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.

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.

Wing work 2/15/24

Got the lower leading edge of the aileron rounded off, and the beveled strip glued to the bottom of the aileron bay. Once that glue had cured, I’ll be able to check the clearance on the down travel and see if any further rounding off is needed. We used a 3/8” radius bit in a router to cut to shape, then cleaned up the edges with a DA sander.

Radius on aileron leading edge

Wing work 2/10/24

This covers a couple days’ work. Yesterday we ripped the CW37 aileron bay TE stock down to 1/4” and I got that installed. Today I’ll glue in the triangular support pieces. And yes, I realized after cutting and gluing it all up that the CW37 piece is supposed to be notched for the rib caps. I’ll remember that for the next time.

I continue to be astonished at how light and strong this wing is. I can easily lift it off the bench and move it around; it can’t weigh more than 20-25# without the aileron installed.

The last thing that was really bugging me about the aileron was that the lower edge of the leading edge plywood still wasn’t glued down. I’ve got to find a better way on the next aileron, but this one had to be done so we can radius the lower edge.

Stew’s idea was to make a grooved board for the trailing edge and use that to clamp a board across the leading edge while the glue sets. He used a length of scrap cedar with a groove cut to match the angle of the TE, and we used four bar clamps to apply pressure. In hindsight – I honestly don’t know if just putting a radius on the front corner and wrapping plywood around it would be better or not. We’ll see how this works out.

In other news, Stew has his 4’ CNC machine in and working, and I’m going to put him to work cutting my torque tube bearing blocks out of some UHMWPE stock I have. Better than plywood, I think.

Aileron progress

It’s been an on-and-off couple of weeks. I’ve had a persistent cold/bronchitis that has kept me away from the shop for days at a time. On days I do feel like working, I’ve got a house cleanup project that’s been sucking time as well.

This evening I got over to have a look at the aileron. I’m not thrilled with the plywood, to be perfectly honest, but I believe it will be OK. I re-glued a couple of the geodetic braces and glued down a couple of corners of the thin plywood that were loos and/or slightly de-laminating. I think the fabric would probably have been sufficient, but I want to make things as close to perfect as practical. I’ve got a list of things to do differently on the next three ailerons.

I got a few corner blocks installed to make sure the plywood stiffeners don’t flex or bow. The pans don’t call for them, but I’ll feel better knowing they’re there. I also got the ends of the aileron nose plywood trimmed and sanded flush with the ends of the aileron. There’s one more round of gluing to do, then I can use a router to put a radius on the lower front edge and it will be done. I did check the aileron travel; 22 degrees up and down will not be a problem.

Returning to work

It’s been a bit since my last update here. In the past couple of weeks we took a nice cruise vacation, and I developed a pretty severe case of bronchitis. It’s possible these two things are not unrelated; one of the risks you take to get a little Caribbean sun and salt air in the middle of winter, I guess!

I’ve been working to get the leading edge of the aileron wrapped with plywood. Honestly, at this point I can understand how someone would make the decision to scrap an aileron and start from scratch. I don’t think I’ll go quite that far, but there have been challenges. I’m adding to my “lessons learned” for the next three ailerons, that’s for sure. Part of it is just developing a process to get the ply to wrap over the pretty sharply curved top surface. This part I solved with a couple pieces of Styrofoam and some dumbbells, to effectively clamp the aileron to the bench with the ply trapped underneath. That should hopefully take care of the upper portion. The bottom edge of the top piece of ply isn’t yet glued to the structure, so I’ll have to figure that out today.

I’m really looking forward to building the next wing. I’ve learned so much while building this one that I’m pretty sure the next will take a lot less time, although I’ll have to figure out the wing walk on the next one. I talked to a guy building an RS-80 Tiger Moth the other day. He told me about improvements he’s made to his wing walk to avoid seeing the wing deflect when someone steps onto it. I’m not sure how much I’ll be able to do on mine, but he’s using carbon fiber in a substantial number of places on his build. Honestly, the wing walk is one area where I was thinking I would need to beef things up a little anyway… if you’ve met me you’ll understand why.

But, of course the devil is in the details. Every time I think I’m almost finished with this wing I am reminded of all the detail work that has yet to be done. I need to cut and install all of the bushings for the bolts; finish cutting, shaping, and drilling the various aluminum mounting brackets; cut and finish the scallops in the leading edge plywood; figure out and build the transition from leading edge to wingtip bow (most likely foam)… there’s a lot of stuff left to do, but fortunately it’s really only a few days’ work.

Cold weather musings

Haven’t done much on the plane for a few days now. We have been in the grips of a winter storm, followed by a cold snap. We got several inches of snow; anywhere from a couple inches in the front yard to maybe 2′ drifts closer in to the house. The temps throughout the 3-day weekend never got above -7, and the wind was blowing. This is not weather conducive to going outside for anything non-essential.

During the last build session, I tried cutting a few of the bushings needed for the wing. The results were not great. While a chop saw will go through and make a beautiful clean cut, it will also randomly launch the cut-off piece somewhere in the shop, often with a nice big chunk out of the end. Not what I was after! I did get one bushing cut successfully, and another done after much filing to get it down to its final size.

After doing some research, I believe I’ll end up building a band saw sled to cut the bushings. I can make it with a nice end stop to cut the tubing to consistent lengths, and it should make it relatively easy to get an acceptably square cut. I’m hoping the cut ends turn out clean enough to dress with a brief time with some sandpaper.

The bloody compass is still very slowly seeping fluid. I suspect the face plate is not perfectly flat. I think for now I’ll leave it, but at some point I’ll need to drain, disassemble, and maybe use a thin coating of Aviation Form-A-Gasket on the black rubber seal. At least everything works well, it looks great, and the LED light is quite effective. I have no idea why I’ve invested so much work into a mag compass, to be perfectly honest… but it’s been an entertaining project. I just like restoring old things.

I’ve had no success at all getting answers out of “CKD.aero” regarding the pricing and availability of parts and subkits for the Celebrity. I’ve been trying to get pricing for the wing tanks so I know whether to plan on using them or not. It just feels like Fisher got bought by people who have no clue what to do with it. The website has been stripped of any pricing or availability information. It took me weeks to get anyone to even respond to an email, and despite a couple of promises I have yet to get a useful response from anyone. I guess I’m on my own. It’s a shame, but I did decide to build from plans; I think I’ll be able to muddle through.

Aileron progress

Building this aileron has definitely been a learning experience. Some things that I didn’t think would make a big difference early on in the process have come back to haunt me… and of course I’ve learned how the whole thing goes together, which isn’t always 100% clear when comparing the plans to the parts received in the kit. The end result will be fine, but the next three will be a lot less hassle to build.

Lessons learned: All of the plywood bits need to align perfectly with each other and with the wing ribs. That means CW36 needs to be shortened and the hole moved, and CW35 needs the hole moved. I will also pay more attention to getting the aileron spars perfectly flush with the rib caps — otherwise there’s planing and sanding to be done. Ditto for the stringer on the leading edge; I’ll want to make sure the notches I cut for that are exactly the correct depth.

As my CW35 pieces were about 3/16″ high on each end, I glued a couple strips of the 1/8 lamination stock along the bottom edge to fill the gap. Once that was dry I planed and sanded to match the profile of the ribs. I had to sand the top down to match the ribs and CW34 contour, and finish getting the bottom of the spar flush with the ribs. There wasn’t much hanging down, but it was still fussy work. With that done I was able to glue the bottom layer of plywood to the aileron. Once that’s dry I can go to work on the rest of the plywood — of course the angle cut in the spruce piece at the bottom of the aileron doesn’t match the angle of the CW34/35 plywood pieces, so I’ll just have to sand a good profile for a smooth transition. Then I’ll be able to figure out the rest of the aileron bay.

Compass overhaul

I think I’ve finished the compass overhaul. The rebuild kit arrived from ACS yesterday. After carefully cleaning the glass with denatured alcohol, I installed the new gasket and the glass. With everything reassembled, I filled it with compass fluid. I had about half a pint from a rebuild kit I had bought several years ago, when I came across an old Airpath compass that ultimately turned out to be an oddball military model for which there are no replacement parts or gaskets. It was leaky around the glass, and I eventually figured out that the cork gasket was slightly oversized. From what I can tell, it’s supposed to apply pressure around the edges of the glass to seal it against the inner black rubber gasket. It was getting squeezed between the case and face plate. After trimming about a millimeter or so from the outside, I finally got it to seal up.

Normally you would submerge the compass in a container of fluid to work out all the bubbles. In fact, the Airpath manual specifies submerging it and pulling a vacuum for a few hours to ensure there is no trapped or dissolved air. I didn’t go to those lengths. I was able to work all the bubbles out and get the fill (or drain) plug in, and so far there’s no sign of leakage.

The new LED lamp works great. In a dark room there’s a nice red light that makes the compass quite readable. I’m happy with it.

I’ll let it sit on the bench for a few more days to ensure there’s no leak and no bubbles develop. If I do see any air, I’ll submerge it in a container and do it their way. I figure it won’t be getting mounted in a panel for at least a year or two, maybe longer, so I’ll have plenty of time to validate the quality of the rebuild. For a total investment of less than $71 I’ve got a completely rebuilt, well lighted Airpath compass. That total includes an extra nine little LED lamps that I’ll use elsewhere; if you don’t count those it’s under $65 total. Not bad considering I see dried-out junkers going for more than that on Fleabay.

Opening 2024 with an aileron

Today I hit a pretty cool milestone – I cut the first aileron free from the first wing! Pretty jazzed about that. I trimmed up the rib cap ends as much as I needed to, and glued on the lower aileron spar and the upper stringer. Lessons learned here:

  • The CW36 pieces (aileron bay end plates that hold the torque tube bearings) did indeed have the holes drilled about 1/8 or 3/16 forward of where they needed to be. Not a big deal, since those will get UHMW bearings attached to them. I did a little cutting and some sanding with a 3/4″ spindle sander drum (hand held) to get them where they needed to be.
  • The CW35 pieces (aileron end plates) have the holes drilled about 3/16″ below where they needed to be. I didn’t realize at the time exactly how the whole assembly goes together, but now I do. What this means is that CW35 on each end is too high to match the profile of the ribs. The top will need to be very carefully marked and cut or sanded to match the rib caps, and the bottom will need to be filled with some spruce or pine scrap. Lesson learned; for the other three wings I’ll re-cut those holes to match the holes in the CW34 pieces. I’ll do that by gluing up the CW34/CW35 stack with the profiles aligned; once dry I’ll use the spindle sander with a 3/4″ spindle to make the hole in CW35 match those in CW34.

The next issue to deal with will be the thickness of the CW37 pieces. The plans clearly show it as 1/4″ thick, but the supplied stock is 1/2″ thick. It’s used on the top and bottom of the aileron bay. Once I have the aileron completed – CW35 bits corrected and plywood attached – I’ll need to install the aileron with the torque tube in place and figure out exactly how to finish out the aileron bay.