Flight Logs: D-Orny-One-III, Part 3

Part 1
Part 2

Aright, time to explain my amazing idea to get somewhere with this…

I redid the tail with just wood and tested it at a bunch of different angles. That’s basically it. But I was proud of my idea to use a layer of aluminum also, to make it easier to redo the wood over and over. It at least kinda worked.

The long explanation is that I completely redid the ends of both the body and tail to be more angular¹and less slightly-phallic so that it would be easier to cut a small wooden triangle to hold the tail at a set angle (since I apparently cannot find a combination of aluminum and glue that is adjustable by me, but not the air). The single piece of metal was mostly there to hold the tail in place every time I reglued it, and not really meant to be load-bearing otherwise.

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I still had to replace the aluminum a number of times, mostly from me having trouble cutting the tail back apart to adjust the angle.²Also acquired a nonzero number of cuts on one finger from this I was aiming for 2-3 degrees between trials, but it was surprisingly difficult to be even that precise, and several times had to get some shavings off a scrap piece of balsa to put in because I sanded it down too far.

Started out at around 20 degrees to be safe, but it wasn’t till I got below 10 that it seemed to start improving at all. Proper science would dictate that I get more than one or two data points for each trial, but I was frequently stymied by my hands freezing or something breaking³Naturally the rest of the bits couldn’t stop going wrong just cause I’m trying to focus on one particular bit or the wind picking up. (Proper science would also dictate that I have a plan first, and not save half of the considering-how-to-do-proper-science until after I’ve already done all the experiments. I think I was expecting the results to be more obvious. Anyway.)

I started out testing everything at 300 turns, and then got bolder and went as high as 500 (also see below about it getting cold). 2 months of trials turned into the graph above. I decided 5 degrees was a nice round number within the range the optimal angle is probably in, and got one trial before the tail fell off, which resulted in the outlier up at 38 seconds. Probably the wind. I’d like to get more but at this point gave up on getting any more flights in December.

Even besides the comparative lack of data, there were a number of incidents to cause difficulty with Proper Science. Least significant⁴probably was more trouble with the crank bearing. While walking back from a test flight I noticed that the wood around the bearing was squishy, and on further investigation found that there was an irregular chunk just missing from the middle of the stick, as if some tiny bug had come and eaten at it. I did my best to fill it in with a mixture of sawdust and white glue without gunking up any moving parts.⁵ Luckily glue is less sticky once you mix a bunch of stuff in it Looking at it after letting that dry, vertical motion was hindered but it could still move side to side. So I tried some more glue encasing, going along the threads and where the metal contacts the wood, with both white glue and then superglue when that started coming off. It again held up better than I would have thought. I also found out, by buying a new bottle of CA for no particular reason, that my old bottle has deteriorated quite significantly. I was startled on opening the new one at how liquid it was, and how much better its working. And I don’t think most of the difference can be attributed to a brand change.

Lessons learned:

• Proper Science requires a plan.
• Glue can still dry out inside the bottle.

More concerning, and more difficult to know the impact of, is the effect of freezing temperatures on every part of my ornithopters. I’ve been focusing on only testing at times with the least wind without paying much attention to the temperature, and going out in the cold hasn’t made anything instantly, catastrophically fail, so I’ve kept on with little change. My cursory research has yet to yield any mention of freezing affecting aerodynamics, but it surely has to mess with the rubber at least. I would like to do some Proper Science to try and see what difference it actually makes, but so far all I have is a) a subjective feeling⁶ Probably backed by something I read, but I forget where that rubber is sometimes easier to wind when its cold, so I need more turns on it to get the same tension, and b) some incidents in which the rubber appeared to freeze (to itself?) and become harder to wind. I tried to let the motor warm up a bit between trials once, and this appeared to make the latter problem much worse, and resulted in me accidentally ripping out the tail hook. Replacing it is another potential concern for Proper Science, but I made the new one closer to the shape on the pattern and I like it much better – sometimes the motor would fall/twist itself off as I try and wind it, but that hasn’t been a problem since making this one.

And this is where I conclude another round of trying to explain myself trying to do things. Not giving up on this one yet, but here’s to better science in 2021!