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Sealing the Glass and Gasket into the Frame

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Leaking around the port's glass is a major concern for me. Is there a "permanent" sealing solution that also will allow the next guy to get the frame and glass apart?

The gasket material in my fixed port frames appears to be vinyl and it is still shiny black and flexible. The inside has a lip that remains above the frame after the glass is seated in the channel. The outside of the gasket seats down below the edge of the frame about a tenth of an inch. There was a beautiful fillet of silicone on the outside that once kept the glass and gasket from leaking. That silicone fillet comes off the aluminum and the glass quite cleanly and easily after 15+ years.

Although it is a tight fit into the frame, the glass and vinyl gasket does not bottom out against the frame. It's designed that way I'm sure, because doing it any other way makes cracking the glass during assembly much more likely. It allows the vinyl to cushion the glass, I guess. I am still considering whether to buy new gasket, if I can find it. The Catalina Direct kits appear to have the lip on both sides of the gasket.

The original gasket has shrunk a little but may be re-usable. There are no cuts or holes in it and it stretches around the glass with some tension. I am still looking for a way to assemble the frame and glass and keep the gap at zero or as small as possible. A small gap left at the top would be filled with the sealer fillet, which can be applied after the frame is securely screwed together, and before installation into the boat.

I am considering a polyurethane (3M 4200 black or white) to replace the silicone fillet. Polyurethane forms a tenacious bond to glass and aluminum which I found from my previous sealing experiment. I have been reading about LifeSeal which is a silicone and polyurethane mixture that is compatible with vinyl. That might be a better way to go. One thing about polyurethane that I like is that it will soften with solvents like mineral spirits after it cures. We all know that there isn't much that will soften a pure silicone sealant. I wonder how LifeSeal would do if it had to be removed once it cured? So, 4200 compatibility with the old seal is a concern and I'm not sure how I can resolve that without doing an experiment. "Some" plastics are compatible with polyurethanes, according to my reading.

Due to the use of regular silicone sealer around the glass on these 4 ports, along with the recessed vinyl gasket, I have decided that I probably do not have to split the frames from the glass on the remaining three. I can just peel off the old silicone fillet, clean up the channel gap and put in a fillet of 4200 or LifeSeal.

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  1. bigd14's Avatar
    Craig- Look into Dow 795. It is a high performance sealant used on glass and aluminum windows in high rise buildings. I think Catalina sells it for your intended purpose as part of their gasket replacement kit. I used it in lieu of the whole gasket on this boat. No leaks this winter yet. On my last boat I just used black Sikaflex 291 instead of gasket material, and it is still going strong 6 years later with no issues. Good luck.
  2. Christian Williams's Avatar
    I used Dow 795 to re-bed big overhead hatch lenses, and the seal between acrylic and aluminum is very secure.
  3. footrope's Avatar
    Thanks for the comments. I looked up the Dow Corning 795. I see it's an industrial use silicone, which should be pretty strong compared to bathtub silicone caulk. I may try it. At least I know it isn't likely to hurt the vinyl gasket. I went back to the CatalinaDirect site and tried to find the Window Reseal kits. Silly me "port" is a search keyword for just about everything on the site (clutch plates?) except the fixed ports. They don't even tell what the sealers are for the most part, using generic pictures with the numbers blocked out. They do have the gray stuff that was probably used to secure the lexan to my Bomar opening ports. That was sticky stuff. I'm using glass and polysulfide in the Bomars now. And they have the Bomar "round" gasket material for the frame. It's available elsewhere, but they might be a convenient source if shipping isn't too expensive. I have some spare and fortunately that neoprene type gasket doesn't degrade much.

    On the two big overhead ports I used a Sikaflex product (10 years ago?) that worked ok. It wore out on the salon port after a few years and started leaking at the corners. The smaller port over the v-berth took longer to start leaking. It doesn't get stepped on as much and since it's smaller it flexes less. I'm not sure when I'll get to that as the ever attractive gorilla tape is working pretty well.