Rudder counterbalance ?

[Richard Strickland]

You guys have got me a little paranoid about my six exits at the 'critical'
area of the fuse.  Since I haven't ever had any kind of flutter problem in
the past with pattern fins and rudders, I started looking at other
possibilities.  On mine, as it turns out upon closer inspection last night,
there is a tiny bit of play in the stab tube and socket. That needs some
work and possibly a little more structure.  There really isn't much there to
keep the stab from wobbling under load--particularly if both stab and/or
elevator halves aren't dead nuts on.  I wonder if the more 'laminar'
flowing, clean design where air flow stays attached has a tendency to
compress the fuse at that point, allowing the stab to move more freely and
that contributes to the problem?   Hmmm....

RS

----- Original Message -----
From: "Peter Pennisi" <pentagon.systems at bigpond.com>
To: <discussion at nsrca.org>
Sent: Thursday, April 28, 2005 5:19 PM
Subject: RE: Rudder counterbalance ?


>
> I am aware of the braces and internal formers. There have been recent
cases
> of failures with all the supporting structures in place.
>
>
> Eric,
>
> How much do your new rudders weigh typically?
>
>
> Regards,
>
>
> Peter
>
>
> Peter Pennisi
> Pentagon Systems QLD Pty Ltd
> P.O Box 4280
> Eight Mile Plains
> QLD 4113
> Australia
> Phone:    61+0738414234
> Fax:        61+0738414264
> Mobile:   0408007206
> Email: pentagon.systems at bigpond.com
>
> -----Original Message-----
> From: discussion-request at nsrca.org [mailto:discussion-request at nsrca.org]
On
> Behalf Of Atwood, Mark
> Sent: Friday, 29 April 2005 4:56 AM
> To: discussion at nsrca.org
> Subject: RE: Rudder counterbalance ?
>
> Well...I can certainly speak to needing this in the Rev Pro...which I'm
> guessing isn't a whole lot different than the Impact in construction.
> The fuselage buckled and snapped in half in flight (and yes...it still
> managed to fly to the ground with relatively little damage).  Added the
> light (4gm) "Ladder" crutch plate behind the wing and no problems at
> all.
>
> I have a photo of the brace if someone is interested...contact me
> offline.
>
> -Mark
>
> -----Original Message-----
> From: discussion-request at nsrca.org [mailto:discussion-request at nsrca.org]
> On Behalf Of Wayne Galligan
> Sent: Thursday, April 28, 2005 2:26 PM
> To: discussion at nsrca.org
> Subject: Re: Rudder counterbalance ?
>
> I have had conversations with a few people that own these airframes
> (Impact)and they along with a few others have strengthened the fuse in
> two
> ways.  A ladder  type frame in the fuse from the wing t.e back to the
> stab
> area and another put a stiffener(former) at the front of the wing area
> to
> decrease the possibility of compression of the fuse in this area.  It is
> believed that compression of the fuse in this area contributes to a wave
> progression all the way back to the tail section.  The tail section
> being
> the smallest and weakest area gets whipped and eventually the fuse
> breaks or
> contributes to tail feather flutters.
>
> From what I've heard....  FWIW
>
> WG
>
>
> ----- Original Message -----
> From: "Peter Pennisi" <pentagon.systems at bigpond.com>
> To: <discussion at nsrca.org>
> Sent: Thursday, April 28, 2005 4:29 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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