On Saturday, October 5, 2019 at 1:23:56 PM UTC-7, Patrick Grady wrote:
I know how to measure a glider's pitch moment of inertia. In our hangar, we use a hanging cradle to lift a glider for more floor space. This means that we essentially have a pendulum with a glider at the bottom.

You could measure the period of oscillation with a glider and without. The extra mass of the glider wouldn't change the period of oscillation, but the moment of inertia would. I've used this technique to measure rotational inertia of bicycle wheels, and I think it's possible to get within about 5% accuracy.

https://en.wikipedia.org/wiki/Moment...pound_pendulum

Patrick,

Interesting. I had not thought about a pendulum's bob's moment of angular inertia affecting itsperiod. I would assume the glider would have to be rigidly mounted to the pendulum arm for this effect to be exhibited and that might be problematic with your sling.

The key thing I am looking for is the pitch-axis model. Most importantly, as simple a model as possible. I want to understand the fundamentals of what the aerodynamics do the the larger mass-spring-mass model. I often paraphrase a quote that was attributed to Einstein, "Every model should be as simple as possible, but no simpler." Only after that model has been established do I need to parameterize it. I suspect X-Plane, which I have never worked with, would have the parameters for some gliders but I believe the models it uses are more sophisticated than what I am looking for. That is where I would hope an experienced aerodynamicist would be able to determine a proper model for the investigation and then help parameterize it; possibly extracting the needed parameters from simulators like X-Plane.

George