21-06: Priming Flap Components

Priming the flap components took a fair amount of time - the nose ribs are especially fiddly. The parts were not dimpled prior to priming - i like to do this afterward; the paint holds up well to the dimpling process, and having no dimples makes the parts **a lot** easier to clean etc.

Each component was cleaned with EkoClean and then etched - these days i am using Alumiprep as it is much easier to obtain (and cheaper) than the EkoEtch from Stewart Systems. The parts are rinsed and left to dry under a heat lamp, then i give one last clean with a soft clean rag and isopropyl alcohol - this removes any small bits of crap, and also picks up any stray water left over. I do not blow them off with compressed air, lest i spray them with tool oil from the air system.

The nose ribs, flap bracket and the doublers which attach to the nose ribs were done in the first batch.

For small parts, i do the preparation in a tub on the bench next to the sink.

A few imperfections from stray paint on the mesh, but the objective is to protect them from corrosion, so it doesn't bother me too much.

The second batch was the flap ribs themselves (the ribs aft of the spar). I had some paint left over, so i quickly cleaned and etched the spars as well. The spars wouldn't fit in the 'spray booth' with the ribs, so i covered everything up in the back room and just sprayed them on sawhorses. The Stewart Systems paint has such a tiny amount of overspray - any that there is just falls as dust. 

There are 2 wings under here, and a tailcone, and tail feathers behind.

Flap ribs after cleaning, etching and rinsing. They are drying here on the sink before being put in the spray booth under a heat lamp.

After priming...

Both flap spars were just sprayed on saw horses like this.

The last batch was the skins - both flap top and bottom skins (4 skins) as well as the nose skins. The skins were cleaned, etched, rinsed and dried. They were then masked at the trailing edge where the trailing edge wedge will be adhered to, and finally a last clean with iso.

This skin has been cleaned, etched and rinsed.

The water forms a 'sheet' on the surface when it is clean. There should be no areas where the water wants to bead up. 

Skins in the spray booth ready for spraying. They fit with barely a couple of mm to spare.

This is what the skins look like after the preparation is complete. No areas of sheen left, and a fairly uniform matte finish.

I always test the gun before spraying. In this case i used a fair bit of flow and a large fan (since the skins were large)

After priming - the surface isn't perfectly smooth. I didn't wet the primer out very much (not looking for it to be too heavy). I just want to protect the skins from corrosion.

An area at the trailing edge was left sans primer.

Next up is some dimpling action!