[OpenSCAD] Challenge in the process of designing an airplane wing

Arleg arthur.legare at hotmail.ca
Wed Apr 4 16:34:26 EDT 2018


Hello,

The current project I am in is an all modular rc plane design. So far, the
complete wing has been openscaded with the exception of the wingtip, which
was planned to be curved... and that's why it ended up being more
complicated than anticipated. Below is what the wing looks like right now
(still working on the servo mount and associated mechanism) :
<http://forum.openscad.org/file/t1378/perspective_aile_en_travail.perspective_aile_en_travail> 

The challenge is in the curved winglet design, where the path it follows is
a quadratic function. To do so, I take the 2D section of the wing (airfoil)
and I put linear fragments (regular linear extrusions) to link the points
along the quadratic path. However, I realized that junctions between linear
fragments are not perfect at all when using a regular custom rotate_extrude
of wing cross-section with an angle specified, because the fragments
parameter ($fn) for an extrusion along axis only apply to a 360 degrees
angle, and not locally to the specified portion of extrusion with an angle.

Here are some pics to help visualize.
<http://forum.openscad.org/file/t1378/vue_du_dessus_saumon_ModulAir.vue_du_dessus_saumon_modulair> 
<http://forum.openscad.org/file/t1378/vue_de_surplomb_intersection.vue_de_surplomb_intersection> 
<http://forum.openscad.org/file/t1378/intersection.intersection> 

I am afraid these bad junctions could make bad STL... and then low quality
G-CODE. Is it worth it? I was planning on getting onto a more advance
polyhedron manipulation, but I can't go anywhere, because I found no actual
way to get the coordinates from a given 2d shape. If it can help, the shape
I want to extract the coordinates from is an airfoil with a kind of inner
wall (inside its perimeter) and I use minkowski to do so. Just like in the
picture below :
<http://forum.openscad.org/file/t1378/inner_contour.inner_contour> 

I was wondering if someone had a solution for this challenge, wether it is a
rotate_extrude with $fn controlling the number of fragements on the
extrusion angle (not the 360), a way to extract coordinates from a custom 2d
shape, or anything else.

Regards, 

Arthur Légaré from Québec.



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