removing paint below the waterline

[jpfx]

Common sense aside I am currently trying to strip the paint off from below the waterline on my CP16. The reason is that I kept it berthed for a couple of months at the end of last season and when it came out; the whole of the underside was covered with small blisters. I should've got to it then but now the blisters have gone leaving a finish not unlike miniature artex and probably just as poisonous.
Before my ownership, the whole hull had been hand painted with an epoxy based paint. Above the waterline came off easy enough with a scraper. Below is another story. There are several paint layers, possibly dried out ablative too with the top coat being the same epoxy paint.
I have been trying to use a 4.5" grinder with 120 grit disk (80 was too aggressive). The problem is the paint is tougher than the fiberglass underneath!
I'm having an impossible time trying to do a decent job. I'm cutting into the FG and I've even gone through to the cloth (marked). The finish is uneven.
I've tried an orbital and paint stripper. Both were ineffective.

I'm at a loss on what to do. I can't wield a 7" grinder (too heavy) and it will take literally forever trying to get close to FG with the small grinder. The whole undersides will be uneven from getting too close/ not close enough to the FG. I can probably flatten this off with an orbital to some extent.
I will fix where I've hit the cloth with marine-tex or marine-bondo; sanding/reapplying as necessary.
After paint removal. I was planing on light sanding the whole hull, wiping over with MEK and then applying several coats of system three primer (sanding after each) before several coats of WR-PLU Topcoat, final coat with 'roll & tip' method.

Anyone experienced this sort of problem? Any suggestions appreciated, thanks.

[jpfx]

to answer my own question (at least try an option)...
I've decided to order some marine paint stripper and see how that works.
I'll post with some results in due course.

[Bob23]

jp:
   There are a number of strippers out there you can buy. No, not that kind of stripper! I think Practical Sailor did a few articles on some of them. If I get a chance, I'll dig through my old issues to see if I can find 'em. My friend did his Morgan 30 with something..worked great but I don't know exactly what he used. When I talk to him, I get the scoop.
Bob23

[newt]

jpfx- I have attacked this problem from a number of different ways- sanding is very toxic and not recommended.  Peel-Away is a butter that you apply, cover with paper, then take everything off about 24 hours later. It works OK. My current bottom job was done by- get this inperfections sanded off by hand (just a few) then cleaned with acetone and new ablative paint installed. Before you think this is nonsense, this was done professionally in the boatyard. It is the way they are doing all ablative bottom jobs up here now. The EPA is forbiddening the paint from coming off, so everyone is just faring and painting over...
Something to think about.

[jpfx]

Thanks both for your thoughts.
A big problem has been that it seems that the previous paint application hid issues that needed attention. Also the surface might not have been prepared sufficiently so that most blisters occurred between the outer coat and the coat below.
I can understand that commercial sanding has been forbidden. I allowed myself a minutes exposure to experience how bad the stuff was and it is very nasty! I was suffering for the rest of the day. I took the project outside, put down plastic sheeting and vacuum up the debris as much as possible.
The thought of working inch by inch at head height (when sat on the ground) seems impossible.
I might need to move the boat back inside to attempt stripping as the temps are over 80. I'll put clingfilm over the paste to reduce drying out.
I'll pressure wash outside first which I should've done last season (ignorant of such things at the time).

[Steve Ullrich]

jpfx - Old post here...

http://cpyoa.geekworkshosting.com/forum/index.php?topic=2675.msg15821#msg15821

Best wishes.

[fafnir]

Been there... 

Just finished sanding the bottom of a Monty 17 which has a lapstrake hull which made sanding very challenging. Once all of the paint was off and the small blisters ground out and refilled with epoxy and chopped fiberglass matt the bottom was covered with 7 coats of Interprotect 2000e barrier coat and then 2 coats of VC 17. 

What worked best for me was a  5 inch random orbital sander (get a good one) and 100 grit paper.  Change the paper often and don't use the edge of the sander otherwise it ends up being uneven. I tried the chemical strippers, I don't think you will find them effective on the epoxy based paints that you may be dealing with.  A shop vac hooked up to your sander (use hose clamps and a good filter in the shop vac) will help with the sanding dust.   I was dreading this project but found that if I spent a couple of hours 2 or 3 evenings a week it really wasn't that bad of a project. 

[jpfx]

First impressions are good!
I pressure washed the hull this morning. This caused some paint to shed and opened a few blisters. I then covered a small test area with 'back to nature aqua strip' that I'd ordered during the week. I covered that with clingfilm (saranwrap) and left it for 2 hours. Instructions suggest anywhere between 30mins and 12 hours. The weather is borderline too hot at 80 and rising and if the stuff dries out it stops working.
A fair amount came off when I pulled the film away. A plastic scraper and a plastic bristled stiff brush also loosened more. A longer application time looks like it will improve how much comes off easily. Cleanup is with water.
One good point is that it doesn't appear to have any undue effect on the FG hull itself. Another is that although it's messy as hell; it's significantly easier and safer than grinding.
I'll post a pic of the results in due course.
Thanks everyone for your input.

[jpfx]

This is what's under the paint: queue staccato screeching violins...


It takes a couple of applications of at least 4 hours it seems. I've dumped saranwrap and am using .35mil painters plastic sheeting. It's cheaper and more manageable.
Here's the next swatch going on.

[mrb]

First let me offer a late welcome aboard.  Welcome aboard.

Looks as if you are finding a few blisters.  I notice that in the area you have stripped there are what appears to be old popped blisters where there still black paint or bottom coat of the same color as un-stripped areas.  If that is true I would suggest carfully cleaning that area to see what type of finish is under that coat.    At any time have you found an area that truly appears to be factory gel coat  ( same finish as that that is above water line).  Reason I ask this is that there is a possibility that blisters could be caused by many layers of bottom coat and blisters forming between these layers. 

Wish you luck and hope you find nice clean bottom under all that finish.  Thanks for post and keeping us informed of what you are finding.

Melvin

[Caboose]

I don't envy you at all. Actually I feel your pain. The former owners of my boat decided to paint below the waterline with a paint that just about matched the color of the hull. I tried just about all the "tricks" and I wound up sanding, sanding, and then "long boarding it". If I had to do it all over again, I'd take it to a marina and have them soda blast off the old stuff. I found out later my cost would have been $400-$500. After all those back breaking and sweat filled days, it looks good though.