How far are we from the perfect electric "homebuilt" ?

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Dan Thomas

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The proper term here is inductive reactance.

XL=2*pi*F*L

As you go to higher RPM your drive frequency has to go up (for a fixed number of poles). Consequently the inductive XL reactance goes up. IIRC, the RPM of a brushless motor is related to the number of rotor and stator poles, by a relationship I don't recall at this time. So you, again IIRC, can optimize the number of poles and drive frequency for a specific RPM to reduce reactance.

Actually, there is no power lost in a pure reactance. It is the resistance of the windings that causes the loss. To avoid the sharp voltage spike when the square wave drive current shuts off (V=L*dI/dT can get quite huge) you can use a step approximation to a sine wave to drive the motor.
Yup. I knew that. Only halfway thru the first cup of coffee...
 

Dan Thomas

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Not only. You may and have to think differently. ie - 100 hp IC motor is not same as 100 x 1hp Ic motors on reliability and weight. On electric - 100 x 1hp motors may be same or even better..
Except that 100 small propellers will be condiderably less efficient than one large prop.
 

stanislavz

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Except that 100 small propellers will be condiderably less efficient than one large prop.
Why ? Ok, lets say one and fourth ?

An example of better airframe for electrification compared to lazair

SPECIFICATIONS:

Wing Span: 35.4ft:

Length: 19.68 ft.

Wing Area: 105.5 ft.2

Empty Weight: 250 lbs.

Max Flight Weight: 470 lbs.

Useful Weight: 220 lbs.

Propeller (wood): 51.2" x 22.8"

Engine Hp Direct Drive: 24. Hp at 3200 rpm

Engine weight complete with prop = 86 lbs.

Operating G-loads +4, -2

Stall speed: 25 mph

Max-VNE: 78 mph

Glide Ratio: 16:1

Climb: 5 5 0 ft./min.

Take off distance (grass): 150 ft.

Landing Distance 180 ft.

Sink Rate: 3 1 2 ft/sec. at 40 mph

Note: Performance figures are with a 165 lb. pilot, at sea level, at standard conditions, and with the 24hp motor.

Please pay attention to glide ratio, and ic engine weight and rpm... And best climb speed

This one should cruise with 3kw of power. And 85 lbs + fuel - will allow to put 1.5 tesla battery modules. 7kwh of useful energy

The question is - go with one two or three propellers.
 
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litespeed

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Here is a old glider that was converted to electric power years ago by the team that made the system for the Luciole MC30 electric. Also did the power system for the record breaking MC15 Cri Cri electric.


Note the power package is quoted including battery @ 76 pounds.

The aircraft features a 5.5-kilowatt-hour lithium-polymer battery pack with management system and controller that produces 26 hp and weighs 75 pounds. The motor turns a 47-inch, two-blade E-PROPS propeller. An alternative feathering propeller is currently under development.


Initial test data shows that the ElectroLight2 can fly for one hour, 45 minutes at 65 knots or produce a maximum altitude gain of 9,842 feet at a maximum weight of 694 pounds.

Naturally it is still quite a slippery machine for old school.
http://www.lightaircraftassociation.co.uk/2012/News/electravia.html
 
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litespeed

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General specs for the glider, not with engine.

Type A60 Fauconnet Immatriculation F-CDLC
Developpment Egon Scheibe (D) Company of fabrication Avialsa (F)
First flight of the type 1960 Number ever built 177
year of fabrication 1970 Nr. 125 Number of seats 1
Wingspan 15 m Length 6.25 m
weight (empty) 152 kg Wing area 11.7 m2
Wing profile
Mu 14 Aspect ratio 19
fuselage construction tube and fabric Construction material wood and fabric
Maximum speed 193 km/h
Best glide ratio 29 @ 85 km/h Minimum sinking speed 0.65 m/s @ 62 km/h
First owner Club Bordeaux
Today´s owner Peter Urscheler Home airfield Challes (LFLE)
Last revision 2001 Hours / Flights 3053
 

Speedboat100

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General specs for the glider, not with engine.

Type A60 Fauconnet Immatriculation F-CDLC
Developpment Egon Scheibe (D) Company of fabrication Avialsa (F)
First flight of the type 1960 Number ever built 177
year of fabrication 1970 Nr. 125 Number of seats 1
Wingspan 15 m Length 6.25 m
weight (empty) 152 kg Wing area 11.7 m2
Wing profile
Mu 14 Aspect ratio 19
fuselage construction tube and fabric Construction material wood and fabric
Maximum speed 193 km/h
Best glide ratio 29 @ 85 km/h Minimum sinking speed 0.65 m/s @ 62 km/h
First owner Club Bordeaux
Today´s owner Peter Urscheler Home airfield Challes (LFLE)
Last revision 2001 Hours / Flights 3053

That would not classify as a Part 103 aeroplane.

Flynano is under 70 kg aeroplane that can take off from water with electric engine..has no endurance.

This is less than half the weight of the A60 Fauconnet : https://www.inverse.com/article/50695-archaeopteryx-lightest-glider-in-the-world
 
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litespeed

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For the Straton, I would do a aerofoil shaped pylon and make it as clean as possible.

That current setup seems extremely draggy and heavy, esp the engine.

But would be a good start for electric at that cheap price.

It probably would be best having the battery in the fuse below the current tank.
 

litespeed

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That would not classify as a Part 103 aeroplane.

Flynano is under 70 kg aeroplane that can take off from water with electric engine..has no endurance.

This is less than half the weight of the A60 Fauconnet : https://www.inverse.com/article/50695-archaeopteryx-lightest-glider-in-the-world
So what? Who said it must be part 103?

The flynano is irrelevant to this discussion and the Archaeopteryx is the most fragile design at the highest cost per pound of aircraft, with a very small ability to take weight for batteries.

It makes the Lazair seem like a cross country machine.
 

stanislavz

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ElectroLight2 can fly for one hour, 45 minutes at 65 knots or produce a maximum altitude gain of 9,842 feet at a maximum weight of 694 pounds.
Nice figures, it is based on old squale glider as i think...

But i do hate to put all load in one fuselage at one point of a wing..
 

Speedboat100

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henryk

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Noe, straton d7 . Dirt cheap here, in eu. Plus already motor glider. And allows to put battery on a pylon - father from pilot. https://www.harrisauctiononline.com/Event/LotDetails/367245/ULTRALIGHT-MOTORIZED-GLIDER-Buy-It-Now
-I think, SWIFT like tailless glider is moore optimal...

f.e. BKB1-A in new,composites technology=

http://www.reaa.ru/yabbfiles/Attachments/_bogdan_laminat_005_005.jpg

+Conter Rotating propellers (moore specific thrust).
https://kasperwing.com/kasperwing-poland/

or=

http://www.reaa.ru/yabbfiles/Attachments/impact_als_motorsegler.JPG

(rigid wing + trike).
 

Dan Thomas

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Messages
5,094
Why ? Ok, lets say one and fourth ?

An example of better airframe for electrification compared to lazair

SPECIFICATIONS:

Wing Span: 35.4ft:

Length: 19.68 ft.

Wing Area: 105.5 ft.2

Empty Weight: 250 lbs.

Max Flight Weight: 470 lbs.

Useful Weight: 220 lbs.

Propeller (wood): 51.2" x 22.8"

Engine Hp Direct Drive: 24. Hp at 3200 rpm

Engine weight complete with prop = 86 lbs.

Operating G-loads +4, -2

Stall speed: 25 mph

Max-VNE: 78 mph

Glide Ratio: 16:1

Climb: 5 5 0 ft./min.

Take off distance (grass): 150 ft.

Landing Distance 180 ft.

Sink Rate: 3 1 2 ft/sec. at 40 mph

Note: Performance figures are with a 165 lb. pilot, at sea level, at standard conditions, and with the 24hp motor.

Please pay attention to glide ratio, and ic engine weight and rpm... And best climb speed

This one should cruise with 3kw of power. And 85 lbs + fuel - will allow to put 1.5 tesla battery modules. 7kwh of useful energy

The question is - go with one two or three propellers.
How does any of that address the efficiency differential between 100 1-hp props and one 100-hp prop?
 
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