Hello everyone,
I thought, I could speed up some projects with  the Cup gun, because it looked easy to clean.
Well, it certainly is, for a spray gun.
But I can't get it working properly. the spray pattern is really, really bad, no matter what I do. And the output is very limited. Additionally, the spray cone is far to wide, i am literally spraying half of my workshop.
First, I thought the polyester gelcoat might be to thick, so I thinned it slowly with compatible polyester resin. Basically with unthicked gelcoat. Still, only "drop throwing". In the very end, it was so liquid, it ran off the nozzle with or without air pressure.
Then I thought a different product might work better. So I took the only thing I got from Ec that was listed in the description of the gun, pattern coat primer. Same result.
Pressure was right, although I played with it later, without getting better results. temperature was 20°C. I checked every connection and every bore of the gun. Everything seemes to be as intended.

It takes some getting used to. After the first time I used mine, I put it in storage for 3 years and thought I'd never use it again... Had a reason to use it recently though, and I'm really glad I gave it another try as I have now got the hang of it.

That said, it is messy, it will always be messy. It's fluid coming out of a 4.6mm nozzle at 60+ psi - there's no controlling the spray pattern on that. Its function is to build gelcoat thickness as quickly as possible, so it is truly rubbish if you are aiming for a nice finish on something, its really only useful for making moulds or applying in-mould coatings. 

Remember that there is no needle like a conventional spray gun, fluid will flow out of the nozzle regardless of air pressure so you have to keep it pointed up right when you're not holding the trigger, and pull the trigger before pointing it down/release after pointing it up. There also isn't much you can do about controlling the overspray, so cover up a 5m² area before you start (after she saw the lawn my wife wasn't as impressed as I was about the volume of gelcoat these things can pump out). About the only thing you can do is play around with the air pressure and the flow control knob on the back of the gun. I find about 2 turns out on the knob at around 60psi works best for me. 

Forget about using it like a conventional spray gun though, it's more of a flamethrower...

I think I got it now. The boring for the air nozzle is out of line quite a lot. When inserting the resin nozzle/cup unit, there is no way the nozzle could reach the tip of the gun. So the sealing doesn't work, and the aerodynamic doesn't work too, it seems. I unscrewed the resin nozzle, and screwed it in only a turn, with lots of teflon tape. This way, the nozzle was able to flex into it's place. After that, the gun worked as intended.
It certainly isn't  a tool for dedicated paintworks, but I was aware of that.
But before my modification, the output was so low, that the resin would have hardened inside the gun, before getting out half the cup. And the spray pattern was like "one big drop here, one huge drop there".
Overall, the alignment of the drilling seems very bad. The hole for the spring mechanism is off by about 5°, too.

Well that's very interesting... Can you take a picture of it, more for interests sake? I must admit, they don't seem like the most precision engineered pieces of equipment, but it still surprises me that they could mess up something so simple. 

Hi Okemont,

Was your cupgun one supplied by us?  If so and there is a defect in the manufacture, we can take a look at  it for you. to replace the dodgy part .


Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant

Yes, I bought it from ec. The dodgy part is the main body. And the main functional piece of it. Here is a picture on how the alignment is, when I first insert the nozzle/lid, and put the gun/lid/nozzle onto the cup. Even in this configuration the nozzle is pushed quite a bit out of place. The second picture shows how far of the spring unit is. Is this usual inaccuracy of this product? Can I hope for serious improvement after replacement?

It doesn't really look TOO different to mine, but your lid doesn't appear to seat correctly so if that due to the nozzle alignment then I guess it is causing some trouble. Although your nozzle tip looks like it still sits in the same position as mine so I'm surprised it doesn't seal or work correctly. Really your spring is pretty much the same as mine, so I don't think there's an issue there.

When i use the gun like in the bonnet video, the spray result is not like in the bonnet video. To be honest, not even usable.
My experience so far is, that this is because the nozzle can't reach it's final position, because of the misaligned nozzle/cup support. The nozzle sits crooked and about 1cm back in it's counterpart, leaving the sealing malfunctioning und therefore leaking. When proceeding as in the video, I cannot, even with great force, get it in place.
I rewatched  the video,  and at 1:29 it seems like the nozzle sits far better than mine, although not 100% at stop.
I guess a few seconds at the belt sander might solve my problem, as the cup support just needs to got down a bit.