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Brian_s
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Hi,
I have got a Gelcoat Gun and find it a bit like using a fire hose.
I am sure it is great for covering a large area but most of my moulds are only about 50mm wide but long.
I only use GC50 at the moment.
Has anyone tried smaller nozzles? If so what size?
Brian.
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Hanaldo
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Yeh that's what they are designed to do. I find them way too much if you are doing anything smaller than a bonnet. Problem is, it isn't totally the nozzle size that is the issue, it's the combination of the nozzle size AND the air pressure required. 80psi is always going to cause a lot of overspray, and while a smaller nozzle might help a bit it won't make it any cleaner. I suggest using a HVLP gun, one that can handle acetone. Use a 2.5-3mm tip and it will work great, you just need to be careful not to let the gelcoat go off in the gun because unlike the G100 it's impossible to clean once it does.
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MarkMK
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I've found the supplied Fn6 nozzle okay with GC 50 but experimenting a bit with the pressure and flow adjuster on the gun might be worthwhile. I'm certainly going to try a smaller nozzle for products like the pattern coat primer, as when you've thinned it with acetone, as recommended, it is very thin and it's hard to always get an even coverage. The firehose analogy is certainly spot-on where that's concerned
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Brian_s
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This is a picture of one of my Moulds.  As you can see it is not very wide but it is long. I made a modification to the cup gun. I usually only spray about 100g of GC50 which is about enough to wet the cup. I used a 3D printer to make an adaptor to fit a smaller cup. It works quite well.  
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VVS
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Very clever!
Can you use the 3d printer to make a smaller nozzle for the gun? 😉
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Brian_s
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I hadn't thought of that. I will give it a try.
Thank you.
Brian.
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AdamHutchin
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I thought I would reply to this as it's a question I'd been trying to find the answer to previously. I didn't want the EC cup gun as it seems to be designed for delivering loads in much higher quantities than I was looking for, like you I wanted to do a comparatively much smaller mold. In the end I just used a normal spray gun with a 1.8mm tip and it worked really well. I would suggest though that you actually look at the gun before buying one as I went into a shop and took two of them apart. One of them would have been a nightmare to clean all the gel coat out of whereas the other is much more straight forward; still not a fun job but manageable. The other thing I found is that it's quite hard to visually gauge the thickness of a clear gel coat as you're spraying it. Even with a 1.8mm nozzle I still ended up spraying it too thickly in some places but I guess with some practice it will become easier.
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scottracing
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what make of spraygun did you go for? Would the cheaper all in one HVLP systems be of use or is it worth going the full hog and buying a decent gun and compressor setup?
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Hanaldo
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The cheaper guns often have rubber seals in them that will melt when exposed to the gelcoat/acetone. So it's better to buy a good quality one; note that doesn't necessarily mean more expensive! Best bet is to ask for something that can handle acetone at a spray paint supply store or similar. Also if you can, get a bigger tip. 2.5-3mm is ideal. Smaller will work, but it's harder to clean and you don't need to worry about orange peel from the bigger tip. Adam, I do recommend buying a gelcoat depth gauge if you're having trouble with the thickness. It can make quite a difference if your gelcoat is sensitive to thickness (which many are), so it's good to have a tool to measure it until you get the feel for it. And they are cheap cheap, so it's a no-brainer really.
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AdamHutchin
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I first of all just went for a cheapo eBay special, I wanted to make sure it would actually work before investing in a better gun. If you're looking at a "decent gun and compressor setup", I'd say always get the biggest compressor you can afford. Air tools like belt sanders etc are really useful for composite work but can use a lot of air. I've got a 100L, 3HP unit and it's big enough to spray/run air tools etc quite happily, fairly constantly. I used to have a smaller 30L one and it was largely useless. It just couldn't keep up. Hanaldo makes some good points about cleaning though, the 1.8 tip is no fun for that! Hanaldo, I do have a depth gauge, I just happened to be spraying it into a mould with lots of curvature in it. the variation in thickness just came from my inexperience of using the gun and I ended up with thicker areas in some of the tighter radii than others. I just need to practice and be less cack-handed. 
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