I want to experiment with airplane design for high efficiency and solar power. I want to try putting counter rotating propellers at the wingtips. I think this can be very efficient.
Building an airplane out of balsa wood seems like way to much work for experimenting. The idea I have come up with is to use a Maslow CNC to cut foam frames and then use a wing covering film, like UltraCote.
Here is my first attempt
There are two chains that pull the router around and a motor on the router to adjust the height. It is a cheap way to be able to automatically cut very large things. We are using 1.5 inch thick Foamular 250. This is pink insulation foam rated for 25 psi.
We have been having trouble going from our CAD tools to our Maslow. However, we can use easel.com to project flat things to a fixed depth and load that onto Maslow. So we had the Maslow hollow out the body of the wing and made some templates to use with a hot wire cutter. We covered the templates with a layer of masking tape and a layer of metal tape so the hotwire would not damage the foam template. Then used gorilla glue to attach templates to the ends. Then ran the hotwire along the template.
Needed some sanding.
Put a layer of 1.5 inch wide fiberglass reinforced "strapping tape" on both sides of the main spare and then covered with UltraCote, yellow on one side and red on the other.
It seems plenty strong enough and very light. Before the covering it was 0.32 lbs It is 58 inches by 13 inches.
Did more with the heat gun to smooth it out.
Also tried to attach a weight to make a sort of hang-glider test:
But could not get it to work well.
We did get it to work like a kite though:
In getting to this point we have "crashed" the wing many times. It really seems very tough. I will probably put strapping tape along the leading edge before putting on covering next time as I feel sorry for all the hits it gets. The final trick that made this work was having the strings on the control board wider apart than on the wing. So if it went to off to the side it will bank back toward the center, so there is built in side-to-side feedback/control. It is still human control on the angle-of-attack.
Once we get the CAD tools working right we will have the CNC do all the cutting and won't need the templates or hotwire. So it will take very little time to make a custom wing. So if it crashes or gets lost at sea we won't feel so bad about it.
Jan 30, 2021