Right Wing

Drilling, dimpling, countersinking ....

Outer wing skin

Started with skinning the wing while waiting for parts from ACS. The new angle for the aft spar/inner rib was wrong as I anticipated. The original was wrong, and a new one had to be made. Today I made a third, and drilled the holes when the skin was laid out. Hopefully this will be correct.

Right wing skeleton finished

Finished the right wing spars and ribs, riveted and bolted together ready for fitting of the skin.

Tried to spray on the Jotun Topgloss BR (Polysiloxane) with a new and much better spray gun. The result was very bad. If it is me who is terrible at spraying, or that the paint is not formulated for spraying, I don't know, probably both. It was full of pin holes or fish eyes (I really don't know the difference), looked awful even where no pinholes were seen. But I rubbed the half of the test piece with Biltema rubbing again, and it was all shiny again. Have to get some Biltema Hard Wax tomorrow and see if also that makes it all milky like the two other waxes I tried.

The 3 in 1 paint is very good. It dries in 10-15 minutes, but then it is rather soft. After 3-4 days it gets all hard and nice. J. S. Cock also has a special primer for aluminium. It is the same stuff as this 3 in one, but specially formulated to stick on very smooth surfaces, aluminium and stainless steel in particular but also glass. It is only on larger cans, not rattle cans.

I have this booklet "How to paint your own airplane" by EAA. What a total waste of paper! All it say is Acid etch, Alodine, epoxy primer and polyurethane top coat. Yes, it works and the result will be top, but the problem is that: 1- Acid etch will creep into joints and corrode your airplane from the inside. 2- disposing used Alodine is almost impossible due to hexavalent chrome. 3- Urethane is poisonous and requires a booth and a breather. 4- Epoxy primer isn't even necessary. Doing all this with all these extremely nasty chemicals is not something to do in your home. A heated garage will work, but the main point is that the only corrosion that will exist on a painted surface of aluminium is filiform corrosion, and to prevent it does not require all these stages. The corrosion that causes most problems is galvanic corrosion, and none of this will do anything to prevent it. Besides, these products are impossible to obtain locally, for me at least.

If I should go for Polyurethane, the process will be scuffing with scotchbrite, etch primer or epoxy primer, topcoat. That will last for ages without any filiform corrosion and the finish will be top. If that was to corrode, it would be due to galvanic corrosion caused by fasteners and similar. This will also require a booth, but it is somewhat doable because I can get the stuff locally. But, the equipment (booth, spray guns, breathers etc) seems like a whole lot of money and time for a one time process, that may turn out bad. Sending the airplane to some professionals may very well be a better solution.

What I (still) hope to do is use this Polysiloxane with paint and roller. Then wet sand with 1000+ grit, Biltema rubbing and wax it. It is only this waxing part that is a problem right now, maybe I can do without waxing? For primer I have four choices; Epoxy, etch primer, Vinyl (Jotun) or Polyester (JSC). Epoxy and Vinyl I know will work, etch primer and polyester I have to try first. All this I can do at home, and the end result will be like polyurethane, in some aspects even better (UV). In the cockpit I will use 3 in 1 rattle cans with a top coat of clear satin enamel, or maybe 3 in 1 spray gun with the special reducer that gives a harder satin finish instead of the matte finish.

The other choice is polish.

Priming and test

Primed the rib doublers and mechanism using this 3 in 1. The rest of the ribs will only be primed on the mating surfaces with vinyl.

I also made a test piece from some scrap 6061. The plan was to put in on my boat, but then I remembered my boat is on land this winter for a little fix up this spring. It's only a few meters from the sea, so I will put it there anyway and let it stay for some years. I just have to test how this 6061 and stainless rivets holds up in a real marine Norwegian atmosphere. So I made some holes and riveted a few rivets.

Half of the piece is primed with Jotun Vinyl primer. From left to right: [-, Duralac]  [-, -]  [primer, Duralac]  [primer, -]. The lower rivets are solid AN rivets for comparison.

I also looked at the Jotun polysiloxane test pieces. It has really cured by now and can withstand Aceton, ethanol and xylene just as good as my old epoxy primer. It is impervious to UV and really hard, similar to polyurethane. It really is high gloss as well. If I could just find a way to put it on so it looks remotely acceptable... Have to try to spray it on tomorrow using my primer gun and see how it goes, but I am afraid it is too viscous. 

Deburring ribs

Deburred all the ribs for the right outer wing.

Found a new (for me at least) paint system. It is called "3 in 1" from Power Coat. It is a modified polyester paint used in the industry for all kinds of things, mostly metals, and is supposed to be very good. It works as a primer and top coat. It can be bought as aerosol and in ordinary cans for roller or spray. Tried it on some scrap aluminium, and will see how it turns out. Polyester is I believe the same as gelcoat. The paint is 1 part, but a special catalyst can be mixed in to increase shine and hardness.

Right outer wing

Finished drilling all the holes in the right outer wing. The paddle hinge reinforcement did not have any pilot holes, so it was done the "old fashion" way.