Landing Gear (Part 1)

I'd decided shortly after starting this project that I wanted to replace the original retractable landing gear with something springier. I decided on a Diehl taildragger setup, which bolts to the front of the front spar. In order to make it easy to keep a good leading edge profile, I glued all my foam in and shaped it to the profile I wanted before I messed with landing gear.

I discovered that, somehow, when I sand on an angle as specified in the plans, I manage to sand deeper than I can when my sanding board is flat. I'll need some extra micro in the grooves, but only on the top of the right side. Next I covered the leading edges in duct tape, then laid up two layers of fiberglass overtop of the duct tape.

The duct tape I used seemed to get very loose with heat. This caused some ripples on the inside of the fiberglass, but the outside shape is still nice and even. After the fiberglass cured, I peeled it off the duct tape and removed the duct tape from the wing. I measured the area I needed to cut out for the landing gear brackets, then used a razor blade to (carefully) cut the foam away in one solid chunk. I set aside the foam and the fiberglass skins, then lined up my brackets and drilled the bolt holes through the spars. 

I had originally ordered the tricycle gear legs, but determined a tailwheel airplane is the way to go, so I had to send the legs back for the other style. Once they arrive, I'll finish attaching the gear, then finish shaping the foam and fiberglass around the landing gear and attach it all permanently. 

(Continued in Landing Gear - Part Two)

Rudder Pedals and Elevator Brackets

I've been making small amounts of progress here and there. I'd been putting off the rudder pedal swingarms, because I wanted them offset to work with the offset seating. In order to generate more shoulder room, the pilot's seat will sit 3" forward of the pax seat. That doesn't sound like much, but it causes shoulders to overlap rather than push against, which makes things much more comfortable. My shop really isn't set up for metal work, so cutting, grinding, and jigging this 4130 has been a challenge.

This was my first jig attempt, and while I did get it to work well enough, it was a huge hassle. The second jig turned out a lot better, and was much easier to build.

These were sent off to be welded, and are now ready to be cleaned and painted. I'll be cleaning and painting the steel parts of the control sticks assembly at the same time.

While I was set up for it, I went ahead and cut my elevator pushrods to length. I have a 5/8" rod from my control sticks to a T lever, which transitions to cables, which run back to another T lever and a 3/8" rod to the elevator.

The pushrods are not yet connected to the rod ends in the picture, but that's not an oversight. I wanted to hook everything up before drilling holes and riveting, to make sure the length was right!

The main reason for my slow progress has been my own work in adjusting existing designs to fit my needs. Specifically the brackets/T-lever assemblies. It takes me a while to fabricate the metal bits, so I try to make absolutely certain that I don't have to re-make any parts due to unforeseen problems.  A few of my sketches are below, showing the bracket and T-lever setups.

This is a 4x scale drawing of my forward T-lever setup. From left to right: sintered bronze (SB) bushing, 3/4" aluminum spacer, aluminum T-lever, SB bushing inside the T-lever, 3/4" spacer, SB bushing. I have SB bushings on both ends, so that's what will contact the bracket, and I have a SB bushing through the actual lever itself to facilitate smooth rotation.

Next is a 1:1 drawing of the rear T-lever, which also incorporates an arm for counterbalancing the elevator. I will preempt this drawing by saying, I did not use this design. Rather, I adjusted it with spacers.

And here's a 4x drawing of the center of the assembly, or the pivot point:

From left to right: SB bushing, T-lever, 3/4" square tubing for counterbalance, 1/4" angle, SB bushing. The problem with this design is, the cables will rub the counterbalance arm when it pivots. As a result, I'll be adding a spacer between the T-lever and the 3/4" square tubing. 

This gives you a better view of the problem. The second and fourth "nut" from the top will have cables attached, and anytime the elevator isn't slightly up the counterbalance will intersect one of the cables. Adding an 1/8" spacer to the pivot point and the pushrod point should give me enough clearance.... or maybe 1/4". I'll be mocking this up *not* in the plane, to make sure I get it right, before I start drilling holes in the wrong spots. Anyway, I hope to have most of this finished after this weekend.