Bottom Paint Question

[bffatcat]

When I bought my boat 9 years ago It had several layers of old blue epoxy bottom paint on it I sanded all the ridges and peel marks on the old blue epoxy smooth the first season. I then applied 2 coats of red ablative paint. Every season since I have lightly sanded off any excess buildup and applied 2 coats
of ablative red. I hauled last week. When the yard pressure washed the bottom I noticed for the first time large areas on the bottom where some of the old blue epoxy had washed off exposing bare fiberglass. Here is my Question. Should I just lightly sand the bare fiberglass and apply 2 coats of
ablative or do I need some sort of barrier coat applied to the bare spors before
I paint the bottom

 

[TimCup]

Bare fiberglass?

I assume you mean bare gelcoat, otherwise, yeah, you need paint! I've always had a base coat of bottom paint, one color, under the ablative, a different color, simply to indicate where the ablative was worn, without having bare gelcoat.

No, you don't HAVE to have a base bottom coat. But gelcoat IS porous. Sunbaked decks show the pores easier, but they're always there. That's why we polish and wax the topsides and deck, right? For the relative low cost, and relative high peace of mind, why wouldn't you bottom paint?

Just one man's humble opinion. Fair winds.


cup

 

[Tom Spohn]

If the original blue paint is a "hard" paint it must be removed prior to painting with an ablative. If you decide to strip down to the original gellcoat I think a barrier coat is a good idea.

 

[Warren Milberg]

I've had good luck in the past with just lightly sanding an old modified epoxy bottom painted hull and then applying an ablative on top of that. The key is how well the old paint is adhered. See the compatibility chart below.

http://www.yachtpaint.com/Images/15_20650.pdf

Since I haul every year, I also have learned that one relatively thin coat of ablative paint is all that is needed in my area of the medium fouling Chesapeake Bay. I have found, however, that on previous boats when patches of whatever is applied to the hull begins to fall off, that no amount of paint on top of that is going to last long. Adhesion problems usually mean either a wet hull or too many coats of paint, or both. While you could probably get by for a few more seasons with just sanding and feathering the bare spots and then overpainting them with ablative, I think you know the time has come to strip the bottom, prep it properly, and start over again....

 

[Barnacle Bill]

I think you are wondering if you should apply an epoxy barrier coat on the areas where epoxy has flaked off before reapplying more antifouling paint. The answer is, if your epoxy barrier coat is peeling off, then probably it was not properly applied with the proper preparation, or was applied over moisture (didn't let the hull dry first). If this be the case, then, if you want a good epoxy barrier coat, you probably should start over and remove all antifouling and existing epoxy (maybe even sandblast or peel it) and then make sure it is dry and start over. If the boat isn't worth this time and expense, then sand the bare spots, put some barrier coat like Interprotect 2000 (Interlux product) and paint on the antifouling to finish it off and go sailing.

 

[Barnacle Bill]

In reply to Tom Spohn, usually if you have a hard antifouling and wish to apply a soft antifouling over it, there are no compatibility problems. You do not want to apply a hard over a soft, but most often can apply a soft over a hard. But, to be sure, you should look at a compatibility chart specific to the product you are applying.