n00bs Gonna Build a Carden

[gareth.ky]

I made it out to the field for the Oklahoma IMAC. Thanks to everyone who had a look at the airplane on Sunday. Everyone had kind things to say and Jim and I came to a conclusion on what to do about the canister tunnel and the DA-85 reversion spray. More on that later.

I finished up the last wing on Saturday. Right now all the surfaces are plain Yellow. The designs will be put on with with the windex/floating method as I get a chance. Its not critical that they be done to fly the airplane. I would really like to fly it this coming weekend so I can get some stick time in before the Huckfest!

So I took Monday off to get started on the painting. This is the step that I was most afraid of. I figured I could handle the rest of it but I have no clue about doing an automotive paint job. So I read DSP Dave's Base Coat/Clear Coat thread. Going in I was still pretty worried that it wouldn't go smoothly.

First all fiberglass parts got a good sanding with 400 grit. This isn't particularly rough paper, it just takes the 'shine' off the parts. If you see some shiny spots then you have more sanding to do there. Then I did the BVM Pinhole filler that DSP Dave recommends. This stuff looks, smells, feels and behaves like car wax. Wax On, wait for it to dry and then Wax Off.

I haven't had a problem with pinholes anywhere but the wheel pants. They look like they were made with a different resin because they are a different color. I had to prep one with Bondo because it had a fissure where the two halves were joined. Both required some shaping with 220 grit paper. The other parts are cut from a different cloth (bad pun intended). Pinholes are tiny, few and far between. The wheel pants have some craters the BVM filler just wont fill. Excellent quality glass work.

Once the holes were filled it's time to meet the Primer coat team. I'm using the same primer that Walt uses, Nason Ful-Fil 421-08 by Dupont. This is their 'low cost' primer. My local paint shop, B&H Supply, doesn't stock the PPG product line that DSP Dave uses so its Dupont for this job. The can says to mix it 1:1 with '441-62' which the folks at B&H tell me is nothing but Lacquer thinner.

Safety First. This primer emits VOCs, Volatile Organic Compounds, which can affect your nervous system or cause cancer and stuff like that. I'm not playing. All the cans are clearly marked "FOR INDUSTRIAL USE ONLY by professional, trained painters. Not for sale or use by the general public". Don't play, be safe. At a minimum work somewhere with positive air flow, in a mask rated for Organic Compounds and wear gloves! I tried out the paint suit thing but my spray booth get's pretty good airflow so no paint was getting on me. After an hour in the suit in 95 degree heat I was soaked in sweat.

Before painting all parts were sprayed down with "Surface Klean A-3990S", a degreaser agent and wiped dry with paper towels. Just before each part was spayed I wiped it down with a tac rag to remove any dust and paint overspray from the last part.

The booth I'm painting in is a big cube I made from PVC pipe covered in plastic. Two holes in the top of the booth allow air to enter and pass through air filters. The fan from my shop extracts air through a filter that stops the overspray from leaving the booth. the kids in the neighborhood think I'm re-enacting a scene from Close Encounters of the Third Kind! It looks just like a hazmat decontamination chamber.

Note; the garage door was open whenever I was spraying, I had to close it because of the wind.

The compressor is a 5 gal Husky from Home Depot and the spray gun is the Porter Cable detailed paint gun from Amazon.com. Pretty cheap setup and the compressor can keep up with the gun for this kind of work. Its very loud.

[gareth.ky]

Not all is smooth sailing and calm seas.

For the first coat I made a number of mistakes. First of all, I didn't mount the parts on stands. I just used the barrel and my hands to hold them up. that was a big mistake. Next I didn't have a hook to put the spray gun on while I move things around. Rookie mistakes.

The really big problem was getting the spray to behave. For the first coat it was coming out like cotton candy or spider webs. Fluffy dried paint everywhere. I tried adjusting the pressure and the spray pattern and got it sort of flowing but not really. Not really knowing if this was normal I sprayed away. the results were not good and I had to sand everything with 400 grit again.

Coat #2 went a bit better. I thinned the primer out some more. I mixed it in a separate container and stirred it well. This time I was able to get wet paint on the parts if I kept the spray pattern tight and the gun about 6" from the surface.

Third coat went about the same. The results are not great. This pic shows some of the problem.

Most of it will just brush off, its not stuck to the finish at all. The finish itself isn't smooth. Even after sanding I can see some areas that are not perfectly flat.

So now I'm left to ask questions:

What was I doing wrong?
What should I do now? Sand and forget about it? Sand and add another coat of primer?

Your feedback is greatly appreciated.

[eagle1]

on all my paints that I mix I try to get it to the viscosity of chocolate milk, I use about 20 to 40 pounds of air( I use an airbrush to paint with) you might be blowing the paint dry with high air flow or your paint is a little thick, I have not used dupont.
what is your air pressure? a pic of the gun would help.thinner may be too hot for the paint
looks like it would do dry wall pretty good

[Simpleton]

I'd say you didn't thin it enough, or use a thinner for hot weather. Just looks like dry overspray, you might turn the air down on the gun to help some as well.

ETA, just about the same conclusion the previous poster came up with :-)

[gareth.ky]

Thanks guys!

Here is the Gun. Its this model that i got through Amazon.com. Its got adjustments for air pressure, spray pattern and paint volume. I was having problems with the vent in the cup cap clogging and choking off paint flow so I couldn't get it to spray consistently.

More thinner seemed to improve things. I tried varying the pressure from about 50 to 30 psi. That's measured with the trigger depressed at the compressor. I think I ended up on the high side of that range.

They make a high temperature lacquer thinner? Its pretty hot and humid around here these days.

I need smaller mixing containers. Its hard to get a precise mix of 4-8 oz in a 1 Quart sized container. I think I was at 1 part paint to 1.2 parts thinner for the last coat.

Sanding of the parts went pretty well but they will need another coat as the fiberglass is now showing in places.

[Simpleton]

Yeah, ask your paint guy, but they make different thinners for different temperature applications. A hot weather thinner won't flash off as fast, and a cold weather thinner will flash quicker so the paint doesn't take so long to dry. I wouldn't sweat what you have down, just sand it good and try for an even coat of primer on top of what you have.

[gareth.ky]

I'm beginning to think my paint guy is taking me for a ride.

[Spdstr280Z]

That's way dry, primer is drying in the air before it hits the parts. Spec sheet says mix 1:1, spray at 35 - 40 psi at the gun. I have always used a regulator at the gun, but it shouldn't make that much difference with your set up. I don't know the regulator on your compressor, but I have never seen one you wanted to set while having air flow. Set it for the pressure you need without having the trigger pulled. It should show the correct pressure, say 35 lbs, with nothing happening, no trigger pulled, etc. I'm wondering if you are setting the pressure too high due to doing it with the trigger pulled, causing it to spray dry.... Get some cardboard or an old car body part and work with it till is sprays correctly, supposed to go on wet.

On mixing, the paint supply place should sell mixing cups with ratios marked on them, makes it easy. Otherwise, take a paint stick and mark off equal parts with a ruler, say this mixes 1:1, so make a line maybe two inches up from the bottom of the paint stick, then make another line at half that, 1 inch. Put this stick in the mixing cup, pour the primer to the first line then the thinner to the second, voila ! Make sure you are doing this in a paint can, or something that has straight sides, tapered sides will screw up the measurement.

Good luck !

Jason

[mark786]

Gareth,
I also was new to painting. I also bought the Porter Cable Detail gun that you have.
Mine also turned out dry. I was lucky enough to be using the paint booth of a paint shop customer of mine so some of the guys gave me pointers and even took the gun away from me a couple of times.
I was used to spray cans that will run. When spraying auto paint with a good gun it takes a lot of paint and it needs to go on wet. That gun will take little air and lots of paint. Much thicker than you would think. You have to make it look wet.
These detail guns don't put out much paint. At one point when doing the clear, the painter took my gun away and went and got his full scale gun. They put that stuff on very thick.
I'm no painter but I think everyone else's recommendations were good as I also think part of the problem is that the paint may be drying before it hits the parts. I left some dry spots without sanding as well as I should have and the paint did not cover so we had to touch up a few spots. Be sure to sand out all those dry spots.
Mark

[gareth.ky]

Primer Round #2

I tried very carefully to mix it exactly 1:1. I'd say chocolate milk is a fair description. I also turned down the air pressure to 25-30 psi. With the trigger squeezed it nearly drops off to zero.

Did a coat on everything and it was a bit wetter. Still not really flowing or anything like that. This time though there wasn't any fluffy stuff. Some rough bumps did appear on the parts though.

So I took my time and sanded down the top of the cowl. Looking really closely at it and some parts are smooth and some parts look kind of like skin. Little valleys and cracks running through the mostly flat surface. So this doesn't look good and I'm pretty frustrated so I decide to go for broke.

I mixed up a batch of paint that was more like 1:3 primer to thinner. That went on wet, even smooth in some places. the bumps were tiny and easy to sand down. I don't know what sort of effect that has on the paint. It does weird stuff as it dries, you can see light outlines in it. Its probably different temperatures in the surface making the thinner evaporate at different rates.

How smooth is smooth? How flat does this primer layer have to be?

[gareth.ky]

Just sprayed the cowl top with the AutoAir base coat sealer. I figured the best way to find out if flat truly is flat is to experiment.

Spraying the auto air is 100% easier than spraying the primer. You can spray it right from the bottle and that what I did and it worked out fine. With the pressure cranked up to 50psi. It took maybe 1 1/2 oz of paint to cover that part with 3 coats. I think a 4oz bottle wont quite cover everything. The local dealer is out at the moment so I have ordered some from Dixie Art.

But I can see I'm gonna have fun doing the color. The stuff flows and its much more forgiving than that primer!

[eagle1]

it only matters after your final primer sand, I use to use K&B paints, the primer would go on soo think it looked like an "Orange Peel" sand down the peel intil it is smooth, no peaks and valleys, after applying the first coat of paint I sand with 600 grit wet sand just enough to take the gloss of the paint, if you are werry about using sand paper you can use automotive polishing compound to get rid of the orange peel effect, when you are satisfied spray your clearcoat, clear coating I would have to ask someone else as I have not had the chance to shoot clearcoat from a gun only from a can

[gareth.ky]

Shots of the evenings work:

[gareth.ky]

This information was most helpful. Apparently the Auto Air base will bind to fiberglass, Lexan and Carbon fiber just find without a primer. So all this primer nonsense has been somewhat wasted time.

The primer did help me fill all the pinholes and fix all the problems with the wheel pants. Better prep would have made it unnecessary. I'll sand the parts till they are smooth, if I sand through to the fiberglass its not a problem. On with the base coat tomorrow.

[gareth.ky]

Got all parts but the canopy painted with the White Auto Air base coat. There is a lot of upside to these paints, non toxic, available in small quantities, cheap, cleanup with water and easy to spray. I'm drying the paint with my covering heat gun. That way turn around time between coats in just a couple of minutes. A single 4oz bottle nearly covered the all of the parts. Colors are going to take fewer coats and less paint.

The first two coats are very light coats. I don't know if you have ever seen the back of a ceramic glazed sink or tub but that what the first coat looks like. Here what it looks like after the first coat:

The third coat is a "medium" filler coat to achieve full coverage. Don't touch the parts until you know they are dry. The paint will go from shiny to dull and hazy when dry. It's subtle but can be seen under florescent light.

The major downside of this paint system for us is that often we want to color match the parts we are painting to the covering. You can't get AutoAir color matched, you have to do it yourself by hand. I'm taking the approach of buying a few colors close to the color I want and mixing them. I start in small drop sized quantities mixed with my finger on some white card. Once I get an idea of the ratio I mix up a larger batch and try to err on the light side of the final color. Then i can tweak it by adding more of the darker color as needed.

I'm trying to match Monokote Yellow using Auto air Lemon Yellow and Sun Gold Yellow. A mix of about 3:1 seemed to work out nicely. I shot the wheel pants as a test. I think its a little light but I wont know until I can see it in the daylight tomorrow:

It took just 2 coats to achieve coverage over the white base coat so less paint is required for color coats than the base coat.