Rudder counterbalance ?
Keith Black
tkeithb at comcast.net
Sat Apr 30 14:20:17 AKDT 2005
Yes you answered the question, and yes I did mean "horn".
The reason I ask is I've seen elevator flutter caused by the pivot point of
the control horn being slightly in front of the hinge line (thus causing the
non-pulling cable to tighten). This could also be caused if the servo pivot
points are offset too much.
I normally try to get the pivot point right over the hinge line, but after
seeing this I've been sure to error on the side of setting the pivot point a
smidgen behind the hinge line rather than in front.
Keith
----- Original Message -----
From: "Grow Pattern" <pattern4u at comcast.net>
To: <discussion at nsrca.org>
Sent: Saturday, April 30, 2005 4:18 PM
Subject: Re: Rudder counterbalance ?
> Keith,
> I don't really understand the first part of your question. Did
> you mean horn in the first sentence? It is a simple Mylar hinge with a
> bevel. Just like a regular rudder.
>
> I fitted a commercial rudder horn bolt which left the horn points slightly
> behind the hinge line. I set my servo arm holes so that the "non pulling"
> wire stays reasonably taught.
>
> Did I answer it?
>
> Eric.
>
>
> ----- Original Message -----
> From: "Keith Black" <tkeithb at comcast.net>
> To: <discussion at nsrca.org>
> Sent: Saturday, April 30, 2005 9:46 AM
> Subject: Re: Rudder counterbalance ?
>
>
> > 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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> >> >> >
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