For those just learning.
Thanks! That is a good read.
Good article 
I had a guy who sprayed boat molds with gel coat for a living for many years. I noticed when he sprayed gel coat with our hvlp gravity feed gun he ran an almost round fan pattern while doing gel coat for mold making. Right away i could see way less overspray with his method and more material being transfered to the work surface.
HVLP guns have an air adjustment knob, not to be confused with the fluid adjustment or fan pattern adjustment. If you want to run minimal overspray play with this knob a little. I think most hvlp guns require only around 30psi but all guns come with instructions on cap pressure. Cap pressure is adjusted by depressing the gun lever fully and taking a reading of the air pressure at the gun. I always use a regulator at the gun with a gauge. This dials in air pressure precisely and allows you to make adjustments and know where you are at.
When i spray gel coat i do the first coat with the fluid knob 2 turns out ( counter-clockwise). Then i take it to about 4 turns out for the remainder of the job.
I never use expensive hvlp guns for gel coat because they will get ruined quickly. My cheap gel coat guns last me 8 to 12 months. I clean them quickly after each use with laquer thinner or acetone. I run 200ml through the cup after i dump out any excess gel coat. Shake the gun agressively with the lid on. Turn the fluid knob out as far as possible during cleaning. Then i pour another 100ml of clean solvent into the gun, shake some more and spray out most of it. When i’m down to 30 or 50ml i loosen the air cap up a couple turns and pull the trigger down. This kinda backwashes the inside of the gun and you will see bubbles blowing inside the cup. Now dump out that last 30-50ml for recycling. Use gun cleaner, acetone, or laquer thinner to wipe down the gun and the cup inside. Now get a clean cup, pour half full with solvent. Remove the air cap from gun, next the fluid knob, spring, and needle. Next remove the spray tip from the gun. Soak all these parts in the sovent cup. Now take the gun and pour a few ounces of clean solvent into the cup and watch it come out the front of the gun where the tip was. Use your gun cleaning brush to clean inside where the tip screws on. Unscrew the cup from the gun using the supplied wrench. Always try to use the tools they giveyou with your gun. The next day or same day use the gun cleaning brush to clean the tip of the gun ( some tips screw on counter-clockwise, or backwards), and the air cap, spring, knob and needle. Now reassemble the gun with the fluid knob turned two turns out. Test the gun with some clean solvent, store it in a clean cabinet or area. Never leaved cheap guns stored with solvent in them, as it can melt the plastic O rings inside the gun. Never submerge a cheap gun in solvent as the same thing will happen.
Sorry to resurrect an old thread… but that is some great info!
I’m just looking to get a compressor for odd jobs at home, this gives me a good idea of what is needed to spray gel coat, primer etc. And I’ll need all the info I can get because I have never used a spray gun before!
No worries just use an air drier or at the very least an inline water separator. Otherwise you get water.