Rudder counterbalance ?

Sat Apr 30 05:39:23 AKDT 2005

Where was the damper installed?

----- Original Message ----- 
From: "Grow Pattern" <pattern4u at comcast.net>
To: <discussion at nsrca.org>
Sent: Friday, April 29, 2005 11:43 PM
Subject: Re: Rudder counterbalance ?

> Jim,
>        I had already converted the IMPACT supplied rudder over to a 
> regular Mylar hinge set up because of the side-play in the hinge-pin 
> design supplied.
>
> It oscillated with the stick pin hinges at the first switch-on. I "pulled" 
> the composite the rudder off and fitted it with a new stern-post and 
> beveled the LE, on the rudder. Then I tried all of the servos previously 
> listed.
>
> I then cut off the IMPACT rudder and fitted the new (red) one as you can 
> see on RCU.
>
> As powerful as our new digital servos are I don't think that they "brake" 
> the return swing as well as they initiate the first movement/response.
>
> It is noticeable that the bigger planes use multiple servos with the 
> thinking that more power is needed. It is more stopping power that, IMHO, 
> the we really need.
>
> I had an 8611 that bounced when used to drive a big old VISION rudder. 
> After fitting a damper from an RC car it performs flawlessly.
>
> Regards,
>
> Eric.
>
>
>
>
> ----- Original Message ----- 
> From: "J.Oddino" <joddino at socal.rr.com>
> To: <discussion at nsrca.org>
> Sent: Friday, April 29, 2005 3:26 PM
> Subject: Re: Rudder counterbalance ?
>
>
>> Eric,
>> What you were experiencing was oscillation of a servomechanism and that
>> could contribute to flutter and flutter could be what is breaking the
>> Impacts but I've never heard anyone say they heard the rudder flutter 
>> before
>> the fuse exploded.  I don't think we understand the root cause yet.
>> Right now I'm interested in the servo/rudder oscillation.  I'm wondering 
>> if
>> the real solution is completely due to the light weight rudder or/and to 
>> an
>> improved hinging system, or did both have the same hinge installation? 
>> Can
>> you hang weight on your present rudder and make it oscillate?  It sure 
>> would
>> be nice to cure this problem for all time because I've seen it on many
>> planes.  I've never heard of it breaking fuselages before though.
>> Thanks for all of your experimentation.  In the end it is more important
>> than understanding the theory.
>> Jim O
>> ----- Original Message ----- 
>> From: "Grow Pattern" <pattern4u at comcast.net>
>> To: <discussion at nsrca.org>
>> Sent: Thursday, April 28, 2005 8:55 PM
>> Subject: Re: Rudder counterbalance ?
>>
>>
>>> 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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