What to use to re-bed hatch glass

[William12213]

I am replacing the hatch plexi on my Catalina. They sell a black adhesive/sealant on the Catalina site but it is very expensive. It is a Dow corning product and I am thinking it is Dow 795 but don't really know. What is the best stuff to use?

Thanks

 

[KD3PC]

Dow 795 works quite well, when used correctly. Given the life and the amount of work involved to rebed the plex...it is not expensive, IMHO.

Initial use of 795 by Hunter and Cat have resulted in 15-20 year lifespans. Correctly used, you can expect similar "next" life.

Be careful buying online or cheaply, as it does have a shelf life/use by date and it may separate or not be 100% if beyond that date. I buy mine much cheaper through an industrial glazier shop, and get current dates at the same time, as they go through pallets full.

Best of luck. And others will chime in with proper prep, clean up and use of spacers and temporary holding till the 795 sets and skins.

 

[woodster]

in the latest issue of GOOD OLD BOAT there is an artical where the fellow use some kind of 3M double backed foam tape to bed his plexi glass windows on page 40.....be thinking about this a lot and may try it with a cobo of the tape and the 795....the tape is supposed to hold very well and my ports are mounting on a curve surface so if that is so it just may be the aswer to holding them in place till the 795 bonds with out all the fight of shapeing them to conform to the openings.....as i said i am still thinking on this.....

regards

woody

OBTW make sure you sand the contact surface of your plexi and you fiberglass with 80 grit paper very well and wipe clean with denatured alcohol befor applying what ever you use.......

 

[dscribner]

Woody,

Structural glazing tape (Tremco SGT is one) is great to adhere the glazing to the hull. It's used to mount windows in skyscrapers and four sided flush-glazed skylights, among other things. But, it's back-bedded with Dow 995 (not 795), which is a structural sealant. Another great product is 3M VHB tape. This should also be back-bedded with silicone. Be careful about compatibility though. Some acrylic manufacturers don't recommend silicone with their product. And urethane sealants should never be used with polycarbonate.

If my boat was clean (and not tarped for a hopeful shot at painting tomorrow) I'd send you a pic of the job that I did. If you mask the edges of the joint, then tool the sealant, the result is a bead that looks like a well formed gasket. And be sure to tool the sealant. You'll hear many a testosterone-fueled boast of how good somebody can caulk, he NEVER has to tool the joint. The joint is NEVER warrantied by the manufacturer unless it's tooled, no exceptions. That's because it isn't waterproof until it's tooled.

I'm not an expert, but I know a thing or two. Among my other projects, I designed the top of the building on the right (Hearst Tower, NC) and designed and helped install the skylight on the left (Lucent Technologies, PA) which rises 80 feet before sweeping down and out in the rear.

Take your time and good luck!

Don,

Biddeford, ME

 

[woodster]

Woody,

Structural glazing tape (Tremco SGT is one) is great to adhere the glazing to the hull. It's used to mount windows in skyscrapers and four sided flush-glazed skylights, among other things. But, it's back-bedded with Dow 995 (not 795), which is a structural sealant. Another great product is 3M VHB tape. This should also be back-bedded with silicone. Be careful about compatibility though. Some acrylic manufacturers don't recommend silicone with their product. And urethane sealants should never be used with polycarbonate.

If my boat was clean (and not tarped for a hopeful shot at painting tomorrow) I'd send you a pic of the job that I did. If you mask the edges of the joint, then tool the sealant, the result is a bead that looks like a well formed gasket. And be sure to tool the sealant. You'll hear many a testosterone-fueled boast of how good somebody can caulk, he NEVER has to tool the joint. The joint is NEVER warrantied by the manufacturer unless it's tooled, no exceptions. That's because it isn't waterproof until it's tooled.

I'm not an expert, but I know a thing or two. Among my other projects, I designed the top of the building on the right (Hearst Tower, NC) and designed and helped install the skylight on the left (Lucent Technologies, PA) which rises 80 feet before sweeping down and out in the rear.

Take your time and good luck!

Don,

Biddeford, ME

thanks Don..

....i totally understand the tooling part...... and it is true that the mocho calkers that never use a tool arnt as good as they think...i remember when i was breaking in on calking aluminum window frames there were some guys that would calk down hill and i was taught to always calk up hill on vertical sides as you got better penitration in the joint....

thanks about the urithane based info that is important to me to know....

best regards

woody

obtw...the tower is a very good looking building....

 

[woodster]

now that i think about the Hurst tower i would almost bet that your favoret building is the Chrysler building in nyc.........

regards

woody

 

[dscribner]

Actually, I find the gherkin in England interesting and very pretty. At my current employ, I design smaller skylights, normally in the $10k - $50k range. Still fun, just many more in a year. This one is at the National Zoo in DC. It ticked me off that the stupid giraffe wouldn't move out of the way. The photo ended up in our sales brochure and everything! Who knew?