James,


This is one of the easiest things to measure.

Just use a spring-draw scale, like the type used to weigh laundry, hook it securely to the tail of your plane and hook the other end securely to a fence-post, or to another stationary upright.

Get the help of someone to read the scale, with the engine running full-bore. It may fluctuate, so the average is the right number.


It will completely convince you that for this, all thrust calculators are worthless (but not for prop-size-RPM-HP calculations. For this some of them are great).