REFLECTOR: STRONG PITCH TRIM SYSTEM

Dave Black dvblack at comcast.net
Fri Nov 5 11:15:42 CST 2004


> Tom,

I too am a member of the "Non-Flyers as of yet" club. But that never stopped
me from testing the integrity of the roll-trim system. When I first assembled
my slip-string, I simulated hard maneuvers by pushing the stick to its limits.
In every case, the string would slip while in the maneuver, and require
retrimming upon exit. There is no reason to expect this system to operate any
better in flight. At the time I never tried belt dressing or an additional
wrap on the string, which I now understand may have solved the problem. 

> By the way 
 I agree on the use of  “Roll Trim” 
 most people
> I have consulted say they don’t need it and don’t use it!  But
> I’m of the thought 
 if you are going to have it 
 it may as
> well work properly and be of sound design.  The “spring and
> string” is ridiculous.  You don’t even have to be a pilot to
> see that.

That's what I thought, also. At least as far back as 1994 the slip-string
system had been identified as problematic. I followed along with several other
builders at the time and replaced the slip-string with a Mac servo. The system
is reliable, works great, and is easy to control. 

But as you mention, most who have flown the Velocity say you don't need roll
trim at all. Except, of course, to retrim every time the string slips! However
if I were doing it over, I'd modify the roll trim to Ground Adjustable only,
eliminating the copy motor, string, and Mac servo. This would be very easy to
do -- simply install moveable spring-end holders to replace the string. 

Dave Black
Stortwing RG


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