GL: Bottom Paint Stripping

[MTStorey at aol.com]

Ken - I looked into soda blasting 3 years ago when I needed the bottom  paint 
and gelcoat removed from my 1979 43' Viking.  The process was  just getting 
started in the Chesapeake Bay area.  I discussed the process  extensively with 
the individual who had the Annapolis franchise.  I didn't  end up using the 
process because he didn't want to come over to the Potomac  River near 
Washington, DC where my boat was on the hard.  I ended up having  it sanded.  My 
current feeling is that if I have to have the bottom  paint removed in the future, I 
will use soda blasting.
 
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?  It is because  gelcoat is slightly porous allowing water to 
slowly pass through and go into the  fiberglass.  This normally causes no harm 
if the production layup and  resin in the construction of the boat is good.  
If it isn't, you get  blisters.  Barrier coat is nowhere near as porous as 
gelcoat.
 
Marv Storey
43' Viking Aft Cabin
Osprey



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