{Stus-List} Gelcoat cracking/blemishing at/below waterline - "fisheyes"?

rspence7 rspence7 at cox.net
Wed Feb 28 23:37:54 EST 2007



Dennis,

After going down-list for responses, I'll add my own.

I had bought  "Frith" an '84  LF38,  on the hard, not in the water for two years.

Frith's  bottom was lightly sandblasted after I bought her in '90; which then exposed lots of small "gelcoat voids", thousands of them, exposed by the blasting.  Yet, none of what I would characterize as "blisters".

My Dremel tool, with a ball headed grinder( used about five of them}, entered each of these "gel-coat voids", and as it penetrated, you could hear the difference between unsupported gel-coat chattering its edges; versus boring into the solid laminate below.   I had used a magic marker to grid off the bottom, to be sure that I worked within my defined area, not outside the boundry.

Once the bottom had been ground out, again with no "blisters" showing, then waiting two weeks for weeping or problems to develop, I wiped the areas liberally with acetone;  then I mixed slow epoxy, and with an "acid brush" diddled into each of the voids within my grids. 

 Before the liquid epoxy fully kicked, I mixed up an epoxy slurry with West collidal silica to a semi runny consistency, push acid-brushed it into the voids, while scraping off the surface of excess.  Hours later, before the runny epoxy slurry had fully set up, I followed with a peanut butter thick layer of epoxy with filler to a bit above surface filler.

Once dried, fairing was completed with a random orbital sander with 100 grit paper.   Then, further hand faired, before the application of numerous coats of Interprotect.


  ----- Original Message ----- 
  From: Dennis C. 
  To: cnc-list at cnc-list.com 
  Sent: Wednesday, February 28, 2007 8:10 PM
  Subject: {Stus-List} Gelcoat cracking/blemishing at/below waterline - "fisheyes"?


  Touche' is on the hard and the bottom sanded.  Found old gray barrier coat on gelcoat.

  There are many dozen "fish eyes" near the waterline.  These blemishes are mostly small, semi-circular cracks in what appears to be an overly thick gelcoat layer.  Some of them have popped out leaving small 1/4 inch or so diameter pits about 1/32 to 1/16 inch deep.  With effort, I can pop others out with a knife point.  They seem to be mostly cosmetic.  They do not appear to penetrate to or into the laminate.  They occur primarily in what appears to be an old boot stripe but continue below the waterline for a foot or so.

  Anybody seen this condition before?

  Any suggested remedies?  Yard has suggested wet blasting then blister repair compound.  I'm wondering about thinned epoxy like wood penetrating epoxy to simply permanently keep them in place.

  I will be applying a full barrier coat during this haulout.

  Dennis C.
  Touche' 35-1 #83
  Mandeville, LA


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