Gluing fixed portlights

[JonnyBoats]

In my LeComte Northeast 38 on each side of the cabin I have two rather large portlights made of safety glass. You can see a sistership at:
http://www.lecomteowners.com

Anyway they leak, and I need to rebed them. A friend suggested using the same adheasive they use to install windshields in cars.

Has anyone tried this? What do you think of this idea?

[Figment]

"safety glass" meaning tempered glass or laminated glass? I'd prefer laminated.

"stuff they use in cars" is "butyl rubber".
DO NOT try to use the preformed butyl tape that they actually use in car windshields. It's an absolute nightmare.

Grab a tube of "gutter sealant" at the hardware store and read the fine print to find the stuff that's actually butyl rubber instead of siliconized acrylic. This will provide the same seal as the preformed tape but will be FAR more userfriendly.

Which is not to say that it's userfriendly, really. It's a gooey mess. invest in masking tape.

-Mike
(the local butyl rubber freak)

[Jason K]

I'll second the recommendation for butyl caulk. Home Depot, Lowes or any hardware store will sell it as gutter/flashing caulk.

It comes in white, grey, or black and can be a mess. As Mike said, mask the area well.

It's extremely gooey at first and, while it does harden up, it will always remain pliable - which is a good thing for a portlight sealant.

Are you going to remove the portlight to rebed it? If you don't, you may find you'll have a hard time taming the leak. However, depending on what sealant was originally used, you may not be able to remove it in one piece.

I recently replaced the tempered glass in my forward hatch with lexan. It was badly cracked. I was able to remove most of the pieces in the center of the hatch in large chunks, but the sealant was well bonded at the perimeter and the glass had to be chipped out.

Here's a couple shots (not because they are necessary to illustrate the point, but just because pictures never hurt and I happen to have a couple):

[dasein668]

I recommend removing and rebedding the ports to have much luck at getting the problem solved.

That said, after I rebedded Dasein's deadlights, one of them had a slight leak. With some inspection I was able to determine that there was a pinhole in the butyl on the exterior of the port allowing water to seep in. I was able to fix this leak by using Boat Life Liquid LifeCalk. This stuff is essentially a runny version of their LifeCalk. I taped around the offending pinhole and squeezed a bit of the LLC into the hole. The stuff ran down into the port (slowly) and over the next couple of days I squirted a little bit of the stuff in there a couple times per day. Eventually it stopped running into the hole and I haven't had any further leaks.

This is a hit or miss procedure, but might help out depending on the severety and location of the leaks.

But again, I think rebedding with fresh butyl is the best route.

Edit: Interesting html-aside... I tried originally to link to the LifeCalk on the Defender website but their URL had some pipe characters ( | ) in it and the phpBB software couldn't parse the URL. Anyway...

[Arcadia]

This is a timely post as I am about to rebed my ports which were removed while repainting the deck and cabin.
I plan on using butyl, but I have two questions. I don't think there is problem using butyl with Lexan, (that is, gluing the Lexan into the deadlight frame before bedding the whole mess to the cabin side)is that correct? And second, I'm curious if anyone is using butyl for other caulking applications? I always seem to hear about butyl being used only in relation to rebedding ports. Is it not suited to other applications, or is it just too much of a mess to use?

Chris

[Hirilondë]

I have been researching the bedding of polycarbonate and acrylic for many months. It is extremely difficult to get good information on what compounds work best, but even harder to find which materials don't work and why. The following link: http://www.sheffieldplastics.com/web_docs/BRO001.pdf is from the brand we most often purchase at the boatyard. You will notice that they recommend butyl tape, but make no mention at all about butyl caulk. Does this mean that uncured butyl reacts with polycarbonate and the partially cured tape doesn't? The only thing I have found that is consistent from brand to brand is that silicone is the only bedding recommended for all applications.

[Figment]

Butyl tape isn't "partially cured", it just has a fibrous substance mixed in to give it that stiffness. Way back in the day this was one of the countless applications for that Miracle Substance: asbestos. If they list butyl tape, then gunned-butyl should have no chemical incompatibility.

It's not just for windows. it'll give a good motion-tolerant seal anywhere you can stand the tackyness. I used it on my chainplate penetrations, for example.

The thing of "gluing the lexan to the frame before bedding the whole to the cabin" is a bit problematic because butyl takes sooooooo long to stiffen up. I'd use a few VERY SMALL dabs of an actual adhesive to ensure that the glass didn't abandon the frame mid-installation.
Butyl is a sealant, not an adhesive.

(I know way way too much about sealants. I shall now retire to my nerdery and stop scaring the little ones.)

[Arcadia]

Thanks for the response.
I'm thinking I'll use silicone to glue the Lexan to the frame. Silicone seems to work well as both an adhesive and as a gasket material when in compression as with the port glazing.
How long does butyl take to tack up? I was reluctant to use silicone here again because it's so hard to clean off to rebed but I had good luck with it before, it lasted 14 years with only one leak. But as Tim has said, it sticks when you don't want it to and doesn't when you need it to. I'll definitely use butyl for the frame to cabin side joint, the silicone was awful to remove here.
I like the idea of butyl for the chainplate covers as well.

[JonnyBoats]

What about using 3M? Auto Glass Urethane Windshield Adhesives?

http://solutions.3m.com/wps/portal/3M/e ... R6DCKBSPgl

[Quetzalsailor]

John, call 3M, Sika, GE, etc., and ask them, too.

Hirlonde, our NE 38, Quetzal, was at Dodsons for years. What's the liklihood that the Sheffield Plastics stuff is what was used for rebedding Q? It looks like silicone to me, clear and stretchy. All 9 fixed ports are still watertight, all were rebedded.

As for using glazing tape: It's a great idea particularly as you get an appropriate thickness of sealant which is important to get the flexibility you need. Two strong negatives need to be assessed: whether the glass and the fiberglass are parallel enough for a uniform thickness of tape, whether the fiberglass rabbet is smooth enough to seal to the tape.

If not using glazing tape, be sure to use glazing blocks to set a minimum sealant thickness. Usually, these are neoprene made to thicknesses and sold for the purpose. I use whatever's handy, like punchings out of truck inner tubes or samples of EPDM roofing on the theory that the blocks are completely encapsulated in the sealant and inert after the sealant cures. Glazers use the blocks to set thickness and to stop the glass from sagging down in the rabbet.

I am under the impression that the automotive glazing tape is polysulfide and that it's used in conjunction with polysulfide sealant out of a tube. The butyl never cures, never gets hard, never is not sticky; the polysufide does. Both are pretty miserable to work with, like 5200, strings of goo everywhere.

[Quetzalsailor]

John, snoop that 3M site; back up to the US menu. There's lots of stuff worth reading.

[Figment]

That 3M stuff is a polyurethane. It ought to work well.

Two different approaches to the problem of sealing a joint that's subject to movement:
1. Let the joint move, move with the joint to maintain the seal.
2. Resist/arrest the movement of the joint to maintain the seal.

The polyurethane, as an adhesive, resists the movement. This is important in car windows as (i'm told) they are now a component of the structural system of the body, a stiff diaphragm that unites other members.
I'm not sure that this is such a great idea when applied to deadlites on an old boat. The hull and cabin structure WILL move. To resist this movement essentially requires that the polyurethane transfer the force to the frame (and the glazing). In practice this may never create a problem, but in concept I'm not a fan. I'd rather let the deadlite float around in the joint, not subject to any strain as the cabin structure works itself around.

I also generally err on the side of easier future disassembly, but that's just my own wacky agenda.

[Ceasar Choppy]

I rebedded a fixed portlight this spring with the butyl tape McMaster sells. It comes in Grey and is approx. 1/4" thick x 1/2" wide (too lazy to look it up right now).

I had to double up on it to use in in the rabbet of the portlight frame and use a clamp to pull the frame together and squeeze out the excess. I used one piece of tape around the frame when I mounted it to the cabin top.

Compared to the other three portlights I mounted with polyurethane a few years ago, the butyl is far superior. You might also guess why I only did one portlight... removing the ones mounted in polyurethane (and esp. cleaning them up) is a PIA!

[Capn_Tom]

I used Butyl tape (actually it was more of a rope) that was supplied by New Found metals to install my opening ports. Other than it's resistance to compression when clamping the ports into place I found it a dream to work with. No drips or gooey residue. Scrapes off of surrounding materials easily with a stiff piece of plastic. I used white sikaflex (I forget which one) on the outside rim of the trim piece to provide a more attractive edge.