Here’s a handy dandy calculator to determine this size and length of a rubber motor for free flight flying models. The calculator was converted from the famous Excel sheet created by Bob Hodes titled “Calculating Scale Rubber Motor Sizes”. An article published in the December 2009 Issue of the National Free Flight Society Digest, Don Deloach, Editor. The following is quoted from the article
I have come up with a tool in Microsoft Excel that might be helpful in sizing rubber motors for scale models. Five data points are needed:
- The wing area of the model
- The weight of the model (without motor).
- The desired motor weight as a percentage of the model weight. (Bob Isaacks, for example, recommends a motor weighing 30% of the empty model weight),
- The hook-to-peg length,
- The desired final motor length as a function of the hook to peg length (for example 1x, 2s, 2.5x, etc.)
I won’t blab anymore, you’re here for the calculator. Enjoy!