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Permalink Reply by Bob Pustell on May 2, 2020 at 10:49am

I have not used that product. My only experience was when I helped a friend scratch build a Thorpe. His windshield was mechanically installed but needed sealant to make it weathertight. So, with the caveat that I don't know if the product I am about to mention will "bond" as opposed to "seal" I offer this experience.

You need a product that will not attack the plexiglas. You also (ideally) need a solvent that will clean up spills or blobs of the sealant yet not attack the plexiglas. Without a solvent you need to work very carefully to avoid squeeze out and/or smears of the sealant.

My friend did a lot of research and his solution worked wonderfully for bedding his windshield to make a wind and weather tight seal. As mentioned already the windshield was retained by screwed on metal trim plates so I don't know for sure if this solution would work for bonding a windshield in place (gluing it into place without benefit of mechanical fasteners).

His solution -- Butyl rubber sealant. It goes on like and when cured looks like clear silicone rubber sealant. It can be purchased in many types of containers. He used the product in caulking tubes that goes into a standard household caulking gun and can be neatly dispensed in beads. This product does not harm or attack plexiglas in any way.

His sovent -- Naptha. Naptha dissolves Butyl Rubber but it does not attack plexiglas at all.

It worked wonderfully - we installed the windshield with sealant squeezed out of the joint all over the place, lots of surplus to assure a good sealing job with lots of it left inside the joint. We then wiped and scraped the worst of the squeezed out surplus off the windshield and fuselage and canopy bow with clean rags. Then we used Naptha soaked rags to clean away the remaining sealant mess from all surfaces. It came out beautiful!!  Twenty years later that plane is still flying and still has a secure and leakproof windshield.

Some RV builders use a sealant to bond canopy sections into place rather than drilling holes in the plexiglas to secure it mechanically. I don't know if the product is the Tigerseal you mention of not. I do know that I have been told by several RV builders that using the product is very nerve wracking and there is little room for error but if done right it gives great results. You might want to go search the Van's RV builders forums for information on that product and process.

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Permalink Reply by John Austin on May 3, 2020 at 6:49am

Butyl caulk also comes in a tape form.  Here's an excellent EAA video "Sealing Plexiglas Windshields with Butyl Caulk Tape."(Requires EAA member login to view.)

It is commonly found at RV (Recreational Vehicle, not Van's RV!) supply stores. I used the tape to seal the Lexan top window to the cabin frame on my STOL 750.  Worked great and no-mess cleanup.

John

N750A

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