The intersection between my limited knowledge of aerodynamics, 3D printing, and CAD. Also wanted a bit of variety / challenge from my seemingly endless iterations on a new 3D printer design.
(Grew up around airplanes and aerodynamics. Watched Burt Rutan do a gear-up landing in a Vari-Viggen.)
Needed a challenge, and some variety, so tried to design a wing.
Apparently there are some issues. Not just with my design ability.
Plastic is kind of a crap material for aeroplanes - heavy and lacking strength. But there is advantage in exact placement of material, and easy fabrication (past the first iteration).
High-aspect ratio wings are more efficient when flying, but more trouble to print, as now seems obvious.
Reducing the weight of heavy plastic wings through a series of design experiments … did not work well. Simply describing the wing as a solid with low infill worked as well or better. (Different infills do work in differing way, however.)
And the latest/current version of Cura unexpectedly added a support tower to the middle of the print (not in evident here).
Flying things have severe requirements on weight and structure, mostly beyond the current state of the art in 3D printing. Still interesting to explore.
To be clear, this exercise was mostly about expanding my design vocabulary. Aeroplanes make pretty severe asks between weight and strength on design, to get something that can fly. We could only meet that ask a bit over a century ago (and not before).
Using FDM to design a workable plastic craft, more than a basic glider, is a challenge.
After the pictured iteration, lightened the wing structure. (Low infill beats simple explicit structure, it seems.) Widened the rafts (as seemingly essential to these tall/narrow prints). Had reason to compare the different sorts of infill offered by the slicer (Cura).
Showed my grandson how the earlier iteration was very strong, and the current iteration sufficient (but less strong), and bled on the result.
Went through a few(?) more iterations, mostly with the aim of reducing weight, but also to make best use of 3D printing.
Getting better wings was … interesting.
Found the default-hidden “Spiralize Outer Contour” setting in Cura, to generate a single-walled print. Added compound curves (easy to fabricate in FDM printing, but difficult for traditional fabrication) to add stiffness in the wings.
Ended up printing the wings at 100mm/s, 240C, 0.3mm layers, 0.5 width, and 140% flow - to get minimal weight with good strength.
The model below is still heavy, and the center of gravity too far back. Printing an adjusted body.
If you look at the trailing wing edge, note some spots are a bit ragged. Not sure the cause. The wing printed with infill has a perfect edge. Guessing the print head motion in “spiralize” mode is … sometimes … leaving too much heat in the plastic. Printed and installed a better duct for the part cooling fan, but no obvious change.