Painting the Airplane: Page 1

After much deliberation about what type of paint to use, I finally settled on Loehle Aero Coatings. The extreme shine, durability, flexibility, and ease of application convinced me it was the way to go. I have seen their demo P-40 painted with their paint system, and it looks great. It's 15 years old! The paint quote I received totaled just under $900 for everything. Compared to the cost of some other systems, I feel this price isn't too bad. ( I actually only used 3 gallons on the whole plane; 1 gal primer, 2 gal color)

The first step in painting is prepping the surface. Instead of traditional alodine conversion coating the surface, I chose PreKote from Aircraft Spruce (Spruce PN: 09-00826). The technical literature states that it is non-toxic, biodegradable, easy to apply, and works just as well as chromates. This appears to be a win-win solution.

After the paint job was complete, I weighed everything that was left from my painting supplies (boxes, packing materials, cans, ect). Since I knew from the shipping label how heavy the boxes were, I simply subtracted the final weight from the initial weight, and came up with 42 lbs. Since I don't know how much weight was lost due to overspray, solvent evaporation, or sanding, I'll just call the final paint job around 30-35 lbs.

Here are a few notes from my painting experience...

I bought the Loehle painting manual and video. The video was a waste of $25! I was very disappointed. It basically shows Mike Loehle painting a test panel....very little about setting up the gun and all the little technical details that you really need. The manual, however, is great. It has specifics and you'll definitely want it.

I used a Harbor Freight HVLP gun, Part #43430, and it took my some experimenting to get things right. One thing I did is to turn up the input pressure MUCH higher than the gun directions said (they said 20 psi). I used 90 psi into the gun, then regulated it down with the built-in regulator to 45 psi. Any lower and the paint would "spatter" out. I also drilled the tip out to 1/64" to pass a bit more paint. This helped a bunch with the thick paint.

The Loehle paint is pretty thick stuff. I followed all the mixing directions, but in retrospect the paint needed to be thinned a bit more. If not, it goes on really nice, then about --5 minutes later, it starts to sag, then run. About the time you start crying, it sets up with nice runs in it :-( I painted a bit dry and let it flow out to smooth. This didn't work 100% and that's why my surface texture is a bit "orange pealed". I think thinning more and spraying less would have worked a bit better, so try this.

One thing Mike Loehle said is that HVLP isn't the way to go with this type of thick paint. A certain amount of air pressure is required to "break up the paint molecules" (his words). My experience confirms this, and the HVLP gun worked fine just turned up to a higher pressure.

The paint would tack up in about 5 minutes, be mostly dry in about 20 minutes, and I was handling it after an hour. The paint is VERY tough, and SUPER glossy! :-) It just looks wonderful (without runs...)! I clear-coated everything after I was done and that was nice too. I definitely recommend that.

I'm sure better results would come from a nicer HVLP gun, although I don't really know which gun to use. I guess that you'd want to spend about $200-$300 for a nice one, but if you know someone to borrow from that'd be better. That's the reason I bought the HF gun....I don't know anyone and the HF gun was on sale for $30.

Loehle sells something called a "nip file". Get one of those....they are great for "nipping" a run without sanding the whole area. It's basically a section of vixen file glued to a wood backing board. Works great!

With any paint, the surface prep is important. The Loehle primer worked great, and when the surface was pre-treated with Pre-Kote the results were great. I love that Pre-Kote! The primer also sanded really easy, so you can get a perfectly smooth surface if you put in the time sanding. I sanded, but didn't get too picky. I wanted to finish, and only sanded a couple of passes. I spent about 3 weeks painting, but like everything, the hours add up quick when you don't really know what you're doing...

After all's said and done, I still really like the Loehle system. It's easy to use compared to Polytone and Aerothane, economical, shines fabulous, and generally gives top value for this amateur builder (me!).

NOTE:  photos link to full size image

The PreKote was transferred from the gallon jug to a spray bottle. I used heavy rubber gloves and goggles while scrubbing the PreKote wetted surface with a maroon scotchbrite pad.
Scrubbing loosens up lots of surface oxidation, which turns the PreKote lather dark gray. The surface is saturated and scrubbed, allowed to sit for 2 minutes, then scrubbed again immediately for the second application.
The lather dripped in several places. After treating and scrubbing twice, the lather is rinsed away and the water sheets off the aluminum cleanly.
The parts are then left to dry and will be primed in a few days. The tech literature says that the surface can be touched up with a PreKote moistened cloth if it gets dirty prior to painting.
Treating the wings took about 2 hours. There's a lot of scrubbing to be done here, but it turns out really nice.
Last up was the fuselage. Total PreKote used to do the entire plane was about 2/3 gal. At $40 per gallon, that's pretty reasonable.
Next up is making the paint booth, I am using a car canopy to house my booth. The canopy that I had didn't include sides or ends, so I bought some inexpensive tarps at Harbor Freight to close it up. It would have been much easier had sides been included, but tarps and LOTS of clamps will also work.
I ran some polypropylene rope along the sides to prevent the wind from bowing in the sides. It stiffens it up considerably.
Lastly, the entire inside is lined with plastic sheeting and all seams taped down with duct tape. This creates an inner bag, hopefully sealed from dust and insects.
With the prep work complete and the paint booth assembled, the taping and masking began.
I had left the bottom skin off for as long as possible, but now it was time to button things up. After double checking everything inside, I clecoed the skin back into place.
Access to the bottom is pretty good with the nose down like this. The fuselage is very nose-heavy without the tail, so it stays put too. I'll do the same thing in the paint booth to paint the bottom, although painting the bottom of the forward fuselage will still be challenging.
Proof that airplane building is interesting, a neighborhood cat wandered in to have a look. I think he wants to go fly!
The paint arrived, and it's time to paint! The Loehle paint process requires a base coat of white primer. I started with the control surfaces to get a feel for spraying this paint. This stuff is really thick! It's like shooting latex. There was definitely a learning curve.
Unfortunately, I got runs in everything :-( Not too bad, but they needed to be sanded out. The good news is that Loehle primer sands very nicely. It's just very time consuming and laborious.


Painting the Airplane:
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Updated: 16 Sep 06