We just spent the last two days In Svendsen’s Marine Yard wet
sanding the bottom with 25 grit green disks, a random orbit air
sander and a water hose.
In the process of discovery, we found bottom paint over,faring
compound, epoxy barrier coat, yellowed epoxy and finally glass mat.
We were instructed to try Interlux Interstrip (pinoff) to take the
paint off (20 minutes to 2 hours wait time recommended on the can)
at $26 per quart, temperaure has a large effect on removal time (60
deg), we did manage to loosten the paint in 1 hour and scraped a
test patch off with a carbide scraper, did not affect the epoxy
barrier coat.
We later tired a test patch of Jesco paint and epoxy remover,
dangerous stuff concerning fiberglass hull, possibility of damaging
the fiberglass they say. We applied it over the bottom paint, paint
started running down the hull in as little as 10 minutes, still no
affect on softening the epoxy barrier coat. We stopped testing for
fear of penetrating the beyond the epoxy barrier coat and attacking
the fiberglass.
For removing the paint only, we found a sharp carbide blade in a
Sandvik scraper with only modest pressure out performed the chemical
strippers, non-toxic, smooth cut and much easier on the wallet.
Best course of action, most painfull, if not tiring, seemed to be 25
grit green disks on the random orbit sander, with water to wash away
the sludge left behind while sanding. The paint came off quickly,
barrier coat took more effort to slowly grind away down to bare
fiberglass.
We sanded down both sides of the hull from the bow back 6 feet, the
barrier coat blister were 1/4" in size and tightly spaced on both
sides, failure probably due to inadiquate hull drying time prior to
application. We found laminate blister under the matt cloth, quarter
sized and widely spaced on the port side; 2" sized blister under the
matt closely spaced on the starboard side, all seem to be shallow at
present limited to the matt.
The current plan is to have Svendsen’s do a peel down to the first
layer of cloth and see what this reveals, we are hopeful from
present visual evidence that only the mat is affected. Planning on
peeling this Thursday or Friday.
Research and conversations with hull builders suggest a times there
is no rime or reason for blisters in some boats, two boats built at
the same time from the same materials, one could develope blister
and the other did not, who knows.
I don’t think the developement of blisters in our boat in anyway
negatively reflects on the BCC as a whole, I’m quite sure from a
structural strength standpoint, she could shed a few layers of glass
and still survive a hurricane, a sound beaching and still come out
of it intact. It’s actually more of a cosmetic issue at this stage.
In any event, I think it is important to discuss what we find, what
products work an to what degree, costs etc, simply for the sake of
education of the group.
The plan thus far is to peel, dry to 5% moisture content, add two
layers of glass with West Epoxy, fare, epoxy barrier coat, bottom
paint and get back to sailing.
Best wishes to all.
Marty Chin, BCC Shamrock.