Gemini Propeller Carving Duplicator PROPELLER CARVER HOME

History of the Gemini
Propeller Duplicator

Dear Fellow Airplane Builder,

Like any builder, I wanted my Pietenpol to be special. It would be built close to the original design, with only minor changes to improve performance.

The Piet would be powered by an upgraded Ford model "B" engine. The bored out, higher compression engine was significantly more powerful than a stock model "A" engine, putting out between 50 and 60 hp. I knew I would have to experiment to get the optimum propeller.

When the time came to acquire a propeller, I was faced with the following options:

  1. I could buy an inexpensive, lower quality, hand carved prop.
  2. I could buy an expensive, high quality propeller.
  3. I could inexpensively carve my own high quality prop.
 I decided to carve my own propeller. I was able to obtain the design for the original Pietenpol propeller (from the original propeller carver), along with recommendations on how to modify the design to pitch it correctly for the most efficiency.

I knew from my experience with two friends in the prop carving business that it would be very difficult to precisely carve two identical blades for a symmetrically accurate prop. So I decided to carve a one-blade master and use a duplicator to carve two identical blades for the final propeller. This gave me the option of modifying the master and easily carving additional props for changes in pitch, diameter, planform etc.

Getting an acceptable duplicator turned out to be the hard part. The inexpensive, plan-built, plywood carvers I found were not rigid enough for the accurate duplication I needed. The mass produced general purpose duplicators were also too flimsy. An industrial duplicating mill was out of the question due to the extremely high cost.

J.B. Allred and 50C I, therefore, had no choice but to build my own duplicator. Fortunately, as it turned out, I had a way to do this. Our company, Allred & Associates, is an engineering design and product development company. We went to work on developing the tool, a duplicator specifically designed for propeller carving. Our objective was to design a prop carver that was simple and easy to use, relatively inexpensive, and rigid enough to repetitively carve an accurate blade.

After I carved the Piet prop, I showed the tool to some local builders who expressed considerable interest in acquiring their own carver. We subsequently decided to make it available to other homebuilders, which is why we are now beginning to sell units.

I hope that this carver will enable other builders make the best, most efficient propeller for their own "special" homebuilt.

J. B. Allred

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Gemini Propeller Carving Duplicator Allred & Associates Inc.
Gemini Carving Duplicator Division
321 Route 5 West
Elbridge, New York 13060
Ph. 315-252-2559
Fax: 315-252-0502