The Barn Find Build

[bbs428]

Yup, measure with a micrometer, mark with a dull sharpie, cut with a chainsaw.

Ralph

Got a chuckle out of that Ralph. So true! Lol.

[Eric Page]

I know real men don't cry, but I was nearly reduced to tears by the task of assembling the control column. The first builder made a mess of the bearing sockets, and one of them was misshapen such that the bearing would sit crooked when the nut was torqued down causing the stick pivot to bind. I must have taken that pivot assembly apart and put it back together a dozen times before I finally removed the right molecule of steel (purely by accident, I might add) to make the bearing sit square in the socket. I may have uttered a few words that would have alarmed my mother, but I did end up with a very smooth, free-moving assembly. It still isn't pretty, but nothing short of a full strip and re-coat would fix that. It's safe, the sticks are parallel and it works well.

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Since I still haven't resolved the control column pivot block mounting, and I haven't re-varnished the floor boards, there wasn't much more I could do with flight controls, so I moved to fabricating a pitot tube mounting plate for the left wing. My wing has the original 90s-era plastic fitting to accept a bent aluminum pitot tube, and it's mounted on a triangular plywood gusset (right side of photo, below). Since I don't relish the idea of removing that gusset and damaging wing structure in the process, I'm planning to put my Dynon pitot tube on the outboard side of the same rib (left side of photo).

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I bought the pre-drilled Gretz Aero pitot mount from Spruce. It's clearly intended to be used on metal airplanes (RVs, specifically), but I see no reason it can't be mounted through a plywood panel and stick through a reinforced bit of wing fabric. I plan to put the bracket's tube through an airfoil shaped hole in the plywood, then sandwich the wood with the supplied aluminum reinforcing plate. Conveniently, Gretz also supply a "washer plate," which, once it's reduced in size somewhat, should make a perfect reinforcement when bonded to the back side of the fabric. At least that's how it works in my head...

Building all of this began with cutting a piece of 1/8" plywood into three pieces, roughly 4" x 5-1/2", and one piece of aerospace tongue depressor,

4" x 1/4".

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The small piece is needed to take up a bit of extra space between the rib cap strip and the lower stringer (indicated by the arrow in the first photo).

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Next I got out most of the clamps I own and did the first two of three glue-ups, laminating two of the larger pieces together and attaching the small piece to the top edge of the third larger one. Once that cures, the pair will be laminated to the single, butted up against the 1/4" strip. It's probably hard to picture, but I'll post more photos as it comes together. If it comes together; I've never done this before...

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[Eric Page]

Today's efforts started with a "Doh!" moment, when I realized that my beautiful new bottom tail rib was installed before match drilling the tailwheel mounting holes through the new gusset that was welded to base of the tail post. With the rib in place, access to the gusset was blocked. To get around this, I drilled two 1/2-inch "lightening holes" in the rib, then drilled through the gusset with a #13 (0.185") bit, and followed that with a 3/16" reamer.

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Next was the third glue-up on the pitot tube mounting plate, which created a lamination three boards thick. It's very stiff, and I think it'll be plenty strong enough for the job.

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Once that cured, I trimmed it to final size on the miter saw, sanded the edges and corners smooth, and test fit it in the wing.

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I decided it would benefit from a gusset to brace the outboard front corner (lower left corner in the photo above), so I cut two identical rectangles of plywood to size and glued them together in a two-sheet lamination. This piece will be bonded to the mounting plate and span upward where it will attach to the top stringer.

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While that cured, I used one of the metal plates that came with the Gretz bracket to mark my wood mounting plate (incorrectly the first time!), then I pecked at it with a step drill until I had removed most of the material from the airfoil area. Interesting fact: you can use the side of a step drill as a make-shift nibbler (at least you can with wood). The line at the bottom will be the final cut for length.

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After about 20 minutes of filing and test fitting, I had a hole just the right size and shape for the Gretz bracket to slip through with a tight fit.

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I was having so much fun learning woodworking that I made a start on mounting my communications antenna. I decided to use the Advanced Aircraft Electronics VHF-5T, which Delta Whiskey used successfully in his build. I shamelessly ripped off his mounting location and method, with a few modifications. I started out by straightening the antenna, which comes curled up in the box. I tried curling it the other way for awhile without much success, then I found that holding it at one end and applying gentle heat from a heat gun makes it relax.

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To attach the top end of the antenna to the top rib in the vertical stab, I cut a short piece of 1x2 with one end angled to match the forward rake of the antenna, then nibbled a 1/8" wide x 1" long x 1/2" deep slot in the square end to accommodate the upper end of the antenna, where it will be glued in place (probably with silicone rather than Hysol).

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I mocked this up in the tail with painters tape, marked the ribs where the antenna would need to go, then used a Roto-Zip tool with a spiral wood cutting bit to cut a slot in each rib for the antenna to pass through. The slots were then cleaned up with flat and round files.

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I've hit the photo limit; more to follow...

[Eric Page]

Here's what it looks like in place. A couple small dabs of silicone at each rib pass-through will hold it in place and prevent chafing. I haven't quite worked out how I'll anchor it at the bottom, but I'm thinking about two wood blocks with thin rubber bonded to them, pinching the end of the antenna between them when a couple of screws are tightened.

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It just occurred to me that I need to verify that this doesn't interfere with the trim position sensor before I finalize the bottom end...

The feed point at the center of the antenna falls conveniently between ribs, right where there's a tube to clamp the coaxial cable for strain relief.

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Finally today, for your amusement, some first-builder tricks. Here's a 5-second video showing the side-to-side play in the forward end of my horizontal stab. If you felt this during a pre-flight, would you fly the plane? Also, see if you can find any problems with the hardware used to mount the nylon blocks (hint: look at the screw heads).

https://drive.google.com/file/d/1qwU...w?usp=drivesdk

[airlina]

See what you mean about those messed up screw heads, but that gives you the opportunity to pull it all apart and put in new screws and sliders because no I would not fly mine with that much play. Bruce N199CL

[alexM]

My horizontal stab doesn't have anything like that amount of play to it. Seems like you could spin one of those blocks around and might even need to file it a bit to get it to slide nicely. That guy was quite a craftsman. No doubt you saved his life.

Following your antenna install for sure. It's been on my want list for a while.

[jiott]

Eric, something seems wrong about that bottom tail rib. Even with the access holes, how are you going to access the top side of that rib with the fabric on? The bottom rib shouldn't be that close to the tailwheel mounting bracket. There should be space between the bracket and the bottom of the rib to get the nut on.
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[efwd]

Hi Eric. I would aim for a tighter fit. Having said that, I have play in mine right now. I would say mine is about 3/4 of that that you have. It didn't start this way and I aim to tighten it up. It is 15-20 degrees cooler now than it was only 4 weeks ago. It has seemed to make my gap bigger. Not to mention 280hrs of use in the past 20 months. Im with Jim on the bottom rib.

[Eric Page]

My horizontal stab doesn't have anything like that amount of play to it. Seems like you could spin one of those blocks around and might even need to file it a bit to get it to slide nicely.

I thought about that, but only one of them looks wide enough to take up the slack if it's turned around, and I'm afraid that would push the stab out of square with the fuselage centerline (one side farther forward than the other). I'll have to try it and see. I'm sure eBay will have a dozen sellers offering UHMW bar...

Eric, something seems wrong about that bottom tail rib. Even with the access holes, how are you going to access the top side of that rib with the fabric on? The bottom rib shouldn't be that close to the tailwheel mounting bracket. There should be space between the bracket and the bottom of the rib to get the nut on.

I think my photos exaggerated how close the rib is to the bracket. Here's a side view; there's about 1/2" of space for the nut. Tight, certainly, but it should be enough.

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[Eric Page]

I spent this morning reading the forum and AC43.13-1b, trying to figure out how to repair my flaperons. [If you know anything about patching airplane skins, please take a look at that link.]

I also spent some time drawing a skin patch, but that was more as a Solidworks exercise than anything productive. I've been trying to teach myself Solidworks lately, so I've been drawing anything that catches my eye.

The rivets I needed for the flaperon hinge brackets in the wing ribs arrived yesterday, so after lunch I got out to the garage and installed them in the right wing. It was pretty straightforward, apart from accidentally putting one of them into rib #4 instead of rib #5 (right after buttering it liberally with Hysol, of course!). All of the rivet holes lined up as expected, so I must not have mixed up any of the brackets.

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Hysol is pretty awful stuff, but I'm proud to say that I got through my first large-scale application of it without getting any on my clothes or beyond the first knuckles on my fingers.

Tomorrow I'm headed to a friend's shop to put the control column mounting bracket on his mill. I plan to remove a tiny bit of the inside radius on the "L" angle at both bolt locations so that the bolt heads will sit flush. He's pretty well stocked with 4130 tube, so I'll probably come away with the 1/4" spacers I need to get the nuts on, as well. If all of that works out, I'll be able to get back to installing control parts.

I also need to get one of my neighbors over here to help me swap wings between the cradle and the rotisserie so I can install the hinge brackets and pitot tube mounting plate in the left wing.