Sealant to install toughened glass with no screws

[CATJAVA]

I’ve got a 48ft Crowther cat, built 1991. Has large tempered glass windows everywhere. Had many window leaks over the years, which I solved by using caulking of various types, none of which worked for long. The problem with most cats is that they “work”, especially in larger seas. I imagine that most of the replies you’ve gotten are from monohull sailors who don’t have boats that work in a sea since it is only a single hull. What I did was to add screws outside the glass to mechanically hold the glass in place, especially at the corners. It’s the same concept as when hanging rain gutters; if you think caulking the joints without adding mechanical fasteners, such as rivets, is going to keep it leak free, guess again. You should always use a mechanical fastener with your caulking if you expect movement from any source, including temperature expansion/contraction. Been there, done that...
Evan on cat Java

[Thumbs Up]

I hope that no one even attempts to try to do this type of work without masking both sides of the bead first and using disposable gloves. It should be obvious but just in case, now you know.

[Popeye46]

Originally Posted by Thumbs Up

Dow 795 silicone is what will be recommended. Lots of recent threads here on it. I have had good luck with the black RTV silicone that comes in small tubes but doubt it as good as the Dow 795.

How would the Dow 795 stick to the existing sealant which looks like some type of silicone. One thread suggests that the original sealant may have been Dow 791.

[Thumbs Up]

The DOW 795, or SILPRUF (pretty similar), is going to seal and stick fine but keep in mind this is not as good as reinstalling the window because when you mount a window like that you "glue" it in place. Then check for leaks and only then apply the "beauty bead". You are doing a patch job more or less. You need to knife out as much of the old bead as you can (or all of it) and clean off all the residue. Don't knick the glass! vacuum out the groove with a crevice nozzle. Mask both sides and leave exactly the width of the bead you want. You have to learn to mask around the curves. It won't hurt to wipe it with acetone if you have some. Apply the tape so it will peel off in one go and pre peel the edges so that you can get holt of them with sticky gloves on. Apply the goo making sure it is going deep into the crack. Finger the bead smooth and flat, and get rid of the excess. Pull the tape off, wad it up in your palm and pull the gloves off turning them inside out which contains the sticky mess. Then take a close look at it and see if you need to flatten it out with a wet finger. I have done this many times, is not rocket science so don't overthink it. The green automotive mask tape works good (3m233+) 1/2" wide should go around the curves fine.

[Popeye46]

Originally Posted by Thumbs Up

The DOW 795, or SILPRUF (pretty similar), is going to seal and stick fine but keep in mind this is not as good as reinstalling the window because when you mount a window like that you "glue" it in place. Then check for leaks and only then apply the "beauty bead". You are doing a patch job more or less. You need to knife out as much of the old bead as you can (or all of it) and clean off all the residue. Don't knick the glass! vacuum out the groove with a crevice nozzle. Mask both sides and leave exactly the width of the bead you want. You have to learn to mask around the curves. It won't hurt to wipe it with acetone if you have some. Apply the tape so it will peel off in one go and pre peel the edges so that you can get holt of them with sticky gloves on. Apply the goo making sure it is going deep into the crack. Finger the bead smooth and flat, and get rid of the excess. Pull the tape off, wad it up in your palm and pull the gloves off turning them inside out which contains the sticky mess. Then take a close look at it and see if you need to flatten it out with a wet finger. I have done this many times, is not rocket science so don't overthink it. The green automotive mask tape works good (3m233+) 1/2" wide should go around the curves fine.

Mate, you are fountain of knowledge, you should make a utube clip. Thank you for your excellent instruction.

[Jacana]

Currently researching a fix for my windows ,tempered glass on 12mt catamaran to fix a leak.Seems best to remove and reinstall.3M VHB tape appears to be the way to go to use for seating and holding the glass in place then bead around outside with a sealant.
Has anyone used this method with this tape ?

[Tia Bu]

A combination of 3M VHB tape (for adhesion) and Dow 795 sealant (for sealing) seems to work well. Don Casey has a few articles online about the process.

[Tia Bu]

I should say, tape and 795 have worked well for me for about a year, so far.


Dow 795 by itself has worked like a charm for 5 years to hold plexiglass lights to aluminum frames on other hatches. Pretty rigorous offshore work.

[Thumbs Up]

The correct way is first to glue it on with sealant, then check for leaks. Then add the beauty bead. The VHB tape is going to have gaps where the pieces meet. I learned the correct way by talking to Sika. I had bad luck with their product though (295UV). That stuff gets all chalky in the sun and leave black streaks when you touch it. The beauty bead is meant to be a secondary seal only.

[coopec43]

Originally Posted by Cadence

I've seen a glass panel on a commercial building replaced, about 8' x 12'. No mechanical fasteners. The above may be worth looking into. It amazed me.
It might be over kill?

https://www.youtube.com/watch?v=NuTds1F48fQ