Draftbags

Bicycles

The late Sheldon Brown compiled an awesome reference for bicycles ancient and new, living on at https://www.sheldonbrown.com/.

Vacuum Molding

Doug Walsh designed and refined the best homebuilt vacuum forming system. His plans are worth the price. The other systems you can find plans for are a joke. You don't want to reinvent this wheel! From https://www.castcraft.com/proplan.htm.

One key element you don't get in the Walsh design is a pre-blow or pre-stretch function, which achieves more uniform wall thickness and avoids webbing. That requires more articulation and complexity, and purchase of a commercial vacuum former.

Computational Fluid Dynamics

OpenFoam is a CFD code base originally commissioned by Sandia National Labs. It was subsequently open-sourced. The guys in Czech Republic at https://www.cfdsupport.com/ made a free downloadable version which runs on Windows under Cygwin. Their latest version seems to run natively on Windows. They make their money doing consulting.

Not sure about the parallel OpenFoam universes at openfoam.com and openfoam.org

CAD Modeling

DAZ 3D is a free program for modeling human forms. Its output can be transformed into other CAD programs for CFD work.

GrabCAD is a good place to find CAD models which people have shared, such as bicycles.

AutoDesk software is free for personal and hobbyist use. Supposedly its tool path generation is functional.

Machining

A CNC router runs a tool path in X-Y-Z space to cut a shape originally designed in a CAD program. The overall process is: Generate a CAD model. Translate to an intermediate format such as .STL. Generate tool paths. Render tool paths to drive stepper motors.

AutoDesk software is free for personal and hobbyist use. AutoCAD has a functional solid modeler. Supposedly the AutoCAD tool path generation is functional.

DeskProto tool path generation software takes a shape defined as .STL and generates tool paths in G-code format. It works well and has a lot of capability, and the price is reasonable.

MACH3 software accepts G-codes and translates them to stepper movement commands. It is the de-facto hobbyist CNC control software and is used in manufacturing as well. Linux CNC is a freeware option.

CNC routers are available direct from China in the $500 - $2000 range depending on size. Quality is ok, but your experience may vary. Support and lack of documentation is a little scary. Check out cnczone.com forums for advice. There is a big hobbyist community building CNCs from scratch using linear slides and leadscrews, for the person who wants an experiment as much as a resultant router.

Bicycle Power Meters

Saris rear hub PowerTap power meters are pretty expensive, but older models can be found on the secondary market in working, and sometimes brand new condition. Go with a version having a cover which is threaded onto the hub. Avoid the oldest models in which the cover is attached by two screws; they leak and are probably broken. An older PowerTap model will not have a disc mount, you will have to be satisfied with rim brakes. PowerTap files are CSV, can be opened outside the PowerTap PC application to munge the contents. Generations of PowerTap are wired -> wireless ANT -> wireless ANT+ -> Bluetooth + ANT+. I've pretty much been using the old wired stuff.

Pedal-type power meters work fine, and are great for knowing how much power you are generating as an athlete. They count all the losses, including drivetrain friction. But for aerodynamic testing we prefer to ignore the drivetrain losses and capture only the power right at the wheel.