Mylar Project

What others have described mirrors my technique but I lay masking tape the full length of the mylar span-wise and crease it sharply at the leading mylar edge using the "handle" of a single-edge razor blade to form the hinge. I do not sand either surface but surgically clean both, first with acetone and then alcohol and clean, cotton cloth. I then never touch the bonding surfaces. The red Tesa transfer tape is best, in my experience. Fresh transfer tape and mylar is preferred. Pre-applied mylar/transfer tape has not worked for me.

Removal is a PITA. The transfer tape may come off with the mylar if it is not ancient and your heart is pure. Be careful not to peel up paint. If not, I then try rolling it up with fingers. If these fail, then solvents and potentially a gooey mess is next. 3M general adhesive remover is best, imo. Get the liquid in a can and place it in a squeeze condiment bottle. I cut paper towels into strips and lay it on the offending tape. Soak with solvent and wait. If is a warm day, I cover it with plastic qrap to slow evaporation. I shear up the softened transfer tape with a chisel-shaped tongue depressor.

It is possible that the trailing edge of the wing is not span-wise straight.. It is also possible that the mylar will not lie straight span-wise. There is essentially zero "give" in the mylar. Let it lie where it wants and masking tape the leading edge down. An extra pair of hands is valuable. Don't touch the bonding surface or let them touch anything else post-cleaning.

Post-Application: The ship and materials need to be warm (70-80 degrees) and kept warm and unloaded post-application for a day or two (more is better). I keep mylar seals unloaded in the trailer by using control locks. I have seen 3 brand-new gliders experience 100% top surface mylar debond since the controls lay in the trailers during shipment at full deflection, keeping the them loaded.

Removal is a PITA. The transfer tape may come off with the mylar if it is not ancient and your heart is pure. Be careful not to peel up paint. If not, I then try rolling it up with fingers. If these fail, then solvents and potentially a gooey mess is next. 3M general adhesive remover is best, imo. Get the liquid in a can and place it in a squeeze condiment bottle. I cut paper towels into strips and lay it on the offending tape. Soak with solvent and wait. If is a warm day, I cover it with plastic qrap to slow evaporation. I shear up the softened transfer tape with a chisel-shaped tongue depressor.

I also use solvent soaked paper towel strips to saturate the old adhesive tape. Surprisingly, Goo-Gone works pretty well, and smells nicer than 3M adhesive remover. It also isn't quite as nasty as the potent "Methyl Ethyl Deathyl" removers. Use nitrile gloves to keep from contaminating the surface with skin oils. Gloves also prevent skin absorption of the aforementioned solvent and the sticky, gummy, snot-like adhesive doesn't stick to your fingers. And for scraping the residue, I use plastic single-edge razor blades.

(https://www.amazon.com/Single-Edge-P...s%2C285&sr=8-7

After scraping and a wipedown with acetone, look carefully at the surface in reflected light to find any spots you might have missed. Then scuff with 200 grit (both the surface and the mylar) and wipe down again. Let the acetone evaporate completely (20 minutes or so).Try to keep any dust from settling on the surface- meaning avoid doing this in a drafty shop with airborne particulates drifting around. Apply fresh Tesa double sided tape (with the pinkish colored plastic backing). I use the edge of the control surface cutout at the rear of the wing as a reference when sticking the tape in place.. Use a roller or a ball bearing as described previously to firmly press the tape against the wing surface until it is uniformly settled. As you press with the roller or ball bearing, you can see where the tape sticks by the color change- it appears a bit darker visually.

The next step seems to have worked for me pretty well. Stretch the new mylar along the forward edge of the Tesa tape (with the pink backing still in place) and tack it into place with masking tape or the semi-sticky blue painters tape at about 12-18 inch intervals. You should be able to avoid any curvature in the line if you are careful. Then, you can lift the end of the mylar and peel the Tesa tape backing off to the side at a 90 degree angle. Pull the backing off to the side while running your fingers along the mylar just behind the backing as it peels away. This keeps the mylar positioned exactly where it should be and prevents it from curving off track. Peel off each strip of masking tape that is holding the mylar in position as you come to it and, when it is finally stuck down, use the roller or ball bearing to press it firmly. Extra effort in pressing it down now will be worth it. Make several passes to be sure you got it right. If it is a bit chilly, a heat gun can be used to raise the temperature of the adhesive until it is warm, (but not hot) as you press the mylar down.

And then leave. You want the adhesive to sit undisturbed for at least a full day to let it set up. Finally, use the very thin Tesa PVC safety tape overlapping the leading edge and the wing surface to keep the leading edge of the mylar from peeling up in the airflow.

I've had pretty good luck doing it this way. Every time I've tried to rush it or take shortcuts, I end up having to do it again. I have also found that you simply can't re-use mylar. Once you peel it up, it will never lay flat and straight again. Do the right thing and order new stuff. You'll save by not having to spend the extra time peeling it up and going through the whole adhesive removal/cleaning/scuffing/reapplication process again.