Rudder counterbalance ?

[John Ferrell]

Don't forget the argument between blunt and sharp trailing edges...

John Ferrell
http://DixieNC.US

----- Original Message ----- 
From: "Richard Strickland" <richard.s at allied-callaway.com>
To: <discussion at nsrca.org>
Sent: Friday, April 29, 2005 10:39 AM
Subject: Re: Rudder counterbalance ?


> 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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