Four Star 60>Aileron Flutter>Crash!
Kristofer R. Wagner
months of work. I had it outfitted with a YS .91AC and a brand new JR
8103 PCM radio. Covered in red/yellow/black to match Sean McMurtry's TOC
plane. Here are some photos:
http://moon.ouhsc.edu/kwagner/images/image12.jpg
http://moon.ouhsc.edu/kwagner/images/image13.jpg
http://moon.ouhsc.edu/kwagner/images/image14.jpg
http://moon.ouhsc.edu/kwagner/images/image22.jpg
http://moon.ouhsc.edu/kwagner/images/image24.jpg
I made several mods to strengthen the plane against mechanical failure,
including:
1) Replaced elevator and rudder pushrods with Sullivan #511 Steel Rods
2) Replaced tailwheel with Sullivan 5-12# 5/24" axle Tailwheel
3) Reinforced stock aluminum landing gear with B&B Specialties 3/16-1/4' LG
Reinf. Standoff
4) Strengthened aileron servo mounts with wood screws countersunk from bottom
of servo hatch plates
http://moon.ouhsc.edu/kwagner/images/image71.jpg
http://moon.ouhsc.edu/kwagner/images/image78.jpg
http://moon.ouhsc.edu/kwagner/images/image80.jpg
http://moon.ouhsc.edu/kwagner/images/image85.jpg
5) Used Radio South fiberglass CA hinges on all control surfaces
We fired up the YS on Tuesday and broke it in with a tank of fuel, and it
ran flawlessly. I met my test pilot at the field yesterday for the big
day and all preflight checks were done without incident. Taxi and takeoff
were smooth, straight and true. He flew it around a couple of laps
without any trim adjustments needed. Then while flying straight and
level, all of a sudden I heard a LOUD vibration over above the deep note
of the YS. My first thought was that the notorious muffler had fallen off
on the first flight! When I looked closer, however, what I saw was much
worse...both ailerons were fluttering like mad for about three or four
seconds and then as he throttled back, it was obvious that he had no
control over the ailerons. He was able to fly the plane inverted for a
couple more laps using only rudder and elevator, but eventually it went
into a spin and cartwheeled. The wing is broken in half on the right, and
the fuse is completely broken at the tail.
Post-mortem revealed that the gears had been completely stripped in both
aileron servos from the horrendous flutter. The ailerons did stay hinged
in though. In looking for the cause, the only thing we could find was the
way I did the aileron linkages. I set them up with the clevis on the
farthest hole from the center of the servo and the nearest hole to the
aileron. All control throws were set at those recommended by Sig in the
manual. There was no slop in the linkages, servos were brand new JR 517s,
aileron were reinforced with thin CA all around the control horns, and the
hinge gaps were nice and tight. Although the YS .91 is on the high end of
power for this plane, it wasn't nearly going full speed when the flutter
occurred. Several other guys in the club have also used the YS on this
plane without problems.
I plan to rebuild, but I'm scared to death to have the flutter occur
again. Has anyone else had this problem with the Four Star 60? What else
should I do to prevent this?
Thanks in advance,
Kris
--
Kristofer R. Wagner
email: kristofer-wagnerATouhsc.edu (please replace AT with @)
Unknown
sounds like it was a freak accident and perhaps
wrong servo horns were used? possibly mixed up
with a larger size on your bench?? could happen..
anyway, if it was pure flutter from wind and speed, the best
curall is to monocote over the hinge gap. in other words,
seal the entire aileron gap with a strip of monocote on the
bottom or top or both, but you only need one side. this will prevent
any airflow going between the aileron and the wing t.e. and
prevent flutter. doing this, u dont have to worry about gaps
either if you happen not to make it as tight. oh, dont forget to
flex the aileron fully up before ironing the bottom and fully down
before ironing the top. whatever u may choose, only one side
is needed.. hope this helps...
and try the stock hardware first. i never heard of anyone with
any 4 star having trouble with the stock hardware. upgrading
isnt always a good thing.. i use the nylon pushrods and
everything stock on mine.. works perfect..
BobH344
all of this ->if your gonna flyem, your gonna crashem!
Good luck on the rebuild, all of the fear of the first crash will be gone.
Bob
bob...@XNOSPAMXaol.com
Please remove XNOSPAMX if responding directly
Thanks
Bob
Dr1Driver
>should I do to prevent this?
I've heard of this on the Four Star. Besides what you've described: Use more
hinges, seal the hinge gap, use one servo per aileron, with straight 4-40 rods
and linkage. Use a threaded metal clevis at the horn and a Z-bend or solder
clevis at the servo arm. You're correct to use the long servo arm and short
control horn. That's a mechanical advantage. However, it's a disadvantage as
flutter works its way back along the linkage to the servo. Try to equalize the
arm and horn length. Use really hard balsa for the ailerons and consider
counterbalancing them. Best of
luck to you!
Dr.1 Driver
"There's a Hun in the sun!"
Bipesmoker
>seconds and then as he throttled back, it was obvious that he had no
>control over the ailerons.
Now that is a REAL tale of woe! It sounds like you did everything as right as
possible, construction wise. I assume you left the ail te's square. The only
SURE flutter preventer is a balanced surface. That means getting the control
surface cg at the hinge line. Only then can you really breathe easy!
Kristofer R. Wagner
Yes, I think that this was it. I had set it up this way thinking that
this would give me the maximum possible aileron throw. Of course, as you
stated, I used the computer radio to turn down the travel to about 75% on
both. My plan was that once I was comfortable with the recomended throws
(later), I could just use the computer to increase them. Fatal mistake.
An expensive lesson in mechanical leverage and flutter.
Kris
In article <383d...@news.internex.net.au>, "Graham Kay"
<grah...@connexus.net.au> wrote:
> Kristofer
>
> I am a little surprised that none of the other replies have suggested any
> doubt about your clevis set up
> If I understand you correctly you have set up the clevis on the servo on the
> furtherest hole from centre and on the aileron horn you have used the hole
> closest to the pivot point. If this is so it is a sure formula for flutter.
> I would guess you would have had to reduce you servo travel considerable in
> the computer set up to get aileron throw down to a flyable level.
> If possible in my opinion you should always try and use the longest lever
> moment that it is possible to use on the movind surface. In fact it is
> preferable to have both the lever lengths of the servo and the moving
> surface at the same langth.
> If you really did set it up as I have understood you, then this is the
> primary cause of the flutter.
> To me mind the mechanical settings of all control surfaces should be set so
> that you are able to use 100% travel settings in the computer. This also
> means 100% on the low rates. High rates would be say 120%. Or at the very
> worst low rates at 80% and high rates say at 120%.
> You can than make fine computer adjustments when you fully trim the model.
>
> I am a little disappointed that your test pilot did not thoroughly check
> this out. I am a test pilot at our field and certainly would not have
> attemted to fly the plane with the settup you have described
>
> Graham Kay
Paul J. Burke
control horn.
Why you would need to do this escapes me!
It's the worst possible position, giving a lot of control motion... too
much too quickly, MOF, and the least possible resistance to flutter.
None of my planes, many of which are super responsive in roll are set
up this way, precisely because of the lack of resistance to flutter,
and don't suffer from any sluggish aileron response with the servo
pushrod in the outermost hole on the horns.
--
PJB's Seriously Aeronautical Stuff
http://www.networkone.net/~pjburke
Sent via Deja.com http://www.deja.com/
Before you buy.
Graham Kay
I am a little surprised that none of the other replies have suggested any
doubt about your clevis set up
If I understand you correctly you have set up the clevis on the servo on the
furtherest hole from centre and on the aileron horn you have used the hole
closest to the pivot point. If this is so it is a sure formula for flutter.
I would guess you would have had to reduce you servo travel considerable in
the computer set up to get aileron throw down to a flyable level.
If possible in my opinion you should always try and use the longest lever
moment that it is possible to use on the movind surface. In fact it is
preferable to have both the lever lengths of the servo and the moving
surface at the same langth.
If you really did set it up as I have understood you, then this is the
primary cause of the flutter.
To me mind the mechanical settings of all control surfaces should be set so
that you are able to use 100% travel settings in the computer. This also
means 100% on the low rates. High rates would be say 120%. Or at the very
worst low rates at 80% and high rates say at 120%.
You can than make fine computer adjustments when you fully trim the model.
I am a little disappointed that your test pilot did not thoroughly check
this out. I am a test pilot at our field and certainly would not have
attemted to fly the plane with the settup you have described
Graham Kay
Kristofer R. Wagner <kristofe...@ouhsc.edu> wrote in message
news:kristofer-wagner...@157.142.20.238...
> worse...both ailerons were fluttering like mad for about three or four
> seconds and then as he throttled back, it was obvious that he had no
> control over the ailerons. He was able to fly the plane inverted for a
> couple more laps using only rudder and elevator, but eventually it went
> into a spin and cartwheeled. The wing is broken in half on the right, and
> the fuse is completely broken at the tail.
>
> Post-mortem revealed that the gears had been completely stripped in both
> aileron servos from the horrendous flutter. The ailerons did stay hinged
> in though. In looking for the cause, the only thing we could find was the
> way I did the aileron linkages. I set them up with the clevis on the
> farthest hole from the center of the servo and the nearest hole to the
> aileron. All control throws were set at those recommended by Sig in the
> manual. There was no slop in the linkages, servos were brand new JR 517s,
> aileron were reinforced with thin CA all around the control horns, and the
> hinge gaps were nice and tight. Although the YS .91 is on the high end of
> power for this plane, it wasn't nearly going full speed when the flutter
> occurred. Several other guys in the club have also used the YS on this
> plane without problems.
>
> I plan to rebuild, but I'm scared to death to have the flutter occur
> again. Has anyone else had this problem with the Four Star 60? What else
> should I do to prevent this?
>
> Thanks in advance,
>
> Kris
Graham Kay
Hear! Hear!
You beat my reply by 9 mins
Graham Kay
Paul J. Burke <burke...@my-deja.com> wrote in message
news:81kttp$j9d$1...@nnrp1.deja.com...
David Larkin
plane is designed, and the most powerful engine in its class to boot, precautions
against flutter are clearly a good idea.. I certainly agree with the suggestions
that you rethink the servo and horn connections, also check the aileron alignment
with SIG's gauge. However there is one further mod which I would suggest.
The energy for the flutter comes from the vortices at the tip. It's a really
good idea to cut the aileron about 2 inches in from the tip and fix the outer
part to the wing. Then there is less energy being fed into the ailerons.
Performance and control will not be significantly affected. There is a range of
kits marketed in England by Chris Foss which are very popular but people
habitually over-power them. Chris went to this arrangement on his designs to
avoid flutter and it works well.
Dave Larkin
Michael Neverdosky
control but the real cause of flutter is unbalanced control surfaces.
Ideally you want surfaces to be mass balanced. That is they have the
same
weight both forward and aft of the hinge. This is *VERY* difficult to
do in most models so we do our best to keep the surfaces light and then
use good control setup to prevent the start of flutter.
Sometimes aerodynamic ballancing is also used but this does more
to reduce control forces than flutter. I am winging this one a little
as I don't have my aircraft design book at hand to look up more detail
right now.
Please use the excellent advice given in several posts about setting up
the throws and control horns and keep those surfaces light, Light,
LIGHT!
Resiste the urge to put extra fiberglass, epoxy, paint or anything else
on
the control surfaces.
good luck and have fun
michael
Hoat Le
force to move the aileron, and a shorter servo arm provides a bigger force.
Simple concept of moment = force x distance.
--
Remove "zzz" from e-mail address if responding by mail
Dr1Driver <dr1d...@aol.com> wrote in message
news:19991125164021...@ng-fu1.aol.com...
.... You're correct to use the long servo arm and short
> control horn. That's a mechanical advantage.....
Hoat Le
solution.
Servo provides a much larger force, while force required to move ailerons
and/or to keep ailerons from fluttering is greatly reduced.
--
Remove "zzz" from e-mail address if responding by mail
Graham Kay <grah...@connexus.net.au> wrote in message
news:383d...@news.internex.net.au...
pjb...@my-deja.com
"Graham Kay" <grah...@connexus.net.au> wrote:
> Paul
>
> Hear! Hear!
> You beat my reply by 9 mins
>
> Graham Kay
>
>
pjb...@my-deja.com
>
> I am a little surprised that none of the other replies have suggested
any
> doubt about your clevis set up
> If I understand you correctly you have set up the clevis on the servo
on the
> furtherest hole from centre and on the aileron horn you have used the
hole
> closest to the pivot point. If this is so it is a sure formula for
flutter.
> I would guess you would have had to reduce you servo travel
considerable in
> the computer set up to get aileron throw down to a flyable level.
> If possible in my opinion you should always try and use the longest
lever
> moment that it is possible to use on the movind surface. In fact it
is
> preferable to have both the lever lengths of the servo and the moving
> surface at the same langth.
> If you really did set it up as I have understood you, then this is the
> primary cause of the flutter.
set so
> that you are able to use 100% travel settings in the computer. This
also
> means 100% on the low rates. High rates would be say 120%. Or at the
very
> worst low rates at 80% and high rates say at 120%.
> You can than make fine computer adjustments when you fully trim the
model.
>
> I am a little disappointed that your test pilot did not thoroughly
check
> this out. I am a test pilot at our field and certainly would not have
> attemted to fly the plane with the settup you have described
>
> Graham Kay
>
For airplanes on their first flights, if it's a new plane entirely, I
generally start with 50% low rates, with 80% high.. and work from there.
On my GP CAP 231 ARF, the low rate is 30% on the elevator, 40% hi. It
will snap at any higher travel... as will most planes of its
configuration and size. It would be UNFLYABLE at 100% (and that's using
the outermost holes). And I prefer -32% exp when the transmitter has it.
Kristofer R. Wagner
<airc...@aircmd.af.mil.nz> wrote:
> I am sorry to hear of your crash. May I ask if you took particular note of
> the aileron positioning gauge that comes in the kit?. I ask because when
> used correctly it 'cocks' the ailerons up into the airflow over the top
> wing. Setting this position is important for several reasons - one of them
> being to minimise the chance of flutter. When set correctly it looks
> 'wrong', but trust me, its right or SIG wouldn't have done it that way. I
> once set my 4 star 60 ailerons wrong (servo not neutralised on adjustment)
> and one aileron 'buzzed' like hell - ON TAKEOFF!! So it's worth double
> checking that aileron positioning guide.
>
> Bob Mc Millan
I used the aileron positioning guide that came with the kit to set the
neutral position of the ailerons. Then I used a Great Planes Accuthrow
deflection guage to set the control throws.
Kristofer R. Wagner
bipes...@aol.com (Bipesmoker) wrote:
> I assume you left the ail te's square. The only
> SURE flutter preventer is a balanced surface. That means getting the control
> surface cg at the hinge line.
No, I did not leave the trailing edges of the ailerons square. I beveled
the L.E.'s and rounded the T.E.'s just as directed in the kit manual.
Several people have mentioned balancing a control surface as you
mentioned, but no one has suggested exactly how to go about this. How
does one do it?
Thanks for the sympathy,
Michael Neverdosky
> Several people have mentioned balancing a control surface as you
> mentioned, but no one has suggested exactly how to go about this. How
> does one do it?
The problem with most RC control surfaces is that the hinge is at the
very front of the surface. The only way to mas ballance one of these is
to add a weight that extends forward. If you are building an existing,
sucessfull kit this is not likely to be needed unless it is in the
design.
The thing you want to do is keep the control surface as light as
possible.
In the Rutan Long-EZ (full size), for example, the ailerons have both
mas and aerodynamic ballance. Part of the aileron extends forward of the
hinge line and at the front edge of this a metal rod is installed. This
gives a better ballance and a nice round edge to a part the extends into
the airflow when the aileron is used to roll the plane. There are
specific
specs to meet on both the total weight of the aileron and the angle it
hangs when supported at the hinge line. If the aileron is too heavy or
tilts too far back it is rejected and must never be used for flight.
michael
Bob McMillan
the aileron positioning gauge that comes in the kit?. I ask because when
used correctly it 'cocks' the ailerons up into the airflow over the top
wing. Setting this position is important for several reasons - one of them
being to minimise the chance of flutter. When set correctly it looks
'wrong', but trust me, its right or SIG wouldn't have done it that way. I
once set my 4 star 60 ailerons wrong (servo not neutralised on adjustment)
and one aileron 'buzzed' like hell - ON TAKEOFF!! So it's worth double
checking that aileron positioning guide.
Bob Mc Millan
Kristofer R. Wagner wrote in message ...
Paul J. Burke
Didn't see the why...
but took advantage of the situation to inspect the structure...
The left wing was almost undamaged except for the last rib bay which had
lost the leading edge. Held it flat on a table and twisted it. More
than sufficient rigidity against twisting. Bent it, and it resists
bending nicely. I tweaked it further than I would one of my own..since
it was in the trash.<g>
And basically despite the lack of "solid" material, the structure is up
to any reasonable task. It's even repairable, more so than the
equivalent sheeted wing would be.
Graham Kay
It seems to me that the % of throw depends what the mechanical set up is on
the plane. If you set the mechanical leverage to the correct deflection (as
spexidied in the plans) while the low rate and the end point adjustments are
both at 100% then everything is at its optimum positioning.
Subsequently fine tuning of the computer will be easier with less change per
% point.
In the modern computerised world of flying we tend to put our linkages to
our moving surfaces with little care and rely too heavily on our computer
radios to fix it all. This is not good practice.
Therefore with due respect, I repeat, throws should be set mechanically so
that the dual rates and EPU on the radio can be set at 100% or close to it.
Graham Kay
Melbourne Australia
<pjb...@my-deja.com> wrote in message news:81mghe$kpd$1...@nnrp1.deja.com...
notme.noway.com
save us all an execution to the physics of leverage in this thread.
uhhh, never heard one complaint with stock hardware, so why change it.
dgam...@nbnet.nb.ca
<burke...@my-deja.com> wrote:
>You identified the culprit.. using the closest hole on the surface
>control horn.
>Why you would need to do this escapes me!
>It's the worst possible position, giving a lot of control motion... too
>much too quickly, MOF, and the least possible resistance to flutter.
>None of my planes, many of which are super responsive in roll are set
>up this way, precisely because of the lack of resistance to flutter,
>and don't suffer from any sluggish aileron response with the servo
>pushrod in the outermost hole on the horns.
I agree Paul, this is sure to allow flutter! ...all else
being equal...
it would be VERY difficult for very strong, tight servos to
"hold" those big ailerons rigged this way!
L8R ! Dave
Miles
Also don't you want a shorter arm at the servo and a longer one at the
control surface. Less chance of external forces effecting the servo.
The R/C Aircraft Proving Grounds
http://www.geistware.com/rcmodeling
rcmodeling(nospam)@ameritech.net
Information on the building and flying of Radio Control Aircraft.
Great new site for BEGINNERS in the R.C. Aircraft modeling world
(Indianapolis, IN)
In article <19991125164021...@ng-fu1.aol.com>,
dr1d...@aol.com (Dr1Driver) wrote:
> >What else
> >should I do to prevent this?
>
> I've heard of this on the Four Star. Besides what you've described:
Use more
> hinges, seal the hinge gap, use one servo per aileron, with straight
4-40 rods
> and linkage. Use a threaded metal clevis at the horn and a Z-bend or
solder
> clevis at the servo arm. You're correct to use the long servo arm
and short
> control horn. That's a mechanical advantage. However, it's a
disadvantage as
> flutter works its way back along the linkage to the servo. Try to
equalize the
> arm and horn length. Use really hard balsa for the ailerons and
consider
> counterbalancing them. Best of
> luck to you!
> Dr.1 Driver
> "There's a Hun in the sun!"
>
--
The R/C Aircraft Proving Grounds
http://www.geistware.com/rcmodeling
rcmodeling(nospam)@ameritech.net
Information on the building and flying of Radio Control Aircraft.
Miles
The R/C Aircraft Proving Grounds
http://www.geistware.com/rcmodeling
rcmodeling(nospam)@ameritech.net
Information on the building and flying of Radio Control Aircraft.
Great new site for BEGINNERS in the R.C. Aircraft modeling world
(Indianapolis, IN)
In article <94362903...@dauntless.cn.ca>,
"Hoat Le" <le...@zzzcn.ca> wrote:
> Sorry, but it's the other way around! A longer control horn requires
less
> force to move the aileron, and a shorter servo arm provides a bigger
force.
> Simple concept of moment = force x distance.
>
> --
> Remove "zzz" from e-mail address if responding by mail
>
> Dr1Driver <dr1d...@aol.com> wrote in message
> news:19991125164021...@ng-fu1.aol.com...
> .... You're correct to use the long servo arm and short
> > control horn. That's a mechanical advantage.....
Miles
Ifthe radio is set up at 100% with optimum control throws then the
plane should be easier to fly and to adjust. If you are going to need
more throw then that is an adjustment that is made AFTER all of the
other bugs are worked out.
I am building the same plane and will use his covering technique. I
will probably use different colors.
The R/C Aircraft Proving Grounds
http://www.geistware.com/rcmodeling
rcmodeling(nospam)@ameritech.net
Information on the building and flying of Radio Control Aircraft.
Great new site for BEGINNERS in the R.C. Aircraft modeling world
(Indianapolis, IN)
In article <383f...@news.internex.net.au>,
Paul Nesbitt
resolution at 100-150%. Why wouldn't you just adjust your linkage so
your maximum comfortable throw is 100% (vs 40%) and low rates are 80%
(vs 30%)? A plane is only unflyable with to much throw, not to much
percent of throw.
Paul Nesbitt
Paul Nesbitt
arm and short horn. The giant scale guys learned a long time ago that
you want to get all of the leverage you can on the horn and then use an
arm that is just long enough to get the throw you want.
For example, when I set-up on of my planes, the first thing I do is
program the radio to 150% throws. Then put the pushrod in the outermost
hole on the horn. Next, using a short arm, I usually try the outermost
hole on the arm. If the throw is to much (hahaha), I move the pushrod
in on the arm. If I need more throw, I will move the pushrod down one
hole on the horn. But, I never go closer in than that on the horn. I
will go with a longer arm if I have to, but only if I want 3-D type
throws.
Paul Nesbitt
Paul J. Burke wrote:
>
> You identified the culprit.. using the closest hole on the surface
> control horn.
> Why you would need to do this escapes me!
> It's the worst possible position, giving a lot of control motion... too
> much too quickly, MOF, and the least possible resistance to flutter.
> None of my planes, many of which are super responsive in roll are set
> up this way, precisely because of the lack of resistance to flutter,
> and don't suffer from any sluggish aileron response with the servo
> pushrod in the outermost hole on the horns.
>
rhar...@ecn.ab.ca
I could not find the original post to do a proper "follow-up" but
here goes anyway.
Had EXACTLY the same problem on my 4*60. Would go up for a couple
of flights, hear a flutter, bring it back down, and find that the inmost
hinge had broken loose. I would fix it, same thing would happen next time
out. Not always the same side though. It wasn't until someone at the field
mentioned "boy that plane sure shakes a lot" that I tweaked on what the
problem "might" be. The engine I was using was a borrowed K&B .65
sportster (bushing engine) and it did shake a lot. I replaced it with K&B
.61 BB ringed engine. CONSIDERABLY smoother, guess what, no more flutter,
no more broken hinges. Just for the record the hinge material was the
cloth CA type supplied with the kit.
Reg
James G. Branaum
> In article <81le9f$le4$1...@newsource.ihug.co.nz>, "Bob McMillan"
> <airc...@aircmd.af.mil.nz> wrote:
>
of
> > the aileron positioning gauge that comes in the kit?. I ask because
when
> > used correctly it 'cocks' the ailerons up into the airflow over the top
> > wing. Setting this position is important for several reasons - one of
them
> > being to minimise the chance of flutter. When set correctly it looks
> > 'wrong', but trust me, its right or SIG wouldn't have done it that way.
I
> > once set my 4 star 60 ailerons wrong (servo not neutralised on
adjustment)
> > and one aileron 'buzzed' like hell - ON TAKEOFF!! So it's worth double
> > checking that aileron positioning guide.
> >
> > Bob Mc Millan
>
> neutral position of the ailerons. Then I used a Great Planes Accuthrow
> deflection guage to set the control throws.
>
>
> --
> Kristofer R. Wagner
> email: kristofer-wagnerATouhsc.edu (please replace AT with @)
I also got to test fly a 4star120 that experienced serious flutter in the
aileron circuit on its 1st flight. The instant I heard it, I cut all of the
power and brought the plane around and in using rudder and elevator. We
could not find a reason for the flutter. I refused to fly the plane again
until some generic corrective measures were taken.
He did some of them, as discussed in this thread, and took the plane to the
field and got one of my friends to fly it. My friend did not manage to shut
the power down before the servos lost the gears and the wing took some
collateral damage. It was found that the covering was not strong enough to
stop the wing from flexing under loads. It had been covered it in Century
21 film.
After the servos were repaired and the wing repaired with a stick "V" in the
outer two rib bays, it was recovered in moneycote and the problem went away.
There was some discussion about this subject on another venue several months
ago and the consensus is that there needs to be a "V" of sticks put in at
the tip of the plane to prevent soft wood from allowing the wing to twist or
move rearward.
Sorry it took me so long to notice and respond to this thread. Hope this
helps.
Jim Branaum j...@flash.net AMA 1428
"Another modeler supplying glue to the AMA"