The Development of a 3D-Printable Flying Wing Parametric Design Process
Below is a paper I wrote to compile the methods and progress of one of my independent research projects. I've had to solve a lot of unique problems and adapt to some pretty interesting workflows, so take a look if you're interested- otherwise, farther down the page is a more concise summary of the actual workflow itself without in depth explanations of the underlying techniques.
THE DESIGN PROCESS
Humble Beginnings: Projects that Leave the Ground
Like all good things, many of my flying designs begin in various aerodynamic simulation software. The two that I've found to be the most accessible are OpenVSP and XFR5. Both are open source, and both provide parametric aircraft design and aerodynamic approximation. This results in a great jumping off point for me where I can vet projects and quickly go through various design iterations based on readily accessible data. XFLR5 is particularly nice because you can work pretty closely with your aerofoils and hone in on chord point and therefore get a better idea of weight distribution and structure, which brings me to the next phase of the workflow.
A jarring photo of a twin boom aircraft I designed in OpenVSP. I went as far as designing the entire structure down to the mechanical linkages, and then I compiled GCODE to 3D print it in a few dozen significant parts, but I haven't actually gotten around to building the thing.
XFLR5 is the other main software I use- it's stronger in terms of analytical tools, which are needed when designing flying wings, aircraft that in a broad sense trade aerodynamic versatility for efficiency. I already did the heavy lifting in terms of design on the wing above- I'm planning on cutting it out of foam at some point.
Analysis on the aerofoil used in most of my flying wing designs- XFLR5 makes you feel really scientific, which is definitely a benefit until you compulsively throw on a lab coat. Here I'm graphing center of mass vs. angle of attack, something relevant to know when making compartments to correctly distribute weight.
In all of it's glory, here is the camber up aerofoil that I've come to know and love through my various flying wing designs.
Heavy Lifting: The CAD Phase
The first and primary step of converting aerodynamically designed geometry is taking the dimensions and remeshing. There's a fundamental difference in the way models are generated in prior mentioned aero software vs. typical CAD: in NURBS style editing, i.e. AutoDesk Inventor, geometry is calculated via mainly booleans and extrusions, and therefore point and triangle based meshes don't work. Hence the first step: replicating all of the dimensions used in the aero simulation, and then slicing the model up into digestible bits that can be individually focused on.
I need to slice up my models into parts because of the constraints of my 3D printer build volume (220mm in the xy, 240mm in the z). Once done, I assemble everything back into a single file and begin making sure the whole thing actually fits together. This includes wing spar locations, wire holes, mechanical aspects like control surfaces, and most importantly for my modular wing design, structurally sound screw in mounts for every single part. Most (albeit limited sample size) 3D printed airplanes throw away a huge advantage of 3D printers (versatility, ability to quickly modify parts) by making every component glue together. I've tried to avoid this in as many places as possible.
I've used similar workflows when designing the 3D printed rockets that makes my TARC team so unique, although the primary simulation software is instead OpenRocket.
Above is plane in the intermediary phase- I've put this project on pause because the large number of parts involved makes it a horrible testbed for scalable 3D printed aircraft.
This is what a work in progress design looks like- I've flushed out many of the basic fittings and structural members but have yet to integrate internal structure, flight components, or mechanical linkages.
Physical Manifestation: GCODE and 3D Printing
Once I've completely 3D modelled the structure and sliced the vehicle into properly sized parts, I can begin optimizing the GCODE. This includes 3D printing infill, width, speed, and a whole slew of other settings that I tweak strategically for the best results. In order to make my models compatible with as many GCODE slicers as possible, my planes typically rely heavily on this phase, because the internal structure of the wing is generated here. I use a cubic subdivision mesh, because my tests have revealed that it offers the best strength in the lateral directions I'm worried about.
After slicing up the GCODE, the printing process can begin. With prints properly scheduled, the printers can be running 24 hours a day and output a significant amount of parts. Seen here is the printing process of two mirror base wing sections. These hold the linkages that join the wing and the body as well as the modular attachment points that join the outer sections.
Once all parts are printed, assembly can begin, and all electronics can be wired up. The plane on the left is an example of the result of the cumulative work outlined in this design process. In this image the plane is mounted on the pneumatic launcher I designed, however, that's a whole separate topic.