040 carbon-fi ber rods
which will be inserted later. The grooves
should be 1/32 inch above the lower
surface of the LE to provide the correct
Phillips entry shape to the LE when it is
later carved and sanded to conform to
the rib airfoil contour.
Notches should be cut into the TEs to
accept the aft ends of the ribs. Build the
four wing panels independently, using
your favorite adhesive. I use odorless
CA, because of a personal allergic
reaction to regular CA.
Note: the inboard dihedral and
outboard polyhedral ribs should be set
at a slight angle to accommodate the
required dihedral and polyhedral when
Genie Redux
Rick Crosslin created a wind
tunnel which allows children
to test fl ying objects they have
created.
The carbon-fi ber brace on the main spar of the wing and dihedral joint
provides for a rigid structure with little weight penalty.
The stabilizer structure shows the carbon-fi ber cap strips installed.
The front of the fuselage has an opening
for the timer.
I must share credit for the success of
these models with my regular design and
engineering consultants: Don Broggini,
John Carbone, Bob Hatscheck, and
Joe Mollendorf. Thanks, guys! Another
thank-you goes to Jim O’Reilly for the
excellent computer-generated plans.
The Genie Redux was one of the
National Free Flight Society’s 2010
Models of the Year.
The Wing
As depicted on the plans, the
wing features a sheet balsa-covered
forward portion to form a standard
D-box structure. However, the
underlying turbulator-spar structure has
demonstrated its strength adequacy in
earlier designs.
I prefer the sheeted version for its
cleaner aerodynamic characteristics. You
will save some weight by eliminating
the sheeting, but be sure to alter the
forward rib profi le to compensate for
Photos by the authorwww.ModelAviation.com MARCH 2012 Model Aviation 43
joined together. Also note that the wing
tips are set at a 45° angle.
As the drawing indicates, the wing and
stabilizer ribs have vent holes in them
to equalize the pressure throughout
the wing. When the model is sitting
out on a fi eld exposed to the sun on
a hot day, the internal air pressure
within the various rib bays can increase
dramatically and erratically, potentially
causing the surfaces to warp. Vent holes
help alleviate that problem.
I make a small, 1/32-inch diameter
hole at each wing and stabilizer tip,
either through the covering or through
the tip itself, to vent any excess pressure
to the outside.
After all of the half ribs, full ribs, and
diagonal ribs are in place, install the 1/16
x 1/8 hard balsa spars. As with the main
spar, these two spars should extend ¼
inch inboard past the centerline.
All outer panel spars—main and
turbulator—should extend inward
past the polyhedral joint far enough to
contact the main panels’ outermost half
rib. The four wing panels are now ready
to be joined together.
The centerline dihedral joint is the
most critical because it sustains the
highest loads, so it is reinforced on its
front face with a 1/16-plywood gusset
and two .050 carbon-fi ber rods on its
rear face.
It is important that the gusset and
rods taper and vary in length as shown
to avoid a localized area of stress
concentration. Join the two panels by
gluing together the mating surfaces of
the two centerline ribs and the mating
angular surfaces of the main and
turbulator spars to form scarf joints. Use
Another shot of David Wigley’s Westland Wyvern. This model photographs great!
The F1J Genie Redux is in the foreground and the 1/2A version is in the rear.
slow-drying epoxy to ensure that you
have time to properly align the wing
panels before the glue sets.
After the glue sets, install the plywood
gusset by cutting 1/16 inch off the aft ends
of the forward central area ribs to create
a slot to accommodate the gusset and
allow it to rest against the forward face
of the main spar.
Similarly, 1/16-inch diameter holes
must be made in the forward ends of
the rear ribs to permit you to insert .050
carbon-fi ber rods against the rear face
of the main spar. When the gusset and
rods are glued into place, reinforcing the
center dihedral joint is complete.
The polyhedral joints primarily
depend upon the angular-cut scarf joints
of the main and turbulator spars for
strength, coupled with the face-to-face
mating of the two W1A ribs. Again, I44 Model Aviation MARCH 2012 www.ModelAviation.com
Genie Redux
recommend using slow-drying epoxy
to allow time to align the respective
inboard and outboard wing panels.
Additional strengthening is achieved
by gluing the inward-extended ends of
the spars to the most-outboard half ribs
of the main wing panels. You should
now have a one-piece, assembled wing,
ready for the LE .040 carbon-fi ber rod
and the D-box sheeting.
The carbon-fi ber rod is installed as
one piece from polyhedral joint to
polyhedral joint, because the relatively
shallow dihedral angle allows it to be
bent without breaking at the centerline,
affording extra strength at the
centerline joint.
The outboard wing panels use
separate lengths of carbon-fi ber rod. The
LE is not yet carved to its fi nal crosssectional
shape; it is still a rectangle in
cross section. The D-box sheeting uses
a simple butt joint at the dihedral and
polyhedral joints.
It is best to install the sheeting on the
inboard wing panels fi rst. I recommend
that the top sheeting be installed fi rst
because its curvature makes it more
diffi cult to ensure proper adhesion to
all the LE, rib, and spar surfaces and
edges. After the top sheeting is tackglued
in place, turn the wing over and
thoroughly apply glue to the mating
edges and joints.
The bottom sheeting is slightly easier
to install because it is fl at and has no
curvature. However, once it is installed,
the D-box is a closed entity and you
can’t get back inside to touch up any
glue joints.
Slow-drying epoxy glue will allow
you time to be certain that you have
properly applied the glue to mating
edges of the ribs, sheeting, and main
spar. After installing the sheeting on the
wing panels, carve and sand the LE to its
fi nished shape so that it blends into the
full airfoil contour.
All aft ribs—particularly the
diagonals—should now be capped with
carbon-fi ber strips. As noted on the
plans, these cap strips (except for the
diagonals) should extend forward onto
the D-box sheeting and aft onto the TE.
An optional step in the wing
construction can be adding a length of
.020 carbon-fi ber rod along the upper
edge of each wingtip, affording damage
protection from nicks and bruises that
occur during normal fl ying activities.
Horizontal Stabilizer
The horizontal stabilizer utilizes a
balsa/carbon fi ber/balsa sandwich-type
spar similar to the wing and a .030
carbon-fi ber rod imbedded into the
LE. Otherwise its construction is fairly
conventional.
As with the wing, the tips are set at a
45° angle and all of the ribs (except the
1/32-inch half ribs) have carbon-fi ber cap
strips. Except for the diagonals, the cap
strips extend onto both the LE and TE.
Installation of the DT-horn/stabilizer
key completes the construction. The 1/64
plywood DT hold-down pad is added
after the stabilizer is covered.
Fin, Vertical Tail, Sub Fin, and Rudder
These are all simple 3/16 sheet balsa
fl at surfaces. The LE of the fi n, sub
fi n, and rudder should be sanded to
a rounded cross section and their aft
portions symmetrically tapered to a 1/32-
inch thickness.
Add a 1/64 plywood reinforcement strip
to the bottom portion of the rudder.
This also serves as a hard pad for the
rudder-adjusting screws. The adjusting
mechanism can be
homemade or purchased
from FAI Model Supply.
Use any type of simple
hinges to attach the
rudder to the fi n.
The vertical tail
assembly is supported
in its attachment to the
fuselage by a length of
1/8-diameter hardwood
dowel extending through
the fuselage. A hole drilled
through the length of this
dowel also serves as the
mount for the tail skid.
The .045-diameter tail
skid is imbedded into the
LE of the sub fi n to help
secure to it the fuselage.
The polyhedral wing
joint has carbon-fi ber
cap strips on the ribs for
added strength.
Carbon fi ber is used on the LE and tip
contour. This shows the framed-up wing’s
outer panel.www.ModelAviation.com MARCH 2012 Model Aviation 45
Pylon and Wing Mount
As are the vertical tail surfaces, the
pylon is a simple, fl at-sided, 3/16 sheetbalsa
structure. It incorporates hardwood
LEs and TEs extending into the fuselage
to secure and stabilize it and to anchor
the wing attachment hooks, which are
bent from 1/16-diameter music wire. The
LEs and TEs are rounded and tapered.
The bottom of the pylon attaches directly
to the top of the fuselage (which serves
as the 0° reference line for the engine
downthrust and wing and stabilizer
incidence angles).
The top of the pylon should be at
1° positive incidence. The wing-mount
platform is pieced together with short
lengths of 1/16 hard sheet balsa with the
grain running laterally. Carbon-fi ber
rods at the LE, TE, and under the wing’s
main spar help stiffen it laterally.
Soft balsa fi llets stabilize its
attachment to the pylon, and 1/16-square
hard balsa rails stiffen it longitudinally.
The rails also serve to stabilize the
wing laterally by matching its dihedral
angle. The pylon is not mounted on the
fuselage until the model is completely
fi nished because its fore and aft position
ultimately determines the model’s
balance point location.
Fuselage
The fuselage top, bottom, and both
sides are identical in shape, yielding an
elongated box of square cross sections,
diminishing in size from nose to tail. The
internal formers are 1/16 sheet balsa with
grain alternating in diagonal directions.
The fuselage box is built with the
corners open to allow installation of
carbon-fi ber rods in each of the corners.
A small balsa plug with an internal
2-56 T-nut fi lls the open aft end of the
fuselage, affording a simple means of
adding ballast if needed.
Completing the forward end of the
fuselage is more complex. My engine
choice is the Cyclon. If you opt for
another, you’ll have to adapt the
engine-mounting arrangement to suit
your own needs.
Cut a soft balsa block with its grain
running fore and aft (longitudinally)
to fi t inside the open front end of the
fuselage. Sand its front face to provide the
specifi ed 3° of downthrust and 3° of left
thrust for a right-power fl ight pattern.
Cut a round disc of 1/8 fi ve-ply
plywood with a diameter to match
the inside width of the front end of
the fuselage. Install 2-56 T-nuts in the
plywood disc/fi rewall to mate with the
engine’s mounting-hole pattern.
Drill a 1/16-inch diameter hole vertically
through this plywood fi rewall to allow
you to install the music-wire forward
skid. Recess the angled front face of the
balsa block to accept the heads of the
T-nuts and glue the fi rewall fl ush against
the face of the square balsa block using
epoxy cement. I recommend 3M Scotch-
Weld Epoxy Adhesive DP-460.
Install the fi rewall/block assembly
inside the front end of the fuselage
box with the front face of the fi rewall
fl ush with the front edges. (Because of
the downthrust and side thrust angles,
they will require slight trimming.) The
fuselage’s front portion must be carved
and sanded to create the transition from
the square cross section of the fuselage
box to the round disc of the fi rewall.
The next step is installing the four
.050 carbon-fi ber rods in the open
corners of the fuselage box. These rods
should initially extend forward an inch or
two beyond the front face of the fi rewall.
Glue the rods in place in all four
corners of the fuselage box from the aft
end of the fuselage to the forward area
of the timer location. Make grooves in
the balsa block and fi rewall so that the
carbon-fi ber rods can be bent inward
to set in the grooves and blend into
the transition from a square to a round
fuselage cross section.
Wrapping a rubber band tightly around
the protruding ends of the rods will hold
them in place while you glue them into
the grooves. This is another good place to
use the DP-460 epoxy glue.
After the glue has set, the carbonfi
ber rods can be cut off fl ush with the
front face of the fi rewall. For additional
security, you can also run a ½-inch or
longer #4 fl at-head wood screw through
the center of the fi rewall and epoxy it
into the balsa block.
Complete the engine mount
construction by applying a layer of
1-ounce fi berglass cloth over the fi rewall
and running aft at least to the timerlocation
area.
Reinforce the side of the fuselage
where you will mount the timer with
a layer of 1/32 plywood. A simple, twofunction
(engine run and dethermalizer)
mechanical timer, such as those available
from Texas Timers, will do the job
because this is a locked-up, non-autofunction
model. I emphasize mechanical
because I don’t think burning-wick/fusetype
timers are accurate or safe.
Covering and Finishing
Polyspan is the only covering material
I use on wing and tail surfaces. It
provides the best characteristics of
Japanese tissue (enhancing a structure’s
torsional rigidity) with only a small
weight penalty. It is durable and
puncture resistant.
The Cyclon engine is mounted with 3° of downthrust and 3° of left thrust, for a right-power
fl ight pattern.46 Model Aviation MARCH 2012 www.ModelAviation.com
Genie Redux
Unwanted warps can be removed
and trim adjustments made using a
heat gun; the surface retains the set you
want. Polyspan’s only shortcoming is
that it only comes in one not-so-vivid
color: washed-out white. However,
inventive applications of colored tissue,
with scarcely any weight penalty, can
yield some colorful results.
Apply at least two coats of clear
dope, thinned 50%, to all surfaces
and edges of the structures that will
contact the covering material. Sand
lightly after each coat. I prefer to use
nitrate dope throughout the entire
covering process, with a coat of fuel
proofer as the fi nal step.
Polyspan can now be applied and
glued to the respective structures’
surfaces and edges with thinned dope.
The Polyspan does not need to extend
forward onto the D-box sheeting
more than ½ inch. A covering iron set
at roughly 300° will help bend the
Polyspan around any small radii such
as the wingtips, stabilizer tips, and the
stabilizer LE as you apply it.
When complete, heat shrink the
Polyspan with a hot iron to remove
wrinkles and tighten the skin. Give all
the covered surfaces two coats of 50%
thinned, clear nitrate dope.
Now, get artistic with colorful
trimming. Applied with thinner, adding
colorful Japanese tissue can make your
model beautiful and visible against
the sky and earth. Apply two coats of
50% thinned dope to all covered and
decorated surfaces followed by a fi nal
coat of your favorite fuel proofer.
I don’t use Polyspan on the all-wood
surfaces of the fuselage, pylon and wing
mount, fi n and rudder, and sub fi n.
Japanese tissue in your choice of colors
and design will do the job. Give the
exposed wood surfaces at least two coats
of 50% thinned dope with the requisite
light sanding afterwards, then apply the
tissue using thinned dope. Finish with
four more coats of thinned dope and a
coat of fuel proofer.
Final Assembly
The fi nal steps include attaching the
nose skid, vertical tail and rudder, sub
fi n, stabilizer platforms, and pylon/
wing platform.
Glue the nose skid into the hole in
the fi rewall with DP-460 epoxy after
roughening the upper portion’s surface
with a fi le or grinding wheel to ensure
good glue adhesion. Roughen the upper
portion of the tailskid wire and glue
it into the hole in the dowel that will
support the vertical tail and rudder.
When gluing the sub fi n and dowel
to the fuselage, take care to ensure that
they are vertical and perfectly aligned
with its centerline. Position the stabilizer
platform as shown on the plans and glue
it directly to the top of the fuselage.
Glue a small, hard balsa pad to support
the stabilizer’s TE onto the fuselage top.
After drilling a hole into the vertical
tail to accept the protruding support
dowel, it can be glued to the top of
the fuselage. Proper alignment along
the fuselage centerline is critical. The
rudder-adjusting mechanism is also
installed during this process.
Mount the timer in its fuselage bay
and glue short lengths (roughly 2 inches)
of 1/16 OD aluminum tubing onto the
fuselage to act as guides for the DT line.
I glue a short length of large-diameter,
carbon-fi ber tubing under the front of
the fuselage to hold my bladder-type
pressure fuel tank.
Mount the engine to the fi rewall and
the remote fuel cut-off to the engine.
Now comes the tricky part—correctly
locating the pylon on the fuselage to
obtain the desired balance-point location.
The pylon position shown on the
plans is intended for heavier, ball-bearing
engines such as the Cyclon, A.D.,
Shuriken, and CS. For lighter, plainbearing
engines (TDs, Stels, VAs, and
AMEs), the pylon goes farther aft to
attain the desired 85% to 90% balancepoint
location.
To obtain the correct pylon position,
the model must be fully assembled
in ready-to-fl y condition. In addition
to engine, propeller, tank, and timer,
you should simulate the weight of the
airborne tracker/locater transmitter by
taping roughly 4 grams of weight to the
Completed wing structures for the 345 (F1J) and 325 (1/2A) models.www.ModelAviation.com MARCH 2012 Model Aviation 47
TE of the pylon (where the transmitter
will be when fl ying). With the stabilizer
in place, you can begin the trial-anderror
process of locating the proper
pylon position.
Begin by attaching the wing to the top
of the fuselage directly behind the engine
with rubber bands. Lay the inverted
pylon/wing mount (with dummy locater
transmitter weight attached) on top of
the wing so the forward edge of the wing
mount is aligned with the wing’s LE.
Support the whole works under
each side of the wing at a point threequarters
forward of the wing TE (which
will be within the 85% to 90% range).
Shifting the wing fore and/or aft,
balance the model so that the fuselage
is horizontal, determining the correct
pylon position.
Measure and mark that place on the
top of the fuselage, disassemble all of
the components (wing, stabilizer, engine,
etc.), and permanently install the pylon
on the fuselage in its correct location.
The pylon’s hardwood LE and TE are
intended to extend into the fuselage and
attach to the balsa block in the front and
the fuselage bottom in the back. Cut
openings in the fuselage top with the
forward one extending down into the
balsa block.
Install a 1/16 plywood pad ½-inch wide
inside the fuselage across its width to
provide a secure attachment for the
pylon’s TE. Cut a slot in one side of the
fuselage at the proper location and slide
the plywood pad in and glue it in place.
Anchor the pylon’s TF with a small
wood screw through the pad.
As with the vertical tail and sub fi n,
aligning the pylon on the fuselage’s
centerline is critical. Mount a small
tube at the pylon’s TE to hold your
transmitter and a couple of small soft
balsa blocks to fair/blend its forward end
into the pylon-fuselage joint.
Align the wing and stabilizer at right
angles to the fuselage centerline each
time they are mounted. Short (¼- to
½-inch) lengths of 1/16-inch dowels,
split lengthwise and glued to the
undersides of the wing LE and TE and
the stabilizer TE will serve this purpose.
(The stabilizer DT horn’s alignment
key will do the job at the stabilizer’s
LE.) Positioning them on the wing and
stabilizer so that they rest against the
fuselage sides ensures proper alignment.
Trimming and Testing
Perform all hand-glide and power
testing with the airplane in its fi nal
fl ight confi guration (propeller, tank, and
transmitter installed). I use my owndesign
propellers, which are available
from Mike Hazel (see “Sources”).
Constructed from carbon fi ber, they
come in fi xed- and folding-blade
versions (blades for the folders are from
Mike; hubs for the folders are from me).
Their basic size is 63/8 x 2 for F1J/.061
use. For ½A/.049 use, I cut the diameter
to 55/8. For more readily available
commercial propellers, most fl iers use
the APC 6 x 2 or 5.7 x 3 or 5.5 x 2.
The Genie Redux is intended to fl y
a right/right-power/glide fl ight pattern.
Initial hand gliding should ensure a
moderate turn with no severe dive or
stall tendencies. Adjust the glide turn
using stabilizer tilt (right tip up for
right turn).
Add ballast to the nose or tail to
correct for a stall or dive, respectively.
These preliminary adjustments should
be considered just that: preliminary.
Fine-tune the Genie after the proper
power pattern is established.
Engine runs on the fi rst few powered
fl ights should not exceed 3 seconds.
Use a short DT setting. The launch
angle should be nearly vertical and its
direction should be slightly to the right
of the wind.
Adjust the power pattern during
these initial, short-engine-run test fl ights
by varying the incidence angle of the
stabilizer: LE up to correct looping
tendencies; TE up to correct diving
tendencies.
Experimenting with washin and/or
washout on the inboard wing panels
is the usual way to correct or induce
rolling tendencies. I prefer washout to
washin because the drag created by any
signifi cant amount of washin can induce
a turning effect that overpowers the
intended rolling effect.
Conversely, any drag and turning
effects from washout tend to work in
concert with the intended rolling effect.
Progressively increase the engine-run
duration by 1-second increments to
the maximum (generally 7 seconds at
most fi elds in the East and Midwest).
Make concurrent trim adjustments as
necessary to attain the desired power
pattern of a nearly vertical climb with
a three-fourths to full turn spiral from
launch to engine cutoff.
As you become more secure in the
power pattern’s safety and perfection,
increase the glide duration and observe
the glide pattern. The goal is a clockwise
circle with a slow, fl at, nearly stalled
glide attitude. Adjustments to the
stabilizer tilt and ballasting to vary the
CG are the means to the desired end.
Wing washout and/or washin can be
used to control the glide’s lateral fl atness.
Make adjustments in small increments.
Adjusting for glide trim will likely
affect power trim. Stabilizer tilt
changes may affect decalage, which
will probably affect the power pattern.
Begin the fi ne-tuning, tweaking, and
compromising to obtain the optimum
balance between the powered and
gliding fl ight cycles.
I hope that you will be as satisfi ed
with your Genie Redux as I have been
with mine.
—J.G. Pailet
[email protected]
SOURCES:
Aerospace Composite Products
(800) 811-2009
www.acpsales.com
The Composites Store
(800) 338-1278
www.cstsales.com
Larry Davidson
(540) 721-4563
[email protected]
Walston Retrieval Systems
(770) 434-4905
www.walstonretrieval.com
Mike Hazel
(503) 364-8593
[email protected]
Cyclon Engines
(530) 757-6058
[email protected]
Texas Timers
(423) 282-6423
www.texastimers.com
Campbell’s Custom Kits
(765) 683-1749
[email protected]
FAI Model Supply
(570) 882-9873
www.faimodelsupply.com