Grinded tons of blisters. Now what?

[boatpoker]

I have several moisture meters costing from $40 to $700.
My favourite and most consistent is the $40 Ryobi from Home Depot.
Moisture Meter Mythology

[JBsurfin]

Not a boat building expert by any means, but my Father-in-law did own a boat building company and I did spend time at the location and learned a lot..

Doing an amateur job on the bottom is risky if you don't make sure that all voids are properly filled. Covering the ground out blisters with a barrier coat will insure that you will be doing it again.. very soon. Not making sure the hull is dry..completely, will insure you are doing it again soon.

I've had this in my archives, as I've restored a couple early 80's sailboats.. He does a good job explaining blisters and repairs. there are 2 parts to the article.
Good luck..
https://www.yachtsurvey.com/BlisterRepairFail.htm

[sbmar]

Regardless of what your final filler is, #1 is to wet out all of the "holes" / "blisters" and the hull with 2 coats of high quality VE resin......2% MEKP.

As to fillers, etc--If my boat, I'd use VE and colloidal silica, or micro balloons, or a mixture of each.. Then, VE with a colorant ( 10% ISO based gel coat)-- 3 coats minimum with alternating colors so I could "SEE" what have been covered.............Epoxies are OK but with the newer VE resins, they do not compare. Do some research outside of the "marine world", which is always a decade behind and all about marketing..

Your call...................


Tony

[rapanui 2]

blister are osmosis, you need to gring the all the gelcoat(not only the blisters)+the layer of mat to reach the roving,,let dry or heat dry, apply two coat of powder mat 300 gr/m² with good brand isophtalic polyester resin or better vinylester resin, and finally apply two coat of white gecoat the first coat non parafinned the last one one parafined, finish with antifouling you are quiet for at last 10 years. cost for a diy job :600 §

[boatpoker]

I have an opinion on "Osmosis" too
"Osmosis Testing"

[Jimmyhenry]

We did a major osmosis repair. After grinding we used a moisture sucking heat pads. When we finally relaunched we must have removed more than a tonne of water. Boat sits up way below the old water line.

Also finished with 10O% coverage resin on glass. And then fairing compound. Brilliant finish.

[ferrailleur]

Originally Posted by Dark Horse

I would not do that.

I'm still grinding.... new pics soon.
No... I'm not going to grind all the gelcoat.
After all is clean and dry, I plan to roll a coat of thickened epoxy... followed by two coats of unthicken epoxy....

[DreamWeaver III]

Originally Posted by ferrailleur

She's my Catalina 27 after soda blasting which revealed tons of blisters. Almost finished grinding!!!!
I was thinking of filling the depressions with West System 105/205 plus colloidal 406.
It's too much work at this point.
Should I instead apply two coats of some Interlux epoxy barrier. The first coat would be thicken so it would fill my grinded depressions?
Your thoughts. Thanks.

We recently had a similar (albeit not as bad) after blasting - filled with epoxy filler, sanded and then three coats of epoxy over the whole boat (interprotect) then antifoul

[Clivevon]

Hi - chipping in to this thread again in case the op is still looking. Here is a link to my post #27 on this thread from 2016:

http://www.cruisersforum.com/forums/...-159293-2.html

This details the osmosis repair on my boat. 2 key points from that:
Turns out that epoxy resin should not be used with CSM because it doesnt dissolve the powders they use in CSM to bind the mat together.

Vinylester resin is very much superior to polyester, doesnt give the problems you get with epoxy & costs less than epoxy.

Actually I think things have moved on a bit from my understanding then - I believe you can now get 2 different types of chopped strand mat - one for use with polyester/vinylester, & a special one for use with epoxy.

Replacing peeled laminate with CSM does add strength and it is much easier to get layers of CSM to reliably bond together rather than using cloth - all according to my surveyor in UK who literally wrote the book on these sort of repairs.

So to repeat what I said earlier - depending on how bad the hull is - in other words, how DEEP the blisters are - IMHO you either make do & mend (& keep mending) so you can go sailing, or you go the whole hog & do the job right first time. Just be aware you are unlikely to get your repair costs back. I dont see much point in trying for some happy medium which doesnt exist.

I agree with earlier posts - I wouldnt worry about what the underwater hull looks like as long as it is reasonably smooth.

In this context. blisters in the gelcoat only are not much worse than just cosmetic

[boatpoker]

Originally Posted by Clivevon

Replacing peeled laminate with CSM does add strength and it is much easier to get layers of CSM to reliably bond together rather than using cloth - all according to my surveyor in UK who literally wrote the book on these sort of repairs.

You'd be hard pressed to find anyone else in the industry that does not feel that CSM is the weakest of all glass fiber formats.

[timeout2]

Originally Posted by Clivevon

Hi - chipping in to this thread again in case the op is still looking.
Turns out that epoxy resin should not be used with CSM because it doesnt dissolve the powders they use in CSM to bind the mat together.

I agree. I had to pull the CSM apart to to get it wetted with epoxy. Thick CSM would simply not wet through and would turn resin into a thick goo. I only used CSM to build out deeper areas so wasn't a huge problem.

Will post results in several years.

[Souzag818]

Originally Posted by boatpoker

You'd be hard pressed to find anyone else in the industry that does not feel that CSM is the weakest of all glass fiber formats.

+1

[Muddy Boat]

Originally Posted by Clivevon

So to repeat what I said earlier - depending on how bad the hull is - in other words, how DEEP the blisters are - IMHO you either make do & mend (& keep mending) so you can go sailing, or you go the whole hog & do the job right first time. Just be aware you are unlikely to get your repair costs back. I dont see much point in trying for some happy medium which doesnt exist.

In this context. blisters in the gelcoat only are not much worse than just cosmetic

Agree with this completely. I have been through the full monty process of peeling gelcoat, washing, hot vac, relaying biaxial and epoxy, then fairing and barrier coat. It is a huge, expensive and time consuming task and one that I would only ever possibly repeat if I had serious delamination.

From what I can see of your blisters, they are small (albeit plentiful) but I would grind out, wash and dry as well as possible soak with a thin resin, then fill before resin cured for chemical bond (mat for the larger ones and filler for the smaller ones) then go sailing.

Unless of course you have time, money and blood pressure to burn.