If you have ever
wanted to try your hand (thumbs, to be more specific) at a floatplane, then this 1/2A
Champion is just the ticket. Although designed by Walt Mooney as a free flight ROW
(rise-off-water) model that easily converts between wheels and floats, modifications
to 3 or 4 channel radio control would be a snap, especially since the plans show separate
construction for the control surfaces along the hinge line. With about a 46" wingspan
and lightweight but strong construction, this model could easily have been designed with
modern electric power and micro R/C in mind (you can scale the plans to whatever size
you prefer). When I saw the photo of the 2-section wing with a plywood center joiner
and removable floats, wheels and struts, it reminded me of an RTF type airplane, but
of course you must build this Champion yourself.
by Walt Mooney
Take-offs from the water are snappy and landings are beautiful to
behold. Let's get going!
On land or sea this flying scale model for .049 power is as real as real can be. Hundreds
of successful hops.
Why make the Champion? To come right to the point, the following reasons explain why
the Aeronca Champion makes a perfect flying scale model.
The full-sized airplane is very easy to fly and, I guess, every pilot likes to build
a model of a plane that he has flown. The "Airnocker" is common enough so that details
are easy to study first hand. It is fabric covered so that true scale appearance with
a light flying weight is easily obtainable. It has the right aerodynamic setup to make
a fine flying-scale model. That characteristic orange-bellied color scheme is impossible
to mistake for a Cub. Convinced?
The original model shown in the photographs is over two years old. It has been flown
in two contests, taking second in a field of 16 in San Diego, and seventh at the last
California Nationals. It has also been flown as a sport ship several hundred times with
and without floats. On wheels, it glides flat and climbs steeply, typical flight times
being 2:33 on a :35 engine run and 3:30 on a :49 engine run. With floats, take-offs are
snappy and the landings are real pretty. Water take-offs work best in calm weather and
with maximum power.
The model is exact scale with two exceptions: these are increased dihedral and a slightly
enlarged horizontal tail. People familiar with the free-blown bulgy windshield on some
of the real Champions will complain about the one on the model, but the windshield shown
is scale for some Champions (not all of them had the real bulgy windshield) and is much
easier to model. The floats are definitely not scale floats but they are semi-scale and
have the right relative size. They were designed to work well on a model.
Don't forget to fasten the safety belt. Increased dihedral, slightly
enlarged horizontal tail are the only departures from scale.
The wings of the Aeronca Champion model have the scale number of ribs and, in general,
scale structure. They are relatively straight forward as far as construction goes. Care
must be taken when cutting out the slots in the three inboard ribs for the plywood wing
tongues, in order to give exactly the same incidence angle in each wing. The wing tips
are laminated from five plys of 1/32 x 3/16 balsa. A form block is cut from boxwood scrap
to the inside contour of the tip, then the balsa plies are coated with cement and formed
around the block. When dry, this gives a very strong tip bow which is nearer to scale
construction than the common flat sheet-balsa tip. Remember to wax the form block so
you can remove the tip bows when dry.
The tail surfaces require no explanation hut don't omit the little triangular gussets
shown. They prevent the corner wrinkles which appear so often on covering and doping
flat tail surfaces.
The fuselage is basically a straight forward box. The two sides are built up, one
above the other, in the interests of similarity, on the plans. The left and right side
can be exactly alike unless you want to make a working door. The door is on the right
side of the fuselage only and is indicated by the phantom (- .. -) line. If you intend
to make a door, fill in the right hand frame with 3/16 sheet back to the front of the
back window; 3/16 square balsa is used for all the basic structure. After all the cross
braces are in, build up the wing center section. Eight center-section root ribs are required
from 1/8 sheet. Four are laminated together for each side. The forward ends are rounded
off as shown in the top view to form the windshield outline. Carve a trailing edge section
and cement it to the fuselage frame, then add the root ribs. The wing box is made from
1/16 plywood. It should be a good fit in the slots in the root ribs. The center section
is probably the most difficult part of the model but studying the plans and a little
patience make it not too hard.
After the center section is on, cut out and cement the formers in place. Next, add
the planking aft of the firewall to the front of the landing gear. The side planking
of 1/8 sheet must be carved after installation to the contour shown in the fuselage section
looking forward. Now add the 1/16 by 1/8 hard-balsa stringers.
Floats and land gear are quickly interchangeable. Floats are not scale,
but are semi-scale and are the proper size. They do work!
The main landing gear is bent from 1/16 diameter music wire. It should be cemented
to the frame and wrapped with thread at the four bends that contact the frame. The 1/32
diameter cross wire is bent to shape and soldered to the main landing gear wire. The
tail wheel wire is made from 1/16 diameter music wire and cemented and sewed to the fuselage
framework. The fairing for the main gear is made from 1/8 sheet balsa.
The motor mount installation shown is made from plywood. Weldwood glue is recommended
for this job because it is not affected by fuel and is very strong. Cut the firewall,
two sidepieces, and the top piece of the motor mount from 1/16 plywood. The front piece
to the motor mount is made from 1/8 plywood. Glue these together as shown on the plans.
If you are using some engine other than the Mac diesel shown, be sure to check and see
that the motor mount as shown will work. If not, you will have to modify the side and
top pieces of the box. Cement the firewall to the front of the basic fuselage.
cowling on the original model was made from fibreglass. This material makes an exceptionally
strong and abrasion resistant cowl. A solid-balsa cowl is carved and finished to a very
good polished surface. Then, a plaster mold is made. The fibreglass cowl is then made
up inside the plaster mold. Advice on the exact procedure to be followed can be obtained
at the same place that the glass cloth and resin can be purchased.
If you don't want to tackle the fibreglass cowl, simply hollow out the solid balsa
cowl to clear the engine installation and use it.
The fuel tank that was used on the original model was made of celluloid cemented together
with model airplane cement. This will work fine with a diesel but if you plan to use
a glow-plug engine, either solder one up out of brass shim stock or buy a small commercial
tank. The filler line to the tank was arranged to stick out one of the cooling air inlets
in the cowl. Therefore, the only out-of-scale hole in the cowl was for the needle valve.
If your engine can be made to operate without adjusting the needle valve, turn the motor
over and face the needle valve down eliminating even this hole.
Standard model procedures can be used for covering the model. The original was covered
with Silkspan, given three coats of clear dope, two spray coats of silver, then three
coats of orange-yellow dope, then the orange belly trim and numerals were added. The
orange was made by mixing approximately 50/50 parts of insignia red and the yellow.
Wing panels knock-off - tongues slide into center-section boxes. Rubber
bands looped over wheel hubs give quick float attachment.
The movable surfaces were attached with soft iron wire as hinging material. The struts
are made as shown on the plans. Although the wire leading edge is somewhat heavier than
usual, it saves a lot of broken struts on the field and is felt to be worthwhile. The
upper ends of the struts slide into aluminum tubing sockets which are cemented to the
wing at the points indicated by X's on the wing plans. The bottom of the struts hooks
into a wire loop that is attached to the fuselage structure. See the strut fitting details
on the plans. Add thread bracing for the tail to simulate the wire bracing of the original
The windows are made from 1/32 thick plastic sheet and care should be taken not to
smear them with cement when attaching them to the airplane.
If you want a seaplane version, build the floats as shown on the plans. These are
made of sheet balsa and must be thoroughly waterproofed. An aluminum tube will be required
in the fuselage to take the aft brace wire for the pontoons. This wire is silked to the
pontoons as shown on the plans. The front support block fits around the wheel hubs and
is attached with rubber bands.
If you want to build only the seaplane version, the author would suggest one change
to the model. With the pontoons in place, less dihedral is required. In windy conditions,
less dihedral would be helpful while on the water, to cut down on the normal overturning
tendency when taxiing crosswind.
A short trip to the airport will supply you super scale fans all the details that
you want. And if the longerons sag on your model because the covering is too tight, take
a camera along and substantiate the sag with a photograph. Almost all the real ships
Make sure there are no warps in the model before you leave home. Make sure the engine
runs. Try it the night before. Unless you have some good tall grass make your first flights
ROG. Otherwise check the glide with some hand-launched flights. It should glide flat
and fairly slow. The elevators can be used for trim. Adjust the rudder for a wide (almost
straight) right turn.
Now try some low power ROG flights. Any drastic turning tendency will show up before
the model is airborne. If there is a turning tendency, correct it. Gradually, increase
the power until the airplane climbs out. It should climb almost straight out and glide
in right circles. A slight left turn under power is satisfactory.
Posted November 28, 2015