I've been trying to find the required motor power for a quadcopter. I first calculated drag power and then I made a linear trend line for motor power against motor weight. I made the motor power 1.5 times the drag power and then used the trend line to find its weight but this seems to give numbers that are much too small. What am I doing wrong and how can I fix this?
What I did was take the altitude, the temperature, estimated weight including payloads, rotor radius and chord, and the speed to solve for drag using the drag equation. An example is alt: 400 ft, temperature: 65 F, estimated weight: 3 pounds, rotor radius: 6 inches, rotor chord: 1 inch, and speed: 20 kts. This would give a drag power of 16 watts and this is so small that the motor weight is negative according to the trendline.