Mylar Project

On Wednesday, March 10, 2021 at 10:08:24 PM UTC+2, Roy B. wrote:
1) Are you saying you actually sand the Mylar taped surface itself to improve adhesion?

Please do not sand your wings, the mylar will adhere quite well to normal surface.

On 10/03/2021 18:49, Roy B. wrote:
I am wondering if some of the more experienced repair guys on this list would share their wisdom on replacing mylar seals. There is lots of stuff on the internet about refinishing a sailplane - but very little about gap seal replacement which at first glance seems easy to do but actually is difficult to do well and professionally.

What are the best products? Sources? Costs?
Best way to remove old seals?
Surface preparation?
Professional application techniques to get a good result?

If this all has been written on before, please direct me to it.
Thanks
ROY


On various gliders, LS for example, the Mylar isn't the air gap seal but
a cap. The seal is provided by a glass backed teflon tape ether as a
strip from wing surface to aileron or an internal S shape depending on
whether the aileron hinge is at the top or in the centre.

See diagrams on the following page

https://wingsandwheels.com/cloth-gap-tape.html

--

Nick Hill

I've done the steps that Bob K mentions below a little differently....

Once the tape is in place and the mylar is perfectly positioned on top of the tape (protective plastic still in place on the tape) I don't flip up the mylar. I leave a 3-6" long strip of the protective film sticking out from under the right or left end of the mylar and I pull the protective film out from under the mylar while carefully holding the mylar in position. Easy enough to practice this on a short segment first, but it avoids anything moving or going "off" when you try to flip a long section of mylar back down onto the, now exposed, adhesive. Just carefully pull a few inches of the protective film out from under the mylar at a time while holding everything stable.


* With the mylar tagged in place, flip the mylar forward over the tags, using the tags as hinges. Then tag the mylar down in this position with a few more tags of tape.
* Peel the protective strip from the adhesion tape.

--Bob K.

On Thursday, March 11, 2021 at 6:29:36 AM UTC-8, wrote:
I've done the steps that Bob K mentions below a little differently....

Once the tape is in place and the mylar is perfectly positioned on top of the tape (protective plastic still in place on the tape) I don't flip up the mylar. I leave a 3-6" long strip of the protective film sticking out from under the right or left end of the mylar and I pull the protective film out from under the mylar while carefully holding the mylar in position. Easy enough to practice this on a short segment first, but it avoids anything moving or going "off" when you try to flip a long section of mylar back down onto the, now exposed, adhesive. Just carefully pull a few inches of the protective film out from under the mylar at a time while holding everything stable.
* With the mylar tagged in place, flip the mylar forward over the tags, using the tags as hinges. Then tag the mylar down in this position with a few more tags of tape.
* Peel the protective strip from the adhesion tape.
--Bob K.

To sand or not to sand..........that is the question?
Rather than restating my Mylar procedure, let me tell you how and why I developed it?
I installed wide Mylar on a ASW-20 and 2 weeks later the ship was sitting back in my shop. Owner said he thought he’d take her up to redline...............ship yawed quite a bit to the right, then straightened out as all Mylar on the right wing disappeared! Owner also showed me the lower Mylar on the left wing was hanging by the safety tape! We decided the left wing Mylar had pealed off caused by flaps not locked in neutral then left in a hot trailer!

No reports of shedding Mylar since we started sanding Both surfaces with 220 grit............some 40 years ago!

You decide?
JJ

Some instructions and Materials:
http://www.craggyaero.com/misc1.htm

Schempp-Hirth diagram
http://www.craggyaero.com/Instl%20Su...stallation.pdf

Richard
www.craggyaero.com

On Thursday, March 11, 2021 at 10:46:53 AM UTC-5, John Sinclair wrote:
On Thursday, March 11, 2021 at 6:29:36 AM UTC-8, wrote:
I've done the steps that Bob K mentions below a little differently....

Once the tape is in place and the mylar is perfectly positioned on top of the tape (protective plastic still in place on the tape) I don't flip up the mylar. I leave a 3-6" long strip of the protective film sticking out from under the right or left end of the mylar and I pull the protective film out from under the mylar while carefully holding the mylar in position. Easy enough to practice this on a short segment first, but it avoids anything moving or going "off" when you try to flip a long section of mylar back down onto the, now exposed, adhesive. Just carefully pull a few inches of the protective film out from under the mylar at a time while holding everything stable.
* With the mylar tagged in place, flip the mylar forward over the tags, using the tags as hinges. Then tag the mylar down in this position with a few more tags of tape.
* Peel the protective strip from the adhesion tape.
--Bob K.
To sand or not to sand..........that is the question?
Rather than restating my Mylar procedure, let me tell you how and why I developed it?
I installed wide Mylar on a ASW-20 and 2 weeks later the ship was sitting back in my shop. Owner said he thought he’d take her up to redline...............ship yawed quite a bit to the right, then straightened out as all Mylar on the right wing disappeared! Owner also showed me the lower Mylar on the left wing was hanging by the safety tape! We decided the left wing Mylar had pealed off caused by flaps not locked in neutral then left in a hot trailer!

No reports of shedding Mylar since we started sanding Both surfaces with 220 grit............some 40 years ago!

You decide?
JJ
I've modified my technique a bit since writing the article in the link. But not much. All suggestions in this chain have merit, especially as to sanding the underside of the Mylar and using clean cloth for everything. Lastly, W&W is selling a plastic "razor blade" that I have found very useful in removing stubborn stickum. So, the article is old, but then, so am I. https://www.ssa.org/Archive/ViewIssu...=2011&month=11

You don't sand the wing, just the depressed area of the wing where the
mylar is attached.

Dan
5J

On 3/10/21 8:53 PM, Kristian Roine wrote:
On Wednesday, March 10, 2021 at 10:08:24 PM UTC+2, Roy B. wrote:
1) Are you saying you actually sand the Mylar taped surface itself to improve adhesion?

Please do not sand your wings, the mylar will adhere quite well to normal surface.

I have never sanded either surface. Only 1 debond in 30 years and that ship had been hard-waxed to the point that the gelcoat was impregnated with wax. I use the application technique described above: Slowly pull the Tesa backing away at a very acute angle, and stick the mylar down incrementally, beginning from one end.

I agree that mylars are not seals, they are aerodynamic fairings.

The way you describe is the way I've seen Fidel do it. The only
problems I've had are with the safety tape getting brittle and flaking
off on one 6 or 8 foot section of the wing outboard of the actuator
fairing, and once when gas from the tank vent soaked the area behind the
vent. I no longer fill the tanks of the Stemme (30 gal) unless I'm
making a long ferry flight.

Dan
5J

On 3/11/21 1:22 PM, Mark Grubb wrote:
I have never sanded either surface. Only 1 debond in 30 years and that ship had been hard-waxed to the point that the gelcoat was impregnated with wax. I use the application technique described above: Slowly pull the Tesa backing away at a very acute angle, and stick the mylar down incrementally, beginning from one end.

I agree that mylars are not seals, they are aerodynamic fairings.

This tool is useful in removing the adhesive from the wings. Read instructions and don't press too hard.

Amazon
3M Stripe Off Wheel Adhesive Remover Eraser Wheel Removes Decals, Stripes, Vinyl, Tapes and Graphics 4� diameter x 5/8� thick 3/8-16 threaded mandrel 07498 Pack of 1

https://www.amazon.com/Stripe-Wheel-...xpY2s9dHJ1ZQ==

Richard
www.craggyaero.com