So how does one know what sort of tip sizes you will need to spray gel coat, clear coat, various paints, etc??? Other then from experience? Should the manufacturer of the stuff you are wanting to spray tell you this info?
Are there any guns where the tips ate changable so that the gun can serve double/triple duty? or do you need a seperate gun for everything?
Is there a general tip size that could do it all?
clear coat, 1.3
gel coat anywhere b/t a 2.0 -> 2.2
primer a 1.5 depending on what ur using
manuf. will not tell you this info. they might, but it wont work… lol
ask around, they will tell u. the above is what i use
oh and pva = a .9? i forget.
Mine are:
Sata Digital HVLP(my best gun) 1.7, for clearcoat, adjustable so you can spray a car down to penny washer.
2 x cheap HVLP 1.7, one for duratec primer the other duratec clear. Once again like all guns adjustable so you can open them up or close them down to spray large volume or very small.
Lastly an airbrush.
Baz
Do you ever spray polyester gel coat with an HVLP gun?
I spray tooling gel out of a SATA knockoff with a 2.2mm tip.
HVLP gun with a 2.5mm tip will spray just about anything thats sprayable! Worth bearing in mind though that you are never going to get very good results spraying clear coats, if you are using a cheap HVLP gun, no matter what set up you are using.
The best way is to have one cheap HVLP gun with a 2.5mm set up for gel-coats etc, and another quality gun for things like clear. If you are doing smaller parts then something like a Sata Minijet with 1.2mm set up will work very well, and provides an acceptable gun finish when you are spraying 2k clear.
I have never sprayed a gelcoat, most of my molds are small so when taking a mold from the plug i use the old brush method. I don`t produce fibreglass parts from my molds only carbon so i will only spray in Duratec clear or nothing.
Baz
so what your saying is that instead of gel coat being sprayed into the mold you will spray the clear coat in first?
Why not spray the clear on the finished composite?
Thanks.
No not the clear coat. Some of my smaller items i.e gauge holders strut tops i will spray in the Duratec clear and just give those a buff and polish when demolded. The larger items that are subjected to a lot of UV i.e the dash, parcel shelf, sill trims etc i will lay up with no Duratec, then clearcoat these with 2k clear. The Duratec will not bond with the epoxy but epoxy will bond with the Duratec. The 2k acrylic clear and also polyurethane will bond well with epoxy, ive used both and had no problems, dont use cellulose clear that does not bond well with epoxy or per at all.
So i guess your saying why not use Duratec on the larger items. Well these items are complicated to mold and can be ruined in my opinion if there is even the smallest amount of air trapped between the Duratec and the carbon, where as on the dash which incidently takes 2 days to lay up, a 2 stage process, stage 1 only lay in 1 layer of carbon then infuse, let cure stage 2 lay in and infuse the remaining 3 layers plus more in various areas. This way if there is any small areas where some air may have been trapped by the weave, im talking about say a dozen or so 2-3mm x 1mm air pockets here not bridging, then the 2k Acrylic clear will easily fill those and i wont have a ruined part.
Sorry its a long winded explanation but i have been doing this a fair while, had my fair share of disasters and this works for me. Others here will do things differently but its all about experience, practice and what works for you.
I assume you infuse the 1st ply of carbon for a perfect finish ,so why wouldn’t that be any different with the extra 3 layers ??? If you are stuck doing the 1st layer by itself why not just hand lay in the extra layers of reinforcements? Do you vacuum de-gas the resin before the shot ?
On something as complicated as the dash i found it best to get the first layer absolutely correct with no bridging, if at this point i had added further layers i would run the risk of moving the first layer and possible bridging. The trouble with me is i am a perfectionist so yes infuse the first layer and the other three, i still want a light part not resin rich and heavy. I have never degassed the resin and never had a problem with air in any of my smaller less complicated parts. I do heat the resin though to get the viscosity to it`s lowest as well as heat all my molds, the heat allows any or most of the bubbles from mixing to rise and pop.
Baz
Astro Pnuematic company makes an inexpensive HVLP gun that is absolutely awesome… model is EVO and costs around $80. It sprays as good as a $300 HVLP gun will. They also sell two gun EVO sets for around $150… you can choose tip sizes. As for clearcoats it really depends on the company and type of clearcoat… anywhere from a 1.2 to a 1.5. Each paint company has their own tech sheets that tell you how to spray their product for best results. I like Southern Polyurethanes Inc. The price is right and it’s a top notch product… won’t yellow and it’s crystal clear polyurethane… costs about $100 a gallon for their high solids clear… more than comparable to other companies $200 a gallon clears. Also check out Southern Polyurethanes website for how to adjust an hvlp gun to spray professionally… most people can’t set up a gun to spray right to save their life.
Also please keep in mind most urethane clears and paints have Isocyanites in them. These are deadly without using a supplied air breathing system. A normal carbon respirator will not suffice.
+1 for the Astro Evo LVLP. I just got one recently and it sprays excellent. Great for users with less than professional air compressors. Inlet pressure is only ~25psi.
with an hvlp gun and automotive finishes:
Primer of any kind 1.8-2.0
Base Coat paint - 1.2-1.3
Clear coat - 1.4 or 1.5
Anything thicker than primer… 2.0-2.2
This info came from professional auto painters.
Don’t waiste money on cheap spray guns… they suck and you’ll be miserable with the results. Buy a good gun like Iwata or Sata for auto paints and clears. If you can’t spring for that much $ get a Astro QUL or EVO models. The Astro guns will spray the same as a $300 gun. www.spraygunworld.com