[SPAM] Re: [SPAM] Re: Rudder counterbalance ?

Ed Alt ed_alt at hotmail.com
Sat Apr 30 01:25:02 AKDT 2005


meant to say stored energy in the flexed hinges, not 'fixed' hinges

----- Original Message ----- 
From: "Ed Alt" <ed_alt at hotmail.com>
To: <discussion at nsrca.org>
Sent: Saturday, April 30, 2005 5:21 AM
Subject: [SPAM] Re: Rudder counterbalance ?


> Eric
> Just curious about more details on the hinging on the Impact. Having just 
> completed an OTOP, I wonder if the Impact has a similar arrangement.  If I 
> would have gone with the stock setup, it would have meant that 4 small 
> Robart hines would be hanging suspended in air over 1/4" either side of 
> the hinge line.  This seemed unacceptable, as I figured it would just 
> break the hinges in short order from all the flexing of the unsupported 
> plastic.  All I did was to add balsa filler blocks for each hinge 
> location.  It required cutting off the nub on the bottom of the rudder to 
> let me slide the blocks in, but that was easy to do and reset the piece 
> later.  Rock solid so far (7 flights) with an 8411 converted to SA and 
> this rudder is realtively heavy as well.  I don't have the weight figure, 
> but can get it from a friends unfinished OTOP if it helps to unravel the 
> mystery.
>
> I guess the point of asking about this is that there may be a combined 
> effect of the relatively high mass of the ruuder and the flex of the 
> hinges if something similar was in play with your original setup.  I 
> understand the way the oscillations could start/sustain with just too much 
> mass for the setup to contend with.  However any flex could make it even 
> easier to commence, as the servo's attempt to arrest rudder movement would 
> be hampered and secondary movements from the stored energy in the fixed 
> hinges would have to be dealt with milliseconds later.
>
> Ed
>
> ----- Original Message ----- 
> From: "Grow Pattern" <pattern4u at comcast.net>
> To: <discussion at nsrca.org>
> Sent: Saturday, April 30, 2005 12:43 AM
> 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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