Maybe someone here can help me out with some minor issues.
I’m using the common ES100 cup spray gun with #6 tip, and about 50psi of pressure with trigger fully pressed. Generally hold the sprayer about 12" from the part.
Currently I’m spraying Duractec surfacing primer onto a perfectly smooth plug, and having issues with orange peel. My objective is as smooth a finish as possible straight from the gun, to reduce all the time consuming sanding.
Yesterday the weather was cooler, and I was using 50psi spraying. That coat came out with medium texture on all surfaces.
Today, the plug was sitting in the sun about 10 minutes prior to spraying, and I raised the spraying pressure to 58psi. Got a nearly smooth finish on the horizontal surfaces, but still getting orange peel on the vertical areas.
Any help on this subject is greatly appreciated. What setup are you using? Are my pressures perhaps too high or low? It’s driving me crazy wasting time and $ with so many coats and associated hours of sanding.
man thats a tough one…no matter what you spray youll have some sort of orange peel
Typicaly youll have more orange peel if you shoot something “dry” meaning too much air for the orfice size and viscosity of the fluid.
Try dialing back a bit or opening up the tip size a tad bit or thinning out the mixture.
I shoot everything out of a HVLP gun I converted to use…it does the same thing on my primer (slick sand) and I just sand it smooth.
Well, I found this: http://www.fibreglast.com/learning_center_brochures/gray_surfacing_primer.pdf on the Fiberglast site. Not sure if it’s specific to HVLP guns, but I only use those for paint and clear. It says to use 35-50psi for spraying the Duractec primer. However I seem to recall the cup gun instructions mentioning 60-100psi.
I got the best finish so far today on the horizontal surfaces, and it could be due to the fact that they were heated by the sun for a few minutes. Perhaps the warmer surface temps helped it flow. Maybe heating the primer slightly prior to mixing, or adding thinner would help. I will have to buy some Duractec high gloss additive and mix it in, as it will thin out the final viscosity a lot. The additive has a viscosity of only 110, compared to the primers 2700! At 1:1, I should have about a 1400cps to spray nicely.
Will also try going up 10 psi, and down 10psi from the current settings next time I spray.
try thinning it down. Thcker materials will always have more orange peel. Also spray it out of an HVLP gun with a 2. or larger tip
A cup gun is relatively crude in relation to an HVLP paint spray gun, and is primarily intended for spraying gel coats.
I you are spraying polyester surfacing primer you will probably find you get far better results using a cheap HVLP gun with a 2.5mm set up.
Problem solved.
A warm mold surface really helps!
Sprayed another coat today with the plug being in the sun for about 20 minutes prior. All the primer came out nice and flat except for one side of the plug that was facing away from the sun and was cool. No big deal, as that’s just excess flange area anyways.
Didn’t change any material or spray gun settings at all.
You can get the same result by warming whatever it is you are spraying also.
must be nice to have “sun” 
No sun and no moon?!?
J/K 