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Old 05-11-2009, 09:57   #16
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It is my understanding that the fixed glass in today's automobiles are actually stressed members of the structure. Otherwise, they actually design in the glass to be a structural part of the design, not just a way to fill in the pukas needed to see out. The only thing holding that glass in is butyl tape. Says something for the ability of the stuff to hang on to things.

Still will stick with LifeCaulk to seal most fittings because it's way easier to use and cleans up without messing up the gel coat.
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Old 05-11-2009, 11:26   #17
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There must be some confusion about butyl tape because I have read several posts here about having problems with it messing with gelcoat. Either that, or this is another testament to "your experience may differ". One of the primary reasons I use butyl tape to begin with is that is so very easy to clean up. It not only removes from gelcoat fairly easily, but has never left any stains or other trouble.

My original pilothouse windows were installed with butyl tape by the factory back in 1988. When I replaced the windows this past year, that old butyl tape was like brand new, had a perfect water tight seal with the gelcoat of the pilothouse, and yet removed easily by simply rolling it off with my fingers. That was my first conversion to the genius of the stuff. It never dries out, it doesn't harden, it seals very well under compression, and is painless to remove from smooth surfaces. It doesn't adhere like a 4200, but when used in situations where there are mechanical fasteners, it is simply the best.

Polysulfide is a total f***ing mess to apply or remove. Getting that stuff off requires solvents and scrapers for sure.

Anyway, that's been my experience.
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Old 05-11-2009, 14:27   #18
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I tried twice to seal the Lexan with LifeCaulk and both times after heavy weather sailing it started to leak. So I figured if it was goodnuf for cars the it should hold on the boat. And yes it is messy! If you don't tape off the edges your in for the "tar baby" effect. Plus, it seems to leave behind bubbles in the mix.

I found the best way to remove butyl was in very cold weather. It hardens up enough that scraping with a razor dipped in solvent gets most of it off.

As for staining the gelcoat, once it's deluted with a solvent it's like a black oil or dirty motor oil. That is mechanical hygenics. One has to be careful when handling chemicals.
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Old 05-11-2009, 14:50   #19
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As for staining the gelcoat, once it's deluted with a solvent it's like a black oil or dirty motor oil. That is mechanical hygenics. One has to be careful when handling chemicals.

Yep I warn of this all the time DO NOT USE BLACK!!!!!! It is available in off white and gray.

My Goiot hatches were sealed with it at the factory 30 years ago. Still bone dry....
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Old 05-11-2009, 15:01   #20
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I keep waiting for a winner to come to the front on this topic since I need to pull and redo the windows on my cabin top. I get a little confused about talk about screws etc as my windows just sit in the cutout. I have a hard time believing the tape is going to be more messy than squeezng a bunch of caulk in the cutout and putting the window in squeezing a bunch out both sides. At the same time I find it hard to believe that a layer of tape is going to squeeze out even enough to seal all the way around the window. Without a doubt the cost of this project is the time and I really don't want to have to do it again for a number of years (like 10).
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Old 06-11-2009, 09:23   #21
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When you write that polysulfide makes a mess you are using a product that has more elements than just polysulfide. May be you mean polyurethane? 3M 101 and BoatLife LifeCaulk are polysulfides. They are sealants, not adhesives, so it needs another primary method of bonding, like mechanical fasteners. Polysulfide cleanup is the easiest thing to do. After cure, a plastic scraper and a terrycloth are all that's needed.

The car windows that are structural aren't put in with butyl tape of course. They use high tech adhesives like from Loctite. Lots of info on-line, use Google. Some yards use that too, matching the adhesive with the window-coating instead of the window material. When you use an adhesive that's good for Lexan or Plexiglass, you must remove that coating (if it has a coating) by sanding before installing it.

ciao!
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Old 06-11-2009, 11:43   #22
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LifeCaulk and 3m 101 clean up very easily with a little mineral spirits/paint thinner. Typically use a 1/2 sheet paper towel to clean up several fittings. The mineral spirits cut the stickyness of the caulk so it is easy to corral and clean up. Trying to clean it up with just a paper towel is a 'challenge cause it's like trying to wrestle an octopus. No matter how careful you are, you've only got two hands and it's got a million ways to escape.

Butyl will clean up just by scraping or carefully peeling it off on smooth surfaces. Not easy to get out of the dimples on nonskid, however. Once butyl sees a solvent it turns into a liquid and soaks into my old gel coat. Hope the butyl cures enough that it won't continue to dissolve at the meer hint of paint thinner. Could see an accidental spill resulting in permanent black streaks.

BTW, the butyl I bought came in a long rope about a 1/4" in diameter. You could pull it into thinner diameter if you needed less thickness or double it up for more.

As far as ease of use between polysulfide and butyl, I'll stick with polysulfide. Trying to get the butyl applied to the padeyes that I set with butyl was not fun. It seemed to be attracted to itself like a magnet and would bond with itself at the slightest touch. Trying to get the butyl all the way around the fitting and on the fasteners was way harder than just squeezing polysulfide in place. Clean up was easier with polysulfide, also. I just used a 1/2 sheet of paper towel and a little paint thinner to clean it up. With the butyl, had to cut around the fitting and peel away the butyl and repeat several times to get a neat installation. I wasn't about to use a solvent on the butyl after my previous unholy mess experience with trying to remove just a tiny bit of it.
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Old 06-11-2009, 11:58   #23
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Trying to get the butyl all the way around the fitting and on the fasteners was way harder than just squeezing polysulfide in place.
Butyl on deck fittings??????

Butyl doesn't cure. The solvents gradually disipate if not trapped.
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Old 06-11-2009, 12:07   #24
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Any commercial glass shop should have butyl tape, in various widths and thicknesses, in rolls like mosquito coils. It is available as well with a vinyl spline down the center.
TremCo supplies me, we use miles of the stuff on big commercial glazing jobs.
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Old 06-11-2009, 13:02   #25
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Butyl on deck fittings??????
You can use butyl to seal anything. Since I'll be removing the deck hardware and painting the deck when I get to Kona, thought I'd use butyl to seal a couple of padeyes that I had to install. Fittings bedded with butyl are supposedly easier to take off later than those bedded with polysulfide and way way easier than those bedded with polyurethane.

Butyl has less bonding strength than polyurethane but has more stretch so probably is a better sealant for large areas with significant expansion. That's hypothetical thought on my part. I've never had a problem using polysulfide to bed anything.
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Old 06-11-2009, 16:17   #26
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For deck fittings you really should use 1/16" thick neoprene sheet instead. It's the final solution. Here you go: Amazon.com: Neoprene 1/16" Rubber Sheet, 12" x 24", Black, 60D Durometer: Industrial & Scientific

$8.48 for a 1'x2' piece.

cheers,
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Old 06-11-2009, 18:05   #27
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I keep waiting for a winner to come to the front on this topic since I need to pull and redo the windows on my cabin top. I get a little confused about talk about screws etc as my windows just sit in the cutout. I have a hard time believing the tape is going to be more messy than squeezng a bunch of caulk in the cutout and putting the window in squeezing a bunch out both sides. At the same time I find it hard to believe that a layer of tape is going to squeeze out even enough to seal all the way around the window. Without a doubt the cost of this project is the time and I really don't want to have to do it again for a number of years (like 10).

Don,

As much as I love butyl I would personally use Dow Corning 795 for that application. It MUST be clean and free of ALL previous residue. If water beads it is not clean enough...
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Old 06-11-2009, 18:15   #28
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3M 101 and BoatLife LifeCaulk are polysulfides. They are sealants, not adhesives, so it needs another primary method of bonding, like mechanical fasteners.
3M 101 is most certainly an adhesive. It will bond at about 130 pounds per square inch. While less than the 300 PSI of 4200 it is definitely an adhesive-sealant, like 4200 is, it's just a lighter adhesion than some others.

The adhesion of butyl tape is in the neighborhood of 10-45 psi and we all know how many car windows fell out at 80 mph? None that I know of... Heck I have seen bodies fly through windshilds and not break the butyl seal and that is 10-45 PSI.. Adhesive...?

P.S. Polysulfides and many polyurethanes should not be used on acrylic and polycarbonate as it can leach the plasticizers out of the plastic and cause it to become prematurely brittle.

This is why structural silicones like Dow 795 are used.. If you must use a pilyurethane Sika 295UV with the primer is a decent choice.

Dow 795 holds large plate glass windows in sky scrapers, acrylic windows in many sailboats and power boats and has only 60 PSI adhesion at 50% extension/elongation. 3M 101 is double the adhesion of Dow 795....
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Old 06-11-2009, 20:25   #29
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3M 101 is most certainly an adhesive. It will bond at about 130 pounds per square inch. While less than the 300 PSI of 4200 it is definitely an adhesive-sealant, like 4200 is, it's just a lighter adhesion than some others.
from 3M US: Marine 101 Sealant
3M Marine 101 Sealant

Provides a weatherproof, watertight seal between mechanically fastened joints to resist weathering and salt water. Non-sagging, non-shrinking, remains permanently flexible.


I removed a deck fitting after 15 years. The 101 wasn't cured. The only cured part was less than 1/4" on the perimeter of the fitting (where it gets in contact with moisture). That is what makes it the perfect bedding compound, a sealant, and not an adhesive. You should not use 101 (or LifeCaulk) without mechanical fasteners. Every sealant has adhesive qualities. The difference in name is because it wasn't developed for it's adhesive properties.



Quote:
Heck I have seen bodies fly through windshilds and not break the butyl seal and that is 10-45 PSI.. Adhesive...?
There's not many new cars with butyl sealed windscreens anymore. I wouldn't know a single one. They use high tech urethane adhesives now, I posted that before. Here's 255,000 links to demonstrate it: auto glass adhesive - Google Search

Quote:
P.S. Polysulfides and many polyurethanes should not be used on acrylic and polycarbonate as it can leach the plasticizers out of the plastic and cause it to become prematurely brittle.
Correct and polysulfides are the main culprit there. Never use that.

Quote:
This is why structural silicones like Dow 795 are used.. If you must use a pilyurethane Sika 295UV with the primer is a decent choice.
I believe Dow 795 is a silicone, right? That is indeed the best choice but it also means that the coating must be sanded off before applying the silicone. The Sika 295UV works well on the coatings. The Sika primer isn't just to help the 295UV, it's also key for UV protection and because it is black, you can't see the adhesive through the window material so it makes a better looking window. There's only one right way of using 295UV and that is described in the documentation you can download from Sika for free. It involves calculating the thickness of the layer of Sika required, making spacers out of cured 295UV and a V-cut of the nozzle so that the beads is a sharp-topped ridge, which prevents air becoming trapped in when the window is pushed onto the bead. I have never seen a DIY cruiser doing it anywhere near right, but they are quick to complain about Sika when it fails some time after without ever considering the problem was their application and not the product.

I once took the time to explain someone exactly how to do it. He slapped the lexan on with 5200 instead. I hope it lasts forever because it will require a lot of fiberglass work when it needs to come off....

cheers,
Nick.
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Old 06-11-2009, 21:15   #30
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I've been rebedding hatches almost as a hobby. I've got over 20 of them. Almost every hatch started leaking after about 5 years, so I went with life caulk. Cleaned, scraped, wiped down with acetone. I'd say of the hatches that I put in the smaller ones didn't seem to leak again, the larger ones all began to leak, between a few weeks to a year later. I'm using now lifeseal with excellent results. I don't even try to be pretty, I put a huge amount down, and leave a small amount on the outside forming a gasket around the edge. So if you do rebed hatches, I'd recommend a lifeseal rather than life caulk(rebedded I think now around a dozen hatches or so). Oh, the biggest work is removing the hatches. By far the best thing I've used is debond 2000. I've used a few others (such as the ones sold at west marine) and I found they took far longer to work (hours as opposed to minutes).
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