Page updated on: September 29, 2008
December 1, 2008
Making a Propeller
Overview
I have decided to build a propeller for the Cozy. The intial reason was to provide a load to test the engine. As long as I need to build one, I may as well build it to be used on the plane.
The initial propeller will be built as a climb prop. When testing an airplane, it is a good idea to get to altitude as quickly as possible.
Research
I have been studying many different websites on propeller building. They all claim it is pretty easy, so we'll see.
I have also found a PDF version of a book that is really good. It was given away for free by the author and can be found in the propeller YahooGroup. How I Make Wood Propellers by E. Alvin Shubert. To access this file, you will need to be a member of the Propeller YahooGroup.
Another resource are NACA technical Reports TN-212, "Simplified Propeller Design for Low Powered Airplanes" and TN-237, "Propeller Design - A Simple System Based on Model Propeller Test Data - III". Both of the reports were written by Fred Weick while he was working for the Langley Memorial Aeronautical Laboratory which was run by the U.S. Navy.
These reports were written in 1925 and 1926 respectively and are still considered to be up-to-date. These two reports give a step-by-step method for designing a propeller. The TN-212 method for desiging a propeller is through the use of graphs. However, the graphs seem to be optimized for engine power ratings of less than 100 horsepower and speeds slower than 150 MPH. TN-237 uses equations for designing a propeller. This is much better for me as it will allow me to input 200 horsepower at a speed of 220 MPH.
These two reports are available for free on the web. The way I found them was by using a search engine, such as Google, to locate them on the NASA website.
Another resource I have taken advantage of is visiting local aviation museums. I'm lucky as there are two large ones near me. The Hiller Aviation Museum in San Carlos and The Wings of History museum in San Martin both have propeller shops with experience prop builders.
The Wings of History's Watson Propeller shop is an actual FAA approved facility. They make wooden props for older antique, but still flying, aircraft. The shop is manned by volunteers and all proceeds go to the Wings of History Museum.
When I spoke with Guy Watson, the owner of the shop, he invited me to come down and see what they were doing. I was given a very detailed tour and learned a lot about propeller making. He has even offered to help me design the propeller.