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Mucho Leading Edge Work

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Warning: This is a long post with lots of pictures. I’ll try to keep commentary to a minimum. (Oh, and I just took the pups for a run outside, and it was cold, so please excuse the typos…my fingers are still a little frozen.)

Well, today was a day off for me (New Year’s Day observed) where everyone else had to go to work, so I got a ton of work (on the airplane!) done. It was really cold last night (and today on our run…brrr), so as soon as I was ready to get out into the garage to work, I turned on my portable heater and turned right back around to go inside.

Hmm. I guess I can devinyl some leading edge skins while the garage heats up and I keep warm with coffee.

Here's the right leading edge.

Right leading edge upside down.

More right leading edge

Left leading edge, upside down. (That hole is the stall warning vane access panel. More about that later.)

Left leading edge again. (That small strip of devinyled leading edge on the left side of the picture is the stall warning vane rib attachment. Again...more later.)

That was about an hour of devinyling, so when I took my leading edge skins outside, it was not too bad temperature-wise. Thanks portable heater!

Note: I am working a little out of order. Technically, I should be prepping the main ribs for priming, then riveting those ribs to the spars, then setting the wing stand up, and then adding the leading edge. Since I’m waiting on some scotchbrite wheels for the rib prep part, I’m jumping ahead to the leading edge stuff.

Here, I’ve got all of the right leading edge ribs (except the inboard, undrilled rib) clecoed into the leading edge skin. Many people have trouble here, but if you follow the directions (which I kind of did), you start from the front end of the rib, top and bottom, and then you are okay from there. The biggest trick I found was to push the rib forward (towards the nose) as you are maneuvering the rib into place. I have long arms, so I could see the holes line up from the back, then reach around and stick a cleco in.

I like my modular leading edge/tank cradle. (No comments about my split triangular piece of MDF, please.)

Anyway, then I put the leading edge on the spar, and stood back in amazement. (Amazement at the size of the assembly, and that all the holes freakin’ line up! I know this is a prepunched kit, but still, everything just always lines up. Thank you Vans!)

Nice.

The dogs must have sensed my excitement…they came out to see what was happening.

Ginger: "Shouldn't you have prepped and primed all of these ribs first?"

Jack (tentatively): "Whoa, that leading edge looks good, but I'm going to stay here...the concrete is cold on my paws."

After playing for a few minutes, they went back inside (it turns out they came out to ask me to turn on the gas fireplace….okay, okay, I will).

On to the left leading edge.

This is an awesome sight. It finally looks like I'm building an airplane in here.

After setting both leading edges on the spar (and securing them from beneath with some #30 clecos through the main spar), I noticed that the spar really needs to be straight and level to proceed, even though it’s not fully assembled yet.

So, even though I know I’m going to take this all down soon, I went ahead and leveled the spar using the trusty (and calibrate-able) iPhone app from Stanley.

I couldn't decide whether negative or positive 0.0 was better, so I left it with negative. My wing stand mechanism sure made this easy. Every 1/4 turn of my adjustment nuts was about 0.1° change. Easy to dial in.

Then, I needed to address the spar bowing in the middle from the weight of all the components. (Once the skins are on the wings, they provide that support, but until they are, there is no (what I’ll call) lateral rigidity.

A variation on a (wing stand) theme. a threaded rod between two 2"x4" blocks.

I thought about this a long time ago, and I didn't know if it would work. It worked great. I know it's not permanent right now, but still, very elegant setup, if I do say so myself.

Oh yeah, I snagged this picture to elaborate on the reason for the larger angle off the outboard rib from the other day. See how the skin overlaps the edge of the rib and spar? I won’t have to notch my support angle to accommodate the skin now.

With the larger angle, there is plenty of room for the skin overhangs.

Okay, time to remove the spar sag.

I tied a piece of string between the top edge of two clecos (actually, it didn’t need a knot…the cleco clamped the string enough).

It's about 1-hole-diameter distance above the hole.

Same on the other side.

Before removing the sag, you can see how much bow there is (look at the row of primed countersinks).

There's about a 1/2-3/4" of bow in the middle of the spar.

A few cranks of my adjustable homemade jack, and the middle of the spar shows the same distance with the string. This was equally as easy to dial in.

Nice and level. (Ooh, that "flush" rivet on that nutplate isn't so flush. I might need a rivet shaver...)

Then, with everything level, I clecoed the leading edge skins to the spar.

Leading edge skins now clecoed to the spar.

Now I can move on to the inboard leading edge rib. It comes undrilled, so first thing, I kind of held it in place and made little marks where the holes were going to go.

You can see my very faint marks.

Then, back to the workbench for fluting (between the hole locations) and flange bending (to 90°).

I had to pretty aggressively flute in some places. Some of these ribs are better than others.

Okay now I need the…what is it?

W-423 Joint Plate.

Okay where is it. I’m sure there are two of them, one for each wing…

[searching shop storage …hmmm…and the airplane room upstairs…hmm…]

Grrr. Where did they go?

Upon closer inspection of the plans…

Oh.

That was easy.

I marked my half inch line and then pondered how I was going to fit this round (straight) peg into the square (rounded) hole.

This goes in there.

[Many loud, frustrated grunting noises…]

Ahh, there we go.

Then, after careful measuring, checking, drilling, remeasuring, and rechecking, I had the right joint plate and inboard rib drilled.

That was annoying. There was no good way to clamp everything, so everytime I drilled a hole, the rib shifted on the other side.

This one turned out pretty good. 11/16″ all around. I repeated that exercise on the left wing.

I don't have the perscribed 11/16" flange that I am supposed to on the left wing for the tank nutplates because everything moved around a little.

It’s only 1/16″ short in some places. I’m assuming I can make it work with 10/16″, but if I can’t, I’ll just redrill a new joint plate.

Anyway, I was staring at the opening for the stall warning vane, so I got curious and fished out the (separately packed…not really part of the original wing kit) stall warning components. They have this doubler that fits in this hole, with a couple locator tabs (in case you are modifying an existing leading edge that was not prepunched with this access hole). Since mine already has the hole, I snipped off the tabs.

These directions are crazy complicated, but they ended up being mainly for retrofit into an existing wing. For new construction, it's pretty straightforward.

I definitely need the access plate doubler and cover no matter what, but I did give some thought to whether I am going to install the stall warning vane.

I am planning on using the Dynon AOA vane, which will give me good stall warning (I believe it is calibrated during some demonstrated stalls for the highest AOA seen during stall for any flap configuration). For awhile, I kept thinking that I won’t need the Van’s vane (and I was a little miffed that they cut a big hole in my leading edge!), but then the CFI in me woke up and thought of a few things.

Every once in awhile during a rotation or flare, I might get a little chirp of the stall warning. Everyone does, and it can’t hurt to have a small reminder, separate and therefore redundant from the Dynon Air Data Computers (ADCs…wait, I think dynon calls them ADAHRS…or air data, attitude and heading reference system) during slow speed maneuvering. The Dynon is based on pressure differential (between the front and the angled top of the pitot probe), and the other is based on direction of relative wind (the vane just lifts up and compresses a microswitch when the relative wind pushes up on it).

I’m going to go ahead and install all of the provisions for both. It will be pretty easy to get everything installed, and just leave the little vane out if I don’t want it in the end, but I have to fill all the rivet holes anyway, might as well not rule out any future decision changes.

I’ll probably install both; you can’t be too aware of low speeds, and frankly, it will probably help resale to have the more traditional stall warning.

Anyway, I drilled the doubler plate to the leading edge.

Then, I found the leading edge vane support rib. They come as a pair of two; one for the RV-9, and one for the RV-7,8. It was obviously while holding it up to one of the leading edge ribs that the one with the sticker on it is the correct one.

So I wouldn’t forget, I tossed the other one in my scrap pile.

The one on the right is the one for the RV-7 (and -8).

Whew. Good day. I’ve made good progress in the last few days. Tomorrow, back to work, but hopefully I can keep this up.

Oh, and for the record, I hardly had enough 3/32″ (silver) clecos to do both leading edges at the same time. I just ordered 100 more, but I am going to need way more that that to keep working on both wings at the same time. This might be a good time to work on one wing at a time…or break down and order the 500 or so that Vans suggests.

3.5 hours.

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3 Responses to Mucho Leading Edge Work

  1. Bob Vosburgh says:

    Andrew,

    Happy New Year! I read all of your posts and it keeps me motivated. Unfortunately, my speaking schedule has been such that I’m not even doing 10 hours per month. Planning to change that this year. Very good post today, and you are clearly moving ahead confidently… good stuff!! BV

  2. Andrew says:

    Hey Bob.

    Thanks. Unfortunately, I’m back at work now, so I don’t know that I’ll be able to keep up my 10 hours per week rate. Besides, if you speed up and I slow down, you’ll pass me.

    Good luck on your project, and keep in touch.

  3. MOM says:

    I think all those things sticking out of the wings look a little wierd, and might affect the aerodynamics. What do you think?

    And what was that about the stall warnings?

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