More Right Tiedown Work, Started Right Rear Spar

September 5, 2010

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Whoa, it’s been awhile since I actually got any work done on the airplane. I’m going to blame my exploding lawnmower (long story), business trips, and the wood floors project.

Anyway, I managed to find a good bi-metal hole saw from the aviation department at Lowe’s, so I chucked that thing up in the drill press and started in on the spacer lightening holes.

Under all that mess is a spacer with a freshly cut hole in it.

I am not really a fan of cutting those things this way, but I don’t have a fly cutter (apparently the one from Harbor Freight sucks), so this was the best I could do.

They actually turned out really nicely.

Two spacers, that go against the spar web.

Like many other builders, I taped them down before putting the tiedown bracket in place, flipping the spar over, and matchdrilling the remaining 7 holes.

After everything has been matchdrilled, I pulled it apart. Looking good so far.

Then, I skipped a couple pictures, but basically You bolt the tiedown bracket, spacers, and nutplates in place and use the nutplates to backdrill the attach holes (small ones on either side of the bigger holes). They all turned out great, except for the upper left set, which for some reason are a little crooked. It doesn’t matter what the nutplate ear orientation is, I was just annoyed they didn’t turn out perfectly aligned.

Somehow that upper left one's alignment got away from me.

Then, you have to countersink the nutplate attach holes (this side of the spacers must sit flush against the spar web).

These rivets aren't set (I still have to prime all these pieces), but I just put them in there to see how my countersinks were. (The lower left one is a little deep, but this is thick spacer, so it shouldn't be a big deal.)

I don’t have any primer, so I decided to move forward (“aft”?…ha…airplane coordinate system joke) to the rear spar. After getting out the W-707A rear spar channel (make sure to grab the correct one, there’s a left and a right) and the W-707E and W-707F doubler plates, I took the blue plastic off of everything and started getting things clamped in place.

The W-707F is laterally aligned with the outboard edge of the rear spar channel.

The W-707E gets laterally aligned by measuring; the outboard edge of the doubler plate should be 50 3/4" from the outboard edge of the rear spar channel. Easy enough.

Then, I fired up the air drill for some matchdrilling.

{air drill noises} Whose finger prints are those?

{more air drill noises} Also, I traced out the aileron pushrod hole onto the doubler plate.

After some though about how to do this, I decided to forego the step drill (Unibit) trick (I don’t have a Unibit…how’s that for a trick!) and just drill some holes and then get the dremel out.

It turns out that all the little fancy metal saw and milling tools aren’t really as easy to use as the 1/2″ sanding drum . Save yourself some time and just get the sanding drum out. Very easy to control.

Looks pretty good to me. (This crazy little torture device that looks like a saw got away from me and cause that scratch. I'll have to buff that out.)

After clecoing back to the spar turns out the thickness of my line made my initial pass a little small. (Better small than big.)

More sanding, anyone?

Much better (still needs some edge finishing).

I totally forgot. Even though I don’t have primer to finish up the tiedown bracket, I can still tap the tiedown hole.

Here's the 3/16" x 16 tap.

After having a hell of a time getting started, they turned out really nicely.

1 full turn in, 1/2 turn out. Wash. Rinse. Repeat.

I managed to get both brackets done, even though I really haven’t started on the left wing yet.

I'll need to deburr the edge, but this should work just fine.

I ended up going to 1 1/4″, even though the directions tell you to only go 1″. Some other builders had to go deeper once they actually got their eye bolts, I figured it would be easier to do now than to wait until the brackets are in the wings.

2 productive hours today.

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More Trim Tab Hinge Drilling

June 27, 2010

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After a motivating afternoon actually getting to sit in an RV-7, I got back to work on the trim tab. Here, you can see my new 3-foot-long MS20257-3 next to the old (and not perfectly aligned) 18-inch MS20257-2 from Van’s. It’s a little wider to give me some more edge distance.

New on top, old on bottom.

First thing, I got the new piece cut to length. It ended up being a little shorter than 18 inches… I made sure the elevator side had a hinge “ear” on each end.

I eye-balled the hinge pin length a little long. Van's tells you the hinge pin they ship with this kit is not long enough to bend and safety to the elevator, and that they'll ship the real one in the fuse kit (or finish kit, can't remember). I guessed it was about 2 extra inches I needed for the bends and then cut the hinge pin.

Then, I spent a good amount of time Just getting everything lined up. I am a little frustrated at this point, because the supposedly straight line of holes on the elevator is not parallel to the supposedly straight line of holes on the tab. This means that with the trailing and inboard edges of the tab aligned with the elevator, the gap between the leading edge of the tab and the elevator cutout is smaller near the root than the tip of the tab.

Inboard and trailing edges aligned perfectly.

Here's my inboard edge.

So, again, I strayed from the directions. I held the hinge in position, making sure the actual pin was directly in the middle of the gap as shown in the picture above at the root (smaller gap) edge and at the outboard (larger gap) edge. I figured as long as the pin was directly centered, I’d be okay. Then, I clamped it in place, and marked a single hole (see below) for drilling. I couldn’t pick the edge hole, because it was covered by my square.

On the drill press, ready to drill a single hole.

I repeated this for another single hole on the tab side, again, making sure the hinge pin was perfectly centered between the two surfaces.

Two holes drilled and clecoed.

At this point, it was close to being locked in place. I did notice that these hinges are somewhat flexible, so while I marked every hole for drilling, I really only drilled a few more before clecoing it in place and match-drilling the rest of the holes.

(A more technical side note…because I upped the hinge size to a MS20257-3, the hinge was too wide to fit inside the radius of the elevator and trim tab spars. When matchrilling, I had to change the order of the skin, hinge, spar to accommodate the extra length, then I went back and ripped a small (1/16″) strip off of the hinges so they would fit nicely in the radii of the spars.)

Here are my feet, ready to keep going on the hinge.

Fast forward after some drilling noises, and here are the two halves, each clecoed to their surfaces.

Ooh, looks good.

I still have a little bit to trim on the elevator skin, but I trimmed enough to allow some motion today.

You can just see the rounded (so it slides in easier) tip of the pin in this picture.

Here’s a closeup of how much extra pin I think I need to make the bend forward (along the spar flange) and then down (along the spar web) to a small safety-wire hole I have yet to drill to safety the pin in place.

Man, that thing is long. (TWSS)

After getting the pin in, I took out every other cleco on each surface so I could move it back and forth.


Tab up (or elevator down trim).


Tab down (or elevator up trim).

After dancing around for a little due to how great the tab looks on the elevator (and how well-aligned it is), I took the thing apart, ripped the 1/16″ off of each hinge half, and fired up the scotchbrite wheel to clean up all of the edges.

Look on the lower right part of the tab. That little angled cutout is so the hinge hides nicely under the tab skin.

I figured now would be a good time to finish match-drilling the tab. Let’s go find E-718 and E-717.

There they are!

Apparently I thought it would be a good idea to show you my scotchbrite wheel. That little groove is just getting to the right size so I can run the edge of a piece of aluminum down it and it perfectly rounds both sides.

I love this thing.

Back to the tab horn. The directions would have you use the clevis pin (don’t have this yet because I haven’t ordered the tab motor) to line up the two horns. How about two perfectly-fitting #30 clecos?

For balance purposes, I put one on each side.

Three of the holes are pre-punched, and two are not.

Just before match-drilling everything.

All done.

All done. (From another angle.)

I was planning on at least polishing the tab for now, so I marked off where the horn sits. I’ll prep and prime this little area under the horns, but I’ll leave the rest polished. (The bottom of the tab is going to be a good place to teach myself how to polish aluminum.)

The horn location, marked for future priming.

Whew. That was a good two hour work session today. It was like a sauna (more like a steam bath…this is the south!) in the garage today. I kept sweating on the airplane. (People say they put blood, sweat, and tears into their projects. I’ve got one covered, and will undoubtedly bleed and cry because of the project sometime in the future. Have to have something to look forward to, right?)

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