Rudder counterbalance ?

[Keith Black]

Eric, where were the hinge points on your original rudder after installing
the new leading edge? Were they exactly over the hinge line, slightly behind
or slightly in front of the hinge line?  Also, did you use any offset on
your servo control arm?

Thanks,
Keith Black

----- 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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