Electric power for dummys......

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Speedboat100

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Nov 8, 2018
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About the electric engine battery degredation:

I recently asked from a hobby dealer the 23 kg batterys price...and we came up to 3 000 euros...for a hour flight in a really small and lite AC.
 

Dusan

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Sep 15, 2014
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130
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Canada
Yeah, but has it flown yet and proven that multiple small props are more efficient?
It depends ... Similar to fixed wings, the efficiency of rotating blades depends a lot on the blades L/D, which is very dependant on the Reynolds number. Considering similar disk loading, smaller multiple propellers could have the Reynolds much lower than a single propeller. For a small 2-4 person aircraft, replacing one propeller with smaller ones doesn't make any sense. Aerodynamic distributed propulsion gains are maybe around 5%, but you loose 20% or more on propellers efficiency.
 

rv7charlie

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Nov 17, 2014
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Jackson
To the point about multiple props:
Everything's a compromise, obviously. Small a/c have a hard time fitting enough prop area for true STOL or even VTOL, but it can be done with 'distributed' prop area. (Mission, mission, mission....)
These guys are showing how it can be done:
Opener

Charlie
 

Dan Thomas

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Joined
Sep 17, 2008
Messages
5,753
To the point about multiple props:
Everything's a compromise, obviously. Small a/c have a hard time fitting enough prop area for true STOL or even VTOL, but it can be done with 'distributed' prop area. (Mission, mission, mission....)
These guys are showing how it can be done:
Opener

Charlie
Looks promising. But it will have to get better before they'll sell a lot of them. In terms of seat-miles per kWh it's not good. An electric car does nearly four times better. It can't fly in any precipitation. In terms of fun and efficiency, it would almost be like a single-seat helicopter except for its short range. Range is too limited, like any electric vehicle. In terms of difficulty, real easy to fly. Computers do most of it. But so much fun!
 

rv7charlie

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Nov 17, 2014
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Come on; it's a toy. Show me a practical pt 103 ultralite. It's the 1st of a new class of, if not transport, certainly entertainment.

Would you buy a bone stock 1896 Land Rover as your only transport vehicle today? Neither would I, but I'd happily take a 1996 version, even though it's already a quarter century old.
 

Dusan

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Sep 15, 2014
Messages
130
Location
Canada
In terms of hovering efficiency, a light helicopter outperforms any multi-copter out there. The advantage of multi-copters are mechanical simplicity and potential transition to a wing-borne flight with a higher L/D than 5, typical for single rotor helicopters, but I'm not sure I've seen any in the plethora of multi-copter designs that are bombarding us lately.
 

proppastie

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Feb 19, 2012
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NJ
The 3,400 tetrahedral cells of Bell’s giant Cygnet kite might have gotten it airborne, but it could never have been a practical flying machine. (Courtesy of the Glenn H. Curtiss Museum, Hammondsport, NY)

The 3,400 tetrahedral cells of Bell’s giant Cygnet kite might have gotten it airborne, but it could never have been a practical flying machine. (Courtesy of the Glenn H. Curtiss Museum, Hammondsport, NY)
 
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