Bottom paint preparation

[theboat]

I have started prepping the bottom of my 32’ O’Day 322 for bottom paint. I may have been slightly aggressive with the sander in spots. The spots in question are pure white. <br /><br />My questions are…. What did I expose? How do I tell if I sanded too deeply? Should I patch or prime those spots? <br /><br />Any help is appreciated.

 

[Reel Appeal]

Re: Bottom paint preparation

Joshua,<br /> If you start to see translucent resin or cloth(fibrous)material,you have sanded too much.What grit sandpaper and what type of sander are you using?If the hull of your sailboat is white then it sounds like your still in the gel coat which is ok.Beware of color changes.Only sand as much as needed.If you are concerned with water penetration,take a look at a barrier coat(2 part) before bottom painting.Barrier coats prevent blistering/water penetration/osmosis problems.Are you sanding all the paint off?

 

[theboat]

Re: Bottom paint preparation

Thanks for the quick reply.<br />I’m using 100 grit paper sanding discs. My hull is gray. In the spots that aren’t sanded through the color is a darker shade of gray than the actual above water gray color. I don’t see any clear or fiber coming through which is good. I’m not planning on removing all the paint because a lot of it is solid. Can I use barrier coat on spots or is it an all or nothing procedure? Thanks again!

 

[flashback]

Re: Bottom paint preparation

I would guess that the white you are seeing is the gelcoat so don't go any further with the sander. as far as spot painting barrier coatings on spots, that is not a problem. as far as not removing all the old bottom paint, be careful of what kind of paint you put back on, as many paints are not compatible and the new paint will cause the old paint to lift.. west marine catalog has some good info on this subject.