Adjustable Prop Bearing by Bob Morris

The photo shows my current CT adjustable front end design. It is made from 3/4" 6061-T6 aluminum angle (available at http://www.metalsdepot.com) and two 2-56 screws. Earlier versions were made from aluminum brackets found in the small hardware drawers at Sears Hardware but they had a tendency to get bent by crashes. The Al part has a 1/8" hole which accepts a Peck Polymers nylon bushing. The prop shaft and bushing are lifted out of the Al part through a slot in the top for winding from the
front. The set screw at the rear adjusts down thrust and bears against a small piece of stainless shim stock glued to the top of the stick. The hold-down screw goes into a threaded hole in a small piece of Al sheet embedded between the bottom of the stick and the thread binding. There is a small piece of sandpaper glued under the front of the Al part to prevent side-to-side slippage. The Al part and two screws weigh in at 1.6 grams. This is working very well and gives stable fine adjustment of thrust.

I find that more and more down thrust and less side thrust are needed as winds increase. I think that the stick is bending some under the tensile load from the rubber. I have considered adding some carbon fiber reinforcement along the bottom of the stick but this could be considered to be not in the spirit of the design. In lieu of this I will look for stiff light sticks and tune for high power climb.

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