LRS motor stick twist

From: Tapio Linkosalo <tapio.linkosalo_at_iki.fi>
Date: Tue, 14 Jul 2009 09:09:53 +0300

I decided to build a LRS along the drawings of my previous one, 13 years
ago. Some home-trimming (indeed, this one can be flown in the living
room!) indicated that the cruise was OK, but when I wound the motor
further, the trim was less impressive: the model banked to the left,
followed by yanking to the right, and ended up inverted. I tried adding
left thrust, tail tilt and rudder, but to avail. Even tried to reduce
dihedral on the wing as it seemed that my rudder area was too small,
before building a new, larger rudder. But even this had a minimal effect.

I then thought of curing the left bank instead of right yaw, reset the
wing supports to give a big amount of wing warp. Indeed, this helped,
now the model climbs with authority, without a sign of bank nor yaw. But
the warp seems way too much for efficient cruise, so it should be cured
for the flight. I already have the wing offset by almost 10mm to the
left, so I do not want to do more of that. Instead, I suppose I'd need a
motor stick, that would twist more under load and give more warps when
needed. The question is, how to do this. The current stick is 1.5 * 5mm,
medium hard balsa. I think the dimensions should be smaller, but going
to 1mm sheet gives me creeps, I'd be afraid that id would buckle under
the motor tension. Maybe a T- or I-beam of thin sheet (0.8 to 1.0mm)
would be strong enough against bending, yet torsionally flexible? Or
should I try to make the wing struts more flexible?



-Tapio-
Received on Mon Jul 13 2009 - 23:10:23 CEST