San Juan 21 Class Association

Hello,

I have a 1979 Mark 2 and last year one of the outside window frames was damaged by hitting another boat after my boat got away from it's mooring. The repeated impacts of the window frame against the other boat forced out the sealant and the window started to leak when it rained. Taking off the frame, the sealant used between the plastic frame and the fiberglass is a gray colored, sticky, non hardening bedding compound of some type. It seemed to work well before the accident and the other windows that are sealed with the same material do not leak. Thus, I would like to stay with using the same material to repair the window. Does any one know what this sealant material is? It dosen't feel or look like traditional bedding compound I'm familiar with.

BadgerJuan
Madison WI

https://www.google.com/search?q=butyl+r ... 3&ie=UTF-8

Was it that stuff? If so, yeah it works well, but I would probably try something different.

Later
C

I think you might be right. I also asked our specification writer at work and he suggested it might be a butyl product. Not sure if the existing joint was from a tape or a caulk gun.

If you didn't use a butyl sealant, what would you use instead?

Badger Juan

Sounds like Butyl tape. it stays elastic, unlike the polyurethane caulks. some love it even for bedding deck hardware. i have never used it, but also have never seen any professionals use it, so am a bit suspicious. I recently replaced my portlights and this was the best overall article i found:

http://www.sailmagazine.com/boatworks/r ... portlights

i know that you aren't looking to replace, but there is info on the caulk for bedding: Dow Corning 795 Silicone Building Sealant. This is a permanent fix and doesn't have any silicone in it, yet is flexible enough to expand and contract. It was cheap on amazon.

I have used butyl tape on hardware and it works well. A good article on sealants can be found here: blog.dankim.com/2009/04/24/marine-sealants/
Don Casey's site is also useful but I don't know what happened to his info. I think he is now only with Sail magazine or something like that.
CHeers
Bill

I have used butyl tape as a bedding compound for years on all kinds of boats with very good success. It provides a good seal and stays pliable for years. I also have replaced windows on two SJ21's using smoke colored plexiglass, 1/8" thick, surface mounted, only using double-sided automotive tape. The double-sided tape is often used to secure exterior trim on cars, so it is designed for a tough outdoor environment. it has excellent adhesive qualities and is flexible enough to allow for thermal expansion and contraction of the pieces-parts.

The problem with butyl tape is it runs when it's warm out, so if you use it for things like cleats, it can run into the holes and gum up the works... It does work excellently and creates a nice bond, but it's always "gooey" so always attracts a bit of dirt, and nastiness. They often use it on RV's, but have started to ditch it for poly type of adhesives.

I wouldn't use anything with a "permanent" bond myself. you'll just end up tearing off gel coat if you ever have to rebed the widows, cleats, etc.

I've used some of Sika products, as well as some of the 3m bedding compounds with pretty good success. They come off, and clean up well.

Later
C

Just as a follow up, I ended up using butyl tape to reinstall the window. It looks like it will work well. Time will tell.

Badgerjuan