another bottom job question

[raslocum]

I'm sure I've gone about this the slow and tedious way, but I have used an electric DA sander w/ 60 grit paper attached to a vac system to grind away my old anti fouling paint. The process was actually not as slow as I expected, I'm about 3/4 of the way through the removal. With the vac running, I get no nasty dust. That alone makes it tolerable. What I'm worried about is what I"m seeing in the gellcoat once the paint is removed. Yes, there are blisters, about the size of a dime or smaller. I'd guess up to maybe a hundred over the entire boat. I maybe have 2 or three the size of a quarter. I have maybe ground completely through only one in getting the bumps faired smooth w/ the sander. Do I really need to grind these all out and fix? I know I've never done a bottom job before, but to my untrained eye, they really just don't seem bad at all, especially for a boat that is as old as I am. Here's the real question, Once I can see the gellcoat and the bottom paint is gone, there is literally hundreds of stress cracks in the gellcoat, in every direction, over the entire hull exactly up to the water line. I would have to completely grind the gellcoat off to remove these, as they go completely through. It is like the gellcoat got brittle under water. Is this normal? I'm more worried about this than the blisters. This is my first bottom job. I don't mind doing it right, but i don't want to waste my time on a non-concern. Please advise.

 

[Loren Beach]

Your bio on this site has no boat info, but from an earlier post:
"I am a new owner of a 1972 25 cb model"
That's over three decades of strength and service. Good boat!
My take on it is that the original gel coat was sprayed a little too thick into the mold, and curing shrinkage resulted. Not common for Ericsons, but not harmful.

As long as the blisters are only in the gel coat layer (i.e. not into the laminate) I would fill them with thickened epoxy and grind 'em smooth. Bottom paint as usual. About 20 years ago, while taking a break from fairing some (gel coat) blisters in the bottom of my previous boat, I was wandering around the boatyard and observed an early Ericson 35-2 with literally thousands of little blisters (dime size and less) that was getting prepped for a layer of epoxy. I distinctly remember that none went into the laminate, and so there was no structural worry. It was quite a pock-marked sight!

In contrast, I have seen other brands of boat with deep blisters that required layers of cloth and resin to build up the laminate after the bad material was ground out and the edge fethered back at 12 to 1.

"All good clean Fun."

Also, use some 40 grit, and finish up with 60 or 80.

Loren

ps: Using a Fein dustless vac once will spoil you for life.

 

[larossa]

Another Bottom Job

I would tend to agree that you got your moneys worth on your bottom. I too would fill as many blisters as you care to fill. Remembering that every blister you fill, you also have to fair. This is where the work is. Having done two bottom jobs, one T Ten and the other my current boat an Ericson 31 it can be quite a job. If you decide to address the cracking, (it’s more of a cosmetic thing) of the gel coat you are now talking about sanding and applying 5 – 6 coats of epoxy or some type of other coating such as Inter Protect. You would have to go into the gel coat for this. There's some great information on this web site regarding blisters you might want to read up on. http://www.yachtsurvey.com/

Good luck


Brian

 

[Tom Metzger]

ps: Using a Fein dustless vac once will spoil you for life.

Do you mean financially? They are pricey.

FWIW, I found an refurbished "Filter Queen" vacuum at a vacuum repair shop that cost $50 including a new 12 foot hose with an end fitting to fit my sander. It works really well with the very fine paint dust.

 

[Loren Beach]

'tis a Fein day for sanding...

Tom,
You are right about the price. I bought my small version a couple years ago when it was only $149.
Mine does not have the auto power on and off for tools, either.
We have actually done finish sanding inside the cabin and immediately tacked off and varnished. Dustless vacuuming is marvelous, IMHO.


Of course everyone will have their own "cost benefit ratio" to suit their needs. I used a howling Sears shop vac for 30 years and finally got tired of the fine dust everywhere in the air and the God-awful noise...

Best,

Loren

 

[NateHanson]

On a boat that size, I'd personally roll on a couple coats of Interprotect when you finish stripping the bottom. Why not. The bottom has lasted 30 years, and is showing some age. If the boat has been out of the water for a few months to dry, treat it to a new bottom. It'll take you less than a day, and cost you a couple hundred bucks. Why the heck not. You'll never have the chance again, unless you plan on doing this horrible sanding job again sometime!

 

[Rob Hessenius]

Bottom Job

Raslocum-- If you have gone this far as to strip your hull, fix the blisters now. It won't cost you much and it will add a little time to your project. Just like stripping the paint it was'nt as bad as you thought, neither will be filling in the blisters. Get your self some 3M Marine Premium Filler, DON'T USE AUTO BONDO" and fill in the blisters and sand fair. This might take a couple layers, but the stuff dries fast. West Systems is some good stuff too. After you have fixed the blisters lay 2-3 coats of barrier coat on the hull. This will fill in your stress cracks and apply your bottom paint. Interlux 2000 is a great product, read the time instructions and plan your applications accordingly. Remember that your bottom paint has to be applied to the barrier right after (up to a couple weeks) the last coat or you will need to apply another coat of BC. It does'nt sound like the cracks in the gelcoat are much of an issue.. You just might have 2-3 more days into the bottom more than you thought. Now you'll have the confidence that there is no water intrusion below. Remember you might sell your boat to someone from the forum. Blisters seem to be the worst feared problem for people. Once your done you'll say "It aint no big deal" Best of Luck.
Rob Hessenius