Unless you are trying to measure the differential or bias between the flaps and the elevator (in which case you will need 2), I kinda like Perry's method. I stopped worrying about how much total control I have (as long as it looks like it is over 30 degrees) when I discovered that I was flying the entire pattern using about 15-20.
I have also come to the conclusion that equal movement of the controls on the ground does not always equate to equal movement in the air. Now, my only control measurement before trim flights is to make sure the flap horn and bell crank are properly aligned. The rest is eyeballed untill I see what she wants in the air.
Having said all that, I used to tape two paper thin yellow plastic school protractors that would slip into the flap/elevator gap with 2 Popsicle sticks stuck to the back to slip over the wing and stab and hold them at -0-. Almost as accurate as the $25 @ professional ones but nowhere near as informative as one test flight.
Ken
Topic: surface deflication indicator (Read 1068 times)