The Restoration of N2120E

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Re: The Restoration of N2120E

Post by joea » Sun Feb 26, 2012 17:06

Nice work and glad to see you have the time to get back at it!

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Re: The Restoration of N2120E

Post by kyleb » Mon Mar 26, 2012 23:22

Nathan (or anyone else whose been there, done that):

On your fuel tanks, did the supplied plywood tank supports work? On mine (Only one aux tank for me, thanks!), the welds on the tank made me relocate the second rib about 1/2" outboard, which necessitated a new tank support.

I'm still trying to figure out how to transfer some of the screw holes from the 2nd rib through the tank skin. If you have any suggestions for the ones that are hard to access (because they are in a pinched spot between the tank wall and the rib), I'd love to hear 'em.

Thanks,

Kyle
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Re: The Restoration of N2120E

Post by MikeB » Tue Mar 27, 2012 09:08

Kyle,
The plywood doesn't seem to serve any purpose (in my humble opinion) other than kind of stablizing things. Unsure what the real purpose is but seeing it was in the kit I put it in. It seems like (been awhile) there was a 1/4 gap or so between the bottom of the tank and the plywood and in my case it was also necessary to move the second rib outboard a bit.

Regarding the holes: I "think" I marked the holes through the ribs from the bottom. Would a 'hole finder' like used on homebuilt aluminum construction also work?. I used one to locate and drill the holes for my upper farings.

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Re: The Restoration of N2120E

Post by kyleb » Tue Mar 27, 2012 13:14

Mike,

I agree with your sentiment regarding the plywood. Like you, I'll include it because my IA would appreciate me following the STC.

Regarding drilling the hard-to-reach holes, a hole finder might work (I've never been pleased with my results using one), but I don't have one that has a #44 pilot. What I'm planning to do is backdrill using a 12" bit.

The other thing I'm doing that is a little different is I'm gonna "tack" the plywood and the outboard edges of the tank to the ribs using 3 or 4 dimpled or countersunk (depending on material thickness) #4 screws per rib flange. It is my opinion that if the tanks and plywood are not properly secured to the ribs pre-cover, things could wiggle around under the fabric and make it hard to get the fabric screws properly installed. We'll see.

This tank install is a real hammer to fit kind of operation. Doable, but if somone buys the kit planning to install a set of perfectly made parts to a set of precision drawings, they're gonna be disappointed.
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Re: The Restoration of N2120E

Post by Nathan K. Hammond » Sat May 12, 2012 13:38

Schools out = I can work on the airplane!

With the Tip Bow blasted and primed, I installed it for the last time. I used counter sunk screws and washers to hold the doubler in place; should make for a clean and smooth look once covered.

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I had pre-drilled the spar for the additional brace which opens up bare wood and a potential for rot. You can either coat the screw in varnish, or in my case, yellow wood glue. Both will prevent moisture from the bare wood fibers.

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Installed the bellcrank block outs and the new trailing edge; all epoxy primed.

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I Krylon'd the inside of the block out white to help reflect light during future inspections.

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Re: The Restoration of N2120E

Post by Nathan K. Hammond » Sat May 12, 2012 13:53

Dad needed a set of leading edges and stiffeners to finish a shop project last year, so I loaned him mine and ordered another set. Only problem, nobody had the stiffener in stock at the time. Not a problem, what I ordered from WagAero was nothing more than a 8' piece of .016" bent 90*; I figured I could make that on metal brake. The snag became 'how do I get this home, 300 miles away.' So I scrapped that idea and started looking for alternates. Derek Landstrom pointed me towards www.CarlsonAircraft.com where I ordered 4 sticks of their "T" stock.

What came, turned out to be too thick on the flat; it makes for great rib capstrip, but not leading edge stiffener. Luckly, Univair came through and restocked their supply of 5-173B. Here's the two side by side.

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Once primed, it's ready to notch for the ribs. It's fairly straight forward, lay the "T" on the ribs, and mark the vertical of each rib. Drill a 1/16" hole at each mark, then make notch using a hacksaw or dremel tool.

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Re: The Restoration of N2120E

Post by Nathan K. Hammond » Sat May 12, 2012 14:06

The notch cut out of the "T" coincides with a relief cut in the ribs, so they nest together nicely. At least for the main ribs; the cut on the Root Ribs is in a slightly different location. I'm not sure if this is factory, or a result of aftermarket parts. I was able to make a slight bent at the wing root and have everything lay down flat, but ended up cutting a large relief for the root rib located mid span.

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The "T" from Univair ships in 90" lengths plus 4" of cutoff, so you have to use two 90" pieces and join them mid span. For this, I used the extra 4" included but cut one ear off the "T" leaving an "L". Normally I would have riveted this together with small #3 rivets, but I don't have any in stock, so I used four #4x4 screws (pre-drilling the holes one at a time with a #44 bit.) When matching the "L" to the "T", I nested the big to little on each side for maximum strength.

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Re: The Restoration of N2120E

Post by Nathan K. Hammond » Sat May 12, 2012 14:17

Leading edge stiffener in place.

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Now we start looking at the leading edges. Both sets (all 8 pieces) I ordered from Wag have a dent in the same place. I'm not sure if it's from the forming, or more likely something was dropped on a stack of them.

I used a plastic mallet and backed the part using a pad of paper. I'm no sheet metal wiz, but I did learn this trick from a metal former... When trying to smooth out a dent don't use a shot bag, because you can push the dent out the other direction. Instead use something with just a little bit of cushion, like a poly-fiber manual in my case, so the metal can stretch back out and have just enough cushion to form, but not leave tool marks.

Before...

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The mallet and pencil marks showing where to work the metal...

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After about 5 blows with the mallet... just a little more touch up and good to go.

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Slid in place temporarily and held with tape. Looking more like a wing.

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Now to back drill all the holes........

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Re: The Restoration of N2120E

Post by james gevay » Sat May 12, 2012 19:16

Very nice Nathan, and well thought out work.

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Re: The Restoration of N2120E

Post by kyleb » Sat May 12, 2012 21:34

Other than the dents, the leading edge looks like it fits very well. Are the new parts pre-formed closely enough that they fit against the ribs pretty well without much help?

I know when I pulled the 60 year skins off of my wings, they sprung open pretty wide, which surprised me.

Did you give any consideration to making your own leading edges?
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Re: The Restoration of N2120E

Post by MikeB » Sat May 12, 2012 22:30

My leading edge from Wag Aero fit like a glove. Glad you're keeping at it Nathan. Hope to see you at Middletown.
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Re: The Restoration of N2120E

Post by Nathan K. Hammond » Sun May 13, 2012 02:32

Mike, I'll be there if the creek don't rise.

Kyle, they are nice. Fit *almost* tight enough to stay on the wing without clamps. Here's a pic that show's one attached and one slid over top. My old skins were the same way as your's.

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Never even considered making my own. Without a slip roller long enough, and not wanting to make a jig out of PVC, then trial/error until I got a respectable set; it was one of the few times, I ordered new without hesitation.

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Last edited by Nathan K. Hammond on Sun May 13, 2012 03:01, edited 1 time in total.
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Re: The Restoration of N2120E

Post by Nathan K. Hammond » Sun May 13, 2012 02:38

Leading edges going on.

Once slid into place, I used ratchet straps to pull the skin down around the nose of the rib. Not wanting to chance damaging the rear spar, I elected to hook onto the ribs. This worked surprisingly well, as I didn't have the straps super-tight, just one click into the "snug" range. Couple things to remember, Put the strap on the web side of the ribs, not the flange side. The web is stronger, and you need maneuvering space for the drill on the flange side.

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Oops, wrong side...

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Re: The Restoration of N2120E

Post by Nathan K. Hammond » Sun May 13, 2012 02:50

My plan is too attach the outer panel first, then over-lap the in-board panel and the the tip section. I don't think there's any right or wrong way of doing it, just a matter of preference. My thinking is; come covering time, I'd rather have the open seam at the tip pointed inboard which should make it easier to file/fill/sand smooth.

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Tools for the job...
I ordered a couple #44 drill bits online in both 3" and 12" With the 12" chucked in my cordless drill, I was able to back drill all five hole on the top surface of the skin. The front two holes were drilled at a slight angle, but didn't effect the screws at all.

The bottom surface of the skins takes a different approach; a 90* drill is almost required, something I didn't have. A quick trip to Lowes and I found a substitute that could run on my Dremel tool. Even though I'm running a generic Craftsman tool, the genuine Dremel adapter plugged right in, working like a charm.

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When drill the bottom holes, a mirror and flashlight came in handy.

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Re: The Restoration of N2120E

Post by Nathan K. Hammond » Sun May 13, 2012 02:56

Little details are the devil...

The root rib was bent ever so slightly; had to use a hook to pull it back into line. (Pro-Tip = only use masking tape, preferably the blue 'low tack' version on fresh paint. Paper box tape over 12hr Epoxy = peeled paint and sticky residue. :evil: )

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Make sure the screws lay down flat. See the difference between the left and right...

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