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Canadair CL-215 Water
Bomber
by Andrew Curless
Finishing
There are many options open to finishing off the model,
I went for a painted finish using aircraft dope, talc and a mixture of
tissue paper and Sig Coverall since all surfaces are sheet balsa.
The whole model is sanded to final shape with 200 grade
sand paper and then doped a couple of times, then sand off the raised
fluff. This is when I fill any dents or hollows, slap on one more coat of
dope then when dry re-sand. Next apply tissue over complete fuselage using
dope as the adhesive, when complete I Iike to give the whole fuselage one
extra coat of pure dope then two coats of a mixture of dope and talcum
powder, sanding between coats with 400 grit wet and dry, this will give
you a nice smooth finish to apply the undercoat.
The wing and motor nacelles were covered in the same
fashion except I used Sig Coverall which is a shrinkable fabric that I
find very useful for going around complex curves and odd shapes. I filled
the weave of the coverall with the dope and talc mix to get a nice fine
finish, then sprayed the whole plane with auto primer and sanded it back
with 400 wet/dry.
Automotive enamel was then used for the finishing top
coat.
Flying
Having had some experience with twin engined models in
the past I cranked up both motors with some confidence only to find when
both engines were running at full throttle that I had very bad engine
vibration in the left engine.
Why is this so? I changed engine mounts which failed to
stop the vibration but did reduce it. What to do? Then I remembered
reading somewhere in the Airborne Engineer about motor vibration and
harmonics in twins with side mounted engines, so I decided to change the
motors to an inverted position which after some fiddling around with
control cables has solved the vibration problem. (Maybe Brian Winch the
Airborne Engineer can give us some clues as to the cause of the
vibration).
So with both motors running smoothly and reliably it
was off to the local dam for some flying. On arrival the CL 215 bomber was
assembled, radio checked and both motors run up and needle valves set,
then the engines shut down and fuel tanks were refilled. We decided to
take some photos, (just in case), before I committed the aircraft to the
sky. With the photos out of the way I restarted the engines put the plane
into the water and tried to taxi out from the bank.
Wrong. This baby don't taxi at low throttle. After
recovering the plane I decided to put her in the water and just cranked
her right open, which resulted in the plane pulling quite sharply to the
left even with full right rudder and aileron applied, after approximately
5 meters the controls had airflow over them and good control was available
the Canadair Water Bomber rose gracefully into the air.
With both motors running well the plane was trimmed for
neutral flight and flown in a scale like manner around the dam, (read no
aerobatics). First flights are always heart stoppers and this proved no
different, although all control throws proved to be more than adequate.
Ailerons 20mm up and down, elevators 20mm up and down and rudder 30mm left
and right. Center of gravity was set at 30% of the wing cord, (on the
spar), a water rudder is required. The only changes done to the plane as
built off the plan is 1degree of down thrust on both motors and to invert
them.
Conclusion
This aircraft has proven to be an eye-catcher and
gracefully flyer. Though not a beginners scratch built model it is an
excellent step up into either stand-off scale or a seaplane when you want
to be a little different.
A most satisfying and rewarding project.
There is an excellent Web page on the SuperScooper and
the address is http://www.superscooper.com
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