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JetFlex WR help

tims88

Well Known Member
I've been practicing with JetFlex WR on some scrap and my old toolbox practice kits before starting to spray parts that will go into my plane. So far I haven't been able to get it as smooth as I would like so I wanted to see if anyone has been able to get a smoother finish and if anyone has any tips. The picture below is about as good as I've done so far...yeah there's a lot of dust in it, I'm thinking about building a paint booth for the real parts.

IMG_20201017_213625771.jpg

This was done with the paint reduced about 50%. I was only intending to reduce it about 25% (based on the paint's instructions) but I was using a very small batch of paint for this and I wasn't very precise with my gallon jug of distilled water. Although, other times when the paint was reduced 25% turned out pretty similar.

Under the JetFlex is a PPG Omni epoxy primer.

I'm using a Devilbiss FLG4 with a 1.3mm tip (read a blog somewhere that said a Sherwin Williams rep told them 1.3 would be fine) and the pressure set to about 23psi with the trigger pulled per the spray gun's instructions. About 50% overlap while spraying.

My guess is that I just don't know how to properly spray a medium wet coat, which is what the JetFlex WR instructions recommend, and I haven't found any good explanations online on how to do it either. The picture below is my best guess of what a medium wet coat looks like right after spraying it. Any dryer than that and the orange peel is worse or it feels like sand paper after it dries.

IMG_20201017_150135292_HDR.jpg
 
Try a couple light fog coats to get color, then a final wet coat. I paint it like I do stewart paint it does pretty good.Mine is textured as well but not as much so. I wanted some texture. I think I got up to 15% water.
 
I bought some disposable measuring cups on Amazon. I pour a small amount of distilled water in the cup and then add the the paint. I'm only mixing about one part of water to 5 parts of paint. I would think that you are thinning the paint too much.

I was having some problem with the surface smoothness too. It turned out that I had the air pressure up too high. Take a look at the application directions it tells you the pressure range for different types of guns.
 
Try a couple light fog coats to get color, then a final wet coat. I paint it like I do stewart paint it does pretty good.Mine is textured as well but not as much so. I wanted some texture. I think I got up to 15% water.

Sounds like it's worth a try. Thanks.

I'm only mixing about one part of water to 5 parts of paint. I would think that you are thinning the paint too much.

The data sheet says that up to 25% reduction is for spraying a smooth coat, and I've read other's blogs that said sometimes even more than that was necessary but I'm happy to give it a try with less water. I bought a gallon so I have plenty to experiment and practice with...it's just scrap parts that I'm running out of.

I was having some problem with the surface smoothness too. It turned out that I had the air pressure up too high. Take a look at the application directions it tells you the pressure range for different types of guns.

Unfortunately I haven't found the directions very helpful for spray gun settings. Here's what they say for an HVLP gun and spraying a smooth coat:

HVLP – Smooth Coat
Gun Binks Mach 1
Atomizing air 40-65 psi (2.75-4.50 bar)
Fluid pressure 6-10 psi (0.41-0.69 bar)
Cap/tip 95P/97
DI water reduction 10-25%

My gun doesn't use fluid pressure, and 40-65 psi atomizing air seems way to high for HVLP unless that's pressure at the gun without the trigger pulled. Mine sits right at 40 without the trigger pulled to get it around 23 when I pull the trigger. Either way, I think I should practice a little more with the paint so I'll try experimenting with the pressure when I do. Thanks for the suggestions!
 
Tim,

Try turning it down to 10 when you pull the trigger. I have a pressure regulator and a gauge right on the gun. I bought the cheapo regulator from HF for about $5. Those gauges are terrible though and I've just broken another one so I can't tell you the pressure I'm using at the moment. I just got my replacement from Amazon though so I'll be ready to spray soon.

If the pressure is too high the air blows the paint around that is sitting on the surface and screws up the natural leveling of the paint. Also make sure that the gun is atomizing properly and not spitting large drops.

I'm still learning too even though I have about half of my interior sprayed.
 
It takes a while to become a good sprayer, probably years of practice with a good teacher, to be able to achieve a finish straight from the gun like you see on the prize winning aircraft. The alternative is to put on some extra paint and rub/polish it. Takes a while but is achievable in a few weeks or months, rather than years.
 
Tim,

I just finished a bit of an education with the WR version of JetFlex myself. It was a bit of a learning curve, but in the end I was pleased....it just took a while to get there. I had to paint the inside of my fuse twice. Lots of fun sanding down the inside to try again!

I'm no expert by any means, but I'd take a look at your pressure and your tip size. Although 1.3 may be OK, I used a 1.4 and it still took a bit of finesse. Also, I ended up right at 20 psi; any thing more made for a dry spray or I had to slow down significantly.

Ultimately, I reduced 25%, 20 psi, 1.4 tip, DeVilbiss GTI-620 gun. Next time I'll probably try the 1.5 tip on some scrap and check the results.
 
I am no pro so take this for what it is worth.
Have you had any runs yet. I found finesse was learning both ends of the scale and learning how to stay in between. Looks to me like you need more paint and maybe less air. Since you are running out of practice parts you might want to try cardboard or paper to get the gun work down. Put it on so thick that you have a few runs and then back down from that just a little.
 
Try a 1.8 tip

Tim-

I was having a tough time getting a nice spray finish with JetFlex WR until I purchased a 1.8 tip for my HVLP spray gun.

The 1.8 tip made all the difference in the world. I was able to get nice smooth results after switching to the larger 1.8 tip and did not need to thin with distilled water more than the recommended amount in the application data sheets.

After the initial learning curve, and using a tooth brush to clean the tip after painting each panel (prevents a splatter), I would lay down two thin coats spaced about 15 minutes apart. I truly like the JetFlex I used on my interior ... it is very durable after a couple of weeks of drying time.

Happy building,
 
It takes a while to become a good sprayer, probably years of practice with a good teacher, to be able to achieve a finish straight from the gun like you see on the prize winning aircraft.
That's a good point. I was hoping all the time I spent spraying epoxy primer on the emp and wing parts would help but I was more concerned with keeping the primer light rather than going for a smooth finish. If I can't get it any smoother then maybe I'll just have to change my thinking and decide that the texture is intentional because sanding the entire interior is more work than I want to do :)

Put it on so thick that you have a few runs and then back down from that just a little.

I don't think I've had any runs on anything yet. Spraying almost to the point of running seemed a little excessive for the 'medium wet' coat that the instructions say give the best results. But like I said in my first post, I don't really know what a medium wet coat is so I'll give that a try and see what happens. Maybe I haven't been spraying it on heavy enough.

Well, it sounds like I've got several suggestions to try out. Lower the pressure a little, maybe reduce the paint less, and larger tips in the spray gun. My Devilbiss gun also came with a 1.5 and a 1.8 tip so I can give those a try, which should help me spray it on a little heavier.

Thanks a lot for all of the replies! I really appreciate the suggestions and hearing about other's experiences with this paint.
 
Ultimately, I reduced 25%, 20 psi, 1.4 tip, DeVilbiss GTI-620 gun. Next time I'll probably try the 1.5 tip on some scrap and check the results.

John-G; said:
I was having a tough time getting a nice spray finish with JetFlex WR until I purchased a 1.8 tip for my HVLP spray gun.

I would lay down two thin coats spaced about 15 minutes apart.

It's definitely sounding like maybe a larger tip size will make a difference, and possibly a second coat. When I've tried to spray thin coats I just ended up with a rough sandpaper-like finish. Maybe I was trying to spray it too thin though or had other issues with my technique, but if I could get smooth results with thin coats that would be my preference.
 
I did some more painting yesterday. I used a 1.8mm tip, reduced the paint 25%, tried various pressure settings, adjusted the fluid amount up and down, and tried spraying heavier and lighter coats. Lower pressure didn't seem to make much of a difference but I only went down to about 20psi, maybe I'll try down to 10psi next time. The smoothest results are on a couple sections where I decided to turn the pressure way up to about 60psi at the gun without the trigger pulled which was around 40psi with the trigger pulled. That resulted in very little, if any, orange peel at all. Unfortunately that amount of pressure is going to blow small parts around waste a lot of paint with overspray, so I'm not convinced that I want to start painting things with that much pressure yet. Here's how smooth that turned out:

IMG_20201022_120938707.jpg

And here's one that I tried to do with 23psi and a little more fluid for 2 coats. There's still some orange peel in the finish:

IMG_20201022_121011455.jpg

I do have one part that I sprayed with my normal pressure (23psi) and opened the fluid control a little more and it has some small spots on it that look really smooth but other spots have some orange peel, so a lot of the orange peel might be related to my technique.

I think next time I'm going to try reducing the paint only 10% to see how that changes things.
 
Tim,

Ok I sprayed some this past weekend. For background I have a 1.7mm tip HVLP gun. I only had a small batch that I had premixed like I said at 20% dilution. I did some searching around for the best pressure like you are doing. 10 PSI with the trigger pulled did seem a little low. I think I ended up at 40 PSI before and around 20 PSI after the trigger was pulled. This does seem to be higher than the what is spec'd in the Jetflex WR datasheet for fluid pressure. The air pressure they spec I think is 40 - 65 PSI. I was tending to want to try a little bit higher pressure.
 
Thanks for the update Ray. Just thinking out loud here...I don't have any way to adjust the fluid pressure on my spray gun so I wonder how settings might need to be different on my gun compared to what is in the instructions.

Anyway, I'll give the 20% reduction at 20psi one more try. Right now I'm waiting for things to warm up a little bit around here since the instructions recommend spraying when it is above 50 degrees.

I think I'm also going to give higher pressure a try again to see if I can reproduce the results I was pretty happy with before. If the instructions do actually mean air pressure at the nozzle when they say 40 - 65 psi atomizing air, then I have been too low for their smooth coat settings and have actually been in the texture coat range.
 
Thanks for the update Ray. Just thinking out loud here...I don't have any way to adjust the fluid pressure on my spray gun so I wonder how settings might need to be different on my gun compared to what is in the instructions.

Anyway, I'll give the 20% reduction at 20psi one more try. Right now I'm waiting for things to warm up a little bit around here since the instructions recommend spraying when it is above 50 degrees.

I think I'm also going to give higher pressure a try again to see if I can reproduce the results I was pretty happy with before. If the instructions do actually mean air pressure at the nozzle when they say 40 - 65 psi atomizing air, then I have been too low for their smooth coat settings and have actually been in the texture coat range.

I'm no pro but here is my $0.02:

First off, ignore static (non-spraying) pressure; it will always be higher. You only need to worry about the pressure during spraying. Also the numbers given are for a different gun (the Binks Mach 1). They don't apply to the FLG-4.

Second, if you have the #3 air cap (that's what mine came with) you're looking to have about 23psi on the inlet (spraying!). If it's the #1 cap you'll be at around 40psi. Devilbiss does sell a cap pressure gauge if you want to get the cap pressure right but you'll spend a bit over $100 to get it.

Third, none of the numbers are absolutes. They're all starting points. The goal is to get a good result. HVLP guns use a LOT of air (hence the "high volume" in the name).

Fourth, the lack of a fluid control doesn't really matter. I've always run the gun wide open on the ones that do.

Fifth, make sure you keep your cup vent clear. You'll have a hard time getting a good spray if it's clogged. Clean it out each time!

Edit: just looked at the docs on the gun again and you're looking for 15-23psi (spraying) to get the 6-10psi fluid pressure the paint calls for. Also be sure to adjust your trigger pull to put down enough paint to match your speed to get the thickness required.
 
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