Saturday, October 17, 2009


On any topic where there is a meaningful amount of room for opinions, you will eventually run into evangelism. For example, most people agree that 2 + 2 = 4, and anyone having a different belief is simply ignored. There simply isn't a lot of wiggle room in whether you believe that simple equation to be true or not. Subjects of any importance whatsoever are seldom (rarely?) as binary as the true or false proposition of mathematics, though. On any more complex subject, the strength of personal opinions will fall roughly into one of these categories: uncertain and don't care, uncertain and open to suggestion, certain but willing to tolerate other opinions, and so certain that no other opinion can or will be entertained. That final stage is what I define as evangelism.

There are three demographics that are well known for the high degree of evangelism in their ranks: the religious folk, the political junkies, and pilots. Get any group of pilots together (and by 'group' I mean two or more) and get them talking about flying (which is easy since that's all they will want to talk about anyway) and you will soon see that at least one of them is evangelical on at least one topic. Some of the more common are high wing vs. low wing, straight-in pattern entry vs. 45 degree entry on downwind, whether or not pilots that check in with a new controller by saying "with you" should be thrown into a pit filled with 1000's of rabidly hungry Chihuahuas, nose wheel vs. taildragger, and Lycoming vs. Continental engines. When it comes to people building airplanes, one of those evangelical topics is the question of whether or not to use primer.

There are two questions, really. The first is how much (if any) to prime the interior parts of the airplane and if so, what primer to use. On the prime-every-surface side are people that live in a corrosive environment, typically those on the coastal regions where there's a lot of salt in the air. The why-bother crowd are folks that live in dry, arid regions. Me? Well, I live on the coast of a corn field. It's not dry, but it's not salty either. That puts me in the group that generally think it's enough to prime parts that have had their alclad coating removed. We've already seen a part like that here at Schmetterling:

The inside part of those assemblies have had the alclad layer sanded off on the sides to smooth them out. I'll want to prime it.

Having decided that, the second question came up: prime them with what? Naturally, there are a dozen answers to that. Two-part epoxy and hours of preparation is at one extreme of difficulty, a spray can of self-etching primer from Napa Auto Parts after a quick wipe-off with some soapy water is at the other. The Napa spray can being on the easy side, in case you didn't figure that out on your own.

Here's what I decided on:

Anything else is overkill. Most of the 40+ year old Cessnas and Pipers you see at any midwest airport are not heavily primed and they're still going strong. In forty years, I'll be 88. Even with an LSA, I doubt that I'm still going to be flying or in the least bit concerned about the state of this airplane.

In addition to buying a can of primer, I also made a trip to Harbor Freight to pick up another mover's blanket. I'm going to be working on a part with all of the blue protective vinyl removed and I don't want to set it on an unprotected surface, especially one with so many protruding screw heads that could put a deep scratch into the vulnerable aluminum. Cost of the blanket? $4.99. Final tally at the Harbor Freight cash register? $42.

Cashier: "Did you find everything you were looking for?"

Me: "Yes, plus another $37 worth, thank you very much."

That happens every single time I go there.

After my morning errands, I picked up Wingman Ted, who is mid-way through building an RV-10 and his Co-pilot Wayne at the airport. Wayne is also going to be building an RV-10. They were looking for somewhere to fly and decided to come visit the Schmetterling Aviation shop. After a nice visit and lunch at BW3 (where I got to see the only good part of the O$U - Purdue game), I dropped them back at Bolton and headed back to the shop.

Today's job was to start drilling the holes in the spar cap I worked on yesterday. And again, there was a little head scratching. Basically what it came down to is whether the instructions that said MATCH-DRILL #30 THESE HOLES meant just the holes I have circled in red or if it included the blue holes too:

It's as if I'm learning the nuances of a new dialect. I understand the words, but their true meaning sometimes still eludes me. In this case, it was a simple matter to look ahead in the plans a few pages and definitively determine that I was to drill both red and blue.

The directions say that you should drill and cleco every fourth hole. That went well enough after the first hole. What happened on the first hole? Well, the bit drilled through the metal and then kept on going, right through the new blanket. The bit pulled a bunch of blanket material back up through the hole. Oops! After that I started putting a small plank under the part as I drilled it so the bit would have someplace less irritating to come to rest. The every-fourth-hole method results in a nice zig-zag pattern:

The next step is do the same on the other side. I can't do that as I am out of clecos. I could shuffle around the handful that I have, but the shop floor will be closed tonight anyway for spouse date night. It'll wait until tomorrow, unless the weather is nice for flying. My RV-6 misses me.

I read ahead a little bit and found that once the other side is drilled, it all gets taken apart for deburring and general clean-up. After that the directions say to "Match-drill the rear spar flange holes."

To which I said, "Huh? Wouldn't I have just done that?" After an embarrassingly long time thinking about it, I realized that no, no I hadn't. I had drilled the web holes. It's another example of that new dialect I'm learning. The 'web' is the wide part of the spar, the 'flanges' (there are two, actually) are the thinner, bent over parts. The sides, if you will.

I'm on hold now until Co-pilot Rick brings over some tools. He will be a welcome addition to the shop; my current assistant Hogarth really isn't all that into it:


Hugo said...

Nice to see Brave Sir Hogarth opted for the safety glasses. I think his lack of an opposable thumb may be a "slight" hindrance to using the cleco pliers effectively.

DaveG said...

Hugo -

You're right, he's really not much help after all. Maybe the look that I took to be disinterest was instead a look of shame for his very low standing in the tool expertise food chain. We're just not far enough along yet - he's going to be great for dimpling skins with those wonderful fangs of his.

Brent Humphreys said...

I have two extra V Stab rear spars extra. One screwed up in shipping, the other by me. The third is successfully installed.

Have fun.

Torsten said...

I had to smile a lot while reading this section. I just worked on the hinges and the rear VS spar over the weekend and I scratched my had at exactly the same places, asking myself exactly the questions you had spelled out.
I think I should save myself some misery and read your comments on a section BEFORE I am working on it next time :-)

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