Rudder counterbalance ?

[Karl G. Mueller]

Peter,

I have tried dynamic counterbalances on rudder and they're
not as effective as I would like these to be.
The most effective assist for the rudder is a boost tab using
approximately 8 to 10% of the rudder surface centrally located
on the trailing edge. With the pressure against the boost tab
there is less chance of flutter and you don't need a 200oz.
servo to move the surface. You will also find that you need
less throw for the rudder to be effective because of less blow back.
WW II Bombers had these boost tabs on ailerons as well and these
were operated by the pilot mechanically ( no hydraulics ) and would
than deflect the surface.
These are my findings with rudder counter balances.

Karl G. Mueller
kgamueller at rogers.com

----- 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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