T&T: Blister repair

[LRZeitlin at aol.com]

In a message dated 8/1/07 12:00:56 AM, Darren writes:


> My surveyor tells me that I have approx 60 small (less than golf ball) 
> blisters on either side of purchase vessel. After a long talk my father suggests 
> walking from deal as this is a painful repair process. I know I can repair 
> but it will be messy and cost in materials and hauling. I am planning on going 
> ahead, but only if this is factored into final price.
> 
> 
Blister repair is a simple but messy process. It is labor and time intensive. 
That's why boatyards charge so much. The material cost is almost trivial. My 
wife and I have repaired boats with as many as 300 blisters, some the size of 
dinner plates. Before you undertake such a project, get the West blister 
repair manual and see if you want to do the job. 

As far as your immediate decision, have the boatyard give you an estimate for 
blister repair. Then knock the estimate off the asking price and see of the 
present owner will go for it. 

If he accepts the deal, here is the drill. For spot repair of the 60 
blisters, block up the boat in a location where it can sit undisturbed for a few 
weeks. Mark every blister with a magic marker. Drill a 1/8 hole in the center of 
each blister, using a collar around the drill so you don't penetrate the hull. A 
nasty brown liquid will probably squirt out. Then get a grinder and grind 
away the surface of each blister with 36 grit paper until you are down to intact 
fiberglass. Be carefull, don't grind through the hull. When you are finished, 
wash the cavities with several changes of water, then go away for several 
weeks to let the fiberglass dry out. Better to move the boat to Arizona but that 
is usually impractical. When dry, paint each cavity with epoxy resin to seal 
the fiberglass. Cut a number of discs out of 10 oz. fiberglass cloth in varying 
sizes ranging from the diameter of the largest blisters, decreasing in size by 
half inch increments. Now for the real work.

Wet each blister cavity with epoxy resin. Before the resin sets place a small 
fiberglass disc in the hole of each cavity. Then go around the boat wetting 
each cavity again and place the next larger size disc in the blister site. 
Continue the process until each blister site is built up to the level of the 
surrounding fiberglass. Let the epoxy cure then sand the repairs flush with the 
hull. Fair with epoxy fairing compound. Put on bottom paint and go boating.

If you are worried that the boat may continue to blister you will have to 
remove all the bottom paint. Then sand the surface thoroughly, apply sufficient 
layers of barrier coat to impede water penetration, then reapply bottom paint. 
This is a much bigger job. In that case, listen to your father.

Larry Z



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