pyprop: prop database validation

[Rahmathulla P]

Hi Cory,

I found the PyProp database is super useful to select the right prop, motor and ESC for an aircraft designed uisng MachUpX. I'd like to know the source of the data in the database. I've made an attempt to verify an APC prop, "apc_8x6" by calculating the thrust and power using PyProp and compared against the values published in their website:

Performance Data - APC Propellers

I've downloaded "PER3_8x6.dat" from the above

The coefficient of thrust (Ct) and Thrust values from PyProp are closer to the "PER3_8x6.dat". Unfortunately, coefficient of power (Cp) and power values from PyProp are different. The following is the comparison:

I've attached the script to calculate the above values. I've also attached the "PER3_8x6.dat" for your reference. I assume the power is the mechanical shaft power (not supply power).

Could you please clarify the source of the PyProp database? Could you please look into the script and let me know your comments why the power doesn't match?

Regards,

Rahmat

[Cory Goates]

Hi Rahmat

The APC data comes from what is (or at least was; this was about 5 years ago) published on the APC website. Are you using a DatabaseFitProp or a DatabaseDataProp? The former fits polynomials to the database data, and so won't give exactly the same results. The latter interpolates the actual databased data and so will be more accurate.

Cory