Tag: Parts

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Aileron spar and parts fitting

Today I got the aileron spar web cut and glued in, along with the top pieces of 1/4″ spar cap. I couldn’t get to the bottom side to clamp those pieces without some significant effort, so I left those for the next session. I also got the CW32 pieces cut and sanded to fit between the rib caps. I trimmed and clamped the CW36 and CW34 pieces in place to locate the aileron torque tube, then marked the CW32 pieces for the holes that will need to be drilled for the torque tube.

The wingtip is nice and solidly in place, so now I just need to sand the blocking and trailing edge flush so I can start installing the gussets and additional bracing.

This time around I plan to NOT screw up the same way I did the first aileron, by assuming that the holes in ANY of the parts are drilled in the proper place. As I did before, I’ll index everything off of the CW34 parts, using those to locate the torque tube, and drill or sand everything else to match them. And of course I’ve already 3D printed a pair of torque tube bearing blocks for this wing. The final parts will be milled out of UHMW or something similar, not 3D printed, but these are great for getting all the holes located without the risk of messing up a flight part.

The more I use it, the more I like my little razor plane. This thing was bought back in the 70s, I think, by my father for use on R/C airplanes that we (mostly he) built in our basement, usually from scratch. It’s a plastic body with a blade that resembled a heavy duty, oversized razor blade. The key thing I found was to use light passes, and hold the plane at an angle to the wood. It’s quite effective for shaving down spruce, plywood, and even the odd bit of end grain. It’s usually quicker than sanding.

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Glued wingtip in place

Today I got the end nose rib notched and the wingtip glued in place. I have the blocking at the spar tips and nose rib, but will still need to block and shape the trailing edge as well as gluing in the plywood gussets. Still, it feels good to have the wingtip on. It looks more like a wing!

I also trimmed the CW36 pieces. These go on the ribs just outside the aileron bay and hold the torque tube support bushings. As supplied they were about 3/8 too long for the inboard side, and 7/16 for the outboard side where there’s an additional thickness of plywood where the wingtip spar web overlaps. For this I just set the miter gauge on the table saw to match the angle of the piece, then set the table saw to cut off the length needed. I won’t glue those two pieces in place until after I have the rest of the aileron structure built up.

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CAW2 brackets

Over the past couple of days I’ve gotten all 14 of the CAW2 brackets shaped. I had drilled all of them already, but the ends needed to be rounded off. One end of each will be hidden inside the wing, but some will have one end exposed so I wanted them looking decent.

I designed a radius guide to help with the bandsaw and sander. It’s just a 1″ diameter disk, with a short 1/4″ button on the center of one face. Stick the button into the hole on one end of the bracket, and the guide is there to show a 1/2″ radius all the way around. My original idea was to use them to scribe a line to follow when finishing the ends. I had 3D printed a couple of them, and found it was just as easy to just leave it in place and work around the edge. Inevitably, of course, you end up nicking one so I printed up a batch of 9 more. I used 3 of them to finish off the CAW2 brackets.

Given that there are a bunch of other brackets to finish, I’ll definitely try the scribed line approach as well. Overall, though, I’m pleased with the results. I used the bandsaw to lop off the corners, then shaped the ends with a disc sander and finished them on a Scotch-Brite wheel. I had planned to paint them, but I may not. I’ve still got a batch of metal etch and Alodine (Bonderite 1201, to be precise), so if it still works I’d like to just give them a conversion coating that weighs nothing; that way they are protected from corrosion but only the exposed parts get paint. I’ll probably try a test piece to see if the Alodine still works; if not, I’ll get some self-etching primer and use that instead.

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Miscellaneous work

Today came and went without mixing up any glue. I sorted out the nose plywood, then went through all of the aileron pieces and got them cleaned up, marked, and re-taped for the three remaining ailerons. I got the aileron spar web and marked it for the notches to clear the ribs, then brought it home and started cutting those notches on the bandsaw. I pulled a wingtip bow down and checked its fit; it looks like minimal trimming will be needed.

I also collected all of the aluminum pieces I had at Stu’s shop and brought them home, and cut the ends on the bandsaw. They’re all CAW2 pieces, I think — I need to dig out the rest of the pieces and get them all drilled and finished off. I’ll finish them on the belt sander and Scotchbrite wheel before priming them. My little 3D printed guide button worked great for this. I don’t recall if I described it or not, but it’s just a 1″ diameter by 1/8 thick disk, with a 1/4″ diameter by 1/8 thick nub in the center. Put the little piece in a 1/4 bolt hole, and the larger piece gives you a perfect guide for shaping the end of the bracket with a 1/2″ radius. They’re disposable if you nick or break one, and only take a little while to print up. I’ll probably print a few more in case I destroy any while using the belt sander.

I spent some time trying to determine whether the wing walk pieces will be of any use to me or not. The plan sheet and plywood supports all seem to be made for some earlier version of the wing. The notches on the supports don’t work (or even come close to working) with the root blocks on the main spar or rear spar. The forward plywood bits are too long, and even if cut off don’t match the curve of the wing ribs. There are supposed to be three installed forward of the spar — but that would only work if I removed one of the false ribs. I still don’t know what I’ll do for the wing walk. I do know that 1/4 plywood for the rear portion would need some curve in it, and I’m not sure about that. The plan notes say to nail it in place until the glue dries… ::shrug:: This is why I’m considering a laminated layup with some wood and maybe a layer or two of carbon fiber.

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Compression members in (lower left wing)

Over the past few days, I have gotten the rest of the ribs glued to the rear spar. I’ve left them unattached to the top of the main spar, as I’m planning to just run the geodetic braces between the rib cap and spar rather than use a separate shim between the cap and spar.

Today I got all four of the compression member assembles cut, fitted, and glued in place, and glued plywood gussets on some of the joints. I ran out of time before I could get the remainder of the gussets cut and glued in.

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The State of the Wing address

The main and rear spars are in place, and half the ribs are glued to them. It’s tedious and intense work, so I’ll finish them up tomorrow.

I dug the CW42 and CW43 plywood pieces for the wing walk out of the crate and tried test fitting them. As with many of the kit pieces, they simply don’t fit. At all. The nose reinforcing pieces will be usable, with some trimming. The rear pieces… not so much. Once the ribs are fully secured I’ll see if they can be used at all, or if I’ll need to order some new plywood and cut new ones. At the very least, the notches for the cross braces are rounded at the bottom from being cut out with a router with a fairly large bit. I can clean those up with a band saw, but the ends are also not right by a long shot. It will take some work to figure out how or if I can use these.

All in all I’m just happy I didn’t pay full price for this “kit”. I’ve found an awful lot of pieces that, quite frankly, I’d have probably been better off making myself. But at least now I know what to expect.

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Wing work through 2/26

Mostly small things over the past week. I cut and installed some more corner blocking that I didn’t get done before, tested a couple new iterations of the bearing block/spacer, and fine tuned the aileron to the opening. Along the way I’ve noted a few new lessons learned…

  • Never trust the plans, or the supplemental sheets included with them. They’re often inaccurate. Like the AL bracket diagrams that call out 3/16″ holes when they will get 1/4″ AN4 bolts… and on and on.
  • Get the torque tubes in place, holes moved or enlarged where needed, and bearing blocks in place and holes drilled before cutting the ailerons from the wing. Otherwise it’s just a bitch getting everything aligned after the fact to locate the bearing blocks. This of course goes along with correcting all of the many problems with the holes that are pre-drilled in those plywood parts.
  • Make sure all of the corner blocking is installed around the aileron bay as early as possible, and certainly before installing the CW40 plywood stiffeners, aileron leading edge skin, and so on.
  • Go over the plan sheet more often and in greater detail to make sure I don’t miss anything that will be a pain to install later on… like corner blocking that would be much easier to plane or sand to shape than to try to cut to match odd angles.
  • Install the compression struts before the geodetics! That cost a couple hours of added time working through tight openings.

Not necessarily a “lesson learned”, but something I’d like to explore. All of the ribs ended up needing a 1/8 shim between the top rib cap and the main spar. Rather than shim them with separate pieces, I want to see if I can maybe cut and install the geodetics at the same time the ribs are glued, or something. Or possibly just use temporary shims, and glue the top cap to the spar as the geodetics are installed. It could lead to neater and better construction.

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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.

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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.

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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.