Tag: Spars

Posted on

Still hacking away at it

Rear spars built, and tip supports added. Now building the tip supports for the main spars. At some point I need to get some AL stock and see if I can find my box of 4130 tubing to see if I’ve already got bushing material. Then I will need to drill the holes for the attachment and strut/wire fittings before starting wing assembly.

The spars don’t look terribly complex on the plans, but there really is a lot of detail work involved. It’s dragging on longer than I had hoped since it’s a trip over to Stu’s every time I want to get a little work done. I think I may need to take a little more structured approach to this — study the plans, then make a punch list for each trip so I don’t waste time while I’m there trying to figure out the next step.

Posted on

Spar update 10/11

Last night I did some work to get the parts ready for the wingtip bow supports on the rear spars. I ended up not gluing them on, since I’ve got to think a little more about how I’m going to clamp the pieces together. I did get the stiffeners glued to the rear face of the upper rear spars.

Up until now everything I’ve done with the spars has resulted in parts that were still interchangeable. Main spars are identical and fore/aft symmetrical, so there’s no right or left side. The rear spars are not fore/aft symmetrical, so now I have a left and a right upper rear spar. I had to take just a few minutes extra to make sure everything was properly oriented before attaching those stiffeners, or I could end up with two left or two right spars. Needless to say, there are some extra pencil markings on them…

Posted on

Spar update 10/6/23

Happy birthday to me! 🎂 This morning I glued the two lower rear spars up – webs to caps only, and set them aside to cure. That’s all four rear spars now ready for the addition of the plywood blocks for attachment brackets, flying wires, landing wires, and N struts. The cut-off pieces of 1/16 ply will make shims for the lower main spar strut/landing wire attachment points that need to be 1/8″ above the spar caps.

In the afternoon I went back over and glued in the blocks and plywood plates on the root end of the rear spars. There are other blocks and structure to be installed outboard, where the struts and wires attach, but after taking the time to figure out the plans and exactly what needs to be done it was getting too late to glue those bits up. The plans could benefit from an oblique view to better show how things go together, or at least two views of the area… but they’re old and drawn by hand, and there’s only one view. One has to hope there’s a reason that parts of it are built the way it’s shown. The blocks in the kit are oversized and will need to be trimmed, and I want to make sure I have plenty of time to make sure everything is in the right place.

Posted on

Spar progress as of 10/4/23

All four main spars substantially built; exceptions are noted below. Two upper rear spars have been started, with plywood web glued to the upper and lower caps – not really caps, but for lack of a better term…

Remaining work: Main spars need to be trimmed to length and dihedral clearance cut made on the lower spars. All holes need to be drilled, bushings fabricated and glued in place. I’ll need to fabricate and glue in shims for the landing wire/N-strut attach brackets on the lower main spars.

Posted on

Progress, up to a point

During two working sessions today I got most of the assembly of the lower main spars complete. “Most of”, because when it came to laying out the plywood blocks for the landing wire attach points… well, after a while studying the parts and the prints and the spars, none of it makes any sense. The upper wing spars were not exactly straightforward; a few of the parts didn’t match the plans, but the end result looked correct in that the location and final layout of the blocks matches the print, even if the parts making up those blocks are a bit different. I’ll need to spend more time studying the plans for the spars, as well as the plans for the N-struts and landing wires to figure out what needs to be done.

I also ordered a gallon of T-88, hopefully I’ve got enough to last me until it gets here mid-week.

Edit: After looking at print #15 of the plans, things are quite a bit clearer. That drawing shows the flying wire, landing wire, and N-strut attachments, with part of the spars shown. Tomorrow I’ll be able to glue in the blocks for the lower main spars and, hopefully, get them finished. Well… “finished” is a relative term, I suppose. I haven’t started attaching the parts for the wingtip bow support, but I may just hold off on that for the time being.

Posted on

Main spar progress

It’s been a busy week. The two upper main spars are essentially complete. Spar caps, stiffeners, and all of the filler and reinforcing blocks are assembled. The only thing not done are the outboard ends, where the tapered pieces for the wingtip bow attachment need to be assembled. The two lower main spars are under construction now. Both have the caps and web glued, and one has the stiffeners on one side. I’m planning to finish as much as I can today on the main spars, and hopefully get at least one of the rear spars glued up.

It’s been a real joy working in a place where there’s plenty of room to work. The availability of a large number of bar clamps – in addition to the 40 or so spring clamps I have – really helps as well. I took the day off work yesterday and was able to get over there once in the morning to set up a spar, then again in the afternoon to take that one off of the jig and glue up the next one.

Stu is anxious to get enough pieces built to start getting wings assembled so they look like wings — I can’t say I’m not in agreement. I was a little tempted to build a rear spar after the first main so we could assemble one complete wing, but I’m convinced that this way is a lot more efficient. For one thing, after the first spar we’ve both figured out enough ways to make the process better that each spar is taking less time than the one before. Just as an example, my process for getting epoxy into the grooves in the main spar caps has evolved and gotten much more efficient with each spar. It’s almost a shame there aren’t any more to do. On the last couple I would get some glue on the long edge of a popsicle stick and use that to spread it into the groove. After doing a foot or so, I’d slowly follow through with an acid brush with the bristles trimmed down to about 1/4″ or so, to make sure it was evenly distributed and get any excess out of the groove. The result was the cleanest glue joints of all the spars.

I’ve been going through T-88 like crazy. Gluing 9 and 10 foot long pieces of wood uses a lot of epoxy, and I know the laminations for the wingtip bows and tail surfaces will use a lot as well. Given the price increases since the last time I bought glue, I think I’ll just order a gallon.

Posted on

Started on the second spar

This morning I went over to Stu’s and finished gluing the root attach blocks and the blocks for the N strut and flying wire brackets to the spar. Other than the tapered extension for the wing tip bow, that’s all of the wood for the first spar. Once the glue is cured, I can start locating and drilling the holes for the attachment bolts and bushings.

With that done, Stu and I started on the second upper wing spar. The bench has threaded inserts set into the edge, and he’s got a long steel rail that bolts on. It’s 2 x 2 inch square steel tubing with mounting brackets welded on. The rails were designed and built to bolt to the table, then he’s got a steel sled that sits on them that he can use to flatten a large wood slab using a router. We bolted one rail to the edge of the table, overhanging the work surface. Now there’s a long work bench with a straight, level steel rail on one edge.

We glued the groove in the spar cap, inserted the plywood web, then glued the other spar cap. One spar cap is clamped against the rail, then the assembly is clamped in place to hold it straight, flat, and properly spaced at 5-3/4″ total spar height along its entire length.

I think about 10 ml of epoxy is plenty to glue one spar cap groove. I mixed two batches today. I’ve been using 60 ml syringes ordered from Amazon to hold and measure the glue – it works wonderfully. I can very precisely measure out even very small quantities.

Posted on

First spar, continued

It’s been a bit of a learning experience building this spar. The amount of glue required, of course, is one thing – about 45 ml or so, I think, for the whole thing. There are still a few pieces of plywood that need to be glued, most of them for the flying wire and N-strut attachment brackets. Yesterday Stu showed me his pneumatic pin nailer, which I plan to use. It’s not unusual to use staples or small brads to hold wood together while glue cures. This thing shoots ridiculously small wire pins — 22 or 24 gauge, I think — with no heads. They’re just enough to hold the wood in place, and won’t need to be removed.

I also found that the spar has about 1/8″ of gradual taper toward the tip end. That was a builder error; it’s supposed to be a constant 5-3/4″ across the entire length. When I assemble the other three they will be correct. It’s not a critical error; I can fix it with shims when the wing is assembled. It’s even noted in the plans that ribs may be shimmed where they attach to the spar. It’s just been an inconvenience. Before I found that taper we’d cut some reinforcing blocks that fit between the spar stiffeners to a constant length. Some needed to be sanded, some needed to be re-cut because they were too long. That’s when I measured the spar height more carefully. I had just measured one end and a spot partway down the spar before — I guess it didn’t occur to me that it would have a taper to it. Everything else is good, there’s no bend, twist, or warping, so it’s good to go.

Other minor things — the plans call out 120-1/4″ for the spar length, but the main caps are 120″. Obviously the quarter inch at the tip isn’t going to make a difference, I’ll just make sure both spars are exactly the same length.

I’ll go over tonight and finish the assembly of this spar, and hopefully get started on the next. I also need to find my box of 4130 steel tubing and see if I’ve got the stock I need to make the bushings for the wings. There are bolts through the wing that hold the attach brackets for the fuselage, struts, and flying & landing wires. All of the holes need steel bushings through them. Simple enough to cut and file to size; I just need the right size tubing. I bought a “grab bag” assortment of random tubing cut-offs from ACS a while back to see if I could learn to weld. If I’ve got a couple feet of the sizes I need, I can use them for this.

Posted on

Gluing up a wing spar

Yesterday I headed over to Stu’s to glue up all of the pieces to the aft face of the upper right wing spar. There are two full length spruce spar stiffeners, four pieces of plywood at the wing root, spruce blocks placed at each rib location, and four plywood pieces for the flying wire attachment brackets. Then I’ll get to flip it over and do the same on the other side.

When I was building wing ribs, I found that a total of 8 ml or so was about right to make two ribs. Since I did that a lot, I got used to mixing up small batches of T-88 epoxy. Yesterday was the first time I have had to mix relatively large quantities — I went through two 20 ml batches, which is about the most I can do in the little medicine cups I bought for this. Even that left me slightly short. There are a couple of plywood attachment pieces that I didn’t get installed yesterday. System Three makes auto-mixing dispensing cartridges, but they’re substantially more expensive to use. As in, over six times the cost. I think I’ll be sticking to mixing cups. I may need to get some larger ones, though — mixing up 20 ml at a time isn’t going to work for a lot of this stuff.

Posted on

Last rib done, first spar started

I just pulled the last two false ribs in the jigs. It’s been a long haul — six and a half years since I built the first rib, but now they’re done AND I’ve got the materials and the place needed to continue the build.

Last night I was over at Stu’s place. One of the main spars has been partially assembled; the spar caps have been glued to the web. I got all of the rest of the parts for the aft face of the spar fitted and ready to glue up. I decided to designate this one the upper right wing. I’ll head over tonight and glue it.

I briefly thought about tearing down the rib jigs now that all of the ribs are finished. I decided not to do that quite yet. For one thing, there’s a chance I may need or want to make more of them for one reason or another. I don’t need two jigs, though. I’ll probably leave the first one I made as is, and pull the blocks and plastic from the second copy. It’s not a high priority, since it will only yield a 4′ x 1′ chunk of MDF.