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Old Jan 06, 2012, 05:52 PM
If it floats....sail it!
FoamCrusher's Avatar
Elk Grove, CA
Joined Sep 2002
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Clear Coating Before or After Color Sanding?

In painting racing sailboathulls I have used the following painting sequence with success:

1. Primer coat(s): Sanding most of the primer off between coats and then wet sanding with 400 on the last full even colored coat.
2. Color coat(s): Usually at least two coats with wet sanding with 400 and 600 between coats to knock down the orange peel and dust.
3. Color sand the final coat wet sanding with 400, 600, 800, 1500 and finally 2000)
4. Polish with three progressively finer polishes up to an "ultra fine" polish.

I haven't used a clear coat before since it is easier to touch up just paint when racing puts the inevitable nicks and scratches in the paint. This time I want to use a color that looked the best in my test patches with a clear coat and I am willing to deal with the repaint issues.

Question: On the last color coat should I color sand all the way to 2000 grit or stop at 400 or 600 and save all the laborious sanding/polishing for the clear coat(s)?

FC
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Old Jan 06, 2012, 09:48 PM
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Stop at the 400 or 600. The clear needs a "tooth" just like the color does.
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Old Jan 10, 2012, 03:04 PM
Will fly for food
Maryland
Joined Sep 2004
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For clear coat finishes, typically you spray just enough to color to cover and then clear coat. No sanding at all.

First time I shot a clear coat finish for a car, I was not sure about this, but it works.
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Old Jan 10, 2012, 07:33 PM
If it floats....sail it!
FoamCrusher's Avatar
Elk Grove, CA
Joined Sep 2002
4,193 Posts
Thanks.

Just clear coating after a thin color coat can be done if you are using a gun and automotive paints that leave a level surface. I will be using rattle cans and with their new low VOC formulas it is difficult, if not impossible, to get at least some orange peel....so each coat needs some sanding.

I will knock down the orange peel with the 400 and 600 used wet and then clear coat.

FC
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Old Jan 15, 2012, 02:11 PM
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Canada, MB, Winnipeg
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Never sand color!
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Old Jan 15, 2012, 08:46 PM
If it floats....sail it!
FoamCrusher's Avatar
Elk Grove, CA
Joined Sep 2002
4,193 Posts
Well, I'm going to have to sand the color coat...at least a little. The rattle can paint (Fluorescent Green Painters Touch - Krylon is similar in my tests) gives a very rough finish - almost like 220 sandpaper. If I tried to just clear coat it without any sanding, it would take several cans and add significant weight.

I will take it down to 400 to smooth it out. Not polished like I do for color sanded paint, but smooth. After all, this is for a sailboat hull and the final surface needs to be baby butt smooth as well as light.

Thanks for all the replies. I will post how it turns out. Second color coat goes on tomorrow.

FC
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Old Jan 22, 2012, 07:08 PM
Will fly for food
Maryland
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If you can sand the color, you put on too much color. There should be JUST enough to cover.
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Old Jan 30, 2012, 11:46 PM
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Leroy Gardner's Avatar
Coeur d' alene, Id.
Joined Jan 2010
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If your having leveling or orange peel problems your paint viscosity is too thick and your paint pressure or tip size is probably wrong for the type of paint your useing. When clear coating base or color coats all you need to do is hit it lightly with a fine scuff, tack cloth it than spray it. Never sand with more than 600 grit for clear coating.Leroy
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Old Feb 01, 2012, 12:31 PM
If it floats....sail it!
FoamCrusher's Avatar
Elk Grove, CA
Joined Sep 2002
4,193 Posts
Gardner & Pinecone:

I was doing this with rattle cans therefore had no control of pressure or possibility of thinning the paint. What you spray is what you get.

Also remember that the goal here is a very smooth surface for the bottom of a racing RC sailboat. At the speed the boat will be moving, the Reynolds numbers are very low so rather than the traditional 400 grit surface you would use on a full size boat, you want the bottom to be as smooth as you can get it. Appearance is secondary.

I sanded the last color coat with 400 and 600 and then added three coats of the clear with a light sanding with 1000 wet between coats, followed by wet sanding the last coat with 800, 1000, 1500, 2000 and then polishing. The results are not show car quality, but the bottom is super smooth....just what I wanted. I will post a picture later after the camera battery is finished charging.

Thanks to everyone who chimed in.

FC
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