Schöön Martin wrote:

Heikki writes:

On the side, well above the waterline, there is an old scar, about the size
of a fingerprint. Around that are fine hairline cracks in a circular
pattern, something line 15 cm (6") wide. I suspect there has been some sort
of impact damage, the gel coat was damaged, and water has started to enter.

I am wondering how seriously I should worry about this blister? Will it sink
the boat this summer? Will it get worse and worse, and destroy the whole
boat in a few years? Or can I treat it as a cosmetic problem, and sail
happily for years without worrying about it?

Any signs of damage on the inside of the laminate?
Have you probed the damage? Tip of sharp knife trying to pry open
gelcoat would yield some information. Tapping the area and listening
would tell you if there is a void or serious delamination. A more
subtle damage calls for ultrasonic instruments to assess.

If the laminate looks ok from the inside and sounds solid when tapped
you won't sink this summer. I ended a season many years ago sailing
around with patch of silver-grey tape over hole in the starboard hull.
The hole was not under the water :-)

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you might consider 'sealing' the hairline cracks from moisture and air with Capt
Tolley's creeping crack sealer - available in just about all the big marine
catalog stores.

paul oman