"Wilbur Hubbard" wrote in message
news.com...
Skippy, you may have dallied too long on the hard. Rainy season has
finally started and where you are you can now expect some rain, often
heavy rain, just about every afternoon.
What kind of resin are you using for the patches? I hope Epoxy resin as
polyester resin is an open invitation to more blisters. But, you'd better
mix it in an air-conditioned room. Why?
http://msdssearch.dow.com/PublishedL...romPage=GetDoc
Can you say hygroscopic. IOW if you mix it in a humid atmosphere you will
be adding unwanted moisture to your laminate the result of which will be
more blisters.
Wilbur Hubbard
Hi, Wilbur (I'm using this character name as it's the one which addressed
me, but now that you've called yourself out recently, even though I knew it
before, it lets me know the intellect and temperament behind the post),
We are using West System epoxy for all the fiberglass work. It's not the
Dow product you referred me to, and has some significant differences,
including shelf life, among others. Polyester is a monomer and only
marginally suited to layup as relates to water prevention; vinylester, being
a polymer and crosslinked as well as, therefore, being much more water
resistant, being much better and not much more bother to work with - but
they didn't know about that in the time that my boat was built. Epoxy (also
a polymer) is the worst to work with, but superior to vinylester for
waterproof characteristics, but we had no layup to do - just little patches.
In the couple of places where we needed buildup, it was 1/4" strand chop,
with a bit of 703 (I think that's the number) West glass thickener to the
degree needed to hold it in place in some volume (a section of the stern of
the keel, e.g., was about an inch we wanted to fill-and-build due to many
prior sandings having taken off the "wrapper of glass on that edge, along
with a slight blister-chase for a 2" length section on the starboard side).
All the filled areas (trailing edges as above) as well as the bottom and
front of the keel will get a couple of layers of 1708 plus a layer of 3/4oz
mat to build it back up to original. The area of the bottom of the keel
which dug a 2-foot hole in the limestone shelf during our wreck will get a
couple more layers of mat, as well, mostly for symmetry, as it's literally
rock solid (the lead ingots, shaped to the interior, were surrounded by an
epoxy/marble-dust slurry prior to closing the keel cavity, thus putting
marble/epoxy directly under the fiberglass and over the lead).
In any event, it's essentially finished, other than just a couple of places
we want to add some more.
Following that will be AdTech fairing compound, which is also 100% epoxy,
but particularly tolerant of many lousy conditions, being milspec.
Sanded while green (anything between about 4 and 24 hours from application),
it's a piece of cake, if laborious due to the square footage we'll be
sanding. After that (which likely will leave a significant skim layer on
top of the non-repair areas, anyway/also), we'll be laying on 30 or more
mils of epoxy barrier coat, after which we'll do the bottom paint. I really
doubt that, absent a fairly significant ding, any water will be able to find
its way to the underlying polyester layup - and, as we've exposed and
removed all that was readily available, it would be an incredible game of
chance for that ding to find someplace which hadn't already been addressed
or voided of WSMs.
After all this time since the steam pressure washing, we've not had the
first hint of additional WSM exudation so, while there may well be areas we
didn't find which are not completely laminated, buried deep somewhere in the
hull, I doubt very seriously we'll have any blistering in the future.
Indeed, we had none when we hauled here. It wasn't until our sander guy
took off not only all the bottom paint, but the barrier coat and a fair
amount of fiberglass, that we saw our small weep points. Chasing them with
the grinder, followed by the keep-it-soaked-under-pressure-washing (not
nearly the velocity, volume or temperature of the steam guy, but it
obviously helped), as proven during the steam cleaning, did the trick for
any which was available.
As to the rainy season, ya, we know. Fortunately, we should be able to get
a great deal done - apply fairing in the AM, wet sand in the PM :{))
Thanks for thinking of us...
L8R
Skip and Lydia
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