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How to Calculate the Prop Size for an RC Plane

One of the most important steps in building your own RC plane is choosing the right propeller. If the propeller is too big or small for the engine, the plane won't function properly. Calculating the propeller size is an exact process, but there is a quick formula. The Propeller Load Factor (PLF) formula allows you to choose the appropriate size. After installing the correctly sized propeller, your RC plane will be ready to go.

Things You'll Need

Calculator

Instructions

- 1
  Check the product specifications in the manual for your RC plane to find the size. All RC planes are labeled according to their size. This is also found on the packaging when you purchase the unit. One example of RC plane size is 9x7. The first number, 9, is the diameter and the second number, 7, is the propeller pitch.
- 2
  Multiply the diameter of the unit by itself. For example, if the diameter is 9, the result would be 81.
- 3
  Multiply the result of Step 2 by the pitch. For example if the pitch is 7, and you multiply it by 81, the result is 567. This is the propeller load.
- 4
  Purchase a propeller that is labeled with the same propeller load as found by your calculations. This is the correct prop size for your RC plane.

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