A Frame Design Change

The other day, I stopped at the hardware store to see if they had small pieces of wood, and their selection of aluminum caught my eye. I pulled out a hollow square tube and while it was extremely rigid, it was also too heavy. However, I’ve seen lots of stuff with holes drilled down the length to lighten it up, so at school on yesterday I stopped by to ask my Engineering Statics teacher how much holes reduced the strength of material and such. I never actually asked him, as I started telling him what I wanted it for, he asked some questions on weight and thrust, and then recommended I use some basswood about the dimensions of an average wood yardstick (1″ x 0.25″?), oriented vertically. Then, because it would want to vibrate left and right as it’s narrow, simply get some fishing line and run it from one arm to the next all the way around, making a square of the fishing line. A quick sketch is handy.
I just used Paint, as I’m feeling too lazy to make a better one in Sketchup. The arms and plate will be made out of wood, no aluminum is planned now. The red line indicates the location of the fishing wire which stabilizes the arms from moving in the horizontal direction. Making it this way should make it pretty light.

My teacher also told me if I want it really light I use a simple truss instead of solid wood, and we start talking about simple truss’s in class tomorrow (now today, Friday). I said I would, but not until I know how to fly good, I don’t want to spend hours making a truss only to destroy within minutes it cause I crashed on my first flight.

My prop balancer arrived today. Looks pretty nice, although I haven’t used it yet. I’ll report back on how I like it once I have props to use it with.

On Wednesday I ordered a 5kg digital kitchen scale, so that I can weight parts as I go along, measure motor thrust, and try different frames in the future to find the lightest ones that are still strong enough for use. Less weight equals less power needed for flight, and less power needed equals longer flight times. I also just recently found a post on RCG that said that for a given frame, the longest flight time will be with a battery that weights the same as the frame does. So lighter frame also equals smaller battery, which is cheaper, and cheaper is always good.

About three hours ago I got an email from HobbyKing, saying my package is packed and sent to shipping, and to allow 48 hours for tracking information to appear on the website. So as long as it doesn’t get stuck in customs, it shouldn’t be too much longer…


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