Fhe credit for the formula used to create these charts goes to Mike Davenport of the Nuts and Bolts Guide to Rigging fame.  Found in Chapter 15, the formula attempts to offer a solution for when you want a quantifiable measure of a change to your rigging. The caveat is that it only works when the blade shape/size stays the same. Even if you can’t directly compare numbers across blade shapes, I still think it gives you something to ponder. In the future I hope to experiment with the formula to better take into account the blade surface area and the efficiency of the blade. The other consideration is that, for now, these charts only cover concept two blades. Feel free to send me your thoughts! Enjoy.