Window sealant

[brak]

I am sure this was discussed before, but I can't find the topic

It is time to rebed a couple of windows (can't call them portholes by design) - they are basically clear plastic (looks like acrylic to me) attached to the topsides with sealant and screws (not thru-bolts as I discovered to great relief today, otherwise I'd have to take apart the entire cabin to replace one window - what a disaster that would be ).

Currently, courtesy of PO, they are installed with silicon and then sealed with some sort of polyurethane around the edge (yikes, that will be fun to remove, on the upside this does hold up pretty well).

What I am looking for is a single adhesive/sealant that works well for windows, providing both reasonable adhesion strength and sufficient flexibility to allow for heat expansion etc. Also, something that is easy to work with/clean up.

[jjablonowski]

I can't find the reference in the archive, but I seem to remember somebody recommended butyl strips used for automotive windshield installation/caulking.

[brak]

I have butyl strips and used them elsewhere with success, but I don't think it will work well for windows. The strip is too thick and sealant has to also act as adhesive which butyl isn't great for.

[sailingdog]

Butyl rubber tape is what is used for automotive windshields, and works perfectly fine for sealing deadlights (non-opening ports). I generally don't recommend using silicone anywhere on a boat, except for possibly covering the tips of cotter pins.

One thing about the ports themselves... the holes should be drilled oversized, so that the ports can expand and contract and the holes should be counter sunk on each side to help prevent stress cracks from forming at the fastener holes.

[brak]

Well, definitely no silicone but I would much rather use sealant than butyl.

[cruisingdream]

All newer cars(since the 80's) use polyurathane for the windshields.
On a boat I would make sure you can access the sealing joint with a razor blade before using polyurathane so it could be removed in the future if necessary.

[sailingdog]

Adhesive qualities don't need to be as strong for deadlights, as the forces on them are generally from the outside in... and butyl tape is much easier to clean up and remove. It also stays far more flexible than polyurethane adhesives.

[brak]

the thing is - currently the window is flush with the cabin side. there is no bezel or anything covering the edge. butyl tape is just too thick - it will be very visible. I'll look at it but I'd like some sort of sealant alternative.

I can always go with my new favorite (Sika 521) but something that was tried and proven to work would be nice (and I am sure it is not 5200 ).

[ahab211]

3M Ultra Glaze sealed my windows nicely on my C @ C 24. I had tried 5200 with little luck and had to reseal the windows. They are nice and dry and have been so since spring. Good luck

[sailingdog]

They make butyl tape in different thicknesses you know.