I am about to paint the fiberglass hood on one of the trucks at work as some practice for the upcoming paint on the Corvette. I am using a urethane enamel from Napa in fleet white. I already have it preped and primed, and will be shooting the paint tomorrow night after work. I have already wet sanded the primer with 600 grit to a dull shine. The questions I have are about the dry time between the coats of paint. the instructions say 15-30 minutes between coats. Does this mean I wait a minimum 15 minutes between the coats after the first tack coat? Can I wait until the paint is dry (24 hours) to apply the second coat, and if so do I need to scuff the paint between each dry coat. Or if time permits spray each coat at 15 minute intervals.
I have all the equipment covered ; the garage is wraped like a condom with intake, exuhast fan filters new Sharp hvlp gravity spray gun, two water/oil removers in the system with a water trap in line, and a garden hose at the ready to spray down the floor.

Your help will be greatly appreciated.
DR. Jay

 

You need to make a block of time available to do the job all at once. Flash time is temperature and humidity dependent. You have to wait at least the recommended minimum time, but no more than the max. You are looking for a chemical bond, which you won't achieve if you split it up over a few days.

 

Thanks Big-G! It is a large hood off an 18 wheeler, and I was afraid that I might not be able to finish it in a few hours that I have. I will have to try to get home earlier so I can get it all sprayed at one time. I would rather practice on a hood that I know the paint job won't matter so much on, so I can do it right when the time comes. (this is one time that I can thank my no driving employees for giving me something to do, but don't tell them that)

 

Exactly right.
I have found the forum below to be very helpful.
http://www.autobodystore.com/forum/index.php

Good luck!

 

You need to follow the manufacturers data sheet for mixing , air pressure and flash times. Too short of a flash time and the solvents don't have time to evaporate properly and you could end up with solvent pop (looks like fish eyes) or runs. Too long and you have adhesion/dust problems.
When you are ready to spray, wet down the shop area and set up your ventilation, wipe the piece down with wax and grease remover to remove any contaminants(includes fingerprints) followed immediately (while wet) with a clean. dry lint free cloth. just prior to spraying go over the unit again lightly wth a tack rag to pick up any dust.
Spray a few test patterns on some masking paper taped up on a wall to get your air pressure, fan and fluid adjustments set up.
the trick to spraying is to keep a uniform distance, 50% overlap and don't stop in the middle of a panel (more important with metallics)
Think like a robot arm Don't try to cover it all up at once, I find 3 coats with an Acrylic urethene seems to cover, or if using base/clear about 3 coats base and 3 coats clear.
Its a lot of fun to do once you try it...Good luck!!

Here is a Kenworth I repaired after smacking a deer, the fiberglass was all messed up with this corner hanging off and a split up beside the rad


and after spraying and assembly..truck came in friday night and had to be on the road to California Sunday afternoon...These trucking guys don't like down time!

 

I just painted the hood & tops of my vette, first time ever held a paint gun Turned out real nice. Follow all instructions above, just make sure you don't have TO much fans or you'll stir up unwanted dust.
A little trick to judge paint readyness for next coat, I was told is to have a place to Touch your last coat (either masked spot or even a piece of cardboard next to your job that you spray each time as well.)
It's ready for another coat when your last coat is tacky but doesn't transfer color onto your finger when you lightly touch it.

 

an old trick I learned when spraying enamel is to touch the paint on the paper (Don't Touch the piece you are spraying) If the paint is tacky and does not come off on your finger or leave stringers, it is ready for the next coat.