Rudder counterbalance ?

Thu Apr 28 19:55:47 AKDT 2005

Peter,
            I nearly got to go to bed.! ...Just ran downstairs...Tripped 
over #2 Son who is back from carrier duty - he said we dropped a lot of 
"stuff " out there. Planes all came back without ordnance,! No lost 
planes....A  bit worried about the local girls however.. it must be that 
uniform thing :-)

Where was I?...Both supplied IMPACT rudders weigh 3.1 oz each without hinges 
or horns

Replacement rudders weigh 1.3 oz before covering.

I tried the supplied rudder and five different servos including an 8611 and 
they all bounced back and forth badly and were potentially destructively.

I then cut it off (the old rudder) and fitted a foam balsa replacement. 
Tests showed no bounce with any of the servos. [8611, 8411, 8417, 8417 with 
8411 gears and the heli 8311 (nylon gears except for output shaft.]

I did managed to stop the bounce another way. I also tried using a single 
wire as opposed to multi-strand. It did work but once in a while I saw bad 
"hunting" as it located the center.

These Impacts have polyurethane foam liners about 1.5-mm thick with a skin 
of glass inside that. They are pretty stiff to begin with.

I did notice that a vertical former at the rear of the canopy area made a 
huge difference in stiffness. Also switching to a four bolt wing retention 
system made the center more rigid.

I have abused my IMPACT #1 and hope that all the mods keep doing their job. 
I still think that the rudder is simply just too heavy and the 
spring/stretch in the pull-pull wire combines to oscillate the rudder just 
like PIO.

Regards,

Eric.

----- Original Message ----- 
From: "Peter Pennisi" <pentagon.systems at bigpond.com>
To: <discussion at nsrca.org>
Sent: Thursday, April 28, 2005 6:19 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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>
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