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Old 12-06-2017, 09:18 PM   #1
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Antifouling first time

Hello fellow TFers!
Next spring will be my first time to redo my (well my boat) antifoulling as after 2 years (or more) it starts to show some sign of wear.
So of course I am questioning myself about the perfect way to do it.
First I will sand the whole hull (under water part) to bare fiberglass to remove the old layer. I noticed that in some part the paint was not perfectly done and was chipped by the water pressure cleanup.
Now the questions.
Should I go with:
1. multi coats of antifouling right after sanding.
2. primer than antifouling
3. some kind of water barrier than primer and antifouling

I just would like to start it right so I can later and some antifouling layer when needed in following years.

Note: I am in fresh water river with not much fouling but some algae growth on the hull. No barnacle up here, some zebra mussels growth but for the last 2 yea it was not terrible.

Thanks for your input.

L
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Old 12-06-2017, 09:27 PM   #2
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Stop, until you get a better idea what to do

[QUOTE=Lou_tribal;615424]Hello fellow TFers!
Next spring will be my first time to redo my (well my boat) antifoulling as after 2 years (or more) it starts to show some sign of wear.
So of course I am questioning myself about the perfect way to do it.
First I will sand the whole hull (under water part) to bare fiberglass to remove the old layer. I noticed that in some part the paint was not perfectly done and was chipped by the water pressure cleanup.
Now the questions.
Should I go with:
1. multi coats of antifouling right after sanding.
2. primer than antifouling
3. some kind of water barrier than primer and antifouling

I just would like to start it right so I can later and some antifouling layer when needed in following years.

Note: I am in fresh water river with not much fouling but some algae growth on the hull. No barnacle up here, some zebra mussels growth but for the last 2 yea it was not terrible.

Thanks for your input.


Please do yourself a favor and read a lot more on the subject. Unless you’re gelcoat is toast, I can’t imagine that you need to sand down to bare fiberglass. Typically, all that is needed, is to remove any loose paint that is on the hull. Repaint with new ablative paint and done. The Above advice of course assumes that the boat has been painted previously with ablative paint.

I see lots of people who have wasted thousands of dollars blasting bottoms of boats or grinding them down to glass with no positive results. Bottom line is that you were not a recent sailboat and if they bottom is not smooth as a babies behind it will not matter.
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Old 12-06-2017, 10:20 PM   #3
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Gordon, thank you for your input.
As background info yes previous coat were ablative paint.
I am doing myself the best favor that is to say asking advises on the subject from more experienced people on the best forum.
If I can clarified my questions, I try to see if only antifouling is enough to protect fb hull from water ingress (or any damage) or if I need any undercoat,and especially on chipped areas. Doing it fast is something, doing it cheap also, just try to do it right

L.
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Old 12-06-2017, 11:01 PM   #4
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Most yards in the States will not allow any sanding of any kind. Not sure about where you are. Usually all that sis needed is a pressure wash when hauled out.
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Old 12-07-2017, 01:22 AM   #5
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Pressure wash, dry, tape off and paint. Some people choose a different colour so its obvious when the paint is finished but that’s your choice.

No sanding unless it needs sanding (it probably won’t) and every 2 years, repeat.
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Old 12-07-2017, 01:39 AM   #6
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Not all antifouling paints are compatible, if not you risk poor adhesion. If you are just getting back to a sound surface without removing all the old a/f, unless you know what you are using is compatible, better apply a primer.
Wet sanding of the old a/f will extend, maybe save ever having to,do an a/f build up bottom strip.
If you are taking it right back,I would prime. Otherwise spot prime any bare areas, you likely lack adhesion there anyway.
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Old 12-07-2017, 02:49 AM   #7
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Its hard to answer your question, there is always some small detail that tends to drive the correct answer.

I like to sand the bottom (I've always been allowed to do this as I use a dustless vaccuum system) before painting, but how much I sand depends on what type of paint I'm working with and what the bottom looks like.

An epoxy barrier coat might be needed or might not I can't answer that with out looking at the boat.

There should be a SeaHawk paint Rep. that works your area, give SeaHawk a call and see if you can't schedual a meeting with the Rep to talk about your specific boat and needs.
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Old 12-07-2017, 07:04 AM   #8
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First question I'd have is what do other boats in your area do? The best answer may be "nothing". If your area's only growth issue is a little algae, it may be a lot more economical to just have a diver clean the bottom every now and then, or run the boat more. Have someone(s) with local recommendations look at the boat when it's out of the water and find out what they'd do.
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Old 12-07-2017, 09:43 AM   #9
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Anti fouling

Quote:
Originally Posted by Lou_tribal View Post
Gordon, thank you for your input.
As background info yes previous coat were ablative paint.
I am doing myself the best favor that is to say asking advises on the subject from more experienced people on the best forum.
If I can clarified my questions, I try to see if only antifouling is enough to protect fb hull from water ingress (or any damage) or if I need any undercoat,and especially on chipped areas. Doing it fast is something, doing it cheap also, just try to do it right

L.
Lou,

Yes, it is good to ask questions. Antifouling paint does nothing to stop water penetration of your hull. The purpose of anti-fouling is as the name implies to keep growth on your hull to a minimal. Many people use a barrier coat such as interlude 2000e to keep water from penetrating into the fiberglass.

Your boat has a fiberglass hull covered with gelcoat. Probably over the gelcoat are up to five coats of barrier coat. It is the barrier coat that ensures water does not penetrate. In my state I am allowed to use a dustless sanding system to remove what is apparently loose paint. If it is not loose it stays on and becomes the base for the next coat.

If you do choose to sand, I would use nothing more aggressive than 80 grit sandpaper. I would also go very lightly and use an orbital sander. In my experience pressure washing probably gets off most of everything that you want removed.
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Old 12-07-2017, 11:42 AM   #10
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Antifouling first time

A lot depends on the condition of your paint now and the applications by previous owners. But Gordon is correct. Anti-fouling paints does not prevent intrusion of water. It reduces growth, but Honestly, I have never heard of a primer coat being applied before hand.

Now that being said, heavy pain buildup gets flakey. While it can be sanded, when you get to a certain point, you really should consider getting the bottom soda-blasted back to fiberglass. Sanding is very time consuming and just a huge PITA. Anyway, what is under there will also dictate you best move. Is there barrier coat? That DOES prevent (or reduces) water intrusion. Are there blisters?

Still, there are times the need to just sand it roughly and slap on a few new coats right after sanding (and cleaning)... and that is FINE. There are also times where you need to not only set the needle back to the starting point, but also learn everything you need to know about what is going on below the waterline. That is a critical part of your boat that is out of sight, but should never be out of mind.

Our most recent trip up the hill had us making the same decision. If not hard enough, I became recently unemployed and we went from a money is no object trip to a “what is the best job we can do for the least amount of money”. Had we been able to afford it and based on the condition of our paint, we should has blasted back and redone the barrier coat. In the end, we backed off several of the minor projects and opted to spend slightly more to hav the yard sand back and feather out some of the worst parts. In the end, it turned put fine and we will cross that bridge again next time.

So how does your paint look now? Do you have any pictures you can share?
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Old 12-07-2017, 03:53 PM   #11
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Thanks a lot for all your comments.
In some areas (small areas) the undercoat has chipped away as I guess it did not adhere correctly. If I can avoid sanding everything I will surely avoid it as it will be a pain. For now I have no build up as it was sanded and painted a year before I got it. There is no blisters just paint chips in 4 or 5 areas. Will post some pics in spring when I get back to the boat.
For now I try to figure put my todo list and budget for next season

L
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Old 12-07-2017, 05:38 PM   #12
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Quote:
Originally Posted by Gordon J View Post
... Antifouling paint does nothing to stop water penetration of your hull... Many people use a barrier coat such as interlude 2000e to keep water from penetrating into the fiberglass.

Your boat has a fiberglass hull covered with gelcoat. Probably over the gelcoat are up to five coats of barrier coat. It is the barrier coat that ensures water does not penetrate... .
Gordon J,I`m looking for a product such as Interlude 2000e. I searched and found a product sheet for it, which talks of applying DFT 5 coats of 2.6mls dry by brush or WFT 5.6mils wet by brush.
If you are familiar with this product,what is WFT and DFT(?wet/dry) and is "mls" short for millimeters, meaning building the product to about 1 centimeter,that seems a very thick coating.
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