Slick Sand or ???

Moving along with the body and paint on my '67 Camaro and while the body itself is straight enough to block out in epoxy, I'm thinking of using slick sand on the underside of the floor. I'm going to apply another 2 coats of SPI epoxy over the filler work, but if I was to apply the slick sand over that after 48 hours, I'm assuming I don't need to sand the epoxy and then can apply a topcoat (likely base/clear) over the slick sand without sealer or do I need a sealer. It says in their spec sheet it can be top coated without sealer, but I'd like to hear from someone who has done that. Thanks, Bill
 

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I would be leary of using too much on the bottom of a car. It will chip much easier than epoxy. May not matter if not driven much. Going to all the trouble you are, I would definitely seal it prior to base. Poly is porous. It can be top coated without sealer, but definitely not ideal, IMO.
 
texasking said:
I would be leary of using too much on the bottom of a car. It will chip much easier than epoxy. May not matter if not driven much. Going to all the trouble you are, I would definitely seal it prior to base. Poly is porous. It can be top coated without sealer, but definitely not ideal, IMO.
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If it looks decent with the epoxy on it, I may not have to use the slick sand, I may be able to just lightly sand the epoxy and topcoat from there.
 
Bill a better way would be to mix enough epoxy to put three+ coats on the underside. Cover it and let it sit 12-24 hours. Then spray the three coats with 30 minutes to an hour between coats. Longer you let the epoxy sit the thicker it gets and the more millage per coat.

Underside looks great BTW.
 
Slicksand would be a real bear to hand sand on the underside of the car, all the dips and crevices ...my carpal tunnel is crying already. Epoxy would be easier to sand imho. A side note on quicksand, the initial cured surface is very hard and with the gummy residue familiar to polyester fiberglass resin, I wipe it off well with a thinner rag before the first sanding, helps keep the sandpaper from clogging (thanks to a forum member for telling me this a few years ago). Breaking the surface is tough and requires ~150 grit, you'll make a mess with finer grits.
 
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i would do epoxy only. no need for high build under the car . over night cure in a covered cup makes the epoxy build well .
 
shine said:
i would do epoxy only. no need for high build under the car . over night cure in a covered cup makes the epoxy build well .
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Thanks Shine and others, I think I'll stick with the epoxy only. I would certainly cut out two steps as well and I have found the SPI epoxy easy to sand. I've been waiting for a shipment from back eastern Canada, but the freight companies aren't delivering to British Columbia yet, with all the highways washed out from the incredible flooding we've had here. Some of the highways will take months and longer to repair, but the main one opened up the end of last week.
 
I did the underside of my '68 el Camino in 3 coats of well induced black epoxy. Really happy with it.
I shudder at thinking about trying to sand slick sand in that area. It was hard enough prepping the metal for epoxy.
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I sprayed the underside of the floor today with 2 coats of SPI epoxy that I let induce for 11 hours. The areas with filler in them still stand out, as if the epoxy hasn't sealed the surface completely. I waited 1 1/2 hours between coats. I'm thinking I should do a third coat, but should I wait 24 hours for the third coat, to let the first two coats cure properly first? I had expected the filled areas to disappear with the second coat, is that wrong?
 
Why did you stop at two coats? I would have planned on four from the get go especially for protection underneath. At this point, block those areas with filler, spot a light coat or two on the filler again and let dry, and put at least two more coats over all if you're within the window. And yes, depending on how the filler was sanded two coats may not be enough. I've never sprayed a coat or three of epoxy over filler and expected it to cover, seal and make the filler disappear. I always block sand any primer on top of filler and repeat until the repair disappears.
 
bill3337 said:
I sprayed the underside of the floor today with 2 coats of SPI epoxy that I let induce for 11 hours. The areas with filler in them still stand out, as if the epoxy hasn't sealed the surface completely. I waited 1 1/2 hours between coats. I'm thinking I should do a third coat, but should I wait 24 hours for the third coat, to let the first two coats cure properly first? I had expected the filled areas to disappear with the second coat, is that wrong?
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Filler on the underside. That is some attention to detail!
 
I have filled and poly'd the bottom of a few cars.......now that I don't paint at a shop anymore I am happy to report I will never do that again!

57 Ford:
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59 Impala:
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70 Chevelle. This one went SPI Matte Black
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Worst one of all: 59 vette
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Np pics, but it was painted silver like the top:
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