I'm working on performance calculations for a plane I'm building. By setting the sum of my drag formulas (one for the wing, one for the fuselage, both with predicted drag coefficients) equal to the thrust at a given power setting, I'm able to come up with some predictions for speed. They seem unrealistically fast, given my experience with previous builds for which I did not do performance calculations. I figure that this is because of the prop, but I do not know how prop performance varies with different air speeds.
My questions are:
- As airspeed increases, does the propeller produce drag similar to a wing while producing the same amount of thrust, or does it produce less thrust?
- How do I take the prop into account in these calculations?
I'm using a 1550 Kv motor, for calculations I am using 7.4v at full power with an APC 8x4 prop, produces 468 grams/4.59 newtons at 8,620 rpm (rpm from data sheet).