T&T: Blister repair

[John Blackburn]

 To give you a price point, during our pre-purchase survey we found that
our 44 DeFever was completely covered with blisters ranging in size from
a dine to half the size of my little finger nail.  It looked like it had
measles.  Osprey Marine Composites in Herrington Harbor North (on the
Chesapeake) completely peeled the bottom, added a layer of fiberglass,
barrier coated, faired and bottom paint for $16k four years ago.  We had
the price before we closed and had an accommodation from the PO.

I would recommend Osprey for any work of this sort.

John Blackburn
44 DeFever "Yak Rack"
Deale, MD

LRZeitlin at aol.com wrote:

  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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