On Fri, 23 Apr 2004 08:47:30 -0700, "Jonathan Ganz"
wrote:

We're in the process of having two windows redone. The person who's
going to do it for us claims that the proper sealant is quite toxic.. some
"professional grade" product. I believe the windows are some sort of
polycarbonate, but I'm not certain. Do you have any info about the
toxicity of these type of sealants? What's there now is ugly and leaks,
so it's got to get redone.

What sort of boat? Are the portlights in frames or frameless?

I am not sure what sort of product he is talking about. Was it Plexus
by any chance? From my days on the C&C list, where folks are quite
experienced in *attempting* to install leak resistant portlights,
Plexus was sometimes mentioned. If memory serves, that might be a two
part product that is a lot more like a glue. Based on my experience,
which is hardly exhaustive, I think the key to leak-free portlights is
a good design in the first place, together with a forgiving and easily
removed/replaced sealant. My C&C had a VERY poor portlight design.
It was an unframed, thin, long piece of *something* (dark lexan,
acrylic, plexiglass) that came to a sharply pointed taper at the
forward end and was expected to cling to the outside of a curved cabin
top. The hot sun would heat things up and things would try to move a
bit against the screws and everything would start to break down and
leak. I don't think that the Plexus would have been a solution for
me, but I never tried it. I try never to do anything that won't let
me remove or replace in the future.

On my current boat, the cabin portlights are also unframed, but are
divided into two smaller portlights, each of which is set into the
routed, recessed openings. The instructions for replacing the
portlights, or rebedding them, is to run a bead of white GE Silpruf
around the inside edge of the portlight opening. Then carefully set
the portlights in place against this sealant/adhesive. There are 4
very small screws, two top and two bottom that are then screwed in
around the top and bottom edges of the portlights to hold them in
place. A larger bead of black GE Silpruf is then applied around the
outside edge of the portlights and faired after it has set up enough
to be worked without still being too "gooey". They won't leak when
designed and bedded this way. (The white inner bead is just for
aesthetics so as not to have black Silpruf all over the white gelcoat
inside the boat).

I like the GE Silpruf product. It is often used to install those
glass panel windows on commercial buildings. Sabre recommends that
for their portlights, which is what I used. I subsequently learned
from my parts buddy at Valiant that they use a lot of it as well. It
is pretty inexpensive. About $6 for one of those caulk gun size
tubes. It doesn't harden and crack, which is where the leaks first
develop. The previous owner of my boat had apparently used Boat Life
and it was a hard, cracked mess.