Bottom paint and sanding

[nestorph]

I sail in Raritan Bay (off the NJ coast). For years I've been faithfully sanding the bottom and applying a fresh coat of West Marine CPP paint. However, I've read blogs where people are getting more than year from their application. While I'm willing to apply another coat this year, I was wondering if I could just get away with power washing the bottom and doing the application or do I still need to sand first?

 

[Ralph Johnstone]

a fresh coat of West Marine CPP paint.

Is CPP an ablative ?

 

[Joe]

From the west marine advisor:

Do you want to haul out over the winter and relaunch without repainting?

Use copolymer ablative type paint. Copolymer paints release biocide at a constant controlled rate throughout their lives, wearing away or “ablating” much like a bar of soap. Paint wears off faster in higher drag areas on the hull and appendages. These paints work well in high-growth areas and continue to be effective after haulout at the end of the season. In the spring, the paint is reactivated with a scrubbing or light sanding and you’re ready for another season. This is a huge time-saver for those living in northern climates. While the percentage of copper in the paint is important for evaluating its effectiveness, copper content is not the only consideration. Controlled polishing, the technology that controls how quickly the paint wears away, is another way we measure the effectiveness in a copolymer ablative paint.

We recommend a covering of two or three coats on the first application. Copolymer paints with anti-slime additives are best for heavy fouling areas. Environmentally preferable: CFA Eco, Ultima ECO and Pacifica® PLUS are ECONEA-based copolymer ablatives.

Ablative paints (of the non-polymer type) work in a similar way and minimize the annual ritual of sanding when applying a fresh coat. Best use is as a single-season paint for boats that are used often, but are not serviced by a diver. Not recommended when you want a super-smooth bottom finish and have a diver maintain it, since scrubbing removes paint and reduces longevity.

http://www.westmarine.com/WestAdvisor/Top-Ten-Antifouling-Paint-Buying-Questions

 

[Ted]

CPP is an ablative paint. No need to paint your bottom every season unless the paint is gone. High ware areas are usually the leading edges of the keel and rudder and the waterline and may need touching up. If you sand every year, you're wasting your money. Apply multiple coats when you need to paint and then you'll be able to skip a season or more. Ablative paint will ware away like a bar of soap and will not build up. So if you see paint on your bottom you're good to go. Read the instructions on the can of paint. They will have information regarding relaunch and repainting procedures.

 

[Warren Milberg]

What you are suggesting is exactly what I've been doing for years. I use Petit Hydrocoat, which is a multi-season ablative probably of similar quality as CPP (only it's water soluble, a big plus in my mind). Although it is supposed to wear away, I find that ablatives do build up to some degree. So what I do is not follow the directions on the can. I powerwash the hull and then apply only one thin coat with a 1/4" semi-smooth roller, touching up with a brush. I find this works well for me in the brackish mid-Chesapeake and reduces or eliminates paint build-up and sanding.

 

[nestorph]

I did what I should have done first, namely, "read the instructions"! The West Marine site provides information about CPP. It's definitely a one-season paint. To add insult to injury, they recommend two to three coats per season and sanding the previous year's coat.
I ended up lightly spot sanding and applying a single coat which has worked well for me in the past. There goes my short cut...

 

[bffatcat]

ablative paint

Im in Massachussetts cold water not a heavy fouling area Most of the sailors I know use ablative paint. They steam clean their bottom at end of season haul out. Most apply one fresh coat of ablative in the spring I do the same. If there are any ridges or rough spots I give them a light sanding before painting

 

[Barnacle Bill]

The reason for sanding is to give the surface a tooth for the new coat(s) to adhere to better. Multi season paints are expensive and so you don't want to power wash your money into the drink (or on the hard). Paint salesmen (like me) will like that, but I try to save my customers money. Since ablative paints, like Interlux' Micron technology works fine after the hull dries (unlike single season cuprous oxide paints) you really should sand with 80 grit (but not sand all your paint off) and apply more coats. But since you can assume your paint is working as long as you see paint on the hull, then you really don't have to recoat until you see bare hull. That is the bar of soap analogy. The paint and the toxicants leech away at the same rate. With single season paints, the toxicant leeches away leaving the paint behind. And you cannot assume you have working toxicants even though you see paint. That is why the ablative type paint is so cool, because you don't get a build up, but you might experience a blotchy look when it gets thin and you see bare gelcoat again. Comprendo?