Painting: Flaps and Ailerons

Wow, this has been some trial and error learning experience. I started with small control surfaces for practice and went through the whole process from two primer cross-coats to two top coat cross-coats and a WHOLE lotta sanding in between.

Here is what I've learned from experience and consultation with Superflite:

1. Superflite Primer: Primer is mixed as follows: one part primer base, 1 part catalyst and 0.5 part flex agent. All pieces to be sprayed were placed horizontally on saw horses, so as to maximize penetration of primer into weave matrix. Also, to further enhance penetration, I thinned paint 25% with reducer on first pass to reduce paint viscosity. One half hour later I then sprayed the next pass in perpendicular fashion to previous pass, which resulted in one complete cross coat. The cross coat was allowed to dry one night and was then wet sanded next day with 320 grit sandpaper. You do not want to let dry more than 48 hours. The second cross coat was applied in same manner and sanded. I used a delivery pressure of 20 psi to the gun (static, trigger closed) and a 1.5 mm tip on the gun.

Here are pics of primer application...

2. Superflite Top Coat: This was mixed at: 3 parts topcoat to one part catalyst. This mixture was then reduced 25% to reduce viscosity. The first 3 passes were sprayed horizontally on saw horses, while the last one was sprayed vertically. Since the last one can not be sanded, I wanted to minimize potential for dust contamination. I increased delivery pressure to 20 psi at the gun when trigger open. I opted for applying this material on thicker, as lighter than primer and more flexible.

Here are action shots of topcoat application....

Finally, here are final products....

Problems encountered: included contamination onto paint surface. I found I reduced this considerably by draining my compressor of water frequently and changing out my airline dessicant/filter on regular basis. I also started using a tac rag or cheesecloth over the surface right before painting to remove dust. Prior to this I would clean surface with a fast drying methanol compound. I found spraying stuff vertically also helped tremendously and will do at a minimum on last pass of topcoat. Spraying vertically increases the risk of runs, but have had no problems with runs yet...

Orange peel of topcoat was another major problem encountered. It's called this because the paint resembles the surface of an orange. I have minimized this problem by increasing air pressure to 20 psi when trigger pulled and thinning topcoat material 25%. Not too worried about it, however, until final topcoat pass, as sanding will take care of it between passes. I prefer the lower gun pressure as it reduces overspray which equals waste and fog in the paint booth. Worried about creating explosive atmosphere in the paint booth coupled with my cheap Walmart fan as an ignition source. I will heat up garage with furnace and then turnoff during painting, spraying in a batch type manner during winter conditions.

Wicking is another problem encountered. This occurs when primer applied to virgin fabric underlain by structure. The paint gets wicked through the fabric leaving weave openings. The way to prevent this is to brush thinned U500 over these areas first.

Reusing premixed paint stored in freezer. I have regrettably done this twice and will never do again. First time was with primer and when used next day it gummed up my entire gun. I was then told topcoat material is less volatile and takes longer to catalyze so tried again with bad paint results.

"Eruptions or blackheads" on paint. I thought I had this going on at first but think what I saw was from contamination particles. This can occur when first pass not allowed to cure before second pass sprayed on. Volatiles from first pass can vent through second pass creating sharp bumps on the paint.