maybe dumb blister question

[bruce123]

much of my recent boat shopping has led me to be interested in Pearsons, 30 to 36 feet, probably early 1980''s vintage. many of these boats are advertised as having a recent epoxy job on bottom. is it fair to assume that most Pearsons (as well as most other boats) in that age bracket will have gel coat problems? and if so, would i actually do better to shop for a boat that has had this problem, but corrected by a reputable boatyard?

[Jeff_H]

A large percentage of US boats built in the late 1970''s and early 1980''s have had blister problems. I really do not know whether Pearsons of this era were consistant to this pattern. There are a number of causes of blisters during this era: 1. poor adhesion of the gelcoat to the lamimate, 2. Deterioration of the resin within the laminate due to contact with water molecules from the EXTERIOR of the hull with by-products of the catalytic process (True osmostic blisters), 3. Deterioration of the resin within the laminate due to contact with water molecules from the INTERIOR of the hull with by-products of the catalytic process, and 4. Resins that produced byproducts during catalyzation that are self-destructive to the resin or resin/fiber bond. I have listed these in order of difficulty to permanently repair.

The problem with gelcoat to laminate bomd has to do with the change in gelcoat formulation in the 1970''s. This new gelcoat was thinner, shinnier and apparently set up more quickly. This made it harder to get a bond between the laminate and the gelcoat. These are very shallow blisters and the gelcoat can be peeled off almost in sheets. the laminate below will appear smooth and shiny and nearly perfect. Breathe a sigh of relief; you have ducked the bullet. It is easy to repair this permanently by removing the loose areas of gelcoat, sanding the laminate lightly and clean the surface well. Then apply either an epoxy or vinylester barrier coat built back to the thickness of the original gelcoat or a bit more and you should be done for life.

Situaltion 2 and 3 come from similar causes but it is much easier to perform a permanent repair when the water is entering from outside the hull and the damage to the laminate tends to be shallower ad easier to fix. When the blisering comes from interior moisture there is almost nothing that you can do to make a permanent repair.

In the case of 4 where the self distructive reactions are a by-products of the materials involved there is absolutely nothing you can do to stop the process and over time the materials will also loose significant strength.

I have no idea what you should expect on ewarly 1980''s era Pearsons.

Regards
Jeff