ADHESIVE FOR NEW HATCHES

[High Cotton]

We just got our new LEWMAR hatches to replace the old ones and are considering several adhesives........

which one would be the best and why?

Thanks for any advice!

[Joli]

I really like polysulfide inner and outer and butyl tape in between. Does that make sense?

[Paul L]

Is the Bomar hatch tape http://www.defender.com/product.jsp?path=-1|6880|6881|320590&id=834176
the butyl tape you were referring to?

Paul L

[never monday]

Lifecaulk, you'll want to remove them later

[Benjamaphone]

Don't use butyl tape! That stuff makes a real mess when you take the hatches out again. I know from many bad experiences of trying to scrap/clean it off the bases!!!

[Rick]

This winter I had to re-bed some hatches and ports when it was cold and wet. This is the only adhesive/sealant/bedding material that I could find (which is new anyway) which specifically would cure in damp and cold. It absolutely cured my leaks and I have come to love the stuff. I even used it to seal a leak on my car where there was a defect allowing rain to leak between two pieces of sheet metal that I could not clean or skuff up:

Henkel North America - New PL® Ultimate Hybrid Sealant + Adhesive Features a Cutting-Edge Formulation and Exclusive Technology


I found it at Lowes, of all places. Not cheap, but not as expensive as the over $10 per tube stuff either. It appears to seal over surfaces that previously had a silicone product on it. Some of you may know just how difficult it is to remove or seal against anything that someone has used a silicone product on (which is why I will never use a silicone product other than to make gaskets between mechanically fastened items designed to have silicone). I hate silicone products that are advertised as "adhesive or sealant" because they will ultimately fail to adhere and seal off moisture when applied to metals or very smooth finishes. 3M 5200 is a good adhesive but lousy bedding material and not resistant to U/V and not easy to remove as others noted.

Give this new "hybrid" urethane silane (whatever that is) a consideration.

[Hud3]

GE SilPruf is a silicone product that bonds very well to metals, fiberglass and gelcoat. About $12.50 US per tube (the size that you use in caulking guns). I've had good results with it sealing my chainplate deck penetrations. It's recommended for hatches, too.

[jrd22]

Sikaflex 291 or 3M 4200.

[S/V Illusion]

Dow Corning 795...
Although other materials can be used, if you want to do it properly as the boat manufacturers do, use a structural silicone such as Dow 795. It is relatively inexpensive, is available in several colors and is widely available.

Silicone is the only sealant that's compatible with acrylic.

If you decide to go with the Sika 295 which is difficult to work with, be sure to use the primer as it won't stick without it.

[Steve Kidson]

Sikaflex 291; works well and can be painted over

[Benjamaphone]

Originally Posted by S/V Illusion

Silicone is the only sealant that's compatible with acrylic.

I think that this thread is more about bedding the frame of the hatch to the boat, versus the acrylic to the frame. It is true that for acrylic to aluminum bonding, silicone is best.

Adhesive? You mean caulking. You do not want to glue the hatches in place. Lifecaulk, sikaflex, and others will all seal a properly bedded down hatch.

The bolts are there to hold the hatch down you do NOT want it glued down.

[Benjamaphone]

Good point. Lifecaulk is what we recommend for bedding. Anything else and its going to be one tough puppy to clean up later. Thats our experience at least.

[roverhi]

Sillycone, no way. Guaranteed to leak sooner than later, a bitch to clean off short of dynamite, hard to clean up, and even a whiff not cleaned up will result in paint failure if painted over.

I've used LifeCaulk on 5 different boats without a single leak. Dow 101 sealant is also a polysulfide like LC. I've got parts that I've removed after 30 years and the stuff was still well bonded and flexible. Used to go by the name Thiokol, btw.

5200 is more an adhesive than a caulk, good for something that will never ever be removed. Hear that it hardens over time and may break the bond in severely flexed applications. don't use the stuff so no personal experience, however. 4200 is also a polyurethane like 5200, but with a better removability factor. I don't like it as well as LC as it isn't as easy to work with. Think SikaFlex is also a polyurethane.

Polysulfides and Polyurethanes react with some plastics causing the plastic to crack. Check with plastic mfg before using on plastic parts. There are non reactive plastics so if you're set on plastic, might search out the ones that work with PS and PU sealants. Your other choice for a sealant on plastics would be sillycone and that's an absolute non-starter for me.

Aloha
Peter O.

[Benjamaphone]

I think there may be a misunderstanding. Nobody is suggesting to use silicone for bedding the base of a hatch/port. I think the confusion came up when S/V Illusion said that silicone is best for fixing the lens into the frame, not the frame onto the boat. As a hatch manufacturer, we recommend using good ol' fashioned Lifecaulk for bedding.