Bottom Prep for Painting

[firehoser75]

I have a few areas along the waterline where the bottom paint has chipped (flaked) off. The largest area is maybe 6 inches long by 2 inches across. They only are a layer or 2 of antifouling and don't go very deep (can see antifouling paint underneath). My paint is an ablative. What is the best way to prep these areas to end up with a "smoother" finish? Most yards around here get excited if you try to any (dry) sanding.
Thanks,
Tom

 

[RichH]

If you have a Fein Tool, etc. and its 'chisel blade' attachment, small areas of poor bottom paint adhesion can be quickly and easily removed. The 'chips' from the Fein tool can be easily caught on a tarp, thus easily disposed. Then fair or sand the exposed area. I prefer fairing using bottom paint thickened with 'micro-balloons' or 'cabosil' applied with a poly trowel to fair in any discontinuity. If you dont adequately remove most of the poorly adhered 'under-layers', youll be chasing paint chips and 'craters' continually into the future.
The use of a Fein tool with chisel blade will quickly remove the poor adhesion zones and will discover where the adhesion is still 'good' .... and no laborious 'sanding'.

 

[Rob2435]

I sand mine, making the area larger so as to insure I got all the bad bonded paint off. Then I prime it with a no-sand primer, repaint and off I go. Spots I did years before still look good.

Not sure about adding micro balloons to the paint as I have heard they will absorb water.

 

[finding41]

Use a good random orbital sander with a dust bag. Remove the dust bag and attach a good shop-vack type vacuum.
I just sanded my whole bottom with 80 grit and applied 2 coats of water barrier and two coats of ablative.
Went from this to this to this to that.
Wipe it down with acetone before you paint.

 

[firehoser75]

Thanks and more questions

Thanks for the replies. I will have to talk to the yard to ensure they are Ok with what I am going to do. Unfortunately my Makita grinder (use it for polishing) doesn't have a vacuum attachment. I will buy a Fein tool and try that route (never used one before). Fairing is something I was looking to do. Rich, any comments regarding the concern raised by Rob regarding microbeads absorbing water?
How long would the fairing compound take to dry, prior to being to repaint?
Thanks again,
Tom