Finding Vx and Vy
I am the lucky owner of a 1963 Jodel D140. It has a rather thin POH, with very little information about climb performance. The POH data is based on an aircraft equipped with a 62 inch pitch propellor. I actually have a newly overhauled 58 inch prop, and would be interested to know Vx and Vy at different weights and altitudes. Weight can vary from about 730kg with just me and low fuel, up to 1200kg MTOW. I fly quite a lot in the mountains, at altitudes up to about 12000ft, where flying at Vx can help one to cross ridges without spending a long time circling.
I imagine that finding Vy is a fairly simple matter of trial and error on a calm day. I don't know how one finds Vx. Can anyone suggest how I should go about this? Also, is it possible to determine Vx and Vy mathematically for different altitudes from one set of measurements, or does one need to repeat the tests?
I don't really need to know - the aeroplane has quite adequate performance and I don't envisage being in a situation where it is essential to fly precisely at Vx or Vy. But I would be interested, and it might give me a purpose (= an excuse!) to enjoy some flying.
Thanks in advance!