Stewart Systems

And I thought building was hard...

I haven't felt this low since bombing my first calc test in college. After 3 weeks of continuous evening work I have everything primed minus the wing panels and fuse. The primer is fairly easy to shoot relative to the topcoat. The trick is laying down a nice light tack coat before subsequent heavier coats. Too heavy too soon = fisheyes and runs. I thin to 10%+- 1%.

Its the topcoat that is giving me trouble. Lesson #1: Dont get it on your skin! I got some paint on the back of my glove then accidentally scratched an itch on my neck. It felt like a moderate case of poison ivy for 8 days.


Lesson #2
Try all colors on a spare part first! I practiced with my primary base color smoke gray on scrap parts until I had decent results then decided to shoot lemon yellow on my elevators. Of course the finish looked great, but the color was terrible! Sand, prime, try again with new color scheme.

Lesson #3
Dont spray it on too thick! Round 2 on the elevators and I decide to lay the last coat on thick. They looked great, everything flowed out nicely with no runs, it was my best work. The next day I went out and found this:

Its a mild case of solvent pop or blushing. Basically, the solvent couldnt find its way out of the paint before the top skinned over. What youre left with is a cloudy soft matte finish that must be stripped off.

Lesson #4
Dont spray when the dewpoint temp is within 10 degrees of OAT or when humidity is above 65%. The paint simply wont flash between coats causing runs, sags, pigment anomalies, etc. I screwed up my right flaps twice before I figured this out.

Lesson #5
Luck. Today I wasted 200 grams of topcoat because my $60 gram scale decided to jump from 39 grams of catalyst to 70 grams in half a second. I didnt know how much I mixed in so I scrapped the batch. Then, after remixing and shooting 3 nice coats, my gun did something I've never seen before. It started shooting strings and blobs of paint on the canopy skirt. Im thinking the pot life was reduced due to the elevated material temps - ill be sure to store the paint in my AC'd house from now on. More sanding tomorrow.

Anyway, Im still learning, but on the rare occasion when this paint does lay down correctly, it looks quite nice.

I labored through the entire paint process of my -8 using Stewart systems. As you said, when it works right it looks fantastic but it is way too hard and too dependent on atmospheric conditions to shoot anywhere outside a controlled booth in my opinion. I spent more time stripping paint off than painting it on.

One trick which helped a little was to to get to the 3rd coat and let it dry completely then start the process again. This helped ensure the full color was showing and the primer wasn't bleeding through.

Also, I kept my water in the garage fridge which helped with pot life significantly.

Devil's in the details...and technique...

Rob - I've been shooting Stewart Systems, too, and have had pretty good results so far, at least for an uber newbie... I still have a lot to learn, but here's what I've found so far.

First, the equipment - (I decided to use the same HVLP gun SS uses because their docs tell you exactly what pressure and fluid flow settings to use.) I'm using a DeVilbus "Finish-line 3" gun with a 1.3mm tip, a CamAIR QC3 filter/dehydrator, and pressure regulators on both the output of the filter (set at 60psi) and a regulator on the gun handle (set at 23 psi) plus another disposable filter at gun handle - pre regulator. This paint system needs LOTS of air volume - the compressor needs to be capable of delivering at least 14 cubic feet per minute constantly with the gun set at 23 psi. I also built a 10x20 paint booth using a 42" shop fan to pull air through.

My first project was a fiberglass pick-up truck bed truck topper for practice. Lesson 1 - need more practice! I think my equipment was right on, but the technique was off. The finish came out shiny but not super-smooth. I was worried about runs so I was holding the gun too far from the surface. Wound up doing 6 coats to cover Juneau White over smoke grey primer. Lesson 2 - Use a lighter colored primer when painting dark colors...duh! Need to keep the gun close (about 6 -7 inches from the surface) and move the gun quickly and steadily.

The next project - RV12 seat backs and roll bar. MUCH better. SS says to let the finish "follow the gun" - don't lay down that 4th and final coat so thick that it looks good as soon as you shoot it. So far it's looked kinda dull but it flows out in 10 to 15 minutes and develops a shine. Again, technique...

I plan to practice on some aluminum roof flashing using the colors I want to paint the 12 in to be sure they're true to the samples and to learn more about taping and pin striping. (SS will send you pints so you don't have to blow $80 on a quart just to find out you don't like). I'm also going to experiment with their clear/metallic top coat - wish me luck!!

Your website indicates you might be using a turbine system. Never used one, but I understand the turbine heats up the air that delivers the paint. This paint apparently does not like heat. Might be part of the inconsistency problems? Dunno...

They have a DVD regarding metal prep and paint - "DVD 6". Jason at the SS booth at OSH spent a good hour with me - picked up a lot of good advice. Give him a call. He's always been super helpful. This paint's too expensive to turn into sandpaper dust!!

Anybody else got any hints?

ram

The Citation 4 stage turbine that I am using is probably just barely adequate. The problem is that I dont have 240v service to my garage, which limits my compressor size to the 7-10 cfm range. I think the high material temps and humidity have caused most failures so far. Cooling the water should really help extend pot life and reduce the amount of heat transferred into the paint by the hot compressed air. Ill try this on the canopy skirt tonight or tomorrow depending on the weather.

My 2 cents on Stewart Systems Paint

I just finished painting my RV-8 mostly Federal Yellow and Bahama Blue.
I would consider most of the plane to be a 1 foot paint job, and some areas are 3 ft.

Overall I am quite happy with the result.

I am a first timer, so my expectations were low, and economically driven.

This is what I learned:

1: Make sure your primer coat is an even tone (I used white primer) otherwise, variations will show through. I found that 3 coats at 1.25 turns (on the gun) 10% by weight dilution on the Finishline 3 worked pretty well.

2: As others have said, control the humidity. I spent the money on a dehumidifier for the paint booth, and brought the level down to 50% before I shot anything. I tried at different humidity levels and it was not good.

3: I put 2 small (25 gal) compressors in parallel through a single regulator and I had just enough air to shoot and keep the gun a 23 PSI.

3: It HAS to be at least 23 PSI ...if not, you will get a rough dry finish.

4: If you use a Finishline 3 gun, and follow Stewarts instructions with respect to timing between coats and gun setting, things turn out quite well.

4a: Use a Finishline 3 gun.

5: I found that moving the gun at about 1ft/second 7-8 inches from the surface with about a 2-3 inch spacing worked quite well. Copy the motion from the video...its like learning to dance. BTW It is possible to paint one coat on an RV8 fuselage in 9 minutes and 30 seconds.

6: If you have to respray due to colour variation or lack of depth, I top sanded with 220 lightly then oversprayed with 3 coats instead of 4 coats using 3/4, 7/8 and 1-1/8 turns on the flow control on the gun.

7: Fellow builders have seen my plane up close, and they ordered Stewart systems for their plane as well, figuring that if I can end up with a decent paint job, they can for sure!


Chris

Great news! I shot the canopy skirt in 53% humidity and had MUCH better results. Then today I shot the flaps and gear fairings in 37% humidity and had even better results. The paint tacks up much faster and in the end flows out much flatter. I would almost have a hard time causing runs and sags in these conditions. Cooling the water also helped with the pot life. Feeling much better now!

Good to hear!

Glad you got some positive reinforcement with your painting, Rob. It do feel good when it works!

I had to re-prep some parts that, while they had a good shine, too much 'citrus texture' . After talking to Dan at SS, we agreed I was waiting too long and letting the paint dry too much between coats (88 degree day). Shot it all again on Monday and it looked great. Felt so good about my new found skills I shot a 'tack coat/wet coat' of their Clear Mica Metallic Top Coat on Tuesday. Added A LOT of metallic sparkles and depth of color.

Wife approved or 'her' paint job...

Shot it all again on Monday and it looked great. Felt so good about my new found skills I shot a 'tack coat/wet coat' of their Clear Mica Metallic Top Coat on Tuesday. Added A LOT of metallic sparkles and depth of color.

Click to expand...

Did you prep the base in any way before applying the clear? I was considering a clear coat because my design would probably benefit from a clear coat sealer. I am basically transposing the plans onto all surfaces - the plane will be a 3d set of plans. I painted about 800 rivet heads black last night...i dont think this has been done before!

No prep prior to clear

It seemed counter intuitive to scuff the paint with scotchbrite prior to applying a clear coat.

So no prep. But I did apply the clear coat within the "time allowed" based on the documentation in SS application instructions - "Depending on temperatures (70? minimum) masking may be done in 24 hours and a second trim color may be applied for up to 10 days without sanding. After 10 days, lightly sand before applying trim color or additional paint."

Wouldn't hurt to check with Dan or Jason at SS to get their opinion.

Clear with mica

I also am painting with Stewart Systems and have had good results considering my limited painting experiance. Jason was very helpful with all of my dumb question which I'm sure he gets on a daily basis. The only problem that I have had was when I sprayed the clear with mica sample the metalic is very slight and is only visable when in sunlight which is what I wanted. When I ordered a quart to spray my elevators it had more mica in it so the change in base color was dramatic. My base color is true blue and ended up being a lite silver blue. Kind of a bummer as the true blue parts turned out great.
I reordered more blue and clear with mica. The sample that I shot was 1% mica and the quart was 3% there is a huge difference in the amount of mica.
What percent mica is in your clear and did it change you base color much.
I also scotch brited all parts before I sprayed the clear as the paint seems to be so hard and had a very shiny finish I thought that it would make for a better surface for the clear to bond to. It really doesn't add much time to the job considering you should be cleaning the surface prior to spraying the clear. The only thing that I'm glad about is that I spayed the elevators and not the rudder that I checkered if I had sprayed the rudder first my paint paint scheme would have changed to a silver blue verse true blue as re doing the checkers would be way to much work. Still very happy with stewart systems.
Regards Paul

Frustrated with my results

No fault of the paint or SS process. My first attempt with bahamas blue worked great and developed the shine just like Dan says after about10-20 min. I rushed yesterday in my portable shade port,with my other sky blue color, it started to drizzle ( so fla), warm temp, poor lighting, and more runs than I've ever had before. I will be building or using a better booth next time.

Has anyone sanded out runs and re-shot? Any recommendation?

I know I can get 1foot results, I'm hating doing it twice because 5-10foot just isn't good enough.