"Ignore the AUW and hover current, I've just realised I don't count in the battery weight..."

"I've also been looking into this.Because of the 2C max continous discharge, I'm trying to work out how many cells in parallel I need to be safe.As an example, my current tricopter will fly for ~13min (general flying about, no flips etc...)…"

"I have the RC Timer 4215 650kv motors and would like to use the carbon fiber 15"x5.5 propellers mentioned in this thread. But what would be the best way to mount the propellers to the motors? These motors have a three point prop adapter so I…"

"As Brad said, getting a copter to hover with payload AUW at the ideal RPM where you have peak efficiency from both the motor and the propeller is a very large order indeed. Especially since performance curves from R/C brands can be somewhat lacking.…"

"I recently ordered a laser tachometer.  For $12.50 it might be a pretty handy tool for working out motor and prop efficiency.  You just attach a little sticker reflector somewhere on a spinning part and point the laser tach at…"

"Interesting to note the requirement for high RPM. That might explain why the standard purple Arducopter motors seem so efficient with 10x4.7 props. Hope to see their graphs sometime or do tests myself. Also wanted to mention some links to micro…"

"Is everyone is starting to get the idea that the optimal matching of motors to props isn't trivial?  Then this is a great discourse. In a BLDC motor, your throttle control directly controls RPM based on the KV rating, of course. …"

"Murrau: You are of course correct that the g/W scale already takes into account motor efficiency loss. But the g/W is calculated for a single propeller, so the figures when you have two propellers stacked and down wash will most likely be…"

"be cautious with the 80% figure. motors are only 80% efficient across a narrow range of load, below that load, they can be ~65%, and above many go down to ~50%. Even though a motor/prop combo can deliver higher thrust, after that thrust curve passes…"

"I agree that 16 motors would start looking a bit like a Christmas tree. The 360-15 motor-prop combination is probably not what you need for efficiency at those weights. Hopefully someone can provide efficiency graphs for stronger motors with larger…"

"Murray: A brushless motor usually has a efficiency around 80%, so the g/W gain must be better then that. If you then consider the added weight and complexity of 16! motors I thing it would not be worth the hassle for marginal improvements in flight…"

"3 bladed props are not as efficient as 2.  The only reason aircraft go with 3 or more blades is because ground clearance requires it."

"Or as I mentioned earlier you can go with 3 blade props.   I think it's less than a hit with coaxial props. I need stability in gusty wind.  That's why I built a heavier quad.  I'm flying around the shoreline. I would…"

"@John: If you want so much lift as well as efficiency then you could consider going co-axial on your octo. The added weight is not as much as when you add arms and the loss in efficiency of a co-axial configuration (typically 15%) would be more than…"

"Yes, but 10g/w is still just about 475g of thrust. Even with an octocopter you can then only lift 3.8kg. Barley enough for the frame and a small battery. For a octocopter with large battery, gimbal and camera you usually need about 6.5-7kg of lift.…"

"On the other hand, it's fine if you can scale up the number of motors. So long as the weight of the extra arms, ESCs, and wiring harness don't drop that efficiency down below around 10g/W, it's still a win, yes?"