Re: LRS motor stick twist

From: Nick Ray <lasray_at_gmail.com>
Date: Tue, 14 Jul 2009 12:47:45 -0400

Tapio,I use virtually no twist in my motor sticks for Minis because it seems
to want to torque roll if the stick isn't matched just perfectly the prop's
flare. What I would recommend is to try and drop your pitch say 2-3* and
then go to a slightly thicker piece of rubber than what you were using and
back off until your launch torque is same less that it previously was. This
should alleviate most of the acrobatics. The other thing that I like to do
is to fly props that are about 1cm in diameter less than the span of the
wing and horizontal stab. This seems to limit the torque's tendency to
rotate the plane.
Nick

On Tue, Jul 14, 2009 at 2:09 AM, Tapio Linkosalo <tapio.linkosalo_at_iki.fi>wrote:

>
>
> 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 Tue Jul 14 2009 - 09:49:32 CEST