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Old 16-02-2011, 10:37   #1
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Wet Hull

The 35 year old boat in question had the entire hull sandblasted down to bare fiberglass and allowed to dry for many months. Two coats of epoxy were applied and the hull 'appears to be dry.' The anti fouling then had to be removed because it would not adhere to the smooth epoxy. The bottom was 'roughed' and re-fouled.
I'm trying to learn more about this so I can make a proper judgment call when I go over the boat with the surveyor. The entire bottom could not be seen due to snow but the visible part was suspect to my untrained, but pretty reliable, eye.
While researching, I came across this; Boat Hull Blisters : My Wet Hull Won't Dry - by David Pascoe, Marine Surveyor which begs the question;

Can a wet hull ever really be dried and sealed to last another 30+ years?


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Old 16-02-2011, 11:11   #2
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Wow never heard of that before - good luck

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Old 16-02-2011, 11:23   #3
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Nothing will adhere well to cured smooth epoxy, not even epoxy... UNLESS is is so recently applied that there is a chemical bond. (Hours with WEST epoxy) and a bit longer with others like Systems Three.

When you say bare glass... do you mean bare gel coat, or bare glass? If it was sandblasted down to bare glass, that does create a good "tooth" for the next step, but slapping on a couple of coats of epoxy is not going to cut it. I have hydrosanded hulls bare. If that is what you mean, you probably ended up with a surface that was in need of re fairing! If it is major, that means squeegeeing on microlite, sanding fair with a long board and/or the 8" soft pad disk, and then coat with epoxy! Always remove the blush before sanding...

If the unfairness is minor, one could coat on 4 coats in one day, sand off two the next... say, three times. MINIMUM... Then a final sand to a glaze, and you are ready for bottom paint. It should stick!

This all assumes the hull tested out very dry with a moisture meeter first! BTW, when drying a hull, it is best to hang a plastic skirt around the hull and put one or two dehumidifiers in there for months, as well as wipe it down with acetone DAILY. (just turn off the dehumidifiers and lift the skirt first, so you don't kill yourself!)

If the hull tested dry before the epoxy, the paint didn't stick because the epoxy was not sanded.

When it comes to the bond between layers of epoxy or ANY two part paints, the surface must be 100% sanded. This doesn't mean just run a sander over the hull, it means that the hull must be fair enough first, that there are NO concaves that the sander misses, and there are NO shiny spots. (Not even the size of a BB!)

I have seen so many people get this wrong, including pros. It is a lot of work, but the poor bonding between layers of anything on your boat, can be years of work, or tens of thousands of $$$. This is no exaggeration!

With any 100% solids epoxy, or LP type paints... To SAND, means to a totally glazed, no shiny spots appearance!

Once you go to the above trouble and have a dry barrier coated hull, it is WELL worth it to keep a dry bilge. You may have to go with a dripless shaft seal, or build small sumps around the shaft / engine, or even the base of the mast. Then epoxy coat these small sumps really well, and install separate small bilge pumps, or have one sump tube drain into the lower sump, and let its pump take care of the small amounts of water. Then have one or two huge pumps up 6" higher for true emergencies. Do what ever it takes to keep a dry bilge, if you want your dry hull to stay that way! Best of luck...
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Old 16-02-2011, 16:02   #4
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Thanks for the replys.
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Old 16-02-2011, 16:26   #5
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Wait a minute! when epoxy cures it leave on the surface an amine blush, this must be washed off with water before you do anything to it. If you paint over it then the paint will not stick, if you sand it you will push the amine into the epoxy making it harder to remove. After coating with epoxy wash, wash, wash, wash
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