What do you think about "e-soaring"?

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The lift would need to be exceptionally strong for a helicopter to climb in it, power off. They have such high sink rates.
 

EzyBuildWing

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Truly "mind-bending" figures for Elektra Trainer.... 2 seats, 5kW cruise, 40:1, 1000 km range, large feathering-prop up front.....qualifies as a glider-trainer and PPL trainer.......aesthetically looks brilliant.........for joy-flights it looks very functional and futuristic......instantly recognizable as new-technology Elektrik.....should attract electric-car enthusiasts especially Tesla-drivers who want to experience eMobility(sports-mobility and eSoaring mobility) in the 3rd dimension.... already ordered by a flying-school because it ticks all the boxes..... I'm blown away by it's engineering!

 

peter hudson

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The lift would need to be exceptionally strong for a helicopter to climb in it, power off. They have such high sink rates.
It's a silly thought, but imagine if the electric helicopter were designed for soaring...Auto rotate, without circling, in the strong core of the thermal, then apply some power to the next lift source. As an esoteric design challenge it's a little interesting. I wonder how the rotor would look.
 

EzyBuildWing

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new, stretched, sleeker 2-seater jet-kit from Sonex could maybe have composite longer optional "outer-wing-panels" for soaring and longer range?
Really like it's profile.
 

peter hudson

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Any thoughts out there on an electric ducted fan (EDF) self launcher?

The sailplanes that use turbines have some advantages in packaging and thrust line. The efficiency of the turbine installation is poor at these low speeds and altitudes, but as an overall system it seems workable.

I'm thinking about either a deploy-able EDF, or maybe better...one buried in the fuse with inlets/exits that open/close. It would be less efficient than a big prop, but less trim drag than a pod (with high thrust line) and cleaner nose than a FES when closed. Again in my mind it's used for a short climb, maybe a short glide extension, and that's about it.
 

addaon

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It’s probably doable, but you’re doubling the compromises — a small amount of air accelerated a lot (EDF, jet) is less efficient than the opposite at low speed, and electric already struggles with energy density. Would have to run numbers, but here’s an example to ask yourself — if the prop self launcher has energy to climb to 8000 ft on one charge (or 4000 ft twice), would you be happy with an EDF design with all the advantages that go with it (which are real) in exchange for only 2000 ft of climb?
 

peter hudson

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... would you be happy with an EDF design with all the advantages that go with it (which are real) in exchange for only 2000 ft of climb?
No...I guess I'd need to establish whether its 80% as efficient, or only 25% over the prop... if it's 80% as efficient, (in Watt hours per 1000 ft of altitude?) and with a cleaner unpowered airframe then it's still "on the table". If it's really as bad as 25% then it's clearly "off the table". I guess it's another thing where I can't form an opinion without quantifying some things a little more.
 

addaon

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Yeah. The starting point (you'll have to go deeper) is pounds of thrust per horsepower (or per watt) at climb speed. Climb altitude is climb rate times time; climb rate is excess thrust; excess thrust is thrust minus drag. Going to an EDF will decrease drag in climb a bit, but not very much in the scheme of things. Typical to see EDF thrust numbers around 1 lb/hp, vs 4 lb/hp for a propeller (at 50 kts or so).... but there's huge variance possible.
 

blane.c

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addaon

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Note that for our purposes motor efficiency is absolutely drowned by propeller efficiency.

Rule of thumb:
1) A BLDC motor designed for efficiency in the 1kW - 100kW range (and even beyond) will comfortably achieve 96% peak efficiency.
2) A BLDC motor of classical design or axial flux design designed for a balance of efficiency and weight (but still containing a traditional flux return path) will achieve 92% peak efficiency.
3) A BLDC motor designed for weight above all else (no iron, etc) will achieve 88% peak efficiency.

A motor controller up to 500A or so using appropriate transistors (SiC for 400V+, GaN below that) will comfortably achieve 98% efficiency for PWM frequencies up to 20 kHz (which will apply to cases 1 and 2 above), or 97% for either higher frequencies (GaN) or with an external inductor (SiC).

Peak efficiencies can be reasonably chosen to occur at cruise power and climb power, the peaks are broad. If peak power is more than 2x cruise power and a weight-optimized motor is used, liquid cooling should be assumed.
 

addaon

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Servo motors for cowl flaps, fan motors for ventilation, pump motors for hydraulic gear power packs, motors in electric-driven backup gyros, compressor motors in air conditioners and oxygen generators, power-adjustable seats... depends on the design, but there can easily be anywhere from zero to ten, and less easily even more, non-drive motors in a small experimental design.
 
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