body work question

what would be the best way to sand down the ground effects??? or is it even possible without screwing something up??? and whats the order i should go in from coarse to fine..right now i think i have 60, 100, and 160 or something like that, it seems to leave it smooth but i have heard from a few people that before i primer the whole car i should go over it with a super fine sandpaper...also does the bondo spot putty work that good at all?? i am sanding it down and getting it super, super smooth but i still keep getting pin sized indentations and then ill use the spot puddy and sand it down some more and they appear again...i cant seem to get rid of them... i have an air gun to shoot the car with primer, what would u recommend???

also..i really want this to look as good as possible, if u have any ideas, or suggestions..let me know

I'm no body / paint guy ... matter of fcat I'm about the farthest thing from it... But as I seem to recall Sand it down to metal, prime, sand the prime smooth reprime if necessary and THEN paint...

But I could could have my head totally up my ass on that one. Buddy of mine did that to a 67 mustang... took it down to metal, primed, sanded, primed... then someone stole it.

lol... that's messed up. i would be even more pissed if somebody stole my car after all that work.

anyway... there is no metal in the ground effects, they are all composite plastic material or very thick fiberglass. this is why you don't want to use a very coarse sandpaper on it, because that would be just like taking a cheese grater and rubbing it on your car. it will make a lot of unremovable scratches.

the lowest grit sandpaper i would use on that, would be 160-200. the clearcoat might take a while to sand off with that grit so you might want to go with the 100grit at first, but be careful not to press hard, because it will scratch the plastic.

the order is coarse to fine. coarse paper is for removing material and fine paper is for smoothing things out. this is what you should do:

lightly sand with 100-160 grit to remove old paint and clearcoat
sand with 200-300 grit to smooth out, press hard
(spot putty here)
go over it with 400-500 grit paper
spray with primer
sand with 400-600 paper
spray with paint
(this is assuming you are hand sanding, if you use a power tool, you apply much less pressure)

spot putty does work, the paper you are using is too coarse and so it is removing the putty after you put it on. make sure you read the intructions and mix it right. before you spray it with paint or apply spot putty, always wipe it down with a tach cloth ...always.

Also I hope you removed the ground effects from the car.. if not its going to be some back breaking work. :lol2:

ok, i just bought a da air sander..what is the best way to get the paint off the front end and the ground effects..i'll prob take the front end off tom..i'll get some pics up then

A DA is going to tear it up, especially if you're unfamiliar with it. You're best off hand sanding, DA's are great for bondo or completely stripping to bear metal.

I have been attending school for a year now for bodywork, hopefully this will help you. Your first question about sanding the ground effects: Since it is a type of plastic it won't rust, so you dont have to use a very coarse sandpaper...I recently redid my front bumper and I used 220 for the whole thing. You don't need to take all the paint off, just scuff it up good. Primer will actually hold better when it is applied on paint than anything else. You dont need to go any finer than 220 when preping for primer, to you it will feel very smooth, but there will be sand scratches after you apply the primer, this is fine because you will need to wet-sand the primer down and that will take care of the scratches. I would NOT use a DA sander on ground effects, do it by hand. Only use a DA on a hood, door, roof, hatch-until you are familiar with it, they can eat through paint very fast. Now on to your question about pinholes in your plastic body filler (bondo). Those will usually appear because you are mixing the hardner and filler wrong. First thing you just need to run one line of hardner across the top of the filler, this will be more than enough. When you mix it use a scraping motion, if you have been using a stirring motion this is most likely how you are getting pin holes. Right before you apply the primer to the car, wipe down with a "Wax and Grase Remover" this will help eliminate lifting in your primer.