Mr. Hauser wrote the following interesting
letter August 1998:
Toni Clark practical scale GmbH
32312 Lübbecke 3.
with this letter I wish to thank you for your superb Piper kit.
This is my first large model, due to my very restricted free time
it has taken me almost 2 years for completion and ready to fly.
The more than excellent instruction manual plus the very easy to
read plans is very helpful. The Piper has now been flown for some
weeks with the ZG 45SL and the Hydro Mount System, and more
recently the Easy Start System. Now with a hot engine, starting
is a lot easier.
In the beginning I had to really exert myself to get the kite down,
as I could not throttle the engine low enough. I had too much play
in the throttle Bowden cable, which I had laid around the front
of the engine in a 180 degree bend. Any Bowden cable that is fitted
with a 180 degree bend has a wide dead spot between pulling and
pushing which automatically causes play to develop. This dead spot
and subsequent play is considerably reduced with a 90 degree bend,
the springiness lays with the Bowden cable outer tube. Your recommendation
is absolutely correct and must not be altered in any way. Perhaps
you can add a few words to your building manual explaining the disadvantages
of altering the Bowden cable layout. I have seen many HMS equipped
models with the Bowden throttle cable laid around the front of the
engine which led me into copying this mistake. I would guess a few
of these modellers are sweating profusely on the finals ... or later
in the modeling room ...
I have included a few photo's of my PA18 Burda Piper; that you
can add to your pin board in case you have such a thing. I have
painted the whole of my Piper with the exception of the cowl, with
a foam plastic sponge roller. Using cheap normal alkyd resin paint
warmed on the kitchen hotplate which has proved to be very successful.
The resulting paint finish can be kept to an absolute minimum reducing
all up weight (9 kilos ready to fly). Spraying is better, but many
modellers do not have this amenity at home. Last winter I rolled
side for side with enough stand down time between in a "requisitioned"
room in the house and one can not see any difference to a sprayed
surface. Maybe this is a helpful tip for other modellers
Our thanks to Herr Hauser for his valuable tips.
On the subject of the throttle linkage a further important
point from me:
The Bowden cable should be connected so the throttle lever
return spring causes the throttle lever to press against and not pull on the Bowden cable. Due to the vibration
induced swinging of the 90 degree bend the Bowden cable is
thrown outwards, similar effect to a skipping rope, when the
return spring pulls against this movement the tickover speed
will fluctuate considerably. One time is the return spring
stronger and pulls the Bowden cable inwards, another time
is the rpm altered and the swinging is stronger (resonance
effect) and the Bowden cable is thrown outwards. This immediately
raises the tickover speed. When you then throttle down the
engine it stops as soon as the return spring gains the upperhand.