Mylar seals for elevator

[[email protected]]

Hey guys, what's your opinion on the use of mylar seals at the
horizontal stab/elevator gap? Specifically for LS ships. Do people opt
not to use them for fear of "lifting" tape or mylar and causing
elevator effectiveness issues? Losing elevator effectiveness is
certainly a valid concern, but does it warrant not using mylar seals
there altogether?

Thanks,
Dave

[JJ Sinclair]

Dave,
I recommend using mylar on all control surfaces and have added it to
the LS-3/4/6/7/8 without a problem. I sand the inside of the mylar
where the stickie will go with 220 and do the same to the horizontal
(just the 10mm area), then wipe both down with acetone before laying
down the stickie and mylar. Next, roll it down with considerable
pressure to insure a good bond, followed by the transition tape over
the leading edge of the mylar. Some have had mylar come loose because
they didn't do the above and or didn't remove all wax from the
affected area. Treat this with the respect it deserves, or take it to
a glider repair shop. We have had a bail-out caused by lifting mylar
on the stab.
JJ

wrote:
> Hey guys, what's your opinion on the use of mylar seals at the
> horizontal stab/elevator gap? Specifically for LS ships. Do people opt
> not to use them for fear of "lifting" tape or mylar and causing
> elevator effectiveness issues? Losing elevator effectiveness is
> certainly a valid concern, but does it warrant not using mylar seals
> there altogether?
>
> Thanks,
> Dave

[[email protected]]

On May 18, 3:45*pm, JJ Sinclair > wrote:
> Dave,
> I recommend using mylar on all control surfaces and have added it to
> the LS-3/4/6/7/8 without a problem. I sand the inside of the mylar
> where the stickie will go with 220 and do the same to the horizontal
> (just the 10mm area), then wipe both down with acetone before laying
> down the stickie and mylar. Next, roll it down with considerable
> pressure to insure a good bond, followed by the transition tape over
> the leading edge of the mylar. Some have had mylar come loose because
> they didn't do the above and or didn't remove all wax from the
> affected area. Treat this with the respect it deserves, or take it to
> a glider repair shop. We have had a bail-out caused by lifting mylar
> on the stab.
> JJ
>
>
>
> wrote:
> > Hey guys, what's your opinion on the use of mylar seals at the
> > horizontal stab/elevator gap? Specifically for LS ships. Do people opt
> > not to use them for fear of "lifting" tape or mylar and causing
> > elevator effectiveness issues? Losing elevator effectiveness is
> > certainly a valid concern, but does it warrant not using mylar seals
> > there altogether?
>
> > Thanks,
> > Dave- Hide quoted text -
>
> - Show quoted text -

Here's the text from the flight manual for my ship (LS1f): "Taping of
upper aileron and elevator gaps, as well as the fuselage wing
connection, is necessary for rudder effectiveness and performance."

How do you interpret that? Are they recommending the equivalent of
mylar seals? Only on the top?

[Eric Greenwell]

JJ Sinclair wrote:
> Dave,
> I recommend using mylar on all control surfaces and have added it to
> the LS-3/4/6/7/8 without a problem. I sand the inside of the mylar
> where the stickie will

I've always used the mylar with the adhesive already in place (I'm
curious why JJ doesn't). That's a lot easier, and one less thing to go
wrong, since you don't have to worry about contaminating the mylar
surface and getting a bad bond. I've never had the adhesive separate
from the mylar, though I've had problems with the adhesive not making a
good bond everywhere on the glider. That was due to poor preparation,
probably not enough sanding.

> go with 220 and do the same to the horizontal
> (just the 10mm area), then wipe both down with acetone before laying
> down the stickie and mylar. Next, roll it down with considerable
> pressure to insure a good bond, followed by the transition tape over
> the leading edge of the mylar. Some have had mylar come loose because
> they didn't do the above and or didn't remove all wax from the
> affected area. Treat this with the respect it deserves, or take it to
> a glider repair shop. We have had a bail-out caused by lifting mylar
> on the stab.

Add "mylar and tape inspection" to your preflight: look for unbonded
spots and safety/transition tape thats brittle, peeling, or loosens
easily when you pick at it. It's easy to replace if you do it every year
or two, before it begins to deteriorate. The top side goes bad first.

--
Eric Greenwell - Washington State, USA
* Change "netto" to "net" to email me directly

* Updated! "Transponders in Sailplanes" http://tinyurl.com/y739x4
* New Jan '08 - sections on Mode S, TPAS, ADS-B, Flarm, more

* "A Guide to Self-launching Sailplane Operation" at www.motorglider.org

[[email protected]]

Maybe I should have mentioned. I have mylars on all surfaces. I did
them last season using all the specified procedures; wax removal,
scuffing/sanding, pressure applied with roller, sately tape, etc. They
are well bonded and in perfect shape. The real question here is
whether to remove the mylar on the elevator as a precaution.

I also inspect them thoroughly every time I rig.

[Bob Kuykendall]

> I've always used the mylar with the adhesive already in place (I'm
> curious why JJ doesn't)...

I've seen that stuff. Whoever puts it together doesn't sand the
underside of the mylar as JJ suggests. Your call.

Thanks, Bob K.

[Bert Willing[_2_]]

> wrote in message
...
.. The real question here is
> whether to remove the mylar on the elevator as a precaution.

The answer is definitively no.

[JJ Sinclair]

Eric Greenwell wrote:
>
> I've always used the mylar with the adhesive already in place (I'm
> curious why JJ doesn't).
Hi Eric,
I used some Mylar provided by the factory with adhesive already in
place on the flaps on an ASW-20 and the heat inside the trailer caused
the mylar to peal off between the mylar and the adhesive. The Mylar
was slick and had not been roughened up. This brings up another point,
recommend control locks on control surfaces while in the trailer,
especially flaps that won't otherwise stay in neutral.

I believe the main purpose of adding Mylar is to reduce drag, but if
you want added control authority, one can think about the combination
of Mylar and zig-zag. I use it on most rudders, but be careful adding
zig-zag to the elevator. I did on my LS-7 and the stall was the mose
abrupt I have ever seen..................took off the zig-zag!
Cheers,
JJ

[noel.wade]

On May 19, 6:09*am, JJ Sinclair > wrote:

> I believe the main purpose of adding Mylar is to reduce drag, but if
> you want added control authority, one can think about the combination

I'm arguably the least experienced pilot on this thread, so I'll try
to tread respectfully - but I was under the impression that mylars are
placed over control gaps for three reasons:

1) To prevent (or at least reduce) high pressure air below the wing
from being sucked up through the control gap to the low-pressure air
on top, disturbing or separating the airflow right at the control
surface. If designed to flow properly, such airflow can be beneficial
in certain flight regimes (see "slotted flap") - but for glider
control surfaces its bad news.

2) To lessen the drag as the low-pressure air goes down the top
surface through the pressure-recovery zone and hits a big lip or gap
or sharp angle that might cause the air to separate, tumble, swirl,
etc. In other words, the mylar helps smooth the transition between
the wing and the control surface no matter what angle the control
surface is at (relative to the rest of the wing).

Take care,

--Noel

[kirk.stant]

On May 19, 9:53*am, "noel.wade" > wrote:

> I'm arguably the least experienced pilot on this thread, so I'll try
> to tread respectfully - but I was under the impression that mylars are
> placed over control gaps for three reasons:
>
> 1) To prevent (or at least reduce) high pressure air below the wing
> from being sucked up through the control gap to the low-pressure air
> on top, disturbing or separating the airflow right at the control
> surface. If designed to flow properly, such airflow can be beneficial
> in certain flight regimes (see "slotted flap") - but for glider
> control surfaces its bad news.

Not primarily - seals are used for that. Either tape (for top or
bottom hinged) or rolling seals (for center-hinged) control surfaces.
Mylar without seals will probably slow the crossflow, but probably not
completely stop it. My LS6 manual specifically shows how and where to
install both rolling seals and Mylar gap covers on all control
surfaces.

Mylar without the rolling seals made my LS6 sound like an RC airplane
at full throttle at about 130 knots - I figure the crossflow was
"buzzing" the mylar on the flaperons. Could turn it on or off within
a couple of knots. Made sneaky low passes a bit difficult! Quickly
fixed by properly installing seals, BTW!

> 2) To lessen the drag as the low-pressure air goes down the top
> surface through the pressure-recovery zone and hits a big lip or gap
> or sharp angle that might cause the air to separate, tumble, swirl,
> etc. *In other words, the mylar helps smooth the transition between
> the wing and the control surface no matter what angle the control
> surface is at (relative to the rest of the wing).
>

What was #3? ;>)


Cheers,

Kirk

[Bob Salvo]

It seems to me that Mylar may only be necessary on the top of the
stab/elevator, since the top surface is the high pressure side. Has anyone
tried this?


"JJ Sinclair" > wrote in message
...

>
> I believe the main purpose of adding Mylar is to reduce drag, but if
> you want added control authority, one can think about the combination
> of Mylar and zig-zag. I use it on most rudders, but be careful adding
> zig-zag to the elevator. I did on my LS-7 and the stall was the mose
> abrupt I have ever seen..................took off the zig-zag!
> Cheers,
> JJ

[nimbusgb]

On May 20, 2:25 am, "Bob Salvo" > wrote:
> It seems to me that Mylar may only be necessary on the top of the
> stab/elevator, since the top surface is the high pressure side. Has anyone
> tried this?
>

The top side is the low pressure side Bob!

[Ed Winchester]

nimbusgb wrote:
> On May 20, 2:25 am, "Bob Salvo" > wrote:
>
>> It seems to me that Mylar may only be necessary on the top of the
>> stab/elevator, since the top surface is the high pressure side. Has anyone
>> tried this?
>>
>>
>
> The top side is the low pressure side Bob!
>
I don't think so, as the tail of just about every airplane or glider has
a download. That's how they achieve stability. So it's backward at the
tail, the top surface is indeed the high-pressure side.

[[email protected]]

On May 20, 6:39*am, Ed Winchester > wrote:
> nimbusgb wrote:
> > On May 20, 2:25 am, "Bob Salvo" > wrote:
>
> >> It seems to me that Mylar may only be necessary on the top of the
> >> stab/elevator, since the top surface is the high pressure side. *Has anyone
> >> tried this?
>
> > The top side is the low pressure side Bob!
>
> I don't think so, as the tail of just about every airplane or glider has
> a download. *That's how they achieve stability. *So it's backward at the
> tail, the top surface is indeed the high-pressure side.

Just to add to this "pressure" discussion, my elevator has a shape
similar to the trailing edge of my wing. The top-side is convex, and
the bottom-side is concave. Wouldn't that be a clue as to where the
high and low pressure areas are? I would think the convex side is the
low-pressure side, which is on top.


Dave


P.S. Any other thoughts on using mylars and safety tape on the
elevator gap?

[Bert Willing[_2_]]

As long as the elevators produces a force downwards, the low pressure side
is on top. This is typically the case for speeds higher than best L/D.
For speeds closer to stall speed, the elevator produces lift, and the low
pressure side is on the bottom.
For an optimum design, the elevator produces no force at all (except
drag...) at the speed of best L/D. But then, not all designs are optimum...

Bert

> wrote in message
...
On May 20, 6:39 am, Ed Winchester > wrote:
> nimbusgb wrote:
> > On May 20, 2:25 am, "Bob Salvo" > wrote:
>
> >> It seems to me that Mylar may only be necessary on the top of the
> >> stab/elevator, since the top surface is the high pressure side. Has
> >> anyone
> >> tried this?
>
> > The top side is the low pressure side Bob!
>
> I don't think so, as the tail of just about every airplane or glider has
> a download. That's how they achieve stability. So it's backward at the
> tail, the top surface is indeed the high-pressure side.

Just to add to this "pressure" discussion, my elevator has a shape
similar to the trailing edge of my wing. The top-side is convex, and
the bottom-side is concave. Wouldn't that be a clue as to where the
high and low pressure areas are? I would think the convex side is the
low-pressure side, which is on top.


Dave


P.S. Any other thoughts on using mylars and safety tape on the
elevator gap?

[Andreas Maurer]

On Sun, 18 May 2008 13:45:39 -0700 (PDT), JJ Sinclair
> wrote:

>We have had a bail-out caused by lifting mylar
>on the stab.
>JJ

Hi John,

what happened?

Bye
Andreas

[Eric Greenwell]

wrote:
> On May 20, 6:39 am, Ed Winchester > wrote:
>> nimbusgb wrote:
>>> On May 20, 2:25 am, "Bob Salvo" > wrote:
>>>> It seems to me that Mylar may only be necessary on the top of the
>>>> stab/elevator, since the top surface is the high pressure side. Has anyone
>>>> tried this?
>>> The top side is the low pressure side Bob!
>> I don't think so, as the tail of just about every airplane or glider has
>> a download. That's how they achieve stability. So it's backward at the
>> tail, the top surface is indeed the high-pressure side.
>
> Just to add to this "pressure" discussion, my elevator has a shape
> similar to the trailing edge of my wing. The top-side is convex, and
> the bottom-side is concave. Wouldn't that be a clue as to where the
> high and low pressure areas are? I would think the convex side is the
> low-pressure side, which is on top.

It's an airworthiness requirement that the glider will tend to pull out
of a dive. So, typically, the concave side is on the bottom to provide
increasing back pressure on the stick as speed increases (sort of like a
trim tab). In his 1989 article on increasing performance, Peter Masak
talked about reducing drag by filling in this bottom concavity. No
mention of the expected drag savings, but lots of words about flutter
concerns.

--
Eric Greenwell - Washington State, USA
* Change "netto" to "net" to email me directly

* Updated! "Transponders in Sailplanes" http://tinyurl.com/y739x4
* New Jan '08 - sections on Mode S, TPAS, ADS-B, Flarm, more

* "A Guide to Self-launching Sailplane Operation" at www.motorglider.org

[noel.wade]

On May 20, 8:17 am, Eric Greenwell > wrote:

> trim tab). In his 1989 article on increasing performance, Peter Masak
> talked about reducing drag by filling in this bottom concavity. No
> mention of the expected drag savings, but lots of words about flutter
> concerns.

Not to mention changing the pressure distribution on the aft section
of the wing/tail - thus changing its Coefficient of Moment (i.e. its
desire to rotate/torque around the center of lift). That effect is
less critical on the tail than on the main wing (doing so on the wing
might require an increase in tail volume to control the added moment);
but the bottom line is that you're essentially making a custom airfoil
when you fill that cusp. It isn't necessarily a bad thing, but if you
don't know what you're doing you could just as easily make it perform
worse...

--Noel

[Craig[_2_]]

On May 20, 8:44 am, "noel.wade" > wrote:
> On May 20, 8:17 am, Eric Greenwell > wrote:
>
> > trim tab). In his 1989 article on increasing performance, Peter Masak
> > talked about reducing drag by filling in this bottom concavity. No
> > mention of the expected drag savings, but lots of words about flutter
> > concerns.
>
> Not to mention changing the pressure distribution on the aft section
> of the wing/tail - thus changing its Coefficient of Moment (i.e. its
> desire to rotate/torque around the center of lift). That effect is
> less critical on the tail than on the main wing (doing so on the wing
> might require an increase in tail volume to control the added moment);
> but the bottom line is that you're essentially making a custom airfoil
> when you fill that cusp. It isn't necessarily a bad thing, but if you
> don't know what you're doing you could just as easily make it perform
> worse...
>
> --Noel

Dick Johnson changed the amount of cusp on his Nimbus 3 to reduce the
pitch up at higher speeds. Jim Phoenix has a nice note on it.
http://www.jimphoenix.com/jimphoenix2/pages/Nimbus/Nelevator/subNelevator.html

Craig

[JJ Sinclair]

On May 20, 7:41*am, Andreas Maurer > wrote:
> On Sun, 18 May 2008 13:45:39 -0700 (PDT), JJ Sinclair
>
> > wrote:
> >We have had a bail-out caused by lifting mylar
> >on the stab.
> >JJ
>
> Hi John,
>
> what happened?
>
> Bye
> Andreas

If memory serves me (big assumption at 74) this intrepid aviator waxed
his ship and then changed the safety tape....................it lifted
but didn't come off and caused such a flow change over the elevator
that he (intrepid aviator) didn't feel he had adequate control to try
and land the bird (Ventus B). Soooooooo, he tidied up the cockpit and
stepped smartley over the side!
JJ

[[email protected]]

On May 20, 2:14*pm, JJ Sinclair > wrote:
> On May 20, 7:41*am, Andreas Maurer > wrote:
>
> > On Sun, 18 May 2008 13:45:39 -0700 (PDT), JJ Sinclair
>
> > > wrote:
> > >We have had a bail-out caused by lifting mylar
> > >on the stab.
> > >JJ
>
> > Hi John,
>
> > what happened?
>
> > Bye
> > Andreas
>
> If memory serves me (big assumption at 74) this intrepid aviator waxed
> his ship and then changed the safety tape....................it lifted
> but didn't come off and caused such a flow change over the elevator
> that he (intrepid aviator) didn't feel he had adequate control to try
> and land the bird (Ventus B). Soooooooo, he tidied up the cockpit and
> stepped smartley over the side!
> JJ

There's a thread on this with accounts from folks who attended that
event. Here's a quote from John Cochrane based on the report at the
pilot's meeting after the accident occurred:

"I too was at Uvalde. The explanation for the Ventus crash given at
the pilot's
meeting was that there was NO thin tape holding down the mylar -- only
the mylar
itself, held down with double sided tape. It started to separate at
the leading
edge of the mylar, resulting in progressively worse elevator control.
Everyone
went out immediately to check that their thin tape was sticking well
in the
Uvalde heat! "

Sounds like the combination of the heat and the lack of any safety
tape was not a good one.

[Bob Whelan[_2_]]

JJ Sinclair wrote:
> On May 20, 7:41 am, Andreas Maurer > wrote:
>> On Sun, 18 May 2008 13:45:39 -0700 (PDT), JJ Sinclair
>>
>> > wrote:
>>> We have had a bail-out caused by lifting mylar
>>> on the stab.
>>> JJ
>> Hi John,
>>
>> what happened?
>>
>> Bye
>> Andreas
>
> If memory serves me (big assumption at 74) this intrepid aviator waxed
> his ship and then changed the safety tape....................it lifted
> but didn't come off and caused such a flow change over the elevator
> that he (intrepid aviator) didn't feel he had adequate control to try
> and land the bird (Ventus B). Soooooooo, he tidied up the cockpit and
> stepped smartley over the side!
> JJ

Kinda-sorta related, mebbe 10 years ago, the owner of a DG-300 launched
from our club's site (municipal airport). I wasn't there, what follows
is hearsay...but some lessons probably lie within...

First tow was aborted due to the need to hold nearly full aft stick to
maintain tow position. On-ground diagnosis followed - no problem found.
Second tow, same problem, safe landing again ensued, further
diagnosis, considerable loose tape at leading edge of elevator's
upper-surface mylar installation found (installation details
unknown-to-me), situation dealt with in some unknown manner, subsequent
flight not problematic.

Lessons?
- sometimes it's best to assume that little voice in your head is right
- inadvertent spoilers always have some effects
- if it ain't fixed, don't broke it

Regards,
Bob - some hearsay probably contains grains of Real Truths - W.

[Darryl Ramm]

On May 20, 12:14 pm, JJ Sinclair > wrote:
> On May 20, 7:41 am, Andreas Maurer > wrote:
>
> > On Sun, 18 May 2008 13:45:39 -0700 (PDT), JJ Sinclair
>
> > > wrote:
> > >We have had a bail-out caused by lifting mylar
> > >on the stab.
> > >JJ
>
> > Hi John,
>
> > what happened?
>
> > Bye
> > Andreas
>
> If memory serves me (big assumption at 74) this intrepid aviator waxed
> his ship and then changed the safety tape....................it lifted
> but didn't come off and caused such a flow change over the elevator
> that he (intrepid aviator) didn't feel he had adequate control to try
> and land the bird (Ventus B). Soooooooo, he tidied up the cockpit and
> stepped smartley over the side!
> JJ

Hi JJ

Is it true that the ship later floated back, falling leaf style, by
itself to earth with some significant damage but was later repaired?

Darryl

[JJ Sinclair]

> Is it true that the ship later floated back, falling leaf style, by
> itself to earth with some significant damage but was later repaired?
>
> Darryl

Yes, I believe that Venti did fly again, but I didn't put it back
together!

I did put an LS-3 back in the air after a bail-out, but it flew with
other wings that came from a wind-shear accident in Texas.

Most abandoned ships will come down in a falling leaf-type maneuver
due the the extreme aft CG that resuls from the pilots premature
departure. The ship's flying at EWCG, usually about 22", rather than
about 10".
JJ

[Rick Walters]

At 19:09 21 May 2008, Darryl Ramm wrote:
>On May 20, 12:14 pm, JJ Sinclair wrote:
>> On May 20, 7:41 am, Andreas Maurer wrote:
>>
Darryl,

The ship was a Ventus A and the bail out occured while flying out of
Uvalde.
The glider received very little damage. Apparently the gear was down and
the gear "cage" took most of the impact. I owned it for a while but it
has
been passed on to someone else. It has not flown since the accident.

Ron Tabery had a similar problem in NZ flying his N3. He landed OK but
with very marginal elevator control. A good item to put on a checklist.

Rick Walters


>Hi JJ
>
>Is it true that the ship later floated back, falling leaf style, by
>itself to earth with some significant damage but was later repaired?
>
>Darryl
>

[Rick Walters]

At 19:09 21 May 2008, Darryl Ramm wrote:
>On May 20, 12:14 pm, JJ Sinclair wrote:
>> On May 20, 7:41 am, Andreas Maurer wrote:
>>
Darryl,

The ship was a Ventus A and the bail out occured while flying out of
Uvalde.
The glider received very little damage. Apparently the gear was down and
the gear "cage" took most of the impact. I owned it for a while but it
has
been passed on to someone else. It has not flown since the accident.

Ron Tabery had a similar problem in NZ flying his N3. He landed OK but
with very marginal elevator control. A good item to put on a checklist.

Rick Walters


>Hi JJ
>
>Is it true that the ship later floated back, falling leaf style, by
>itself to earth with some significant damage but was later repaired?
>
>Darryl
>

[Rick Walters]

At 19:09 21 May 2008, Darryl Ramm wrote:
>On May 20, 12:14 pm, JJ Sinclair wrote:
>> On May 20, 7:41 am, Andreas Maurer wrote:
>>
Darryl,

The ship was a Ventus A and the bail out occured while flying out of
Uvalde.
The glider received very little damage. Apparently the gear was down and
the gear "cage" took most of the impact. I owned it for a while but it
has
been passed on to someone else. It has not flown since the accident.

Ron Tabery had a similar problem in NZ flying his N3. He landed OK but
with very marginal elevator control. A good item to put on a checklist.

Rick Walters


>Hi JJ
>
>Is it true that the ship later floated back, falling leaf style, by
>itself to earth with some significant damage but was later repaired?
>
>Darryl
>

[Rick Walters]

At 19:09 21 May 2008, Darryl Ramm wrote:
>On May 20, 12:14 pm, JJ Sinclair wrote:
>> On May 20, 7:41 am, Andreas Maurer wrote:
>>
Darryl,

The ship was a Ventus A and the bail out occured while flying out of
Uvalde.
The glider received very little damage. Apparently the gear was down and
the gear "cage" took most of the impact. I owned it for a while but it
has
been passed on to someone else. It has not flown since the accident.

Ron Tabery had a similar problem in NZ flying his N3. He landed OK but
with very marginal elevator control. A good item to put on a checklist.

Rick Walters


>Hi JJ
>
>Is it true that the ship later floated back, falling leaf style, by
>itself to earth with some significant damage but was later repaired?
>
>Darryl
>

[Darryl Ramm]

On May 21, 6:00 pm, Rick Walters > wrote:
> At 19:09 21 May 2008, Darryl Ramm wrote:>On May 20, 12:14 pm, JJ Sinclair wrote:
> >> On May 20, 7:41 am, Andreas Maurer wrote:
>
> Darryl,
>
> The ship was a Ventus A and the bail out occured while flying out of
> Uvalde.
> The glider received very little damage. Apparently the gear was down and
> the gear "cage" took most of the impact. I owned it for a while but it
> has
> been passed on to someone else. It has not flown since the accident.
>
> Ron Tabery had a similar problem in NZ flying his N3. He landed OK but
> with very marginal elevator control. A good item to put on a checklist.
>
> Rick Walters
>
> >Hi JJ
>
> >Is it true that the ship later floated back, falling leaf style, by
> >itself to earth with some significant damage but was later repaired?
>
> >Darryl

I always wondered as well about something that happened to me. I was
flying my DG-303 out of Parowan and I landed and then noticed shreds
of the top surface elevator transition tape handing from the
tailplane. The underlying mylar was perfectly OK. so I just cleaned
off and reapplied the transition tape. All I recall that happened on
that flight was I was rained on a little in some virga - and there
were some very small hail pellets. I was up to 18,000' on that flight
and with full ballast, but never really fast. There was not a mark
elsewhere and the aileron transition tapes were fine. The transition
tapes were in mint condition, the glider never spent time tied down in
the sun etc. I though it was strange and asked around and an ASW-27
had exactly the same thing happen to his glider as well on the same
day and if I recall correctly had also flown through some virga/light
rain.

So is this a known thing - maybe small hail pellets will take off the
transition tape? Why only the elevator tape?

Darryl