Painting Before First Fight

Again, He said to me, "Prophecy to these bones, and say to them, 'O dry bones, hear the word of the Lord! Thus says the Lord God to these bones: "Surely I will cause breath to enter into you, and you shall live. I will put sinews on you and bring flesh upon you, cover you with skin and put breath in you; and you shall live. Then you shall know that I am the Lord."'"

Ezekiel 37:5-6

painting

I really think it is best to paint the aircraft as you go. After final fitting of all the parts and subassy's it seems much easier to paint it while it is apart. I see no reason to worry about damaging paint while making minor trim adjustments, or even adding trim tabs. One tip, as I have posted many times before, Paint the belly before you roll over the canoe. Fit up your antenna doublers and such first if you are going to install them on the belly. Once the airframe is up on the gear, you won't have much chance of damage to the belly paint. Painting on a creeper is hard work. You'll hate it. tape it to the side skin intersection, and back tape it to paint the rest of the fuse. I opted to cut in my side steps at the same time, as these could be tough to work around when shooting the fuse sides.
Takes a lot of work to paint one of these things...lots of parts!!

HTH...Chris

Tweeks after FF

I required no adjustments so painting first had no impact on after first flight (except that the plane looked great for FF and I never need to take it out of serve to paint).

plehrke said:

I required no adjustments so painting first had no impact on after first flight (except that the plane looked great for FF and I never need to take it out of serve to paint).

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I think this is the experience of most RV builders. The aircraft are so proven that if you build it correctly, your aircraft isn't likely to need any significant tweaks to make it fly properly.

That said, if you need to squeeze an aileron or something, that *could* crack the paint, so save a pint of your paint so you can respray an aileron if necessary. As for rudder trim, you can always install a trim tab later and paint the trim tab at that time. Nether of these potential touch up jobs should keep your airplane grounded for more than a couple of days...

I totally agree with all the other posts but will add one other data point.

Composite parts are subject to something called post curing. Even prepreg parts like the cowling. In fact the cowling is as prone as any other parts because it is getting significantly heated and then cooled over and over.

This post cure process stops after a while and the part is then stable.

What happens if you paint before the part is fully post cured, is the glass weave texture begins to have what is referred to as "print through". This is where the glass weave texture actually begins to show in the surface of the paint.

It doesn't seem to matter what surface filler/primer and paint products you use.

There are two ways to deal with this (actually three, just ignore it if it does not bother you much).

One, is to not paint composite parts (particularly the cowl) until after the airplane has been flying for a while. Wing tips and other fairings will get post cured by being out in the sun, and the cowl by the engine heat.

Two, is to just paint the entire airplane. After post cure has finished, you can lightly wet sand the cowl and wing tips (and any other parts you wish) and respray them with one wet finish coat to be back to a smooth shiny surface. This is not the best solution because you are spraying fresh paint on fully cured paint, so the adhesion will not be as good (the paints solvents can not soften the surface of the old paint). The other limitation to this choice is if you use a two stage paint system (base coat/clear coat) it is not practical.

Scott Chastain said:

Thanks for the input, Scott.

Yeah, I know all about the "weave factor." The good news is two-fold in that regard: 1)the cowling is all prepreg epoxy, not the polyester that Van's used for years. The post cure of polyester goes on forever and will continuously shrink over time. Epoxy has a post cure, too, but not nearly as long and it does not continue shrinking with time. The cowling was purchased in June of 2004 and has been stored in summer-like heat for more than enough time to allow for post cure to set in.


Thanks for the input, guys!

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I agree the polyester cowl was much worse, but I was talking about the prepreg cowl. They do it also because of the elevated heat from the engine, regardless of how long it has been stored.

Can a bodyshop do the post cure?

Can a bodyshop do the post cure? They bake (or at least used to) cars with lacquer paint jobs.