Tag: Modification

Posted on

Wing work thru 2/20

Top and bottom leading edge plywood has been scalloped. That wasn’t as big a chore as I thought it would be. We used a thin stainless scale to establish a curve between each pair of ribs, marked along it with a pencil, and cut the wood with a utility knife. Some cleanup with sandpaper and Bob’s your uncle.

I’ve made a few iterations of the bearing block. Today I’ll print a couple more test pieces and I think I’ll be done. They fit great, the aileron is very well located, all in all I think it’s a lot more precise than a piece of plywood and a chunk of PVC pipe.

I’ve been preparing some of the wing attachment fittings. I have one or two of each part drilled with 1/8 pilot holes; I’ll use those to match drill the rest, then enlarge the holes for the AN4 bolts. The biggest question was hot wo round off the ends. For that I drilled a 1/8 hole exactly 1/2 inch from the disk on my disc/belt sander. Now I can use the tail end of a drill bit as a pivot pin and put a nice radius on the end of the fitting. I’m glad I kept my gray Scotch-Brite wheel on the bench polisher; it makes quick work of cleaning up the ends of the AL bars.

Posted on

Wing work – 2/16, and a better idea

Yesterday (2/16) I cut and glued in some corner blocking I had missed on each end of the aileron and the ends of the aileron bay. Lesson learned: that would have been a lot easier had I done it before the geodetic bits and plywood stiffeners had been installed.

I’m getting to the point where I kind of need the torque tube bearing blocks installed. Then there are the 3/8” spacers, which the plans call out as pieces of PVC pipe. I figure, since I’m going to CNC machine the bearing blocks anyway, why not just make those and the spacers one piece? I pulled up the design in OpenSCAD and added the spacer. I gave it a slightly larger ID than the bearing block so it doesn’t add drag to the aileron control. I 3D printed a couple samples to use for fit & function testing. If that goes as expected I’ll get a chunk of 1” UHMW and pass the design file to Stew for machining. I’d planned to use some 1/2” UHMW I have for the bearing blocks, but I’ll keep that for now and use it for something else.

3D printed test part. It’s difficult to see but there’s a step in the bore for the torque tube.

Posted on

Rib modifications

I built all of the wing ribs exactly to plans, per Sheet 1 of the plan set. Unfortunately, that sheet has not been updated since the rear spar was changed from using 1/2″ square spar caps to 3/4″. As a result, the X braces just aft of the rear spar were way too far forward in all of the ribs I built — all except for the 16 aileron ribs, which don’t get those X braces. Installing the rear spar would require extensive trimming or notching of the geodetic stock — I just wasn’t happy with that. Plus, there’s another piece of square stock on the aft face of the rear spars on the upper wings. It already needs to be beveled to clear the ribs, and with the braces in place would need to be cut down to almost nothing.

So, out came the razor saw. I cut those two X braces from every one of the ribs, cut new ones, and glued them in place with enough clearance for the rear spar. It was a couple hours’ work, but since I have a lot of extra rib geodetic material wasn’t that big of a deal. On the bright side, I got to test the glue joints on all of the pieces I pulled out. We want the wood to fail before the glue does. Every single one of them broke the brace or separated it along a grain line before the glue gave up — 100% successful tests. That was not unexpected, but was reassuring nonetheless.

Now we can move forward with assembling the wings.