Soda blasted bottom to discover no gelcoat

[Barry7363]

I'm in a quandry ... our ("new to us" June 2008) 1986 Catalina 34 was hauled early to get on with some projects, one of which was to remove the excessive layers of bottom paint. We opted for soda blasting with the idea that a fresh start in the spring with a well protected gelcoat would be worthwhile. Today, as the layers of paint came off, the blasters were soon exposing what appears to be a "variously" well adhered barrier paint, with approximately 50% exposed fiberglass... the gelcoat under the bottom paint had been completely removed by a previous owner by either grinding or planing. There is evidence of blister repairs (many, generally small 1/8" to 1/4" in diameter). Our survey indicated that the loose paint was simply the result of excessive build up, and there was no indication of blisters, although concluding that with certainty is a stretch.
My question is what do I need to do to protect the fiberglass from osmosis? Is it necessary to apply gelcoat before building up a barrier coat, or can the barrier coat be applied directly to the fiberglass?

I appreciate that there are likely varied opinions on this subject, and would appreciate whatever suggestions might be forthcoming. We have the boat in Halifax, N.S., and haul every year. The previous owner was in Long Island, and prior to his 6 year ownership, the boat was in Annapolis, R.I. ...

Help!
Barry

 

[RichH]

Gelcoat is only 'cosmetic', so is the matting layer underneath the gel. There is no need for gelcoat below the waterline.
Go to http://www.yachtsurvey.com/blisters.htm for probably the most comprehensive discussion on boat bottoms, osmosis, blisters, etc.; then, make your own decision. Follow the various 'blister', etc. links once you get to the website. BTW ... that these blisters havent reappeared through the bottom paint, etc. is a 'good sign' and usually means that the previous repair is fairly well done.

 

[Stu Jackson]

Barry,

Congratulations on your new C34. This board has a great group of folks willing to help.

I also suggest you check the C34 Website out, starting here: http://c34.org/bbs/index.php?topic=2629.0

Also www.c34ia.org

We welcome you to join us there, too.

Best regards,

Stu

 

[higgs]

Not sure but....

....i do know it was not an uncommon practice in the early 60's for fiberglass boats to have only the raw FG with no gell coat below the waterline.

 

[Manny]

Were there any fresh blisters discovered after the soda blasting? If not I wouldn't lose sleep over it. I met someone a few years ago that had an absolutely beautiful older boat (Bristol I think) that he had the bottom stripped down due to blistering. Basically they took a sort of planer and shaved off all the gelcoat below the waterline, let the hull dry, then put layer after layer of epoxy back on to build up the thickness. Cost him $10K.
What I am getting at is that if there aren't any new blisters then it looks like the repair worked. It doesn't matter what it looks like under the water line, bottom paint will cover it. If you are concerned, in the spring rough up the bottom with 80 grit paper and "paint" on a couple of coats of West System epoxy or barrier coat, then bottom paint. The first time our boat was hauled I had discovered hundreds of little blisters. I spent that whole winter grinding them out then covering each one with 3 coats of epoxy. Each successive haul-out I have been there to immediately inspect for blisters and so far not a single new one could be found. If you soda blasted the bottom of my boat it would look pretty crappy!
Check out the link RichH provided, also use your favorite search engine to find out more info, then make a determination on how you want to proceed. I'd also to get a professional opinion from a surveyor.

Just my 2 cents -

Manny

 

[Stillraining]

Being as far north as you are maybe this isn't and issue as it might be really dry there in the winter ...but if not Id tent it over and let it dry out for a month or three..If you rush and seal in moisture you'll be wasting your efforts

 

[Barry7363]

Thank you all for the encouraging feedback, (and the links). As the soda blast process continues today (he didn't finish yesterday due to equipment problems), I will be in a better position to re-assess next steps. It is (and was) my intention to allow a full winter drying out timeframe.

Cheers, and thanks again to all
Barry

 

[Ross]

Several of the epoxy suppliers have advise on building a barrier coating with epoxy in some form. Your boat has come through the first 22 years in good shape there is no reason to think that it isn't good for another 22 years with a little care.

 

[Jim]

I agree 100% with Ross

Several of the epoxy suppliers have advise on building a barrier coating with epoxy in some form. Your boat has come through the first 22 years in good shape there is no reason to think that it isn't good for another 22 years with a little care.

You did the hard part and got the old paint off. I recommend at least 5 coats of epoxy paint. Ross is right , you should get at least another 20 years.