What Sandpaper grit for new bottom paint prep

[duffer1960]

I want to repaint my hull before the start of this season using the same paint I used the previous seasons (I have a couple of gallons extra). Anyway, the existing, and new, paint is an epoxy based paint (read NON-ablative). I only want to scuff the existing paint to get good adherance with the new paint. I DO NOT, I repeat, DO NOT want to remove the existing paint. Therefore what is the best grit to use? I am used to automotive refinishing where the final prep is with 320 grit paper, but I know that is too fine for this case. Is 150 the answer? I know 50 and 80 would be too coarse because that is what I used a few years ago to remove the previous coating of ablative. Thanks.

[sailingdog]

150 might be a bit fine... I've used a 120 grit with good results. Don't forget to wear a good full-face respirator with a dust filter in it, as the dust from sanding bottom paint is a heavy metal toxin.

[LarryandSusanMacDonald]

I'd get a piece of 120, 150, & 180 and try it - starting with the 180. Wear a mask. A tyvek suit would be good, too. And gloves. You're probably right, though 150 should be close.

[BarryL]

Hello,

What does the paint vendor recommend? When I was applying new bottom paint on my boat, Pettit, the manufacturer, recommended using 80 grit.

Barry

[sailingfool]

For most paints I'd use 80 grit, see the thread http://www.sailnet.com/forums/gear-m...iler-boat.html and call the US Paint 800 number if your situation is not otherwise addressed.

[christyleigh]

Originally Posted by duffer1960

Is 150 the answer? I know 50 and 80 would be too coarse because that is what I used a few years ago to remove the previous coating of ablative. Thanks.

I've always used 60 or 80 on a 5" or 6" random orbital with a vacuum attached for my yearly or bi-yearly scuff before painting. Anything over 100 and you'll need a hundred discs to do your 38 footer as it will fill up in no time at all.