priming

[dspender]

Just beginning my 10 empennage kit. In Van's construction manual it mentions all aluminum bar, angle, and tube used in the RVs, especially the main spar bars, must be primed or anodized to assure corrosion resistance. Aside from prime or not, what are some examples of parts that are aluminum bar, angle, and tube. I could guess but would like to hear some part names so I have an idea what is meant. Also I have wondered in Alclad parts, when holes are drilled or drilled to size, the inside part of the hole is not Alclad metal. Why is that not primed?

[YellowJacket RV9]

In general, pre-fabbed / pre-punched parts like ribs, empennage spars, skins, and any other "shiny" aluminum pieces are alclad. The main wing spars come anodized, and only need to be spot primed in areas where they are countersunk or otherwise compromised.

Pieces that are not alclad are things like thicker aluminum channel that is used to fabricate brackets, the metal stock used for the wing tie-down bracket (at least it my -9), etc. As you build, you will find that some things such as brackets you fabricate from larger pieces of supplied metal stock. These are non-aclad usually. I'm not building a 10 so don't have too many examples, but you can tell because it has a duller finish. Even easier, pieces that are alclad come covered in that annoying protective blue vinyl.

As to the inside of holes drilled in alclad parts, I don't have a great answer other than seeing as the hole will be filled with a rivet, there probably is not much exposure to the elements. I am priming my plane as I live in a salt-air environment, so haven't worried about it.

Chris

[aerhed]

Some examples are: The longerons (where straight sides meet curved top skins). The horizontal stab attach bars. Elevator stop. On small stuff like the attach bars I'll 400 sand them after drilling and toss them in a ziplok with a splash of Alodine. Keeps the air out and the Alodine in contact with the aluminum. Turns a nice gold like anodizing. Rinse. Prime, if obsessive.