CO2 power for model
airplanes gained a lot of popularity in the 1950s and throughout the 1960s and then waned
for some reason in the 1970s. The same cycle was exhibited in Jetex type engines. CO2
engines run off a cylinder of compressed carbon dioxide gas. A metal tube feeds the top
of the cylinder where a metal ball under pressure from the gas seals off the cylinder
until the piston pushes up on it. Doing so forces the piston down to where the gas is
ejected at the exhaust port. Momentum from the propeller mass swings the piston back
to the top of the cylinder where it once again opens the ball valve to start the cycle
all over again.
See the "Push-Air CO2-Powered
Free-Flight" article from the February 1970 American Aircraft Modeler and
"CO2 Power Is Coming Back"
in the April 1969 American Aircraft Modeler. Here is a link to my
DP-03 CO2 motor.
Fizz-Wizz CO2-Powered model Airplane
Clever approach to real ''gas'' flight designing
utilizes Herkimer's C0-2 motor
By Aubrey Kochman
With Herkimer Tool & Model Works' CO2
engine again in production here's a plane designed expressly for this novel powerplant.
The challenge of CO2 designing is as rewarding
as the flights attainable with this engine. Shallow climbing turns and graceful glides
to perfect three-point landings bring back the realism so long missing from free flight.
And no noise to bother your neighbors!
The engine maker offers rough limits for a suitable model suggesting wing area be
between 115 and 165 square inches - our Fizz-Wizz has 135. Allowable "bare" model weight
of up to 5 ounces (less engine, metal fuel cartridge, cartridge holder, fuel line tubing
and propeller) in our opinion is too high. Structurally Fizz-Wizz has more than adequate
strength yet weighs in at a low 2 1/2 ounces (5 with engine and accessories ready to
Since air temperature plays a part in the power output of this engine hot performance
in cold weather is not to be expected. Fizz-Wizz is meant to be a realistic sport model
rather than a high performance contest flyer. Test flights indicated, however, that under
ideal conditions (3 to 5-mph winds, temperature above 80 degrees) Fizz-Wizz with a little
additional trimming should turn in some really respectable durations.
Before starting construction bear in mind the weight and temperature factors. Cold
weather operations call for the use of the lightest possible balsa. For those who year-around
enjoy warm temperatures some additional weight can be tolerated ... although it is not
If you use light balsa your model should balance as indicated. The cartridge holder
location and its angle keep the plane's C.G. from shifting as the cartridge empties.
There is slightly over an ounce difference between a full and an empty cylinder.
Build the tail surfaces last as a means of balancing the model. Should the model turn
out nose heavy, use a heavier grade of balsa for the rudder or stabilizer or eliminate
the cutouts in either or both surfaces. For tail heaviness reverse the procedure ...
use very light balsa, make the cutouts larger and apply a minimum amount of dope.
Begin fuselage construction by cutting the two side pieces to shape; 4" wide sheet balsa
was used. With some careful planning both sides can be obtained from a single sheet.
Cut off the "power-pod" section and put the pieces aside where they won't be used by
mistake for formers. Cut out all formers and check that F1 through F6 are all the same
width ... F10 and F11 should also be of this same width. F1, F2, F10 and F11 should also
be set aside with "power-pod" sheets.
Loading a carbon dioxide fuel cartridge into
Fizz-Wizz "power-pod" is easy. Little chance of kinking or fracturing brass tube which
carries gas to C0-2 engine.
Attaching "power-pod" to fuselage. Full size
working drawings for Fizz-Wizz and Wizzo-Won are on Hobby Helpers' Group Plan # 362.
Assemble fuselage by cementing both sides to F5 and F6. Draw tail together, check
that fuselage is true along center line seen from the top. Cement tail together, add
remaining formers. Sheet cover top and bottom with grain running lengthwise - moistening
underside of top sheet with water between F6 and F7 will make this bend possible. Water
moisten outside of side pieces between F3 and F5 and apply a coat of cement to the inside.
As cement dries and with a little assistance on your part the side sheets should assume
their proper curve. Cement F3 in place, trim side sheets so they butt together. Cement
in appropriate lengths of 1/16" x 3/16" so half their width extends into the "power-pod"
section. These strips act as guides or keys to hold pod from shifting.
Before constructing the "power-pod" ... a word of explanation. The standard way of
loading a CO2 cartridge has been by pulling the holder down through a hole
in the fuselage bottom. Because the brass tubing through which the CO2 flows, although flexible, is quite stiff we felt that
the less bending required during the loading operation, the less chance there would be
for a kinked or fractured tube. Our "power-pod" eliminates these possibilities. Since
the lower end of the cartridge holder and thumbscrew extend outside the fuselage, the
cartridge may be replaced and plane assembled for flight without your having to launch
the model immediately.
Then, too, the cartridge can be pierced properly but the thumbscrew not backed off
enough so that gas flows to the engine. With cartridge completely enclosed, it is necessary
in such designs to disassemble the model to make the necessary adjustment.
This powerplant can operate clockwise or counter clockwise. Should the engine fire
up backwards you don't have to grab the prop with your hand, just stop it by tightening
But enough of this ... back to construction. Make F10 by cementing the two pieces
together - with grain crossed at 90 degrees: Bend landing gear to shape as shown on front
view and bind it to F10 using strong thread and plenty of cement. Mounting holes for
engine should be drilled in F1 and mounting nuts secured to rear of former. "Devcon"
2-ton epoxy glue does a good job of holding metal to wood, eliminating the need of soldering
the nuts to a metal plate. This glue takes overnight to harden. An alternate method would
be to mount the engine with small wood screws. With no glow fuel to slosh around the
engine compartment, and barring hard knocks, this latter type mounting should prove adequate.
cartridge holder bed F11 and assemble "power-pod." Check that it mates properly with
the main fuselage. Water condensation forms on the outside of the spent cartridge so
waterproof the inside of the pod by applying at least 3 coats of clear dope. The cartridge
holder is bound to the 1/8" x 14" strip and F11 with strong thread and cement. Lower
end of holder was cemented to the bed using the 2-Ton glue.
Our wing, quite simple, is built in halves. It is assembled with a dihedral brace
and short lengths of spar stock to form the flat center section. The 1/16" sheet tip
outline should be level with the top spar. Light construction dictates that all parts
fit properly before cementing. Don't rely on cement to fill spaces between poorly fitting
parts. As cement dries and shrinks over a period of days, it could pull misshapen parts
out of alignment. And this type of built-in warp is the most difficult to eliminate.
With construction completed go over entire framework with fine sandpaper, then make
sure all joints are strong. Apply a coat of clear dope to all framework and allow to
dry. Another light sanding may be necessary to take down the fuzz raised by the dope.
To keep weight low entire model is covered with colored Jap tissue. Remove any warps
that occur during the covering-doping process. The stabilizer requires constant vigil;
should it show a tendency to bow or curl, pin it to a flat surface until thoroughly dry
- preferably overnight.
The tail surfaces may be cemented permanently in place or held to the fuselage with
light rubber bands. Latter makes flight trimming easier.
First flights should be on a calm day. Make test glides with the cartridge in place.
Stalls can be dampened out by adding some positive incidence to the stabilizer. However,
if more than 1/16" positive is required add weight to the nose instead.
For warm weather testing (above 75 degrees) don't launch the model until the initial
burst of power has subsided. Then if all goes well, subsequent full power flights are
Cold weather requires that the model be launched as quickly as possible, even on first
flights. Hold the model in launching position and have a helper flip the prop so that
no time is lost in the plane getting airborne. The CO2 engine develops most
power as soon as the prop is flipped and diminishes thereafter so considerable altitude
can be gained by this quick-launch method.
CO2-Powered Model Airplane Plans
"Fizz-Wizz" Materials (Balsa unless otherwise noted)
Two pieces 1/16" x 4" x 36"; (1) 1/32" x 3" x 36"; (1) 1/16" x 3" x 36"; (2) 1/8"
x 1/8" x 36"; (2) 1/16" x 1/16" x 36"; (1) 1/16" x 1/8" x 36"; (1) 1/8" x 5/8" x 36"
tapered trailing edge stock.
Also: 1/8" plywood; 1/8" dia. birch dowels; 1/16" dia. music wire; 1/32" dia. music
wire; 1 pr. #3 Trexler wheels; cement; clear dope; colored Jap tissue; celluloid.
The AMA Plans Service offers a full-size
version of many of the plans show here at a very reasonable cost. They will scale the plans any size for you. It is always
best to buy printed plans because my scanner versions often have distortions that can cause parts to fit poorly. Purchasing
plans also help to support the operation of the Academy of Model
Aeronautics - the #1 advocate for model aviation throughout the world. If the AMA no longer has this plan on file, I
will be glad to send you my higher resolution version.
Try my Scale Calculator for Model Airplane Plans.
Posted September 2, 2013