Propulsion System Help

Hi All,
I’m looking to build a quad or octo-rotor with the goal of flying my payload for 40 minutes, I want to be able to fly this in a hot environment (110F in summer), so I’m looking for something that will normally run pretty cool.

I know about ecalch.ch but I’m having trouble using it properly I believe.

Can someone guide me in the right direction?

What’s the payload weight? I built a quad that would fly for ~45 minutes but it couldn’t take any payload to speak of and do that. These are also known as Hover Machines with little practical value. Lightweight, low kV motors with large props and a low C 6S battery.

I built a 650mm size copter w/ 16" props, ~500kv motors, 4s 15,600mah batteries (3x5200mah), and it will hover for over 40 minutes. It has a brushless gimbal and gopro size camera, as well as a little servo gimbal on the FPV cam.
I doubt it could carry any additional payload, and if it did, that would obviously cut down on the hover time.

I just looked at the motors… they’re
KDE2814XF-515
I know technically I’ve got them over propped, but have had no trouble… I don’t do much more than hover w/ this copter, so I did not design it to run at full power. I’ve flown for hours for a job in relatively strong winds (weather forecast said 20mph) and it was fine.
But I think the people who do things ‘by the book’ would have issue w/ my choices.

Also, I built it before the low kv pancake motors and higher S batteries existed, else I might have ended up going that way. But I’ve seen a lot of posts from people having issues w/ the very low KV motors, and like I said, I’ve never had any problems w/ this one.