Bottom Care Advice

[Kevy]

Hello all,

I have our 2000 Hunter 320 scheduled to come out next month. I've arranged for dustless blasting down to the gel to take off the last 20 years of whatever was put on it (owned it for 2 years) and make a few repairs (see pics).

My question is, once happy with the glass/gelcoat does it sound reasonable to use a barrier coat (i.e. Interlux) followed by several coats of antifoul paint? I've heard different opinions and while this is a costly procedure, I love the idea of a repaired, fresh bottom that should require only painting for years to come.

Thoughts?

 

[jssailem]

That sounds like a solid plan. Some might say more than is needed, but it is your boat and you need to be happy.

You may discover that some of those spots are blisters which need to be addressed with some epoxy to seal the fiberglass. Then a little faring and sanding to smooth and even the bottom. Then the barrier coat... I would be inclined to give 2 coats of barrier coat since I have it out of the water and have gone to the expense of prepping the bottom. Then yes a couple of coats of antifoul and back in the water. You should be happy for a couple of years.

Your baby will feel sleek and smooth in the water. Like a smiling mermaid...

 

[Barnacle Bill]

You have quite a cocktail of bottom paint. If you are going to remove all of it to gelcoat, then for sure you should apply an epoxy water barrier coat over the bare gelcoat. Extra expense, yes, but as long as you have it down to the gelcoat, that is a great opportunity to apply epoxy. Interlux makes an Interprotect HS which is a later generation of their original where you need not apply so many coats to do the job. You can, within a certain window, apply antifouling over the epoxy without the need to sand. I don't know where you sail, but I assume it must be in a high fouling location so that maybe the paint on the hull is only a single season paint and hence the build up. There are ablative antifouling paints that leach away from the hull to the point that it is all gone and there is no buildup. It sort of works like a bar of soap. As the bar gets smaller, it continues to do the cleaning job. With single season paints, the toxicant leaches away from the paint and so the paint builds up, but there is no effective toxicant to do the job of keeping the hull clean. if the boat stays in the water for long periods of time (and is not pulled for winter storage), then single season paints are great. But, because of the cuprous oxide biocide in single season paints, even if you have a fairly new application, there is a chemical change that takes place when the boat is pulled and the hull dries that renders the paint ineffective. You can do some light sanding to open pours again, which will help. I suggest that you do some research on fouling paints and see what works best in the area that you sail. Good luck.

 

[dlochner]

After getting to bare gel coat a barrier coat is essential to prevent blisters and to seal the gel coat. It will also provide a better substrate for the anti-fouling paint.

It does look as though you have at least one blister in the last image or a poorly done repair after the boat hit something. Once the paint is off you'll have a better idea.

The keel does not look like it is encapsulated, so when the paint comes off it will be bare metal. Not sure if Hunter used lead or cast iron. The lack rust suggests it is lead. You'll know when the paint is off. Keel castings are pretty ugly when they come out of the mold, expect to see a lot of fairing compound on the keel. The bubbles on the keel may be caused by a poor fairing job or poor preparation for the barrier coat. If the keel is bare metal, it will need to be barrier coated as the antifouling paint won't adhere well.

Interlux, Pettit, TotalBoat, and others make barrier coats. Do some research, pick your poison and follow the instructions explicitly!

 

[Kevy]

Thanks for all the replies so far folks, much appreciated. I'll have some expert help from the brother-in-law so that will be nice.

 

[Kevy]

Just resurrecting this thread as the boat comes out tomorrow and get's dry-blasted. I'm having trouble finding a solid answer on how much barrier to use. Interlux 2000E seems to be the most popular option around here, but there's not great advice on how much? A few things on the intra-web say to use an Interlux calculator - but there isn't really one that I've found.

Some things say "to 10 mils" which is great is you're that fancy, but there has to be a more simple answer of how many coats to put on. Following that I'm thinking 3 coats of antifoul? (Micron CSC - probably red, blue, blue for colour).

Appreciate any tips.

 

[jssailem]

The anti foul does nothing to keep the water from getting to the hull base. That is the job of the barrier coat.

10 mils

The InterProtect can then be rolled or brushed onto the hull. To be effective the final barrier coatsneeds to be at least 10 mils thick. This means about five or six coats of InterProtect are required. Additional coats can be applied as soon as the previous coat passed the “thumb print” test.

 

[dlochner]

10 mil will be about 3 or 4 coats. Go to an auto paint supply store and buy a wet film thickness gauge. This is a little device that allows out check the depth of the paint. Follow Interlux's recommendation. It is easier to add additional coats now, than when the antifouling paint is on.