Butyl Tape vs Polysulfide Caulk on Rebedding

[Dreamcat]

I will be replacing our older hatches with new ss frame hatches. I would normally use 3M 101 or Life caulk but the more I read the more I find that butyl tape may be the new and better alternative. Any past experience ? Thanks

[Maine Sail]

Originally Posted by Dreamcat

I will be replacing our older hatches with new ss frame hatches. I would normally use 3M 101 or Life caulk but the more I read the more I find that butyl tape may be the new and better alternative. Any past experience ? Thanks

Butyl tape is great, but not new. Many builder used to use it but it is slightly more labor intensive, and was not also used below waterline, so they moved away from it in favor of polyurethanes.

Either 101 or butyl would be fine just don't use black butyl or you can have a real mess on your hands. As always slightly bevel the screw holes to create a small o-ring type effect. If you have the time it's a good idea to pot the holes in the deck with epoxy..

[Dreamcat]

Thanks MS. I saw your great pics you had on your site. Also enjoyed your article on replacing seacocks...another project this month.

[delmarrey]

I have custom made inlayed windows (no frames) that no matter what I did would start to leak after a rough sail (twisting of the hull/deck) So, I went to butyl tape and haven't had a leak since. I put butyl on the mating sides and filled the gap with poly.

But as MS said, if your in hot weather, it may get a little messy. But the excess goo can be cleaned up with a scraper and MEK.

[Benjamaphone]

We don't recommend using butyl tape for bedding hatches. It doesn't spread out evenly and wont seal the screw holes as well as a product like sikaflex or lifecaulk.

The way to do it is you have to use too much adhesive and tape the deck around where the frame is going to go. That way when you place the frame down, the excess squishes out onto the tape. The excess is then taken off with scraper. This process provides the best seal, both aesthetically and functionally. Plus, butyl tape is horrible to clean off when you eventually have to rebed them again.

[mikereed100]

Originally Posted by delmarrey

I have custom made inlayed windows (no frames) that no matter what I did would start to leak after a rough sail (twisting of the hull/deck) So, I went to butyl tape and haven't had a leak since. I put butyl on the mating sides and filled the gap with poly.

But as MS said, if your in hot weather, it may get a little messy. But the excess goo can be cleaned up with a scraper and MEK.

Delmarrey,

The windows are beautifull. I'm curious, did you use Butyl as the only adhesive (along with the poly)? I ask as i dont see fasteners and I have often thought that as sticky as butyl is it would make a fine adhesive, not just sealer.

I used to live in a motorhome in the desert and I bedded a new AC unit on the roof with butyl. The AC was heavy so made a depression in the roof which became a pond in the summer when the AC was on, which was all the time. Summer could get up to 115 degrees and winter down to 20 but it never leaked a drop.

Mike

[roverhi]

I just rebedded one of my large windows with Butyl tape. It was cool, around 70 degrees, when I did the installation. The butyl did not flow well and the outside trim ring did not suck in completely leaving about a 1/16" strip of butyl showing between the frame and hull. Hope when I get to warmer waters, it doesn't start oozing out. I cut the butyl that oozed out with a knife around the frame and peeled the excess off which was surprizingly easy to do. I wet down the area around the window so the butyl wouldn't stick when I installed the window. I needed to jockey the window around to fit it into place. If I hadn't used the water, never would have got the window in place as the butyl sticks to FRP like an octopus without the water. After I got the window in place, let it sit semi loose for a couple of hours to let the water evaporate before screwing the window down. It does seal well which the old sillycone caulk didn't.

One big problem I had was a small piece of the butyl tape got loose and was kneeled on. It got thoroughly stuck to the non skid. I peeled off as much as I could with a scraper then used Paint thinner on the little that was left. BIG, BIG mistake. The butyl turned to liquid as soon as the paint thinner hit it and left an ugly stain on the Fiberglass that I couldn't get off. The more I worked on it, the larger and uglier the stain got. Didn't try MEK or Acetone on it as the Paint Thinner seemed to cut it real good.

[Blue Stocking]

We use xylene to get it off glass. Don't know what it will do to gelcoat. Be careful, the stuff is deadly.

[delmarrey]

Originally Posted by mikereed100

Delmarrey,

The windows are beautifull. I'm curious, did you use Butyl as the only adhesive (along with the poly)? I ask as i dont see fasteners and I have often thought that as sticky as butyl is it would make a fine adhesive, not just sealer.

I used to live in a motorhome in the desert and I bedded a new AC unit on the roof with butyl. The AC was heavy so made a depression in the roof which became a pond in the summer when the AC was on, which was all the time. Summer could get up to 115 degrees and winter down to 20 but it never leaked a drop.

Mike

Well, it's working as an adhesive too, The curve in the cabin is about 15 mm per meter and it's manage to keep the Lexan sucked up to the register. I put butyl just on the back side (6 mm wide) and pushed the Lexan against it and it held in place. I tried pushing on then a couple weeks ago and It feels like they'll never come out, no flex at all that I could feel.

Then I taped off the edges and laid in black BoatLife until flush, waited for the surface to cure and then pulled the tape. I had to wait a whole month to get 1/4" (7 MM) wide butyl from 3M. The lip on the window sill is 3/8" (10 MM) wide and I didn't want it squeezing off over the edge. There were a couple spots on the inside that oozed up, so when the cold weather hit I used a razor blade and trimmed it flush with the sill. And then cleaned it up with mineral spirits (paint thinner). And yes it will dissolve in thinner, Butyl is basically a thick petro tar. It smells like black oil/roofing tar.

[bwindrope]

This is one of my favorite topics because I am such a fan of butyl tape. I buy mine from an RV supply store because it is cheap there and used to do so many things on RV's. I have several posts on my boat blog about my conversion to butyl tape for my pilothouse windows and other miscellaneous above the waterline projects. http://gulf32aeolus.blogspot.com

I don't have much new to add to what has already been said here, but if the weight of another opinion can matter, add mine to the list of those who use and love butyl tape. I've heavily used every type of sealant out there and now stick with butyl tape in most above the water applications. My days of suffering through polysulfide messes are almost entirely over.

[Christian Van H]

Originally Posted by roverhi

I peeled off as much as I could with a scraper then used Paint thinner on the little that was left. BIG, BIG mistake.

THIS: Meguiar's Direct Cleaner Wax - Liquid is what you should use to get butyl off fiberglass, and most other surfaces!

See here: http://www.newfoundmetals.com/pme/st...el/slide17.htm

[mikereed100]

Originally Posted by delmarrey

Well, it's working as an adhesive too, The curve in the cabin is about 15 mm per meter and it's manage to keep the Lexan sucked up to the register. I put butyl just on the back side (6 mm wide) and pushed the Lexan against it and it held in place. I tried pushing on then a couple weeks ago and It feels like they'll never come out, no flex at all that I could feel.

Then I taped off the edges and laid in black BoatLife until flush, waited for the surface to cure and then pulled the tape. I had to wait a whole month to get 1/4" (7 MM) wide butyl from 3M. The lip on the window sill is 3/8" (10 MM) wide and I didn't want it squeezing off over the edge. There were a couple spots on the inside that oozed up, so when the cold weather hit I used a razor blade and trimmed it flush with the sill. And then cleaned it up with mineral spirits (paint thinner). And yes it will dissolve in thinner, Butyl is basically a thick petro tar. It smells like black oil/roofing tar.

Thanks Delmarrey,

That's pretty impressive that 1/4" of butyl will hold windows that size. Too late now, but I wonder if you could have just used butyl rubber rope instead of the 3M stuff. You can get it at most RV stores and it comes in widths several "ropes" wide. The individual strands, about 1/4" wide, can then be peeled off the bunch so you can have widths of about 1/4", 1/2", 3/4", etc.

Mike

[s/v Jedi]

So, that roll on the photo is 2" wide?

ciao!
Nick.

[delmarrey]

Originally Posted by mikereed100

Thanks Delmarrey,

That's pretty impressive that 1/4" of butyl will hold windows that size. Too late now, but I wonder if you could have just used butyl rubber rope instead of the 3M stuff. You can get it at most RV stores and it comes in widths several "ropes" wide. The individual strands, about 1/4" wide, can then be peeled off the bunch so you can have widths of about 1/4", 1/2", 3/4", etc.

Mike

No offense but that doesn't look like butyl. First, if you touch butyl to butyl you'll never get it apart. What's in the picture looks more like a plumbers putty which I've found on RV's. It would make good window sealer but will pull away after time. It would not stand up to the extreme weather nor the twisting of the boat.

Butyl is self healing, once it separates it can be pushed back to seal again. But trying to get it to separate is another story. If I were to push on the windows they'd break before coming out. If one wants to remove the windows they'll have a job ahead of them. I my case I'd have to run a piece of piano wire around between the window and register while pushing on the Lexan. I'd also have to keep a coat of solvent/thinner on the wire to keep it from gumming up.

Butyl is almost permanent and messy to remove. Chemicals required!

[mikereed100]

Yes, I think you are right. After posting I researched the GM stuff a bit and it looks like a different animal. More expensive but surely worth it. I have been planning to attach my windows with GM VHB tape but my cabin sides are not perfectly fair and the tape is only 1.4mm thick. I could layer it where needed but the butyl tape might be a better solution.