I've been hearing more and more boaters talk about using butyl tape
for sealing hardware bolts, boat windows and similar items on boats.
It it used only where two items are screwed or bolted together. It is
the soft, tacky stuff used by window installers. I've been using it
on my boat lately. It is very easy to apply and work with, compared
the usual 3 sealant types (silicone, polyurethanes, polysulfides), but
I am interested in what others think.

According to some internet research, some boaters have used it for
years, and after years under a fitting it remains pliable. According
to one manufacturer, it has these properties (quoting their website):

# Adhesive: Butyl rubber has excellent adhesion to most materials,
(But it is not an "adhesive" like 5200) such as: all of metal, wood,
glass, zinc, concrete, etc. (fiberglass is not quoted here.)
# Heat & Cold resistance: Because of heat-resistance and
cold-resistance, Butyl rubber can be used under any temperature
conditions.
# Excellent Dielectric insulation
# Anti-corrosion: Butyl rubber prevents surface corrosion from
moisture and steam.
# Easy application.
# Excellent resistance against UV rays.
I would add "conformability".

I found this at a competitor's site: "In recent years, all butyl tapes
have become taboo to our industry, and for good reason. Butyl tapes
are not an adhesive and should never be used to install a windshield
or any glass that is not mechanically fastened to the vehicle.". But
I use it only around bolts, to prevent water ingress.

The truth??

Jim

I have installed many windows with it and think that is the best application for it. Most windows have an inner ring that that screws to the window. Many times the ring and window will not tighten to the structure either because the structure varies in thickness or the inner ring is made for a thicker structure. The butyl tape provides a seal as well as a gap filler. Butyl tape is somesimes confused with a window putty. Both of these products are sold at RV supply stores and usually sit next to each other. The butyl tape is more like silly putty and the other product is more like that oily clay we used to play with in elementary shcool. There are also different types of butyl tape, some are "thicker" and a little less stickey than others. While butyl tape is not an adhesive it does "stick" to surfaces and is a very good sealer for areas like windows. I ust only for bedding windows where a gap filler is needed and leave the hardware bedding to Sika Flex or 5200.
---Joel---

On Sun, 27 Mar 2005 11:08:00 GMT, Jim Thompson
wrote:

I recently had to remove a port light I had installed 10 years ago
with butyl tape. It was still in suck condition that I didn't even
bother to replace it. I simply reshaped it by hand to reform the
seal. But, what you heard about it not being an adhesive is correct.
It is not a substitute for 5200 or other adhesives and, IMO should
only be used in conjuction with mechanical fastening of some sort.

Joe