Rudder counterbalance ?

[John Ferrell]

I have thought a little about it but have not done anything towards proving 
my theories.

First, by counterbalance I assume you mean there is an area ahead of the 
hinge line that acts to reduce the power required to operate the surface.

That will impart a "twisting" load on the hinge line. It will induce more 
drag closer to the rudder centerline and higer up the rudder post. I would 
think this force would tend to pull to the canopy (may be good, may be bad). 
since the servo load is less, the damping action would be less. It would be 
more susceptable to flutter with a loose return side on the pull-pull 
rudder.

I have a Goldberg Extra 300 and a Midwest Cap232 that both have this 
arrangement and no problems. I am not aware of either of the planes having 
the problem.

Just my opinion, go ahead & shoot it down...

John Ferrell
http://DixieNC.US

----- Original Message ----- 
From: "Peter Pennisi" <pentagon.systems at bigpond.com>
To: <discussion at nsrca.org>
Sent: Thursday, April 28, 2005 5:29 AM
Subject: Rudder counterbalance ?


>
>
> Hi all,
>
>
> Most of you would be aware that a number of Composite ARF "IMPACT" have
> failed from suspected rudder flutter.
>
>
> I raise a couple of questions to this forum;
>
>
> I know that the purposes of counterbalances are to reduce the loads on
> servos and linkages in our application but what are the side effects.
>
> Can a rudder counterbalance create undesired torsional stresses on the
> fuselage?
>
> Can a poorly configured and tensioned pull-pull linkage to the rudder be
> more susceptible to flutter if the rudder has a counterbalance?
>
> What other types of forces are at play with counterbalances?
>
> I am just trying to find a reason for the relatively high failure rates
> against this design.
>
> It is the same old thing- why are some people having problems and others
> don't. (Similar story to 4-stroke exhaust headers)
>
> I will be test flying my model soon so I am obviously concerned.
>
> Regards,
>
> Peter
>
>
>
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