Weather is bad, so time for development.
For the Simla we need a tool to analyse engine performances during testflying coming season and in the HP 42S I did implemented a solver program to do this for me.

Inputs are: barometric pressure (mbar), power (HP/PS/Watt), crankshaft revs (RPM), diameter and pitch (inch) and propeller constant (x). The solver program calculate the not existing value for me, for example power when all other are known or measured by the logger.

RPM and airspeed for example will be logged with the use of MODIS.

Static thrust can be measured with a force sensor and checked with use of a separate calculation program.

Interesting to see the Top Flite propeller of 14 x 4(!) does generate a thrust of 7lbs at a shaft power 1 HP.

To have an indication of accuracy I also will do the measurements with the Replica Top Flite Taurus because the IC motors do have the same displacement.

All to find the best propeller (dimensions and brand) for the Simla.

More to come

Cees