Acrylic window separated from porthole - what to rebed with?

[Enyar]

Seems like there are lots of opinions about this, what should I use?

[Kello]

Butyl rubber tape, don't smash your window up against the hull, leave a small space so you don't squeeze out all the BRT (this goes for most sealants). Difficult/impossible to use in cold weather, long-term sticky edge that attracts dirt, if installed correctly never needs to be renewed and never leaks.

3M 4200, there are two kinds, use the UV one. I don't recommend it if you must use white - it quickly dries out/gets chalky along the edge strip exposed to the weather. Seems to always need to be rebedded in 5 to 8 years.

McMaster-Carr has all sorts of cool adhesive tapes, I haven't tried any of them, but it is worth your time to take a look. If you go that route, use a closed-cell foam tape, be sure to pick one for outdoor use.

Someone should be along shortly to recommend appropriate Sikaflex products.

[Enyar]

Originally Posted by Kello

Butyl rubber tape, don't smash your window up against the hull, leave a small space so you don't squeeze out all the BRT (this goes for most sealants). Difficult/impossible to use in cold weather, long-term sticky edge that attracts dirt, if installed correctly never needs to be renewed and never leaks.

3M 4200, there are two kinds, use the UV one. I don't recommend it if you must use white - it quickly dries out/gets chalky along the edge strip exposed to the weather. Seems to always need to be rebedded in 5 to 8 years.

McMaster-Carr has all sorts of cool adhesive tapes, I haven't tried any of them, but it is worth your time to take a look. If you go that route, use a closed-cell foam tape, be sure to pick one for outdoor use.

Someone should be along shortly to recommend appropriate Sikaflex products.

\

To be clear this is the hatch I am talking about, I believe I need some sort of clear sealant

[Enyar]

Originally Posted by Kello

Butyl rubber tape, don't smash your window up against the hull, leave a small space so you don't squeeze out all the BRT (this goes for most sealants). Difficult/impossible to use in cold weather, long-term sticky edge that attracts dirt, if installed correctly never needs to be renewed and never leaks.

3M 4200, there are two kinds, use the UV one. I don't recommend it if you must use white - it quickly dries out/gets chalky along the edge strip exposed to the weather. Seems to always need to be rebedded in 5 to 8 years.

McMaster-Carr has all sorts of cool adhesive tapes, I haven't tried any of them, but it is worth your time to take a look. If you go that route, use a closed-cell foam tape, be sure to pick one for outdoor use.

Someone should be along shortly to recommend appropriate Sikaflex products.

The tape needs a fastener to keep it secure correct? This acrylic lense isn't fastened by anything and relies on the adhesive for strength. I am thinking Sika 295 or 3m 4000UV

[Jammer]

Contact with acrylic will cause polyurethane sealants to degrade chemically over time, causing the bond to fail. Accordingly, Sika 295 and 3m 5200, 4000UV, and similar sealants, despite their high overall performance in the marine environment, are a poor choice for bonding acrylic.

The last time I did this I used Dowsil 295 795, a high performance silicone adhesive sealant. I would recommend that.

Bonding acrylic in place is one of the few places on a boat where a silicone product is a good choice.

[thinwater]

The pretty-much standard material in the US is Dow 795. It is made for this purpose. Polyurethanes (3M and Sika) require a special primer to block the UV from the bond area. It's in the manual. Otherwise they fail in 2-4 years.

There are many videos on re-glazing hatches. Take it home and do it right. Removing ALL of the old silicone and residue is key.

[Kello]

So your opening HATCH LENS needs to be rebedded, not a PORTLIGHT.

Thanks thinwater, I have a hatch lens that has been leaking a little, and I'm thinking about fabricating new lenses for all my opening hatches.

[thinwater]

Originally Posted by Kello

So your opening HATCH LENS needs to be rebedded, not a PORTLIGHT.

Thanks thinwater, I have a hatch lens that has been leaking a little, and I'm thinking about fabricating new lenses for all my opening hatches.

It's not hard. Re-Mov helps with getting the silicon out of the frame. Also a hose pick is handy for cleaning the grooves.



I did an article for Good Old Boat, but they don't seem to have it on-line. Mostly it's just a matter of working slow and clean.

[Enyar]

Silicone it is. I can't find a clear Dow 795 and black is only available by the case?


What about a 3m product? https://www.amazon.com/3M-08019-Mari...1zcF9tdGY&th=1

[Jammer]

Originally Posted by Enyar

Silicone it is. I can't find a clear Dow 795 and black is only available by the case?

It doesn't come in clear but you can get white if you want. There are several places that will sell you individual tubes.



https://metrosealant.com/product/dow...-37GQeMu1d7V7w


https://wgsonline.com/dow-corning-79...xoCkycQAvD_BwE

[s/v Jedi]

You want to use 3M VHB tape to attach it to the flange, then a window sealant around the perimeter to seal it. Dow 795 is the best for that and you can order it from McMaster Carr.

[OldGreyB]

Originally Posted by s/v Jedi

You want to use 3M VHB tape to attach it to the flange, then a window sealant around the perimeter to seal it. Dow 795 is the best for that and you can order it from McMaster Carr.

Yeap, Jedi's answer has my vote!

In 2019 we did all the acrylic ports and hatch lens on my friend's Catalina, they still looking good and none leaking.

Methodology:
Fully removed all old sealant and completely cleaned all surfaces
Surfaced abraded the acrylic sealing contact areas and then etched metal surfaces with Wattyl Super Etch© Primer (black).
Installed using 3M VHB tape (black), holding the new ports under tension for 12 hours.
Final external edge sealing with Sikaflex 295 (black) only because Dow 795 was not available at our location.

Note the 3m tape is available in white / clear / black. Dow 795 is available in thirteen colours.

[stormalong]

When I replaced the windows in my hatches close to 25 years ago I used GE Ultraglaze 4000. It is black, you said you want clear. Anyway, about 25 years later it is still good. The windows are 1/2 inch smoked plexiglass.

[abraley]

I installed acrylic windows to fiberglass on the cat I built. First go round used VHB tape and a recommended sealant. Did not work.

Second go round I did what Jedi suggested above. VHB tape and Dow 795. No problems with this install.

[Noahr]

Another vote for Dow 795.