GL: Bottom Paint Stripping

[Ralph Yost]

Ken
Before you go spending all that money on a barrier coat, I suggest you
go to
http://www.yachtsurvey.com/
And read David Pascoe's articles on blistering and barrier coats. His
theory coincides precisely with the events described below by Marv
Storey and why his barrier coat failed.

And, coincidentally, I just had a long conversation with a fiberglass
guy who had learned his trade from Dave Lennox, a pioneer in blister
repair processes in the Chesapeake Bay area. This fellow told me the
same thing as Pascoe's conclusion - barrier coats don't work. He said
Interlux used to GUARANTEE their barrier coat product against
blistering. They did 14 boats with it, and even had a representative
from Interlux on hand to observe the application technique verifying it
was in accordance with Interlux's instruction. Each boat had been
sandblasted, allowed to dry over the winter, and thoroughly checked with
a moisture meter. Then the barrier coat was applied. A few years later,
all 14 boats had blisters and Interlux had to pay to have it all
removed. He stated emphatically that only PEELING will provide the
desired result (see below).
The bottom line is that blistering is comes from water penetration from
WITHIN the boat when it finds its way to small air pockets in the
fiberglass layers. It is not a result of coming in through the gelcoat
as a barrier coat might imply to protect against.

Some other good reading for you, BEFORE you spend any money on barrier
coat, is
http://www.zahnisers.com/repair/blister/blister1.htm
And
http://www.zimmermanmarine.com/docs/blisters%201.pdf


This is an intense technical subject to discuss for an email list of the
Great Loop, and perhaps too much for this list. There are so many
opinions based upon years of standard industry practices which makes it
harder for the industry to change.
Today's real solution for blisters is the have the boat PEELED in which
the fiberglass layers that are infected with air pockets (ie blisters)
are removed, then the fiberglass is replaced. This can only be done by
intelligently taking care samples to determine the depth of peel
required (See Zimmerman Marine article). It will be expensive. Can U say
CHA-CHING $$$ ? I know of at least one person in this email list who has
had it done and perhaps he can add to or correct anything I have
presented.
R.

---------

On another subject that I hope you have already thought about ---- Make
sure 
the boat bottom fiberglass is completely dry before applying barrier
coat.  
Measure with a moisture meter.  I found out the hard and very  expensive
way.  
My boat was barrier coated the year before I purchased  it.  The bottom 
survey, including moisture checking, was good. (Moisture  meter couldn't
read 
moisture through the barrier coat.)  The bottom looked  great.  The
second year I 
had the boat, "gelcoat" blisters the size of BB's  appeared over the
entire 
bottom that was in the water.  After checking with  several experts,
including 
someone who I consider a master of the subject in  Great Britain, my
conclusion 
as to the cause was the following: The previous  owner, with all good 
intentions, removed all the bottom paint and then barrier  coated but
did not allow 
the fiberglass in the bottom dry completely.  The  barrier coat trapped
moisture 
in the fiberglass under the gelcoat causing the  gelcoat to blister.
There 
were no blisters in the fiberglass.  I had  to have the gelcoat removed
then 
left the boat on the hard for a year allowing  it to dry properly.
(Once the 
gelcoat was removed, the moisture meter  showed a high moisture content
in the 
fiberglass.)  I then had the bottom  epoxied and barrier coated back to
the 
original thickness of the gelcoat.   Why was there moisture in the
fiberglass in 
the first place?