Wednesday, December 22, 2010

It could be worse...

Still lacking the missing rib, all I could do on the left wing was move it out of the way so I could start on the right wing. The wing is still very flimsy with the ribs being unsupported on one end and I was worried that they'd get bent while in storage, so I clecoed on the aft spar.

The inboard end of the aft spar has four holes that will eventually be riveted to the matching rib, but the rib only has the same three holes as the rest of the ribs. Two of them align with the top and bottom holes in the hinge brace on the spar; the other two get match drilled.

The wing is still light enough for me to move alone as long as I'm careful to pick it up at a balance point, but I'm still very paranoid about schlepping it around. There's 15' 3" of mayhem that can get caught up against something and cause an unfortunate accident.

Things are really getting tight in the hangar. The wing is still narrow enough that I can fit it into the gap between the sailboat and the RV-6. That won't last forever, though.

With the left wing parked off to the side, I was able to start on the right wing. The ribs get clecoed in in the same way as before.

I'm still a little paranoid over the question as to which side of the spar flange the rib gets placed. You can see that the drawing requires a degree of interpretive effort. The tie-breaker for me was that the drawing shows the holes in the rib to be visible; if the rib was placed on the other side of the flange, the holes wouldn't be visible from the angle shown.

In an odd and inexplicable case of asymmetry, the right wing is structured very differently from the left. On the right wing, seven of the ribs still have their front flange. That flange gets riveted to the spar. It's the same kind of tight fit that gave me so much grief when I was attaching rib flanges to the spar. This close-in riveting requires the use of the wedge thingy, and I was having a problem before with the mandrel of the rivet breaking off in the rivet puller. I went out and bought a new riveter in the hopes that the mandrel breaking problem was a symptom of a worn-out riveter and wouldn't reoccur with a new puller.

The good news: the very first rivet broke off cleanly. The bad news: the very first rivet broke off cleanly and the mandrel got jammed in the new rivet puller. Uh-oh!! I had visions of every single rivet of the next twenty-eight behaving this way!

The next twenty-seven rivets went fine, though. While I still don't like using the wedge thingy and it took a long time to get the rivets in, I figured it could have been worse.

Of course, I can't think "it could be worse" without thinking of this:

But it was done, and as I said, it could have been worse.


Well, I went to check on the next step and saw this note that I swear hadn't been there before:

I had used LP4-3 rivets. On all of them. They'd have to all be drilled out and replaced with LP4-4s.

Now you're probably asking yourself, "How in the world could he have missed that?? Big, bold font and everything. What more could they do? How much more obvious could it be???"

Well, here's how it is. I had Goetta for breakfast again today. It's a little known historical fact (by which I mean that I just made it up) that Hitler had Goetta for breakfast on the morning of the day that he opened an Eastern front by attacking Russia, and we all know how that worked out for him.

Not buying that? Well, I don't blame you. What really happened is that I looked at the right wing as basically the same as the left wing and only glanced at the plans enough to figure out which style of rib went where. It was careless, and I paid for it by having to drill out all of those rivets and replace them with the correct size.

The head of the rivet drills off easily, but because the rivet is too short for the hole, it's tough to get the rest of the rivet out of the hole. It's all swelled up in there, you see. It's like a monkey trap.

monkey trap



1. (literally, probably folk-lore) A cage containing a banana with a hole large enough for a
monkey's hand to fit in, but not large enough for a monkey's fist (clutching a banana) to come out.
Used to "catch" monkeys that lack the intellect to let go of the banana and run away.

2. (figuratively) A clever trap of any sort, that owes its success to the ineptitude or gullibility of the victim.

    Pay particular attention to definition #2.

    Anyway, This tool helps. What I did was take a $5 Harbor Freight center punch and grind down the pin. It works very well for pushing out the remainder of the rivet in cases like this.

    Unfortunately I ran out of time or I would have proceeded to rivet the aft spar into place.

    It looks like a wing, anyway.

    1 comment:

    Anonymous said...

    I posted this "gotcha" on the forum but wanted to give you a heads up. Also I did a post about installing the light kit while building the wing. Not sure if you are doing lights. Just got the flaperons finished and everything fits great.

    FOR THE WINGTIP: Figure 2 on page 17-06 shows the correct angles to bend the tabs. Another forum post had a great tip about making little paper triangles to help - that worked great.
    There is one shortcoming though, in Figure 2 regarding the bend of the leftmost tab (the 116 degree one.)

    Notice how on the right side of that figure, you are shown to "Bend along line tangent to notches for this section." Notice that the 116 degree tab is similarly an odd-shaped tab in that it is not symmetrical like the other tabs. But, there are no special notes about the line to take when bending it.

    Well, do NOT bend it along a line drawn like that other guidance! Instead, "pretend" it is a symmetrical tab just like the one next to it (the 82 degree one) and bend along that theoretical line. The results will be much better.

    Good luck!
    Bill H. N412BR reserved

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