Bottom Paint - 1 coat or 2 ???

[rfrye1]

Its time for bottom paint (in San Diego). I am getting quotes for either 1 coat with 2 at the waterline OR 2 coats with 3 at waterline. There is pretty big difference in price. I am told that 2 coats dont last twice as long as 1 coat.

Can someone clarify and offer some light on this subject for me?

Thanks Bob.

 

[Stu Jackson]

It's called 1 1/2 coats at least up here

2 don't usually last twice as long, maybe another season. I suggest talking to "qualified" dockmates and see what seems to work in your area, because the longevity of bottom paint, regardless of how many coats, is a purely local thing based on the water and the type (manufacturer) of the paint that you use.

I used to go with 1 coat, then 2 now do 1 1/2, because the upper part of the hull is where the nasties seem to grow here.

 

[Rick D]

I have never put on one coat nor know anyone who has unless they had the boat for sale. I think the usual standard is the second option altho I also ask for three at the leading and trailing edges of the rudder and keel also. I get four years out of Trinidad with a monthly dive service. However, if you are adventurous, you can go with the one coat and see what happens. The worst thing would be you would have to haul again sooner, but that's not the end of the world either. And, I would check the manufacturer's recommendations too. Probably available on their website.

 

[sailaway78]

Two coats

I agree that it depends on your area, and also depends on how you use your boat. Here in the gulf coast region, I use two coats of Trinidad, with three on the leading edges of the keel and rudder, and also three on the waterline. I get over three years on a bottom job, with no problems, and only an occasional water line scrubbing. I do use my boat a lot, which does help.

 

[Deadline]

Regardless of 1 or 1.5 or 2...

...be sure to pick another color so you can see how readily it holds up.

 

[MoonSailer]

2 coats over 4 years ago. Will repaint this year but bottom is still OK. Freahwater last three years.

 

[Barnacle Bill]

Bottom paint 101

If you read the product info on the can of the paint you are using, they usually suggest how many coats to use. You might think that they are trying to sell you paint, but it might not be so.
If you have a single season paint, then usually two coats are recommended. If you have a multi season paint, then usually 3 coats are recommended.
A single season paint is usually harder and has a cuprous oxide biocide. The toxicants leech away from the paint application during use. You can look at an old paint application and see paint, but not necessarily realize that there is any toxicant in the paint. Also, with a cuprous oxide paint, when the boat is pulled and the hull left to dry, there is a chemical change that takes place leaving the paint not so effective. If there is toxicant left (fairly fresh application) then you can lightly sand or burnish the surface to open up the pores.
If you pull your boat for the winter and use a single season paint, then it is expected to apply fresh coats the next season for best protection.
If you have a multi season paint, then the toxicant and the paint leech away at the same time. Therefore, the more paint you have on, the longer it lasts. And as long as you see paint, you can assume you have antifouling protection unlike the single season paint.
Also, multi season paints do not have an adverse affect when the boat is pulled and the hull dries. You can relaunch and expect good protection with this type of paint and that is why it is recommended for trailer sailors.
The single season paint, will, in time, build up and then it needs to be removed to get your hull smoother. The multiseason paint will eventually wear off. Some people will put one color on as the first coat and then the color you want in the next two coats. That way, when you see the first coat showing through, you know it is time to paint, but you haven't gotten to the point of not having protection. Multi season paints are a bit softer and so that is one way they leech off keeping your bottom clean. Sometimes you get a blotchy appearance - especially when it is getting down to bare hull. This is to be expected.
It is the nature of the paint.
Depending on where you sail, you choice of paint must be determined. If you are in a very hot and tropic climate, then you need something quite strong with a toxicant level that is high (hence more expensive). Pettit's Trinidad has a toxicant level of around 80 percent. Interlux's Ultra is slightly lower. Both are good for those areas. Multi season paints do not have that high of a toxicant content, but I have seen them very effective in salt water environments.
So many factors enter in to antifouling effectiveness. Type of fouling, salt or fresh water, warm or cold, industrial contaminants in the water, length of season, etc.
A paint that is different from the above types would be VC17, which is also a single season paint, but it will not build up in time. It has a Teflon component which makes it really slippery for speed. Racers like it. It is better for fresh water use and is particularly good against zebra mussels. But, not great for salt water. They have VC Offshore for that application.