Figuring Control ratios:

Let's assume that most bellcranks rotate 45 Degrees in each direction. If we want 45 degrees of flap, the ratio is easy, 1 to 1, but what if you want 30 degrees of flap rotation?

Using simple Algebra we can solve these types of questions.

In this type of problem, we will have 3 out of 4 variables. Usually, these fixed values will be the bellcrank rotation, the flap horn length, and the flap rotation we want. The number we're missing is the bellcrank moment arm.

The 4 attachments are PDF's and are sized for a standard sheet of paper. You can download and print them with your printer if you desire.