16 MODEL AVIATION
nFrank Baker
The author has built this design in two sizes. His O.S. .26-powered version poses with
its 1⁄2A Norvel-powered little brother. Note long tail moment arm.
AltHOuGH tHE DEsIGN of the de
Havilland D.H.60 Moth dates back to
1925, the introduction of the 100-
horsepower Gipsy engine in 1928
resulted in the D.H.60G Gipsy Moth.
The Gipsy Moth was a very popular
sport airplane during the early 1930s, and
many distance records were set in it.
A 54-inch-span Radio Control (RC)
Gipsy Moth construction article was
published in the September 1994
Model Aviation. It was powered by an
O.S. 26 four-stroke. This was an ideal
combination of model and engine. When I
want to go out and fly for fun, the Gipsy
Moth is my favorite model.
The advent of 1⁄2A engines that
have reliable throttle control, such
as the Norvel series, has opened up
a new dimension to flying small
models. A smaller version of the Gipsy
Moth seemed to be just the model to take
advantage of this new dimension.
The 32-inch-wingspan Gipsy
Moth is a replica of the earlier
model.
CONSTRUCTION
As is the case with all small RC models,
weight has a direct impact on performance.
Add this 1⁄2A version of the popular 1930s
British sport airplane to your model fleet
Use the lightest balsa that is consistent with
the strength of the component under
construction. And sand all balsa sheets
before cutting out parts.
Begin construction with the wings; they
will be fitted to the fuselage before the
model is completed.
The plans show that the two main wing
spars are 1⁄8 x 1⁄4 spruce; however,
basswood or hard balsa could be
substituted. The plans show one size of
wing rib, even though there are ribs of
different lengths.
In the tapered sections of the wings, cut
the rear part of the standard ribs to the
lengths shown on the plan and glue them in.
After removing the wing from the
building board, sand the ribs until they
conform to the 3⁄4 trailing-edge stock.
However, do not thin the wing rib; the
maximum height of all ribs should be the
same.
Each wing is actually a three-piece
assembly, with two outer panels and a
center-section composed of a short spar
and dihedral braces.
At the front of the lower-wing front spar,
the dihedral brace has a rectangular section
that sticks out above the top of the front
spar; this serves as the rear of the three-layer
plywood main landing-gear retainer.
The Sullivan #507 tube and cable for
aileron control should be installed after the
lower wing halves and center-section have
been joined. Check the cable and the
ailerons for freedom of movement.
The two root wing ribs should be in
place, but should not be glued until the
bottom wing has been installed on the
fuselage.
The brass shim stock wing-strut fittings
are designed so that they are folded around
the wing spar, then soldered along the top
edge, and the tab is bent up 90° to the spar.
Pay attention to which fitting goes on
which spar; there are different fittings for
the front and rear spar.
Once the fittings are installed, glue in
the pieces of sheet balsa that surround the
vertical tab. The balsa provides a place to
attach the covering material.
On the full-size Gipsy Moth, the centersection
of the top wing contains the gas tank.
After the dihedral braces have been
glued to the center-section spars, the top
outer wing panels can be attached. Glue the
four large center-section ribs in place, and
sheet with 1⁄32 balsa. Lengths of thread
could be glued on, to simulate the tank’s
corrugated metal.
Install the four top wing-strut fittings
with the tabs facing down and pieces of
sheeting glued around each one.
Do not install the cabane strut retainers
at this time.
Set the wings aside for now.
Fuselage: Cut formers F1 and F2 from 1⁄8
plywood, and use epoxy to install the 1⁄4 x 3⁄8
hardwood engine mounts in these formers.
The Cox Tee Dee .049 and Norvel
.061 share mounting-bolt hole patterns,
The Gipsy Moth has a distinctive tail shape. The rudder and elevator control horns are
made from 1⁄16 plywood, but they accept the normal nylon clevis.
With the cabane struts installed, the fuselage turtledeck can be sheeted and the cockpit
openings crafted. The real Moth character emerges at this point.
In this view, you can see how the lower wing center-section spars fit into the slots in
the bottom of the fuselage. Plenty of radio equipment room here!
January 2001 17
Photos courtesy the author Graphic Design by Carla Kunz
the tops of the diagonal struts to the front
cabane strut, and solder them.
Make the aileron servo plate from 1⁄32
plywood, and slip it in the fuselage. Hold
the lower wing in the spar slots, and lay the
aileron servo in. Adjust the servo-mounting
plate until the aileron servo is in the proper
position to drive the cable, and can be
concealed by the hatch cover.
Glue the aileron servo plate and the two
1⁄8 square supports in place.
The lower wing can be removed for
now, and the fuselage can be set aside.
Empennage: The rudder and elevator are
built flat on the building board.
Cut all the ribs from 1⁄20 x 1⁄8 balsa, and
cut the 1⁄16 x 1⁄4 slots for the leading and
trailing edges.
Use scraps of 1⁄32 balsa to hold the 1⁄4-
inch outlines at the centerline of the ribs,
and glue in the ribs.
The hinges are made from .005-inch
frosted Mylar™, which you can purchase
at a local art-supply house.
Use an X-Acto™ knife to cut slits in
the spars, and slip in the Mylar™ strips.
Once positioned, a drop of cyanoacrylate
(CyA) on the frosted side will hold the
hinges in place.
Wait until the covering is completed to
glue the hinges.
Sand the rudder and elevator ribs to a
symmetrical airfoil. The rudder and
elevator control horns are cut from 1⁄16
plywood.
Glue the elevator assembly to the
fuselage, and make sure that the rear
elevator spar that rotates is in front of the
rear post of the vertical fin.
Remove the 1⁄8 square stock that was
pinned in when the fuselage was
assembled, and replace it with the post of
the vertical fin.
Installing servos: An annoying problem is
that servos from different manufacturers
rotate in different directions.
Therefore, it is imperative to check
servo rotation before installing the control
tubes and cables, to learn the direction of
the control surface motion for a given
transmitter input.
In this model, you can use double-stick
servo tape to hold the servos in place. Be
sure that the servo wheels are spaced away
from the fuselage sides.
Install the Sullivan #507 tubes and
cables, with a 1/32 wire Z-bend soldered to
the cable at the servo end and a quick link
at the control-surface end. Be sure all
control surfaces are in neutral when
soldering the cables.
Install the throttle servo, and run the
nylon tube through holes in F3 and F2.
You will have to install the throttle arm
on the Novel .061 so that it points up
(rather than down). Do this carefully; the
throttle barrel rides on a screw thread; it is
possible to lock the barrel in one position,
and it is tough to get free.
Solder a Z-bend piece of 1⁄32 music wire
so the engines can be easily
interchanged. Drill the engine mounts
for 3-48 bolts, and install blind nuts in
the beams.
I like to make metal tanks for my
models, because they can be custom-fitted
to the confines of the individual model. Cut
the tank from K&S #524 tin sheet, using
the pattern shown on the plan.
Fold up the left and right ends and
solder the overlap, but leave the sides
down for now.
I use 1⁄8-inch soft copper tubing for
the fuel line and vents. Mount the engine
on the beams, and decide how far the
tubing will extend into the engine
compartment. Cut one long and one
short vent line and the fuel line, then
solder them into the tank.
Fold up the sides, and finish soldering
the tank. Be sure to pressure-test the tank
for leaks at this time.
Drill the holes in F2, and slide the tank
on. Use epoxy to hold the tank to the
firewall, and seal the space around the
tubes.
Use contact cement to glue the 1⁄64
plywood doublers to the 1⁄16-sheet-balsa
fuselage sides. Cut the fuselage sides to the
shape shown on the plans.
Glue the 1⁄32 plywood tripler to the
inside of the fuselage sides, then cut the 1⁄4-
inch-high slots for the bottom wing spars
and a slot for the aileron tube and cable
into the lower fuselage.
Glue the fuselage sides to the outside
of former F2, and check the engine
mounts for zero down-thrust and zero
side-thrust.
Install former F5, and pin a piece of 1⁄8
square plywood at the tail post. Check that
the fuselage sides meet properly at the tail
post, and are not twisted.
Once the glue on F5 has set, glue in F6-
F9; do not sheet the turtledeck or the
bottom of the fuselage at this time.
Bend the front cabane strut from 1⁄16
music wire, and cut the plywood pieces for
F3 approximately 1⁄8-inch oversize.
Lay the cabane strut in the slot cut in
the 1⁄16 plywood, coat both sides with
epoxy, and clamp on the 1⁄32 plywood. Be
sure that the struts are parallel to the axis
of the plywood sandwich.
Use your Dremel™ saw to trim the
plywood sandwich to the shape of former
F3, and glue the former to the fuselage
sides.
Bend the diagonal cabane support
from 1⁄16 music wire, and cut the three
plywood pieces that form the support
plate. Put the wire in the slot in the 1⁄16
plywood, and glue on the top and bottom
sheets. The wire need not be rigid in the
sandwich.
Lay the plate across the top of the
fuselage and bend the ends of the diagonal
wire to match the front cabane strut.
The bottom ends of both struts extend
roughly 1⁄16-inch beyond the sides of the
fuselage. Once fitted, glue the plate to the
top of the fuselage, use fine wire to wrap
The bottom wing is built on the spars in
halves. The first rib on either side is left
unglued until after assembly.
GIPSY MOTH
18 MODEL AVIATION
Type: RC Sport Scale
Wingspan: 31 inches
Engine: Norvel 1⁄2A
Functions: Rudder, elevator, aileron
Construction: Balsa and plywood
Covering: Heat-shrink film
to the cable at the servo end and a quick
link at the engine end.
Check the throttle for range of motion
and low- and high-speed positions.
Mounting the Wings: Place the bottom
wing in the spar slots and check the angle
of incidence (it should be +2°).
Glue the lower wing. Make sure it is
aligned properly in relation to the fuselage
centerline, and is parallel to the elevator.
Slide the root ribs up tight against the
fuselage sides, and glue them in place. You
can also add the top and bottom 1⁄32
sheeting between the first two ribs.
Bend the rear cabane strut from 1⁄16
music wire and make the plywood retainer
plates. Place the strut in the slot, and glue
the plates together.
Slip the rear strut assembly into the
fuselage, but do not glue it. The upper
ends of the front and rear cabane struts
should slip into the slots in the plywood
retainers. Use a clamp (a clothespin
works well) to hold the top wing to the
cabane struts.
Check the incidence of the top wing (it
should be +21⁄2°); the rear cabane strut can
be slid up or down in the fuselage, to get
the proper angle.
Check the top wing; it should be
parallel to the bottom wing and square to
the fuselage centerline.
When everything is in order, glue the
rear cabane strut plate into the fuselage.
Before installing the top wing, build the
upper fuselage hatch.
Lay 1⁄16 cross-grain balsa in the cockpit
area, and glue formers F4 A-D to the sheet.
Glue in the two 3⁄32 square cockpit rails,
and cover the whole hatch with 1⁄16 balsa.
When the glue is dry, cut the cockpit
holes and drill holes for the cockpit hatch
front and rear retainer screws.
With the hatch out of the way, you can
install the top wing. Apply glue to the
cabane strut retainer plates, and reassemble
the top wing to the struts and hold in place
with clamps. Check the alignment again
before the glue sets.
At this point, the top and bottom 1⁄32
sheet can be glued between the first two
ribs on each upper wing panel.
Cut the wing struts from 3⁄32 basswood,
and check their length in place. Use the
holes in the shim stock brass strut fittings
to mark where the 2-56 blind nuts will be
installed. Attach the wing struts to the
wings with short 2-26 bolts.
landing Gear and Aileron Servo Hatch:
Bend the main landing gear from 3⁄32
music wire, and cut the retainer plates
from 1⁄16 plywood. Clamp these to the
front dihedral brace, and check for
alignment.
Bend the wire until the axles are level
and square to the fuselage centerline. Glue
the assembly to the dihedral brace.
Bend the forward landing gear from 1⁄16
music wire, and cut the retainer plates from
1⁄16 plywood. Clamp the assembly to F2, and
bend the ends of the wire to point up along
the main landing gear.
When everything fits, glue the plate
assembly to F2, wrap the wires together
with fine wire, and solder. The 1⁄16 crossgrain
sheet can be glued between F2 and
the main landing gear plate.
Glue in the 1⁄8 plywood hatch retainer
strips at the front and back of the lower
wing center-section. They should be roughly
3/64-inch below the bottom line of the root
rib. This provides a base for the aileron
hatch cover and the screws.
Completing the Fuselage: Fit a balsa
block between F2 and F3, and carve the
transition between the formers. Hollow out
the block to a 3⁄32- to 1⁄8-inch wall
thickness, and glue in place.
Lightly tack-glue the nose blocks with
the idea that they will be removed, and
carve the nose to shape.
Once the blocks are rough-shaped,
mount the Norvel .061. Make sure the
muffler clears and that the needle valve
can be rotated, and check that the fuel line
and vents are accessible.
Remove the blocks; hollow them to
approximately 3⁄16-inch wall thickness and
glue them in place.
Remove the engine and coat the inside
of the engine compartment with a light
coat of epoxy, to fuelproof it.
Glue on the 1⁄32 balsa turtledeck, and
glue the cross-grained 1⁄32 sheet to the
bottom of the fuselage.
Covering: Before covering, give the
exposed balsa areas a coat of AeroGloss
balsa filler coat and sand smooth. Give the
tops and bottoms of the wing ribs a couple
coats, with sanding in between.
Being from the old school, I cover
small models with silk and dope, although
you could use silkspan. If you want to use
Mylar™, get the lightest weight available.
The Gipsy Moths came from the
factory in an all-silver finish with a
minimum amount of trim in one color,
such as blue, green, or red.
The registration numbers were the
usual large letters across the top of the
wings and medium-size letters on the
fuselage sides in the trim color.
Add a Williams Bros. one-inch scale
pilot to the rear cockpit.
Flying: Available space in the fuselage is
limited, so small radio equipment is a
must. I used the Hitec RCD Micro 555
receiver and HS-60 servos, although other
equipment could be used (such as FMA
receiver and servos).
The center of gravity should be 11⁄4
inches behind the leading edge of the top
wing.
The battery pack contains four 250 mA
AAA-size batteries, and it gives plenty of
flying time.
Because of its size, the Gipsy Moth
should be hand-launched with a smooth
departure. Once in the air, it is a niceflying
model and the throttle control lets
you do low, slow flybys that were not
possible with most 1⁄2A models in the past.
It also will loop and do open rolls.
On several occasions, we have had the
“big” and “small” Gipsy Moths in the air
at the same time, which is quite a sight.
One of my favorite maneuvers is
performed at sunset, when the sun is at a
low angle. I pull up into a down-sun
wingover, and the registration numbers
seem to glow when the sun’s rays hit the
upper wing. MA
Frank B. Baker
5301 Burnett Dr.
Madison WI 53705
