Rudder counterbalance ?

[Grow Pattern]

Peter,
           The answer to the hatori header failure difference was heat :-). 
Mine only broke when I upped to the summer YS 30%. which made the metal 
brittle.

I have just about every rudder shape and counter-bal.  that you can think 
of, including all moving rudders - no flutter.

I am convinced that the IMPACT rudder is too heavy and the recommended and 
specified 8411 gets into a death-dance. Mine did it repeatedly on the bench 
and it was extremely violent. One new 2 oz lighter rudder later and bye-bye 
unstoppable oscillations.

Regards,


Eric.

----- 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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