Wet Sanding Gelcoat

[Lieutenant Dan]

I see lot's of threads that talk about the steps to take to restore Gelcoat to its glory. Most speak of wet sanding with various grits of paper followed by machine cutting / polishing / waxing and I appreciate all of the different takes that people have on this.

But I am a complete noob when it comes to the subject of wet sanding. How do you do this part right? I have read that you should use "soapy" water. I have seen comments about using a block or a sponge. I have seen conflicting opinions about using a back-and-forth motion and on other forums have seen that one should very lightly polish with a circular motion.

Can someone fill me in on the proper technique(s) for this?

[sp0tts]

Wet sanding should be done with a back and forth motion and a block. I've always just used water with no issues, but I'm sure a little soap wouldn't hurt. A lot of people have different takes on what grit paper to finish with, the grit paper you use to start with really depends on the job and how deep you have to go. Basically you want to start with a lower grit paper and work your way up (like say start with 600 and work your way up incrementally to 1500 or 2000 (opinions vary here)). The idea with starting with a lower grit and incrementally working your way up is that you won't have to sand as hard as you would if you tried to do the whole thing with a higher grit paper (trying to do a whole job with 1500 or 2000 grit could wear out your arm).

After sanding, you need to buff with compound, polish, and wax. Buffing and polishing should be done with a variable speed electric polisher. I like to use 3M Compound and Finesse It with their recommended double sided bonnets (contour to the curves better than something with a firm pad).

[martinarcher]

Good thread with a ton of info here.

[TipoFloe]

I see lot's of threads that talk about the steps to take to restore Gelcoat to its glory. Most speak of wet sanding with various grits of paper followed by machine cutting / polishing / waxing and I appreciate all of the different takes that people have on this.

But I am a complete noob when it comes to the subject of wet sanding. How do you do this part right? I have read that you should use "soapy" water. I have seen comments about using a block or a sponge. I have seen conflicting opinions about using a back-and-forth motion and on other forums have seen that one should very lightly polish with a circular motion.

Can someone fill me in on the proper technique(s) for this?

This is what I found while I was looking for a solution for my own gelcoat problems...

Gel Coat repair by Malibu Technician

[rodman]

Dan rule of thumb if you can catch your finger nail on the scratch you will have to sand. If you can not you can always get it out with compound or a fine polishing compound.

Like Spotts said finish out with as fine of a grit as you can get.

The reason for using soapy water is to keep any you from digging into the gel to deep. We also use baby oil as a lubricant on the finer scratches.

Remember the deeper the scratches you put into the gel with sand paper the harder you will have to work getting them out.

Edited August 31, 2010 by rodman

[wienrdog]

Dan,

Sanding - linear motion with a block or stiff sponge.

Polish - circular motion with buffer preferred - DA polisher will be ok, but will take longer.

One recommendation that I haven't seen here it to change directions of sanding when moving from one grit to another so you're cutting down the small peaks & valleys that sanding with the coarser grit created. It should make it easier to see when you're ready to move on.

I'll be attacking much of my boat with compound & polish hopefully sometime this fall when it's not so hot outside, but don't believe I'll need to wet-sand any more than I've already done to repair some minor dock scars from a slightly backed out screw head encountered down at Norris.

I do have a heavy duty Porter Cable DA polisher if you'd like to use it.

[rugger]

Depending on how bad it is you might be fine polishing with a rotary buffer (not DA) and wool pad with a heavy cut compound like maguiers 105. Least invasive first in my book, and that's a pretty powerful combo. Either way, a rotary is best to finish up with after sanding anyway. Might try it first.

[99response]

Depending on how bad it is you might be fine polishing with a rotary buffer (not DA) and wool pad with a heavy cut compound like maguiers 105. Least invasive first in my book, and that's a pretty powerful combo. Either way, a rotary is best to finish up with after sanding anyway. Might try it first.

+1 on that, but make sure to wash the area you polished with IPA or soap and water as the residual polish makes the surface look better than it really is.