yet another blister problem!

[sailorbaz]

My boat is a Sunbeam 23 built in Austria in 1982 and has only ever been in fresh water. On lifting out at the end of last season, I found blisters for the first time.
There are 5 vertical lines of 2-3 mm blisters running from boot top and dying out towards the keel. The spacing looks to be about the width of a paint roller. Also on the skeg (triangle 30 x 20 cm) there are six 10 mm blisters. All are only on the starboard side. I opened up the blisters immediately and all were dry. A moisture meter gave 4-6%. Antifouling is International VC17.
Should I get all of this off? Would the caustic/wallpaper paste method in a recent thread work?
I had planned to fill the opened blisters with West epoxy mixed with micro-ballons.
Is this a good plan and then would it be worth coating the hull below the waterline, including the cast-iron keel with epoxy?
Many thanks in advance for any advice.
Sailorbaz

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[beneteau_305_553]

Would seem likely to be caused by air bubbles in between the gel coat and the laminate. When the gel coat is brushed on to the mould the brushmarks leave quite deep grooves. If the first layer of mat is not wetted out enough to remove all the air bubbles small voids are left . These bubbles eventually fill up with water due the porosity of the gel coat then with changes in temperature the water expands and creates a water filled blister.

If they are ground out and the laminate is sound underneath the gel coat then filling the gel coat with Gel coat epoxy repair paste should make a good repair.

Removing the old AF will be necessary to make sure you find all lumps and bumps. Make sure the gel coat is completly clean and sanded down before applying an epoxy coating. This should prevent any further blistering as epoxy is much less porus than gel coat.

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