Best hatch lens adhesive / sealant ?

[sailfree20770]

From what I've read so far, the 3 best options for plastic lens sealants are:
3M 4000
Dow Corning 795
Dow Corning 995

Has anyone used 3M 4000 for sealing acrylic hatch lenses to aluminum frames? This seems to be a relatively new product... haven't seen much discussion. It's worked very well for some other bedding applications, and is available at the local chandlers. It may be the most universal adhesive / sealant so far.

There are just a few viable sealants for plastic hatch lenses. One of the most popular seems to be Dow Corning 795. That and the other products often mentioned for the task are not available locally.

I'm not sure Dow Corning 795 product is the best for this applications. For surface mounted (glued on) glazing it may be better to use Dow Corning 995. Small difference in name, but quite a difference in strength. Has anyone used 995?

I've read about others using a Sika-flex product that requires a primer and cleaner. Why get that complicated if one product will do the job?

There are other silicon type sealants, but the types found in stores aren't up to it. There is probably a GE product that's similar to each of the Dow Corning's, but those aren't readily available either, so haven't considered them much.

That leaves me down to the 3 choices listed above. Would like to narrow that down if possible.

 

[Maine Sail]

Cero (company now sold and can't remember new name) the makers of Acrylite GP, the most commonly used cast acrylic hatch lens, gives UV4000 a "not-compatible" rating with their product. This was straight from one of their engineers as of about four years ago....

Sikaflex 295 UV *with the special primer
Dow 795
GE SSG4000

Are what the industry uses..

 

[bananabender56]

I had Select Plastics supply and install new hatch plastic into Bomar aluminum frames.
They use Dow Corning 795 and guaranteed the work.
I've used 795 when replacing hatch lenses on older Lewmar frames - worked very well as long as follow the instructions.

 

[woodster]

the Dow 795 has a 50% elongation that is critical in the bonding of acrylic to frp as the two do not expand the same in the same heat conditions and one can find this in 10.5 oz tubes for as little as 7 dollars a tube it takes about 30 days to be fully cured but it will hold i 48 hrs as long as no one abuses the bond

 

[KD3PC]

. One of the most popular seems to be Dow Corning 795. That and the other products often mentioned for the task are not available locally.

Dow 795 can be procured from most any professional glazier or commercial glass business. It has a "use by" date, so make sure the date is still good, if you buy from an auction site.

 

[agprice22]

I used Dow 795 on my new acrylic windows, it works easily. It seals well. When I took off the 30 year old windows which were cracked / crazed, the old Dow 795 was still sticky! I think that is optimal.

Thanks,

Andrew

 

[Allan Frey]

You can get dow 795 from McMaster-carr. They are a very good company to work with.

allan

 

[Phil Herring]

We always have some in stock, as well:

http://shop.sailboatowners.com/prod.php?52190

 

[njlarry]

I used black 795, it comes in about three colors, from D and R Marine. One cartridge did both large fixed ports and the forward hatch with about 20% left over. Hardens in the open cartridge tip quickly so plan to do it all in a few hours? The tip of one came cracked and after two days shipping the entire tube was hard. ( a replacement was quickly shipped)
Worked great. Preped with acetone. Mask well and don't move the parts while setting up.

 

[sailfree20770]

Thanks for all the input guys. The consensus seems to be much in favor of the Dow Corning 795. It is nice stuff to work with, and seems to be the only sealant with a published 20 year warranty. It will be winter before I get around to the job, so I had some time to check around.

I have a slight bias toward the 4000 UV (if it works as well as 795) because it seems so universal for boat work. 795 is not recommended for below water, can't be painted, and has the shelf life issue.

woodster: The elongation of 4000 UV is listed as >700%, so I'm not sure that 795 is better in that regard. The 4000 UV also appears stronger, but comparing the data sheets is a bit difficult to do directly as the terms are different. I suppose the sealant could be TOO strong in some cases, an aluminum frame expanding could crack the acrylic glazing.

Main Sail: Thanks for the info from Acrylite. EVONIK has a web site for Acrylite now. I'll try to confirm the "not-compatible" rating. They have their own adhesives for gluing Acrylite, but none look like the flexible kind used for glazing. Anyway, I'll write 3M and EVONIK to see what they say.

 

[Guts1236]

Dow Corning 795 / Note full adhesion 14 to 21 days

working time 20-30 minutes
tack free 3 hours
cure time 7-14 days
full adhesion 14-21 days

I helped a friend of mine reseal his Windows on his Erickson 35 and he used 795 to seal the aluminum to the fiberglass. After resealing my Catalina 30 with the kit I bought using 3M 4000 for the Windows to the fiberglass and 795 for the gasket that goes inside the window frame and the glass to the gasket. So I use both kinds... I think they each have a purpose but if I was sealing something to fiberglass I would use the 3M 4000 I did not like the way the 795 state loose for a long period of time after you clamped the window in. I think they're both excellent products, but after using the 3M 4000 and on mine and using the 795 on my friends boat I preferred the 3M 4000 to work with.

 

[sailfree20770]

I agree the 4000 UV is easier to work with. That's why I wanted to use it.

Checked with both 3M and Evonik (ACRYLITE). Evonik says 4000 UV is not compatible with acrylic. 3M says 4000 UV is fine, but recommends their primer P591 should be used on acrylic.

It seems a bit puzzling to the consumer to have two conflicting recommendations from companies that should know their stuff. Hard to know which one to believe.

 

[S36_Osprey]

Interesting video...
http://m.youtube.com/watch?v=mReJB4qc9QU

 

[Brian S]

Too long, didn't watch. Informational videos often waste my time. I bet whatever the results were, I could have read in 3 minutes, and saved 8 or 9 minutes over the 11 minute run time of the video. (Haha, here I'm wasting 3 more minutes typing this rant! )

What were the results?

Interesting video...
http://m.youtube.com/watch?v=mReJB4qc9QU

 

[shemandr]

Too long, didn't watch. Informational videos often waste my time. I bet whatever the results were, I could have read in 3 minutes,...

I'd rather read too. I can skip ahead and repeat parts more easily.

 

[Patrick17430]

Butyl Tape as Window Sealant

Water coming in from the fixed windows ruined my countertops and rotted the woodwork so I wanted to redo it all but first I needed to stop the flow of water into the boat. It's been 2 1/2 years now and not so much as a drop of water has entered my boat . I used butyl tape on my new then Plexiglas windows that were through bolted directly to the fiberglass of the house on my 66 Wayfarer. Easy to use. No mess. Just trim off the excess that squeezes out with a pocket knife and peel it off. It's still very pliable and soft after being baked in the sun. I highly recommend it. Here"s a great price. http://www.campingworld.com/shopping/item/butyl-tape-3-4-x30/39160 I think I paid $30 for a roll at Svendsens Boat Yard for the exact same stuff.

 

[shemandr]

Or you could buy it from our in house - very generous with his knowledge - Mainsail. That's Compass Marine if you don't know.

 

[woodster]

that video is way to boring for me....... why do they talk so much about nothing dang people cut true the chase and geter done

 

[S36_Osprey]

The video showed some dude performing a silicone caulk adhesion test on a piece of lexan at home. All 3 caulks were different GE flavors of silicone. Clear winner was GE 55 silicone, which really surprised the dude. The stuff is labled for use on plastic sheet and other plastics.
Apparently the guy is into building rather large aquariums, where caulk failure will spell disaster to someones living room

 

[S36_Osprey]

Also - you can get the stuff at home depot for under $8 per tube