Latex House Paint for Experimental Airplanes

This is the presentation that I presented at Airventure 2013, Oshkosh, WI.  I'm posting it here for those that could not make it to the forum.  I hope you find it useful.

My technique for finishing with latex paint is very simple, but does require a little elbow grease and takes a little longer than others, but I think the results are well worth it.  Have a look.

 

This presentation will start with a little history about latex house paint on experimental aircraft and my own experiences with other paints.  Then it will go on to discuss what techniques I use for applying and finishing with latex.  It will also discuss the tools that I have found to be useful.  And finally, a few words about care of the finish.
The first question that you need to ask when contemplating a latex paint job is whether it's appropriate for your airplane.  For high end, expensive, glass paneled, $75,000 and up airplanes, you probably will take it to the paint shop and write a check with lots of zeros on it.  But for simpler kits and plans built aircraft costing a few thousand dollars, a $5000 paint job is out of the question.  I hope to show you that you can get a very nice finish for just a few hundred dollars, and no one will believe it's latex.
Builders have been finishing their experimental airplanes with latex house paint for quite a few years now.  A quick internet search will reveal a wealth of information on the topic.  One of my favorite web sites on latex paint is the Fly Baby site. Others have tested latex outside on test panels with very good results.  And, there are UV tests that show how well latex performs.

The Cheapaircraft_Covering user group on Yahoo.com is a great source for information also.

My experience with painting airplanes started with my Briegleb BG-12 sailplane.  I refinished the wooden fuselage with PPG automotive paint.  The product was very expensive and the fumes were quite toxic.  I made a mistake in the application of the white color by not using a hardener.  This caused the second coat of paint to lift the first coat resulting in an alligator skin texture.  Surprisingly I was able to sand out most of the texture leaving an acceptably smooth and very glossy finish.  This made me think that you could probably apply the paint with a roller if you were willing to sand it smooth!

 

I also finished the fabric covered control surfaces of a Blanik L-13 using the Polyfiber system.  These are great products with a proven record.  But like the automotive paint, they are toxic and expensive.  Polytone leaves a flat finish which may be appropriate for your application, but I prefer a little shine.
My first venture into latex came when I recovered my Kolb fuselage.  I used Polytack to glue on the fabric but then switched to latex for the finish.  I applied 3 coats of thinned latex with a foam roller (each color).  It was very inexpensive and required no paint booth.  The finish was a little glossy but I could not get rid of the "orange peel" texture created by the roller.
I hit upon real success when finishing my Pietenpol Air Camper.  I used Behr high gloss latex over Glidden primer.  The primer was brushed on, and the color was sprayed on.  Then the finish was wet sanded and polished.  The result was a nice shine and the surface is smooth as glass.
I finished my Titan Tornado with the same technique.  This time I used Sherwin Williams high gloss latex.  The paint was applied to fabric, fiberglass, and aluminum, with great results on all materials.
Traditional MEK based products are highly toxic.  Additionally, this process requires a lot of different, expensive products to complete the application. And, if you have to get them shipped the hazardous materials fees can be painful.
This is a good motto for life!  My shop is attached to the kitchen, so any fumes would put me in the dog house in a hurry.  Even when I had a separate shop I would have to remove my clothes after I painted with auto paint, before I entered the house, and then head for the shower.
Latex house paint is more eco-friendly, has little smell, is available in many finishes and unlimited colors, and it's a bargain.

Here is the sequence of steps that I used in finishing the Air Camper.  I attached the fabric and the tapes using Ekobond.

The fabric was given 3 coats of Glidden primer, thinned about 30% with water, applied with a foam paint brush.  The primer was lightly sanded with 320 grit paper (dry).  I added a little more primer around the edges of the tapes to try to smooth these areas.

Latex has great UV protection.  Early experimenters used black primer thinking it would give the best UV protection, but studies have shown that white is actually better.  The bottom line is that any color will perform quite well.  You may want to get your primer tinted to match your finish color.

 

 

I tried different rollers, foam brushes, expensive synthetic brushes, and natural brushes, but nothing could compare with a sprayed finish.  Three coats of each color were sprayed.  The paint was thinned about 30% with windshield washer fluid.  I read about using windshield washer fluid on the internet, and it did seem to work better than just water, but I have no empirical evidence.  The final coat was allowed to dry for a day or two, then it was lightly wet sanded with 1000 grit wrapped around a sponge.  The process was repeated with 1500 grit.  Then the surface was polished using 3M polishing compound applied with an electric buffer.
A few tips on masking.  I found that cheap plastic drop cloths work great for masking and for hanging on the shop walls.  Don't use them on the floor, they are slippery.  Use canvas drop cloth on the floor.  Also, use a good quality painters masking tape.  Do not use electrical tape as it will lift the finish.
Let me walk you through the entire process using this Micro Mong rudder.  The steel rudder frame has been primed and painted with Rustoleum.  I use non-certified 1.8 oz cloth.
 

By far my favorite glue is Stewart Systems Ekobond.  It's very easy to use and has no fumes.  There are some great videos on Youtube that show how to use this product.  I will never use MEK glues again.

The Polyfiber covering manual is a must if you are covering with fabric.  It details the how to cover including how to rib stitch.

The rudder is covered and the fabric has been shrunk with an iron.
Then the ribs are stitched and the reinforcing tapes area applied.
The first coat of primer, thinned 25-30% with water is applied with a cheap form brush.  Brush east-west for the first coat, and north-south for the next.  Keep alternating the direction on each additional coat.  Apply the paint heavy enough to get complete coverage, but don't flood the surface.
Use 320 or 400 grit paper, dry, to sand between coats as soon as the paint is dry.  I carried the rudder outside into the sun and it dried in 30 minutes.  Sand to smooth the surface, remove dust specks and brush marks.
The next coat is brushed perpendicular to the first.  I continued for a total of six coats, sanding after each had dried.  The primer is inexpensive, dries fast, and fills the weave.
Off to the paint store.  My favorite paint so far is Sherwin Williams Inter/Exterior Hi-Gloss Latex Enamel (green cans)
Lots of colors to choose from. (I picked lime green!!!)
Now we are ready to paint.  I thin the color coats with washer fluid since I will be spraying.
Little mixing cup.  (can also be used for coffee)
Add washer fluid (25-30%).  You may have to experiment a little based on your paint, paint gun, and painting technique, but I have found the exact mixing amount to be very flexible.
I don't have a paint booth so I hang cheap plastic drop cloths on the walls and as a room divider, and use canvas on the floors.  We will be wet sanding later and water on top of plastic drop cloths would be a bad combination for the floor.
Here's the rudder ready to paint.
I tried several spray guns.  A cheap Harbor Freight gun and a cheap Craftsman gun would not spray the latex unless it was thinned to almost water.  However, A cheap Harbor Freight touch up gun worked very well for small areas.  The real star of the show was a $50 Lowes Kobalt latex spray gun.  The nozzle must be different on this gun.  It sprays the latex extremely well.  A word of caution on cleaning the guns.  You need to have water available to run through the gun IMMEDIATELY after you finish.  Then run for the sink and disassembly the gun and rinse everything.
The latest star of the paint gun department is this Harbor Freight HVLP gun, on sale from $11.99 to $15.99 depending on coupons.  It is easy to clean and sprays latex just great.
I have a large compressor but it is not needed.
The first coat is sprayed using a back and forth motion.  Just like brushing the primer you spray the next coat perpendicular to the first.
I have no sink in my basement so I use a bucket full of water to clean the gun.  Remove the can and dump any remaining paint back into the mixing cup.  Rinse the can.  Submerge and slosh the gun.  Then fill the can with clean water and spray the water through the gun for a few seconds.  Finally dry the gun with air.
I use cardboard for testing the spray pattern before I start spraying each coat, and to spray water at for cleaning the gun.
Since I don't have the best paint shop I end up with dust specks in the dried paint.  This will happen even in the best shops, but not as much.
I sand after each color coat has dried for a day.  This is done using 600 grit wet paper.  The idea is to just remove the imperfections in the finish.
Here you can see where the color coat has been sanded away at the edges of the pinked tapes and where the rib stitching is.  No big deal on the first coat, but be very careful on the remaining coats.  Keep the sandpaper away from these areas.
Three coats of color have been applied and we are done painting. 

At this point we have a very respectable looking finish and you might consider stopping here.  That's fine of course, but with just a little more work you can really make it smooth and glossy.

For the Airventure forum I only finish sanded and polished one side of the rudder so that people could see the difference.  Both sides looked good, but the sanded and polished side looked better.

Now it's time to smooth the finish.  We will start with 1000 grit to smooth the surface of imperfections, the 1200 grit to remove the scratches from the 1000 grit, and finally 1500 grit to remove the 1200 grit marks.
Wrap the paper around a small sponge, keep it wet, and lightly sand back and forth.  The water will help keep the paper clean.  Stay away from edges.
After the sanding is done you will have a smooth but very dull finish.  Don't worry.  The polishing will bring the shine back.
More Harbor Freight stuff.  This is the buffer that I have been using the 10 years ($35) and It's still going strong.  A wool or form bonnet attaches with hook and loop.  Either bonnet will work fine, but I like the foam one a little more.  Use very light pressure and again, be careful around edges.  I use 3M polishes (Ease-it or Finesse-it).  Just use a polish that is made to remove 1500 grit sanding marks.  I have never tried a random orbit polisher, but my guess is that it might be more forgiving than the rotary one that I use.
Done polishing.  Apply a good coat of car wax.
Nice shine and smooth as glass!  No one will believe that it's latex paint.  I even showed it the the folks at Sherwin Williams and they didn't believe it was their paint.
Care for your finish.  I flew the Kolb for 3 years and the finish held up well, including places where I spilled fuel on it.  The Titan finish is about 2 years old now and still looks fantastic.   I have found that car wax does a nice job of cleaning and protecting the finish.  The paint has performed great on fabric, aluminum, and fiberglass.

I hope you have found this information helpful.  Please share any experiences, good or bad that you have using latex paint for airplane finishing.  We all can benefit from each others knowledge.

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