Re: Acid bubbles above waterline.

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Posted by Blomberg Bengt on April 01, 2000 at 14:46:07:

In Reply to: Acid bubbles above waterline. posted by Ron Visser on March 31, 2000 at 01:52:26:

: I have just purchased a 45ft. monohull Cape Vickers sailing yacht in Richards Bay, South Africa. Apparently this yacht was built with GRP and no gelcoat, as Kevlar was also used in the construction. The boat is 9 years old and and has formed a lot of acidic bubbles, approximately 10mm in diameter and 50 per square meter, above the waterline under the Latex paint coat. It does not seem to have affected the laminate layers.(however not sure)

: A professional boatyard in Durban, South Africa is effecting repairs and has sanded the Latex paint coat down to the laminate level. They have suggested to refill with epoxy and to use a cheaper paint from the automotive industry in order to effect DIY bubble maintenance.

: The surveyor could not confirm if the were any of the bubbles below the waterline.

: This yacht will not be used for racing and I am planning to go bluewater cruising for the next 8 to 9 years.

: Two questions arise:

: 1) Acidic bubbles above the water-line?

: 2) Automotive paint?

: Your advice on this matter will be greatly appreciated.

: Regards
: Ron Visser
: S.Y. Akela
: Cape Town
: South Africa

Hello Ron,
In order to give a proper advise I need more info
about the laminate lay up.
Were is the first kevlar layer situated?
Were vinyl ester used in any layer?
Is the laminate cored or solid?
If it is possible for you to obtain this information,
please inform me by e-mail.

From what you told so far I can just say that it is the
the latex eventually in combination with vinyl ester
which have caused a hydrolyse to start in the polyester.
If there is a superficial fiberglass or kevlar layer
laminated with vinylester or epoxy, this layer must be
remowed before painting.
If there exist vinyl ester layers in the under water area
on top of normal polyester, they must be peeled of.
Otherwise you will sooner or later have them delaminating
from the polyester. If there should be epoxy layers it is
o.k. if there are no blisters. Eventual latex must of cause
be removed.
For painting the top sides you should use IR heating for a
couple of days and then apply an etching primer, not epoxy.
Then I suggest an one component automotve paint in a VW colour
where you can find spray cans all over the world for scratch or
local blister repair. Without the latex I do not think you will
have any blister problems however over the water line.
Bengt Blomberg

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