Yes, but 8 props will be considerably less efficient then one prop in generating that thrust in the first place. For instance:
One 300x8 inch prop will generate roughly 1 ton of thrust while spinning at 330RPM and consuming 12kW of energy. So, let's say we go with your prediction, and assign a 30% air flow efficiency to the one prop system. So in reality, according to you, it is generating 700 kilos of thrust. 700/4 is 87.5 kilos. So now we need to figure out how big of a prop we need to generate 1/8 of the thrust of the 300 inch prop, or roughly 88kg. I am going to use 60 inch props, because that will allow us to space 8 props in a circle roughly the same size as the original 300 inch prop.
Ok, so a 88x8 prop, spinning at 2350 RPM will generate roughly 88 kg of thrust wile consuming 6.7 kW of energy! That's 6.7 kW x 8 props, or a total of 54 kW, or almost 4.5 times less energy efficient than the one prop system, and that's taking into account your proposed 30% efficiency gain from multi-bladed systems and ducts.
I build these things all the time, there is a reason why the industry still uses helicopters with a single prop. It IS more efficient.
You're making a mistake. There is no 1 ton helicopters with 12 kW power on shaft. Even with 24 or 36 kW. I'm on iPhone so can't say exactly what thrust 12kw would produce on 6m prop. Around 300kg I'd estimate.
And another thing. 8 60in props aren't equivalent to 1 300 in wrt power loading. You need 16 of 60in to get equivalent of 1 240in prop.
Anyway, you've just calculated an octocopter with 700kg+ thrust on 60kw power. Is it bad? My neighbor's 400kg single-seater has 100kw gas turbine and it isn't 4x excessive power.
>You're making a mistake. There is no 1 ton helicopters with 12 kW power on shaft. Even with 24 or 36 kW. I'm on iPhone so can't say exactly what thrust 12kw would produce on 6m prop. Around 300kg I'd estimate.
Based on what, please provide at least some reference to an equation or calculator.
>And another thing. 8 60in props aren't equivalent to 1 300 in wrt power loading. You need 16 of 60in to get equivalent of 1 240in prop.
>Anyway, you've just calculated an octocopter with 700kg+ thrust on 60kw power. Is it bad? My neighbor's 400kg single-seater has 100kw gas turbine and it isn't 4x excessive power.
Can you give me an example than using some kind of calculations from a reliable source, not the "my neighbor" anecdotes. For instance, what makes you think that equivalent for a 240in prop would be 16 x 60 inch props? I understand that 16 60 inch props would have roughly the same area, but you do realize that 16 props arranges in such a way as not to create interference with each other would take up significantly more area? This is the main problem of a multirotor, you wither have to use smaller, less efficient props, or you have to make it much larger to accommodate the props.
In any case, when you are at your computer, if you feel like it, please do calculate, with references, a single prop machine lifting 1 ton vs an octo lifting the same 1 ton. I understand that a machine that lifts 1 ton would need to provide more than a ton of thrust, of course, but let's make it simple. Just a simple calculation. One prop producing 1 ton of thrust vs 8 props which can be arranged in such a way at to take up no more then 150% as much area as the original 1 prop, producing the same 1 ton of thrust.
If you really can show me that 8 props can be as efficient as 1 prop, please, by all means, prove me, and every one else who designs flying machines, wrong. But please do so with calculations I can verify.
One 300x8 inch prop will generate roughly 1 ton of thrust while spinning at 330RPM and consuming 12kW of energy. So, let's say we go with your prediction, and assign a 30% air flow efficiency to the one prop system. So in reality, according to you, it is generating 700 kilos of thrust. 700/4 is 87.5 kilos. So now we need to figure out how big of a prop we need to generate 1/8 of the thrust of the 300 inch prop, or roughly 88kg. I am going to use 60 inch props, because that will allow us to space 8 props in a circle roughly the same size as the original 300 inch prop.
Ok, so a 88x8 prop, spinning at 2350 RPM will generate roughly 88 kg of thrust wile consuming 6.7 kW of energy! That's 6.7 kW x 8 props, or a total of 54 kW, or almost 4.5 times less energy efficient than the one prop system, and that's taking into account your proposed 30% efficiency gain from multi-bladed systems and ducts.
I build these things all the time, there is a reason why the industry still uses helicopters with a single prop. It IS more efficient.