Wet Sanding

[Vic Suben]

Surprise's bottom needs light touch-up sanding this year.  I would like to wet sand the bottom.  But each time I have tried wet sanding in the past (with wet/dry 80 or 100 grit sandpaper) the paper has loaded up so quickly that almost as soon as I started the sander, the paper was loaded.

Does anyone have any tips on what I am probably doing wrong? And how to do it correctly?

Thanks,

Vic
Surprise/Hull No. 453

[Gene Regan]

Vic,i
Here in the body shop I run, we wet sand everything. One of the things you need to consider is the word wet. We we sand we keep a hose running at a slow trickle on the work  so we don't load up the paper. The  second thing is how aggressively you sand. The harder and faster you go the more problems you create. If using a machine sander be sure its rated to do wet sanding and remember wet and slow works better than fast and damp. Rinsing the sanded surface frequently is also helpful. You must get that sanded slurry away from the work and clear the paper to be effective. Papers differ in quality as well. We have found Norton Gold to work better than 3m. It lasts longer cuts easier and faster and is less expensive per sheet than 3m. Remember WET is the word, if your sanding upside down the water does not stay there long so make it wetter and keep it that way. If you can give me more specifics on you material and sander I can help you more.
Good luck

[Vic Suben]

Gene, thanks for your comments.

I'll be wet sanding the bottom of my Catalina 34.  The paint is an ablative copolymer.  When the yard power washed the bottom at haul-out, they hit the bottom full strength & removed the top coat of paint (otherwise I wouldn't have to paint this year).  I just need to smooth it out a bit before adding another coat of paint.

I have used a machine sander in the past, but in light of your comments, it seems as if hand sanding would work better with the water.  Also, when I wet sanded in the past, I dipped the paper in a bucket of water before attaching it to the sander.

I have no way of regulating the speed of my sander.

[Roc]

Vic,
I use Micron Extra ablative paint.  When I wet sand to 're-activate' the paint in the spring, I use a coarse Scotch brite pad.  I dip the pad into a 5 gallon bucket of water and sand away, dipping the pad every so often to clean it out.  

You can get the pads at Home Depot.  They are very thick and easy to hold.  You can also get a plastic handle that the pad sticks to if you want.

[Vic Suben]

That sounds easy enough.

Thanks again,

Vic

[Ron Bukowski]

I didn't think that one was supposed to sand ablative paint to re-activate it. That would be a waste of what is on and unnecessary labor. Am I wrong?

[Vic Suben]

I am not trying to re-activate the paint; I intend to add another coat to replace the coat that was washed away when the yard was over zealous in power washing the bottom.  Ordinarily, the paint that I use does not need to be re-activated, and two coats is supposed to be good for 3+ seasons (with some touch-up).

Before painting, I just want to make sure that the bottom is fairly smooth & there is no paint that is about to fall off.

Vic

[jentine]

I have typically used a stiff bristle brush and a copious supply of water to prepare the bottom for painting with great results.  Wet sanding tends to get me wet, an unpleasant idea in spring in the Northeast.

Jim Kane

[Roc]

If you read the instructions on the Micron ablative paints (CSC, Extra) they suggest 'sanding', either wet or dry.  I used the term 're-activate', only for lack of a better description, because in a sense, that's kind of what you are doing.....lightly skimming down to a fresh layer of paint.  Micron ablative paint is Multi-season, so by sanding it in the spring, the paint that is left over will still have it's antifouling properties, but the directions call for sanding in order for that to work.  When I wet sand, I'm not pushing down so hard, using all my elbow grease.  If you do that's true, you'll just take the paint off.  Just a light buffing is all you need to do.  Using water and wet sanding is much easier because there is no dust.  That's the beauty of a multi-season ablative paint, you put a few coats on, then every spring, just wet sand it (lightly) before launch.  No need to wear a nuclear fallout suit and be covered in blue dust......It's a good idea to put a signal coat first, so when you see the alternative color showing through, you can touch up those areas.

[Jim Fitch]

My friend got me using a type of sandpaper that the drywall guys use.  It looks like a piece of screen and I think I buy 80 grit.  We cut them into sheets that fit the head of a sponge mop and tie them on with two pieces of string and dunk them in a bucket of water every once and a while to clean the screen.  You may have to do some hand touch up afterward with the same type of sand paper, but the long pole of the sponge mop makes the work a lot quicker and the sponge gives enough to match the shape of the hull.  It works great on ablative paints, he uses it on regular bottom paint as well.