Window sealant for outside mounted plexiglass

[Old Hand]

Hello all, I know this has been covered many times and there are so many choices of sealants. I have tinted windows on my First 285 Beneteau that are through bolted directly in the cabin top. I removed the foam tape years ago from being dried out and leaking. I've used butyl tape with good success in the sealing department but it is sticky, collects dirt, and more importantly it gets soft in the heat and runs. It need to be tightened down to reseal and than gets squeezed out and after a few seasons is a mess and no longer seals. I have taken the windows out again.... seems like a job to be done every few years. I'm now wondering if there is a better sealant that will not run but will seal around the bolts and still let the windows be removed in the future without a cutting wheel?

[Chotu]

There are lots of types of butyl tape. They make stiffer ones that won't melt in the heat. Possibly this your best bet?

I know the basic gray one they sell in Ace hardware here in the states in the plumbing section is very tolerant to heat. Possibly they have something similar at Canadian Tire?

[john61ct]

Ask Maine Sail about his
https://shop.marinehowto.com/products/bed-it-tape

Current other thread
http://www.cruisersforum.com/forums/...d.php?t=229125

[billknny]

I will second the comment that all butyl tapes are not the same. They are made for different purposes, with different properties. You used one not appropriate for the application. Remember, up until recently, butyl tapes were the way that all car windshields were installed. They didn't have the kind of problems you report.

BUT...

If you use a proper adhesive sealant like Dow 795 or GE SCS2000 you will never have to remove the window until it has scratched or sun crazed so badly that it needs replacing. So who cares if you break it getting it out?

[gamayun]

I've been very happy with 3M 4000 UV. Clean up the edges that ooze out with alcohol before it sets completely.

[coopec43]

I had serious doubts about using an adhesive to secure the toughened glass ports on my yacht.

But having used it I am supremely confident. I used the same adhesive that auto-makers used ti fix windscreens into motor-cars.

[SVTatia]

Originally Posted by gamayun

I've been very happy with 3M 4000 UV. Clean up the edges that ooze out with alcohol before it sets completely.

Either that or: Dow 795, Sika 295 with primer or just EPDM rubber from McMaster Carr, the stuff they use on car windows - weather resistant EPDM rubber.

https://www.mcmaster.com/rubber

Butyl is great but it has its cons: it tends to ooze for a while, specially on very hot days, collects dirt, and it also "runs" - a dark grey ooze that needs to be cleaned up from time to time. I don't think I would use it for this purpose. And this is "the" Butyl, the one from Maine Sail.

Previous discussion on similar topic:

Fixed window replacement - Dow 795 still the sealant of choice? [Sitemap] - Cruisers & Sailing Forums

[dennismenace111]

Originally Posted by Chotu

There are lots of types of butyl tape. They make stiffer ones that won't melt in the heat. Possibly this your best bet?

I know the basic gray one they sell in Ace hardware here in the states in the plumbing section is very tolerant to heat. Possibly they have something similar at Canadian Tire?

I bought some at Home Depot that is used for sealing metal roofs. Its very heat tolerant.. and seems to be working great on all my deck hardware and the lens in my old Bomar deck hatches..plus...its inexpensive. I think I paid $5.00 US for a roll that will last me a few years.

[George DuBose]

After 10 years of fighting with my Pearson's 3/16" safety glass which isn't available anymore, having mildew growing between the layers, cracking when reinstalling, I have a new plan...

I want to bond 1/2" Lexan directly to the exterior aluminum frames with 3M's VHB, a double sided acrylic tape. It comes in various thicknesses and widths and is supposed to be water and UV resistant.

Due to the expansion of the Lexan, I am still considering what sealant to create a bead around the exterior edge of the Lexan.

Currently considering 3MTM OEM Polyurethane Glass Adhesive Sealant 590.

I will paint a border around the inside of the Lexan with possibly POR-15, but I need to do more research on what paint bonds to Lexan. I just don't want to see the beige VHB through the Lexan.

[allatsea99]

Maybe a v low modulus silicone. In Australia where temperature ranges are extreme I’ve used Sealproof by Adhseal. It’s v v low modulus like a hard jelly - great for heat & dealing with plexiglass/ polycarbonate expansion. Used to use it bonding CRT tv tubes to tv screens.

[ArmyDaveNY]

following

[boatbroke]

Hi Old Hand,

I would only trust Sika products (be sure to use primers and try times) for any window fittings, no matter if its glass or plastic, metal trim ect.

Had too many issues with other products over the years.

We were able to use Sika on a sport boat that was previously through bolted, allowed for a bigger flange and did away with the bolts. No plastic cracking and modernised the boat. I'm sure a different story if your going offshore.

Good luck!