Very Flexible Sealant (not adhesive) For Polycarbonate?

[CaptainMarkS]

Originally Posted by Chotu

Sorry for the delay.

After all the debating, looking into different glass, adhesives, sealants, etc...

I went back to the lightest, strongest and most problematic material. Polycarbonate.

I got the real stuff this time and (stolen idea from the glazier who was too busy to do the project ), am going to use frames. He wouldn’t guarantee a mount without frames.

So I have some pretty big anodize J cap or J channel to allow an enormous bonding surface to come in contact with the boat and allow for a very large expansion slot to let the windows float in. I’m not sealing them at all, unless it gets too drafty.

The J cap, all the way around the windows, bonded to the hull, will keep all water out anyway. I’ll drop a sealant over the top J cap at the point it joins the hull for added protection.

Water will (as it always did with my crappy wooden U caps), just flow over the top cap, onto the polycarbonate and down to the deck, off the boat. It always worked before. I guess the internet just got the best of me making me want to try these sealant only windows. No more.

I don’t anticipate any problems as I never did have any problems until the old wood/epoxy U caps rotted away.

There is 1/2” room for expansion/contraction and I can use full, 4x8 sheets of real Lexan (Sabic UV protected, 10 year warranty) which eliminates the seam, so no need to caulk that either.

Putting them on next cold snap so it’s not so brutal on the roof.

Very cool. I'd love to see photos!

[reiner]

Originally Posted by LakeSuperior

I have found that the polyurethane based caulks generally have the best adhesion, flexibility, and lifespan. They are usually pretty pricy but seem to work the best. I like the Sikaflex products.

Sikaflex doesn’t stick very well to Perspex .