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Closet Powerboater
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Discussion Starter · #1 ·
My limited understanding of bottom paint tells me that ablative paint is supposed to deliver copper to the surface of the hull and to rub off over time. Barnacles are discouraged from implanting by the copper, and if they do, they fall off, taking a bit of paint with them when they go.

It stands to reason that more coats of paint would last longer yes? I understand that more coats of hard paint is not necessarily a good thing but what about ablaitives? I can get a good deal on Navy surplus 5 gallon cans of ablative paint, so if I do 3 coats, will it last much longer than one coat? If I do 10 coast will I make it all the way to Australia without painting again. ;)

Hmmm.... I wonder who has a paint shaker for a 5 gallon can? :confused:

MedSailor
 

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I think this depends on the mechanism that the paint uses to ablate and so the specific paint being used. Is this mystery paint, or can you check with the manufacturer?

One downside of going too thick is that it is going to wear at different rates. You could end up running through your 10 coats at the leading and trailing edges of your rudder, but still having 10 coats of thickness is low wear areas on the hull.
 

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In general you dont want to apply more ablative paint than is likely to be used up by the time that you can apply a replacement coat. If you get 4-5 or so coats of ablative paint accumulated then paint will tend to chip just like the hard stuff does, then you have a messy bottom. It;s ideal to have a base paint coat of a different color, that way you know when you are down to the first coat...
 

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I've also been told by coatings companies (don't you dare call their products "paint" in front of them! Paint isn't worth $300/gallon, coatings obviously are) that 2-3 coats is all you want to go, with that last coat just as extra on the leading edges of the rudder and keel, etc. Didn't ask why but I'd guess thicker just isn't better, maybe it has to do with how the chemicals leach through the layers.

"I wonder who has a paint shaker for a 5 gallon can? "
That's easy. Put can in car, drive down old cobblestone road.(G)

But I would expect USN bottom paints to be designed for high-speed craft, and that's not the same as ablative for low-speed craft. Might not be a bargain for a sailboat.
 

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Bristol 45.5 - AiniA
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Good point. We could have bought a really well-regarded Aussie bottom-paint in Fiji for a great price but it was specifically designed for 15+ knots. Make sure this paint is suitable for slow speed use (not saying your boat is slow, but with a sauna and maybe washer/ dryer you never know.
 
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As sailingfool stated ... thinner is better; but, with an 'indicator coat' of a contrasting color beneath the 'working coats'.
Thick build up will eventually, after a few years, 'ablate' under the newer coats and then lose adhesion at the hull surface, then release in the form of scabs and craters.

To prevent such 'build-up', I apply the newer coats, as 'smooth as possible' (with WEST roller and a large plastic polyethylene trowel, etc.) ... such yields less 'effective' surface area which (to me) translates to longer service life and less paint needed to be applied ... and faster sailing in the 'light wind' conditions, etc.

My method for recoating:
1. lightly sand to promote a flat surface for the poly trowel to 'ride'. The light sanding will produce the equivalent of teeny 'mesas'.. dont worry about minor valleys and dings, etc. between each teeny 'mesa', as working the trowel will fill them in later.
2. Apply a 'stripe' of new paint with a WEST SYSTEM roller - about 1-1/2± 'roller-widths' wide. Immediately/quickly, draw the trowel across the stripe at a quite low angle to fill-in the valleys between the flat topped mesas.
3. Leave a 'dry' space almost to the width of the first troweled and leveled stripe and repeat.
4. Clean the trowel when needed ... I simply 'spritz it' with thinner, then wipe, then spritz.
5. Let dry/cure.
6. Return the following day or so and paint/fill-in the areas between the stripes already laid down, etc. If the previously applied paint can be 'dimpled' with a thumbnail - wait a day or more until it takes some thumbnail pressure to create the 'dimple'.

For scabs and craters that do release from the hull, I rough sand where the missing paint 'was' to establish 'tooth' in the surface, mix in a bit of 'micro-balloons' (fairing filler) to a small amount of paint and build the crater back up to 'flat and level' using the poly trowel. This is done before re-coating as a thick application can take a long time to dry/cure.

I use MUCH less paint; what I do seems to last much longer (I long distance sail a lot and it may be sometimes 2 years until I can 'recoat').
Once you master the roll-and-tip-with-a-trowel technique you can produce a bottom that is almost as smooth as a baby's ass - faster, more easier driven boat, less heel, good for 'light winds', etc..

Also, with a smooth bottom, any slime that attaches is more easily released by 'sailing'.
Less slime equates to less barnacle and hard-growth attachment, even with such paints as Micron-Extra.

hope this helps.
 

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Once everything is coated, it's done. That may take two coats, or even three in a few areas. I can see why paint companies routinely suggest 2-3 coats, but I have talked to paint company professional types who say it is not helpful once everything is covered.
 

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Having recovered from 20 coats of this



To reach this



i can say season one looked like this after the powerwash which removes a LOT OF PAINT



Season two ended like this after powerwash which was pretty perfect as there was no buildup which would lead to flaking

keep in mind Northport is a very heavy fouling area and i require a wipe down every two weeks

I would guess three coats at the waterline would be pretty much the maximum :confused:
 

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Once everything is coated, it's done. That may take two coats, or even three in a few areas. I can see why paint companies routinely suggest 2-3 coats, but I have talked to paint company professional types who say it is not helpful once everything is covered.
That is absolutely ridiculous. It doesn't even make sense. Anti fouling paint longevity is based primarily upon how much biocide is available to be released into the water and it doesn't take a rocket surgeon to understand that two coats means twice as much biocide as one coat. And that translates to roughly twice as much paint lifespan.

The rule of thumb is always two coats everywhere, three at the waterline and leading/trailing edges of the appendages. You know, unless you like having to haul for new paint every year, something I guarantee you we do not do in California.
 

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Closet Powerboater
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Discussion Starter · #10 ·
The rule of thumb is always two coats everywhere, three at the waterline and leading/trailing edges of the appendages. You know, unless you like having to haul for new paint every year, something I guarantee you we do not do in California.
Rule of thumb yes, but if paint were free (or cheap in my case) would more be better, or is more worse and will cause flaking and other issues?

How does one find out if a paint is designed for high speed craft? Not a spec that I thought existed, but I suppose it might.

MedSailor
 

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Rule of thumb yes, but if paint were free (or cheap in my case) would more be better, or is more worse and will cause flaking and other issues?
I leave the anti fouling paint application answers to those who are expert at it. I am not. I do know however, that since water ingress into the paint matrix is essential for it to work (regardless of paint type), that it is possible to apply more coats (read: mil thickness) than water can penetrate. The additional paint in that scenario being useless and wasted.

How does one find out if a paint is designed for high speed craft? Not a spec that I thought existed, but I suppose it might.
Typically the manufacturer's web site will indicate appropriate uses for their products. Of course, one supposes that it is known who the manufacturer is and what product is being used. I know that many US Navy vessels use the same ABC anti fouling paints from PPG Marine Coatings that are available to you and me.
 

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Closet Powerboater
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Discussion Starter · #12 ·
Thanks. Yes, the surplus paint was in regular (albet large) cans with regular labels. Can't recall the manufacturer but I think it was 64% copper or thereabouts...

I was quite disappointed that they were regular paint cans. I had hoped they would be in black cans only marked with the words "Highly Toxic." ;-) Still, 5 gallons can be had at a cheap price, and 5 gallons is probably worth 3 coats on my boat, so it might be a good way to go.

MedSailor
 

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Don't call me a "senior"!
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Any paint store or HomeDepot/Lowes will have a shaker capable of handling a 5 gal can. Or you can just get an attachment for your drill and mix it that way.

As others have indicated, two coats is usually plenty as a general treatment with an extra coat or two at the waterline and on the leading edges of the appendages. One thing I've noticed was that barrier coat (epoxy) doesn't soak up much paint, but old bottom paint acts like a sponge. So, if there is a lot of old paint still on the hull you might want to thin the first coat a bit more than subsequent coats. Otherwise, it can be a little difficult to get the paint to "flow" as you apply it to old bottom paint.

I just redid the bottom of my boat (first time in five years) and I also noticed that the area around the prop (from about 12-18" in front to about 12-18" behind) was pretty bare of paint when we hauled the boat, so I added extra paint in that area also. I also noticed that the trailing edges of the appendages were pretty bare, so I added coats there.
 

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It amazes me that the rule for private vessels is to use the so called safe for environment antifoul, yet I see 200000 ton tankers in Pusan getting the old real antifoul still put on there hulls(how many 35fters = just one of those)I used to be able to buy the real stuff in Fiji a couple of years a go, would last 2 yrs. and look as clean as the day I put it on. Out of all of theme I find International extra the best.NO 5 I found you have to be doing 10 to12 kts for the slim to even start to come off.
 

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That is absolutely ridiculous. It doesn't even make sense. Anti fouling paint longevity is based primarily upon how much biocide is available to be released into the water and it doesn't take a rocket surgeon to understand that two coats means twice as much biocide as one coat. And that translates to roughly twice as much paint lifespan.

The rule of thumb is always two coats everywhere, three at the waterline and leading/trailing edges of the appendages. .....
I don't think it's ridiculous and in fact, I think it makes total sense.

Ablative paints will begin to lose adhesion around 15 mils of thickness. Maybe my slow-moving sailboat doesn't ablate at the same rate as your fast boat. But I don't like to see those big recesses where paint is flaking off, and that comes from putting too many layers of ablative paint on. More is not better.

I have gone 3 seasons without needing paint. A good healthy thickness of a good bottom paint does great. Like I said, as long as an ablative coating is on the hull, it keeps off the growth.

Re the "rule of thumb." Did you get that from the International/Interlux Website?
 

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Med,

For around here, 2 layers every where, and an additional 1-2 for leading edges, waterline will work for 2-3 years depending how salty vs mixed fresh/salt/brakish water you are at the marina you are in.

I find in Edmonds where it is very salty, 2 yrs, up in Everett where I had the Snohomish river running thru the marina, I could go a bit more.

Some like Interlux's micron, needs 5-6 knots to ablate, others like petit sr40/ wet marin PCP (same stuff different label) needs 2-3 knots. I prefer the later due to a typical max 5-6 knot sailing/motoring speed. Altho I have been as fast as 11 knots........but I do not sail down wind with a full main/110 combo in 35-40 knots of wind a lot surfing 6' waves here in puget sound.

If you were going offshore for a few years, maybe an additional coat or two would be good from the start.........

Marty
 

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A cruise into Lake Union and Lake Washington every once in awhile should help keep the bottom clean.
 

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A cruise into Lake Union and Lake Washington every once in awhile should help keep the bottom clean.
That works for those of us close to these estuaries, Med is a day sail/motor north! Altho he might be able to get up the skagit river a mile or tow, achor and let the river current remove some junk along with the fresh water killing the salt water stuff.........
 

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As sailingfool stated ... thinner is better; but, with an 'indicator coat' of a contrasting color beneath the 'working coats'.
Thick build up will eventually, after a few years, 'ablate' under the newer coats and then lose adhesion at the hull surface, then release in the form of scabs and craters.

To prevent such 'build-up', I apply the newer coats, as 'smooth as possible' (with WEST roller and a large plastic polyethylene trowel, etc.) ... such yields less 'effective' surface area which (to me) translates to longer service life and less paint needed to be applied ... and faster sailing in the 'light wind' conditions, etc.

My method for recoating:
1. lightly sand to promote a flat surface for the poly trowel to 'ride'. The light sanding will produce the equivalent of teeny 'mesas'.. dont worry about minor valleys and dings, etc. between each teeny 'mesa', as working the trowel will fill them in later.
2. Apply a 'stripe' of new paint with a WEST SYSTEM roller - about 1-1/2± 'roller-widths' wide. Immediately/quickly, draw the trowel across the stripe at a quite low angle to fill-in the valleys between the flat topped mesas.
3. Leave a 'dry' space almost to the width of the first troweled and leveled stripe and repeat.
4. Clean the trowel when needed ... I simply 'spritz it' with thinner, then wipe, then spritz.
5. Let dry/cure.
6. Return the following day or so and paint/fill-in the areas between the stripes already laid down, etc. If the previously applied paint can be 'dimpled' with a thumbnail - wait a day or more until it takes some thumbnail pressure to create the 'dimple'.

For scabs and craters that do release from the hull, I rough sand where the missing paint 'was' to establish 'tooth' in the surface, mix in a bit of 'micro-balloons' (fairing filler) to a small amount of paint and build the crater back up to 'flat and level' using the poly trowel. This is done before re-coating as a thick application can take a long time to dry/cure.

I use MUCH less paint; what I do seems to last much longer (I long distance sail a lot and it may be sometimes 2 years until I can 'recoat').
Once you master the roll-and-tip-with-a-trowel technique you can produce a bottom that is almost as smooth as a baby's ass - faster, more easier driven boat, less heel, good for 'light winds', etc..

Also, with a smooth bottom, any slime that attaches is more easily released by 'sailing'.
Less slime equates to less barnacle and hard-growth attachment, even with such paints as Micron-Extra.

hope this helps.
This looks like what I need for my 40-footer before I head south. Any idea of a reasonable price for a job like this?
 
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