Kang Lee’s All Carbon VP
Back view of VP hub.
All joints are glued using thin CA. Kevlar is used to secure the hub to shaft sleeve joint, as well as the screw holders to hub joint.
Spring is 9.5 turns of .008” music wire formed over a .025” mandrel. Here, prop shaft is .013” music wire.
See diagrams for the dimensions of hub components. All carbon components are off-the-shelf, affordable, and fairly easy to work with.
The VP hub as shown weighs 70 mg. The hub is both stiff and light and can probably survive exploding motors.
There is some binding between the rod and the tube. I can hear the VP pop into low pitch. One solution may be the use of graphite lubricant.
Your feedback is welcome.
Front side of the hub. Here, a spring wound using a .031” mandrel is shown. The spring doesn’t seat well over the .028” OD carbon tube “shaft sleeve”.
Carbon tube “hub” before prop shaft sleeve hole is drilled. The lever arm is glued to the spar “rod” using thin CA. Only tack gluing is needed. The lever arm is later securely glued to the end of the prop spar.
Please click here if you would like do download a PDF of Kang Lee’s CAD drawings
Indoor News and Views 
I think some binding is always going to occur with this design. You have a carbon rod bearing on the inside of a carbon tube with a lot of side load. You might try polishing the carbon rod. Chuck a piece into a drill press and use some 2000 grit or finer sand paper to polish it. The smoother you can get it the less friction you’ll have.
One other thing you could look at to smooth out the transition is using a stiffer spring. 9 turns of .008 wire is fairly weak. I would try .009 wire and fewer turns.
Kang, Thanks for posting the photos & text. The diagrams with dimensions were especially helpful in clearing up some of the details. The use of off the shelf materials is very interesting to me because I have never built a VP hub, yet.