Advice needed on blistering hull

[hugy]

Hi all,

Wanted to ask your advice on how to proceed the bottom job of my boat.
It is a 1986 Jeanneau Sun Legende 41.

We just hauled out the boat and there are numerous blister spots on the hull. They are numerous and cover the whole hull (except the rudder). Allmost all of them are very small, between 5-10mm. We have been scraping the hull the past 2 days to remove most of the bottom paint. After sanding multiple spots with the RO with 40grit all of the damage seems to be in the chopped mat layer. None (so far) have been into the woven mat.

My reasoning is that after 34 years in the water probably everything that can happen to the hull has already happened. The blisters thus seem numerous but of small and shallow nature.

See the attached pictures.

I'm now thinking of multiple options.
1. grinding out all the visible blisters, drying them out and fairing.
2. getting the gelcoat peeled, grinding the spots out, drying and fairing
3. leaving as is and only fixing the worst spots as the spots are very shallow and small.

We were planning on using copper coat, maybe with a barrier coat. What is your advice on this with the state of this hull?

There also is a gap at the front of the keel, is this normally covered with sikaflex or something else. Or is this keel gap too large and should we investigate further?

We are not looking for a perfect finish for racing. We just want a sound hull for the coming 10 years of cruising.

Looking forward to any advice on how to proceed.

[svspirited]

I had to deal with a similar problem on mine two years ago. Same situation, loads of them but most were in the chopped mat. This is actually not a water intrusion problem on the boats of this vintage, it is actually the epoxy trying to work its way out. In the '80s they were using a fire retardant resin that is the cause for so many of the blistering problems people see today. What that means is it is nearly impossible to get rid of permanently, even if doing a full peel.



A few went deeper than that and required more work but for those that are shallow I used thickened epoxy, in my case West Systems 105 thickened with 406 colloidal silica. Start by grinding everything down as you have then wash the entire hull with soap and water, let dry then wash it again with soap and water and let dry. Wipe everything down with Acetone to make sure there is no waxy residue left anywhere you will epoxy, this is key so take your time and do it right. You should also give it a couple of weeks to see what continues to weep, they may be deeper than you think.



Once the surface is prepped you will want to roll on a coat of the 105 without the 406 and let cure to the point where it is a little wet but mostly tacky. From there start loading on the thickened epoxy and build it up with a couple of layers, never letting it fully cure before you do the next layer. This will ensure a chemical bond, and not just a physical one. Again this is key to getting a strong repair so work in areas you can do this through that are small enough to not cure on you before you get to the next coat. If you have peel ply when you get the final coat on there apply it to help cut down on the amount of amine blush you will end up with. Any shiny spots will need to be knocked down by sanding them a bit then wipe everything down again with Acetone.


Now comes the fun part, mix up some 105 with 405 to begin fairing. You can go super crazy with this or just enough so your hull doesn't look like a golf ball. When I did mine it took three passes and I used a tool from flexi-sander to make things as fair as possible. It was worth every penny for that. Once you are happy with the shape sand and prep for a sealer, don't skimp on sealing the hull and just go to paint. We did three coats of sealing primer followed by three coats of Trinidad.



For spots that are deeper or any in areas near the keel or rudder you will want to build those up with some glass then fair with the 405, how much will depend on how deep. West System has a pretty good guide on how to do these repairs and their support is actually very good, worth the small bit of extra cost of their products IMHO. Good luck with the repairs!