What do you think about "e-soaring"?

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John.Roo

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Letohrad / Czech Republic
Swift electric glider looks good (has 10kW motor).....batteries last about 1 hour.......seems like there's nothing out there that gets more than about an hour........

Question is - do the pilot interested in soaring needs more than hour of endurance?
When I spoke with glider pilots about optimal performance majority had following requirements.
Capability of takeoff to min. 600 m (2 000 ft) AGL + remaining energy to come back home from any position of FAI 300 km triangle. Or 2x takeoff to 600 m (2 000 ft) AGL.
 

John.Roo

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Looks so easy...
Wingspan 24 m
Weight 39.9 kg 👍
Pilot Kit Buchanan (age 27 weight 61 kg) = not really typical pilot weight :D
Power 300 watts (approx.) 👏
Distance 2 636 m
Duration 6 m 22 s
Airspeed 9,8 m/s (= 35 km/h = 5,3 kts)
 

John.Roo

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Messages
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Location
Letohrad / Czech Republic
Looks so easy...
Wingspan 24 m
Weight 39.9 kg 👍
Pilot Kit Buchanan (age 27 weight 61 kg) = not really typical pilot weight :D
Power 300 watts (approx.) 👏
Distance 2 636 m
Duration 6 m 22 s
Airspeed 9,8 m/s (= 35 km/h = 5,3 kts)
Hopefully interesting....
Yesterday I spoke with my friend - he is installing "pedelec" (electric pedal assistance motors) on bicycles.
Legally can electric motor "help you" with max. 250 W of power. So typically producers set limit 300 W of max power going out from batteries. Complete system weight is below 10 kg. That include motor (version for central installation - not in rear of front wheel), wiring, display and 20-24 Ah battery.
24 Ah battery can give you over 2,5 hours of assistance - that should be enough to cross The Channel.

Central motor is standard unit - with small modification would be possible to make some weight reduction.
24 Ah battery is also maybe too big - would be possible to use 20 Ah or maybe even smaller.
So finally could be possible to stay below 8 kg of installation weight.
This technology is really cheap - whole system you can get for +- 1 000 USD (depending on battery size).
I am sure that organizators of Icarus Cup 2021 (Cross Channel Race 2022) should think about this idea to make the Cross Channel flight more safe, attractive due to use of modern (and very affordable) technologies and also allowing "normal" pilots participation (not only high end athletes) :cool:
 

John.Roo

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To achieve really low energy consumption is necessary to combine low weight and as good as possible L/D.
In Germany is existing UL category with max. EW 120 kg. Requirements are +- similar to FAR part 103. And here is list of accepted airplanes.
Interesting is section "Segelflugzeuge" (glider) and "Motorsegler" (motorglider).
I took a detailed look to newest self launch glider - Birdy.
However I found one interesting paradox.
In rules are two requirements difficult to achieve with composite airplanes.
1) 25 kg/m2 wing load
2) 55 km/h stall speed
And in both parameters is Birdy "out of box".
Reported stall speed is 63 km/h.
Wing area is 8,3 m2 and MTOM is 280 kg = 33 kg/m2
Solution may could be to report lower MTOM. 25 kg/m2 * 8,3 m2 = 207,5 kg.
207,5 kg (MTOM) - 115 kg (reported EW) = 92,5 kg for pilot.
So that really could be the way... if there is no requirement for pilot weight range (typically between 65-110 kg).

And what is nice....
"We consider the weight of an electric battery to be fuel, and therefore not part of the empty mass." 👍
 

John.Roo

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It is interesting that the German 120 kg class requests stall speed of 55 km/h. From my point of view is stall speed 65 km/h safe for all pilots trained in UL or on gliders. In opposite - during a bit windy day or day with medium/strong thermals is low wing load and low stall speed airplane less comfortable and can be more dangerous.

The UK SSDR category keeps stall speed at 35 kts (65 km/h).
This is recomended wing area for SSDR builders:
SSDR.jpg
Too low wing load and too low stall speed may not always lead to higher safety. If you are allowed to fly with the German 120 kg class airplanes without medical check, then is this category obviously aimed to old glider pilots and old UL pilots. And they know how to handle an airplane with a stall speed of 65 km/h. Personally I would focus more on predictable and easy flight characteristics.
 

dog

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Dec 29, 2019
Messages
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It is interesting that the German 120 kg class requests stall speed of 55 km/h. From my point of view is stall speed 65 km/h safe for all pilots trained in UL or on gliders. In opposite - during a bit windy day or day with medium/strong thermals is low wing load and low stall speed airplane less comfortable and can be more dangerous.

The UK SSDR category keeps stall speed at 35 kts (65 km/h).
This is recomended wing area for SSDR builders:
View attachment 111894
Too low wing load and too low stall speed may not always lead to higher safety. If you are allowed to fly with the German 120 kg class airplanes without medical check, then is this category obviously aimed to old glider pilots and old UL pilots. And they know how to handle an airplane with a stall speed of 65 km/h. Personally I would focus more on predictable and easy flight characteristics.
In my area in eastern Canada,there are very few
true ultralights and I have never seen a "trike" or single surface ultralight.
The ONE ultralight that I see regularly is only
flown in perfect conditions by a massivly overqualified pilot.
Wind baby,and few landing strips and hilly terain coverd in spruce.
100 or 200 kg's??,Nooooooo,three times that
and watch the weather close and accept that
there are going to be days when suddenly its going to be a realy rough ride and its going to be a wrestling match to get back on the ground
Very cool that batteries are not considered as part of empty weight.
 

John.Roo

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In my area in eastern Canada,there are very few
true ultralights and I have never seen a "trike" or single surface ultralight.
The ONE ultralight that I see regularly is only
flown in perfect conditions by a massivly overqualified pilot.
Wind baby,and few landing strips and hilly terain coverd in spruce.
100 or 200 kg's??,Nooooooo,three times that
and watch the weather close and accept that
there are going to be days when suddenly its going to be a realy rough ride and its going to be a wrestling match to get back on the ground
Very cool that batteries are not considered as part of empty weight.
I can imagine that in Canada is a lot of wind and not that many landing areas :)
2 seat LSA with MTOM 600 kg or single seat with at least MTOM 300 kg with wing loading approx 35 kg/m2 or even a bit more would be reasonable minimum.
I was flying in Canada (in area near Toronto) only once and I really enjoyed every minute 👍
 

John.Roo

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I can't believe how beautiful advertising Red Bull did to the Czech and Slovak Republics...
And.... yes. One of world best aerobatics pilots Martin Sonka is there as well (from 3:44) :cool:
 

dog

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Dec 29, 2019
Messages
578
Still one of most beautifull electric airplanes :)
That is a very beutifull airplane and it displays
a friendly confidence in the designers and builders.Looks very comfortable too.
The wing must have a good effective span and
perform well despite its modest overall span.
 

John.Roo

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Messages
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Location
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That is a very beutifull airplane and it displays
a friendly confidence in the designers and builders.Looks very comfortable too.
The wing must have a good effective span and
perform well despite its modest overall span.
I met Eric Raymond personally on AERO Friedrichshafen long time ago.
Slika_7..jpg
(on photo you see tail of our OK-QUA98 and also electric EGO Trike of my friend) :cool:
Eric did amazing job - airframe of Sunseeker Duo is extremelly light. However 22 m wing span is far too much.
23 % solar panel efficiency allows to get only 5 kW of power from whole surface of wing and horizontal tail unit. Imagine - only 5 kW of power necessary to keep horizontal flight of two seater with MTOM 470 kg.
Better efficiency of solar panels could solve ongoing problem with energy density of batteries and move environmental friendly aviation to new level.
 

blane.c

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capital district NY
There is another thread now discussing (sorry about the bold and big it is how it copy's and paste)
Nenadović biplane

"over a monoplane of the same profile of 25% less drag, 15% more lift, and 51% better speed range."


Vigilant1 said:
FWIW, here's what Wikipedia shows for the AS-37A (split wing, twin prop pusher):
General characteristics

  • Crew: 2
  • Length: 6.00 m (19 ft 8 in)
  • Wingspan: 6.30 m (20 ft 8 in)
  • Height: 1.60 m (5 ft 3 in)
  • Wing area: 13.60 m2 (146.4 sq ft)
  • Empty weight: 400 kg (882 lb)
  • Max takeoff weight: 620 kg (1,367 lb)
  • Powerplant: 1 × Citroën GS 1220 4-cylinder air-cooled, 48 kW (65 hp)
  • Propellers: 2-bladed
Performance
  • Maximum speed: 185 km/h (115 mph, 100 kn) at sea level
  • Cruise speed: 170 km/h (110 mph, 92 kn) at sea level
  • Range: 1,500 km (930 mi, 810 nmi) with 90 L (24 US gal; 20 Imp gal) fuel
  • Service ceiling: 4,500 m (14,800 ft)
  • Rate of climb: 3.5 m/s (690 ft/min) at sea level
  • Take-off run: 200 m (655 ft)
  • Landing run: 140 m (460 ft)
_----------------------------
If it is to be believed, that's pretty darn good for a two seat plane running on just 65hp. The large disk are would have been a help for TO and climb, especially given the modest power available.

The Wiki article also indicates a simpler single prop pusher version with a single low tail boom was built (the "Knoepfli VSTOL")

;;
There are also pictures of single engine single propeller tractor version and single engine dual propeller tractor version.

Are you aware of anyone playing with this concept for glider?
 

henryk

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krakow,poland

John.Roo

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Joined
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Messages
902
Location
Letohrad / Czech Republic
There is another thread now discussing (sorry about the bold and big it is how it copy's and paste)
Nenadović biplane

"over a monoplane of the same profile of 25% less drag, 15% more lift, and 51% better speed range."


Vigilant1 said:
FWIW, here's what Wikipedia shows for the AS-37A (split wing, twin prop pusher):
General characteristics

  • Crew: 2
  • Length: 6.00 m (19 ft 8 in)
  • Wingspan: 6.30 m (20 ft 8 in)
  • Height: 1.60 m (5 ft 3 in)
  • Wing area: 13.60 m2 (146.4 sq ft)
  • Empty weight: 400 kg (882 lb)
  • Max takeoff weight: 620 kg (1,367 lb)
  • Powerplant: 1 × Citroën GS 1220 4-cylinder air-cooled, 48 kW (65 hp)
  • Propellers: 2-bladed
Performance
  • Maximum speed: 185 km/h (115 mph, 100 kn) at sea level
  • Cruise speed: 170 km/h (110 mph, 92 kn) at sea level
  • Range: 1,500 km (930 mi, 810 nmi) with 90 L (24 US gal; 20 Imp gal) fuel
  • Service ceiling: 4,500 m (14,800 ft)
  • Rate of climb: 3.5 m/s (690 ft/min) at sea level
  • Take-off run: 200 m (655 ft)
  • Landing run: 140 m (460 ft)
_----------------------------
If it is to be believed, that's pretty darn good for a two seat plane running on just 65hp. The large disk are would have been a help for TO and climb, especially given the modest power available.

The Wiki article also indicates a simpler single prop pusher version with a single low tail boom was built (the "Knoepfli VSTOL")

;;
There are also pictures of single engine single propeller tractor version and single engine dual propeller tractor version.

Are you aware of anyone playing with this concept for glider?
Thanks for interesting post 👍
From my point of view maybe could be this concept interesting for "normal" airplanes.
I see main advantage in small dimensions.
However gliders and motorgliders - especially actual generation - are usually even more efficient.
 
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