> I heard someplace local that the sidearm HLGs are experiencing structural
> problems at 60" spans while at lower spans like 50" this is being reduced.
> Something like the wing is not holidng up.
>
> Does anyone have any observations on this situation and potentiallhow the
> resioultion people are seeing?
>
> Thanks,
> CA
>
Chris,
There has been some work lately on making aileron sidearm ships flutter
proof. More than likely facing the ailerons with cf or stiff balsa and
reinforcing the stress riser where the aileron ends will solve it.
There is no real problem with the fixed wing planes. Thanks to "Father
Discus", Dick Barker, these have been ironed out thanks to many hours of
experimentation.
There are different forces applied to the airframe, naturally. Stress
points show up at the wing to pod mounting area, and at the wing tip.
The Europeans are convinced that a peg is the way to go, and there have been
reports of molded hand launch ships getting 60 meters of launch height.
This is sort of taking the 100' number of last summer and putting it in the
trunk!
While we were all obsessed last year in getting the weight down, the
Europeans (Austrian, specifically) were working on optimized planforms such
as their elliptical plane that was at about 13 oz. This plane can cruise
very well, and at a place like Poway, that is the name of the game in the
afternoon. A 7 oz plane, no matter how slick, can not come back from the
hill in a 15 mph breeze. How does this relate to sidearm? It appears that
weight has very little to do with launch speed, as opposed to overhand
throws. This means that you can throw a 13 oz plane VERY high due to the
carried momentum.
The primary force along the wing, once it is spinning, is tension. This is
an easy one to take care of; carbon fiber is excellent in resistance to
tension. The torsional components, consisting of the lift factor and more
importantly, the pilots holding/releasing of the plane, are taken up by
biased construction in the lay up.
I've retrofitted some wings by placing a 1/16" cf rod under the spar in the
tip, and Dick has told me he is fiddlin' with some 1/16" vertical grain
balsa shear web material.
I have successfully flown a wing with just a center flap. There has been no
sign of flutter or failure, maybe due to the inboard proximity. This wing
has a lot of promise, for controlling the speed is important for the ladder
events.
As far as ship size goes, Bill Watson of your old club has made a 100"
sidearm plane that weighs 17 oz.! It is really a thing of beauty, yet
ironically, the handling capability when close to the ground is
"compromised". Maybe there is an optimum size for hand launch, and it is
close to the legal size we currently have.
JE
--
Erickson Architects
John R. Erickson, AIA
RCSE-List facilities provided by Model Airplane News. Send "subscribe" and
"unsubscribe" requests to [EMAIL PROTECTED]
