Treating blisters

[pcatterall]

Coral Wind has been in the med for about 6 years and has been in the water for 4 complete years except for antifouling.

We came out for antifouling and the '10 year insurance survey' last month. The moisture readings were high and there was extensive blistering apparent and this of course figures in the report.
My first question is what the insurers will think or say about the osmosis, has anyone been refused insurance because of this?

We cannot afford to have the full works to cure the osmosis for some years but plan to attack the blistering during our next and subsequent lift outs. I did this years ago on our Colvic Atlanta, we did one side one year and the other side the next year. It certainly seemed to work as, on the second year the treated side had far less blisters than the untreated. 4 years later there were only a handful each year.
I would like to get a 'kit' ready to take out to Spain for when we lift out again and will appreciate contributions as to equipment and techniques.
What have you used as a 'gouger outer' ? some kind of drill bit I assume? We would plan to use a small car type steam cleaner to wash out the hole and then a heat gun (?) to dry it out (will we burn the boat?)
What material should we fill with? is it just an epoxy paste filler or what?
Most grateful for your assistance here.

If we wanted to go for a more comprehensive fix then would the following work? boat out of water in spring, hull gel coat removed professionally ( blasted or pealed?), dry out over the Spanish summer, following acceptable readings when the weather is cooling off apply 4 coats of West system ( This was what we did 12 years ago when Coral Wind was in UK).

 

[V1701]

West System pdf guide to blister repair...

 

[dankilb]

What have you used as a 'gouger outer' ? some kind of drill bit I assume?

I couldn’t have done the blisters on ours without my Milwaukee 12v die grinder. Anyone from a workshop background will know an air die grinder can be indispensable (especially for 50mm quick lock/Roloc discs). But they’ve only recently become available as (expensive) cordless tools and I’ve not really heard them discussed on here yet. I use mine on the boat for almost every job requiring grinding - and that’s a lot!

I guess you could use a drill or a skilled operative could get blisters with a ‘touch’ from the edge of a 4” grinder flap disc. But imagine how much easier it is with a 50mm flap disc and a one-handed cordless that spins to 22k rpm when you need it?! For very small blisters, I even sometimes used a retired carbide metal grinding round burr (12mm).

 

[Uiseag]

The best tools I found (for about 500 blisters..) were a zirconium flap disc for the larger ones and a countersink drill bit for the small ones.

This type of flap disc:
Erbauer Flap Disc 115mm 80 Grit

Go very lightly with the flap disc as it will go through GRP like the proverbial hot knife through butter.
First use a grinder to blunt the countersink bit to a dome shape and then it will eat away at the blisters very easily and safely.