# Re-bedding Windows: 3M-4200 v. Butyl Tape



## saildork (Feb 20, 2007)

I'm Re-bedding the windows on my Catalina 22 using the kit from Catalina Direct. I replaced the windows into the new glazing channels using Dow Corning 795 from the kit and then into the frames, also using the DC 795 per the instructions. Now I'm ready to put the windows back into the cabin. The kit includes 3M 4200 for this job. The instructions call for the 'Don Casey method' of applying the 4200 and partially tightening the screws the first day and then completing the tightening the next day. 

The old compound that I removed from the frames and the residue left on the gelcoat seemed more akin to butyl rubber than 4200. I could tell, however, that it came out of a caulking tube. I use the 'Maine Sail method' for mounting deck hardware using the butyl tape. It's great stuff and the best way I've found for mounting thru-bolted hardware. I'm inclined to use the butyl tape for the windows as well, but I'm not sure. Any suggestions out there?


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## Faster (Sep 13, 2005)

I wouldn't use 4200 for this.. butyl should work if you're happy with that, but I expect 795 would work here too.


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## ccriders (Jul 8, 2006)

Saildork,
Hey I just did this using the Catalina kit. I did not use 4200, but butyl tape instead. So far it has worked just fine. And, the butyl tape is cheap at the local RV store and is very easy to use. No mess whatsoever. Now I have a big tube of 4200 with no place to go.
John


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## saildork (Feb 20, 2007)

Since the 795 is a silicone-based bedding compound, I am not inclined to use it to seal the window frames against the gelcoat. I do like the ease-of-use of the butyl tape. I guess I should call the Catalina Direct folks and ask them why they would use the 4200 vs. butyl tape.

Anyway, thanks for your input, Faster. 

Pat


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## saildork (Feb 20, 2007)

ccriders said:


> Saildork,
> Hey I just did this using the Catalina kit. I did not use 4200, but butyl tape instead. So far it has worked just fine. And, the butyl tape is cheap at the local RV store and is very easy to use. No mess whatsoever. Now I have a big tube of 4200 with no place to go.
> John


Thanks for your input, John. I called Catalina Direct and they could think of no technical reason for not using butyl tape...a matter of personal preference, really. I'm going to use the butyl tape. I find it easier to work with, and if I have to re-do any of the windows, I find the butyl tape easy enough to remove and reapply. Thanks again.


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## Faster (Sep 13, 2005)

I'm sure you'll do OK with butyl tape.. just try not to squeeze it all out as you tighten the window into place.

FWIW I do know firsthand that DC 795 cleans up easily if you ever need to redo that seal and it works just fine against gelcoat. Again it's important to retain some 'gasket thickness' when done.


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## AirborneSF (Dec 14, 2010)

I've used the 4200 on my C&C 26, and it is leaking again. These are 'flush' mounted portlights, and I was thinking of 1/8 thick 'weather stripping', this time around. The tape idea sounds good, I know I need 'movement', how tight can you go with the tape?


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## saildork (Feb 20, 2007)

AirborneSF said:


> I've used the 4200 on my C&C 26, and it is leaking again. These are 'flush' mounted portlights, and I was thinking of 1/8 thick 'weather stripping', this time around. The tape idea sounds good, I know I need 'movement', how tight can you go with the tape?


Airborne, as Faster states above, just don't tighten your windows down so tight that you squeeze out all the butyl rubber. This stuff has the consistency of plumber's putty, roughly. It stays workable and flexible forever. I should think it would work in your application.

Maybe someone else out there with windows like yours has tried it successfully. Anyone???


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## copacabana (Oct 1, 2007)

Sailordork, I'm going to try the butyl route on one portlight this weekend (if it doesn't rain). Never tried it before, but from my research it seems to be a viable option for sealing portlights, but not for fixing them in place. That requires an adhesive caulking or screws, bolts, frames etc. 
I'm going to use some two-sided automotive adhesive tape as a spacer and to prevent the buytl from being squeezed out from around the edge of the portlight. I'm hoping this will contain the butyl permanently in place. My portlights are through-bolted to the cabin sides and I intend to use butyl on the bolts as per Mainesail's instructions in the butyl thread. I'll take some photos of the job and post them later. My thinking is that if the butyl route works, it is a practical, inexpensive solution and one can carry plenty of extra butyl tape on board for future work without worrying about it drying up or expiring. Please let us know how your windows come out on your Catalina, as we can all learn from each other's experiences with butyl.


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## jarcher (Jul 29, 2008)

There is a ton of discussion about what to bed windows with on this board. Windows are a special case and need special adhesives. I'll try to find the thread and post a link. Its worth the effort to rea it, as there is a pile of good information there.


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## jarcher (Jul 29, 2008)

Not the thread I was hoping to find, but a good one:

http://www.sailnet.com/forums/gear-...e-products-sealing-deck-hardware-windows.html

A lot of it will come down to what is holding the windows in place. Are they bolted or held by some other fastener? If so teh butyl tape may work, but personally I would not use it. If any structural integrity comes from the adhesive (the 4200 that came int eh kit) then you are not going to get them from the butyl tape.

Windos also tend to move, which is a point in favor of butyl tape actually, since it remains goopy forever.


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## saildork (Feb 20, 2007)

Well, the re-bedding job is done. I used the butyl tape, and I think I achieved a good, water-tight seal all around each window. The butyl was very easy to work with, and clean-up of the residue was a cinch.

On the C22, the outside frame is pulled inwards by the use of screws that go from the inside frame to the outside frame thus bringing the two frames snug against the cabin sides. The screws are not exposed to the outside of the cabin, and they don't go through the cabin sides. I'm guessing that butyl will be a good choice for this job because of the flexing that most likely happens routinely on a boat such as the Catalina 22. When I removed the windows at the start of this project, two of the four windows had never leaked since I've owned the boat for 13 years. And the previous bedding compound (it might have been the original from the factory) was still gooey. Not bad for a 27 year old boat. 

Our dockmaster here uses butyl tape for all similar applications, just as Maine Sail has discussed in previous threads. Time will tell if butyl tape was the right choice for this job.


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## Barquito (Dec 5, 2007)

Just wondering, should the window bolts be tightened just as much as deck hardware? For bedding deck hardware, you can't leave a 'gasket' by under tightening. Presumably there will be less movement if the bolts are snugged down.


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## ahab211 (Jan 6, 2008)

I wouldn't overtighten the windows though. I have homedesigned bolts and nuts on my C&C 24 windows and don't seal well. I used 3M Ultra Glaze sealant and it is black and messy but sealed well. I wouldn't use 4200 or any silicone sealant as they don't work well on windows but I've heard nothing bad about butyl tape.


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## saildork (Feb 20, 2007)

Barquito said:


> Just wondering, should the window bolts be tightened just as much as deck hardware? For bedding deck hardware, you can't leave a 'gasket' by under tightening. Presumably there will be less movement if the bolts are snugged down.


Since my windows are secured with Phillips-type screws, they can't be torqued down very much with an ordinary screwdriver. Thus the risk of squeezing out all of the sealant is minimized. But they appeared to have been tight enough to prevent them from shifting around too much.

As I stated earlier, two of the four windows had never leaked, and the sealant was still pliable. And the screws were about as tight as you would hope them to be. With my deck hardware, OTOH, they are through-bolted and torqued down pretty hard. Apples and oranges on this boat, I think. It might be different on a boat with through-bolted windows/ports.


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## Faster (Sep 13, 2005)

ahab211 said:


> .... I wouldn't use 4200 or any silicone sealant as they don't work well on windows but I've heard nothing bad about butyl tape.


There are acceptable silicones such as DC 795 - generally the silicones to avoid are those that smell like vinegar - like most available at Home Depot, for example.


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## knotted (Feb 22, 2011)

Something else to look for while at the Depot, is window glazing shims or spacers. They keep the frame spaced away from the glazing at the thin edges, (see how they're usually used in this illustration by Lamateck) and they'll also keep the frame away from the flat glazing surfaces as the frame is tightened onto the glazing if used on the flat surfaces of the glazing at the edge. Cut them to appropriate size, or maybe wrap them around three sides at the edge of the glazing if they're flat and flexible.

The edge of the frame open to the elements needs a continuous bedding around it, so the spacers should be set back from this edge. With the spacers in place on both sides, inside and outside, of the glazing, tighten all you want (within reason  ) and you won't squeeze out all the bedding, which would give a dry joint  but one that leaks 

The spacers are very important if you have glass glazing rather than Perspex (avoid Lexan - it clouds) as they allow flexing of the hull without stressing the glazing.

If you direct bolt the glazing onto the hull, oversize the holes in the glazing to avoid stress cracking/breakage of the glazing caused by hull flexing. Countersink the outside (top) of the hole, and pack with butyl tape to seal. (See Maine Sail's excellent write-up.)

Good luck and no leaks! 



> _"You start with an empty cup of experience and a full barrel of luck. The trick is to fill your cup before the barrel runs dry." - bljones_


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