Part 1 here
It was perhaps slightly naive of me to hope more power would be the single answer to everything. It might still be. After another 2 months I have yet to find out…
My next attempt at getting the base of the pylon to not break was to completely replace the little block at the bottom with this thread reinforcement system I completely made up. But it has held the bearing on so far, and after the wood snapped a few more times I coated the surface of the entire section in superglue. Somewhat amazingly, this actually did some good, and it’s only broken once since then.
Around this time I also bought a small 5:1 rubber winder, and some O rings to make motors with. It was strangely difficult for me to wrap my head around how to make loops when I have to tie the knot last, and I gave up on braided ones for now. My first attempt I was apparently not paying attention at all and ended up with just a single loop with a ring on it, which was not much help. 1 Though I guess it at least proves that less power is an anti-answer. Also, turns out it’s pretty much impossible to use the winder without a ring, or some more-rigid part to get the motor hook into. (I tried anyway, of course. This may have caused a few of the aforementioned breakages.) It was a feat of coordination at first to get the rubber transferred to the motor hook, even with a ring, but I’m getting the hang of it.
I also finally thought to turn to the ODM for any ideas on what might be going wrong. The “not that great” performance mentioned last post usually consists of seeming to be flapping decently, but not getting any forward motion and therefore (I presume causation) no lift, a behavior the ODM describes as “mushing.” Common causes listed are a center of gravity too far aft or too little stabilizer area. The most obvious way to help this is somehow lessening the amount of sheet metal holding on the tail, so here begins a bit of an odyssey…
I found an aluminum can to cut up! After a bit of googling, I decided the thickness of the metal is most likely around a fourth of the thickness of the sheets I have, so for the first attempt I used six layers (still thinner than the two I had previously) and also decided I could make the piece around half as long. I cut out a thin strip and folded it into an accordion shape, and superglued each of the layers together before attaching it to the main body. Turns out that many layers of glue is far stiffer than two thicker pieces of metal, and once I had it on there I was not going to be able to bend it without just ripping the whole thing off, so I ended up cutting a bunch of tiny wedges out of the tail piece in order to attach it at a reasonable-looking angle. But it did seem to help.
At the same time I did some messing with the lengths of the conrods, with the goal of increasing the dihedral slightly because of one day where it kept flipping over for some reason. I had originally cut the upper conrods to allow for another hole 1/8” farther apart, so I cut those, and then made new, longer lower conrods. Which turned out to be slightly too long, so I found room at the end to again lengthen the upper conrods. Ended up with lengths of 3 1/8” for the lower, and 4 7/32” and ~4 9/32” for the upper. (They have apparently been different lengths the entire time. I don’t recall when I figured this out, but you have to put them on in a specific order for the mechanism to work without catching. I suppose I need to just redo the wings so they all match, but that’s so much work.) It didn’t seem to have any particular effect, but so much for me trying to be all scientific and only change one variable at a time. Higher dihedral is probably better, so I’ve been keeping it.
Anyway. next I tried replacing the tail attachment with only two layers of can metal. It was immediately apparent this was too far in the opposite direction, so I somewhat imprecisely cut a third layer and added it on top. It didn’t attach very well, and when I took it out to test the wind kept pushing the tail up to almost 90 degrees and back, and after a little of this the original two layers snapped in half and gave up on the third.
On to the next attempt!
Next was a four layer accordion. It came unglued within a couple of trials, but seemed like a promising compromise on stiffness. After putting it back on with a bit more reinforcement, it flew well for another few flights, until I tried to adjust the tail a bit higher. Then it started going floppy again, as before but to a lesser degree, and I soon noticed that the bottom two layers had snapped. At this point I realized that, just maybe, the plans said “soft” metal for a reason, and even if I could set it to the perfect angle that a stiffer piece is not necessarily better. But I don’t know how to reconcile this with needing it to stay put under wind.
In a logical leap of somewhat dubious merit, I decided to make another four layers, this time held together with white glue and making sure to clamp them together a good long time. On a whim, I thought I’d see what would happen if I encased the old, half-broken metal in just a great glob of the same white glue before going through the effort of replacing it – not expecting this to last any longer than its predecessors.
But it did! And after I finally straightened the tail out2 By leaving it clamped between several textbooks for half a week (apparently I can’t glue the thing on straight to save my life), it stayed in the air for the longest time yet!3 An entire 30 seconds. I can’t decide whether to feel accomplished or underwhelmed at myself… I’m not sure how much weight is really being saved at this point compared to the original, but I was hesitant to break it. Luckily this was decided for me next time I went out. Failed to get anywhere near the previous record for no apparent reason, and after a few flights the tail snapped. I would say the below-freezing temperatures were related, but it was just as cold the time before. (More variables, whoo!)
In any case, I got to try the other thing I made. Had some trouble gluing it on, but even once I had it there it did not seem promising. The wind kept pushing it either too high or too low, much as before, and after a few launches it came off again, but this time the bottom layer of metal was also kinda bent off from the others. So this idea is also a no-go.
I’m running out of ideas for how this metal was supposed to work; perhaps in the future I will discover what Mr. Garfinkel knew that I do not. In the meantime I have some vague ideas for how to more or less get rid of the metal all together, and maybe finally make some progress. Hopefully it pans out so I don’t look like an idiot for leaving this as a cliffhanger, but this is long enough for now!