Does anyone have any advice on what Adhesive/Sealant to use to attach a
Lexan window to a steel hull boat? I tried using 3M Marine Adhesive
Sealant 5200. It did not bond with the Lexan.

Any thoughts or recommendations?

Hello:

Spent last year searching this group, calling tech support departments,
Google searches for answer to same question. Lots of excellent advice
found in this group. However I would first advise a thorough SEARCH on
your own (instead of asking).

I found this in about fifteen seconds:

".......the correct product number is Dow Corning 795
structural silicon adhesive/sealant. Trust me it aint your
grandfather's silicon seal. An excellent choice for polycarbonate
needing a bedding/sealing/adhesive. Still needs to be fastened
mechanically. There are others including Sikaflex product. But some
require a prime coat before sealant application......"


Okay, I've been landlocked for the past two weeks with way too much
coffee and way too much time on my hands. So you're your gonna get
luck today.

In a nut shell:
1) use only sealants that DO NOT MELT polycarb. 3M 5200 is not
compatible with Lexan. Read the directions! Other sealant-adhesive
types are compatible.
2) drill holes in the Lexan way oversized. Lexan moves around a lot
plus it also allows sealant to flow into the area where fastener passes
through Lexan.
3) Bevel the Lexan holes next to boat surface. This allows more surface
area around hole and forms an "o-ring" space in the Lexan.
4) Make sure that you use 1/4 inch spacers between Lexan and boat
surface. I used two nickels. The two nickels were cheaper than the 12
cent spacers I needed. Besides I could spend them later.
5) Dry fit Lexan to boat with ¼" spacers.
6) apply sealant and make sure you get the applicator tip stuck next to
your fastener so it gets into area where the fastener passes through
the Lexan. I used a Starbucks plastic straw taped to end of sealant
cartage tip. This allowed me to stick the sealant into that ¼" gap
between the Lexan and the boat.
7) smear the excess sealant off. Remove your blue tape immediately.
8) Most sealants will take 7-10-14 days for FULL strength. When cured
have one person in the boat and one person outside the boat. One person
holds the fastener to keep it from ROTATING and the other person
torques the nut. DO NOT LET THE FASTENER ROTATE!!!! That will break the
seal where the fastener passes through the Lexan and boat. And you
guessed it, your hours of work are for not. The ports will leak.

Check the torque guidelines for 1/4" 316 fasteners. If I remember it is
only about 8-12 ft. lbs.

9) Now that the sealant is cured, ¼" spacers are removed, and your
fasteners are torque you should have an amazingly effective 1/8"
gasket to keep the water out.

Oh, do not use the UV protected or the Hardend Lexan regardless of what
others may say. the Lexan guys said the UV and scratch protection is a
layer on top of the Lexan and MAY seperate/break when bent. But others
may disagree. I wnet with the cheeper stuff.

I hope others in this group respond to this method. That's how things
get improved. Peer review. For example I was in a boat yard a couple
years ago in Portland, Or. There was another boat owner hard at work
replacing ports and rebeding hardware. He was an airline flight
attendant interestingly enough. He was the one who passed on the secret
of the "bevel bit" that created the "o-ring." Where ever he
is....... Thank you.

Bob

Auto Glass sealer 3M 08612 ?? with or without primer.

Bjarke


"Leonard" wrote in message
oups.com...
Does anyone have any advice on what Adhesive/Sealant to use to attach a
Lexan window to a steel hull boat? I tried using 3M Marine Adhesive
Sealant 5200. It did not bond with the Lexan.

Any thoughts or recommendations?