04-06-2018, 10:50 AM
Great day flying yesterday with about half a dozen members down at the field by about 10:30am. Conditions were still a bit cold and windy, but not as bad a Saturday. There were a few poor landings though, as well as one rather catastrophic crash. Sadly Andrew's gyrocopter has now seen better days, but repairs may be possible if somewhat challenging.
The previous evening I did a bit more work trying to tune the hopelessly non-linear and inaccurate (especially at the amp levels I am pulling) current sensor on my little flying wing and was keen to give it a bit more time in the air to collect more data. This flight lasted just under 67-minutes, with 2106mAh being consumed from the 3S 3350mAh Li-ion pack. Extrapolated out, that suggests the aircraft is pulling an average of ~20.7W (~1.9A @ 10.8V) and could theoretically fly for ~101-minutes on a 100% depth of discharge (perhaps more in cleaner air and finer conditions). I am really happy about this, as it means my estimation of 150-gram cruise thrust is higher than is obviously required to maintain the desired 10.5m/s airspeed and that the airframe is more efficient than I had anticipated. Calculations suggested the necessary thrust power would be ~21W while bench tests with the relevant battery, esc, motor and prop indicated ~19.3W. But, factoring that the autopilot, sensors, servos, camera, osd and vtx collectively draw ~5W, thrust power turns out to be less than 16W. Two factors will be likely be contributing to this apparent increase in efficiency though, one being the fact that I did my thrust calculations at a 4S voltage rather than the 3S it is now flying with, and the other being the fact that I had done my calculations based on an AUW of 430-grams while the actual AUW of the aircraft is just 393-grams. I am finding it really fun working with such a small aircraft, much less stressful than bigger birds I have had in the past. Heaps more gains to be had, back to the bench...
The previous evening I did a bit more work trying to tune the hopelessly non-linear and inaccurate (especially at the amp levels I am pulling) current sensor on my little flying wing and was keen to give it a bit more time in the air to collect more data. This flight lasted just under 67-minutes, with 2106mAh being consumed from the 3S 3350mAh Li-ion pack. Extrapolated out, that suggests the aircraft is pulling an average of ~20.7W (~1.9A @ 10.8V) and could theoretically fly for ~101-minutes on a 100% depth of discharge (perhaps more in cleaner air and finer conditions). I am really happy about this, as it means my estimation of 150-gram cruise thrust is higher than is obviously required to maintain the desired 10.5m/s airspeed and that the airframe is more efficient than I had anticipated. Calculations suggested the necessary thrust power would be ~21W while bench tests with the relevant battery, esc, motor and prop indicated ~19.3W. But, factoring that the autopilot, sensors, servos, camera, osd and vtx collectively draw ~5W, thrust power turns out to be less than 16W. Two factors will be likely be contributing to this apparent increase in efficiency though, one being the fact that I did my thrust calculations at a 4S voltage rather than the 3S it is now flying with, and the other being the fact that I had done my calculations based on an AUW of 430-grams while the actual AUW of the aircraft is just 393-grams. I am finding it really fun working with such a small aircraft, much less stressful than bigger birds I have had in the past. Heaps more gains to be had, back to the bench...