Rudder counterbalance ?

Grow Pattern pattern4u at comcast.net
Fri Apr 29 20:43:41 AKDT 2005 

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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