7850 rpm on an 18 x 8 is barely 1.5 hp and 3.75 kg thrust according to ThrustEstimator. A strong 61 two stroke makes that horsepower!
MVVS-prop-power-calculator gives 2.17 hp and 7kg thrust.
Will be interesting to put a scale behind it and do an actual thrust measurement.
Must try APC props !
OK, Here is field measurements taking with electronic scale (fish scale max 20kG):
SAITO FG-36B (Stock ignition replaced with RCEXL hole sensor based ignition).
Prop: Xoar 19x8
Max RPM 6870-6980 (Note: It is not optimum RPM for this engine in order to get max HP out.)
Static thrust 5.5kG - 5.7kG
I am going to use APC 18x6W in order to get my target of 8500RPM (8300-9000RPM considered the best for max HP output).
I hope static thrust may go up a bit due to low pitch prop working better in static conditions.
From today test I think 19x8 is a bit too much for FG-36 in order to get max HP output.
With Xoar 18x8 I have measured earlier I was getting somwhere around 8000RPM. No thrust measurement was done at that time.
Need to repeat my experment with 18x8 again and measure static thrust while waiting for APC 18x6W to arrive.
Anyone can share field measurements with other props?