What do you think about "e-soaring"?

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John.Roo

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800 V system and oil cooling are promissing parameters.

However main problem for electric airplanes is not the motor.
They are many available good motors with bit better or bit worst efficiency or cooling.
Just... where to get enough energy?
For example typical Tesla car has impressive power, but for how long you can us it? And in Tesla you have 75, 90 or 100 kWh battery. It means 375-500 kg battery (probably heavier due to temp. management).

So... max. power is not really a parameter I am looking for :)
For me more important is:
- max. continuous power (power I able use keeping temp. of motor, controller and batteries in reasonable temp. range)
- efficiency during cruise power settings (this is affecting endurance and in this "power setting" is motor runnig most of time - so I need best possible efficiency).

When you look for electric motor for your airplane project also take a carefull look to construction. For example - sometimes I am really surprissed what types of bearings are used. But this is another story ;)
 

Dusan

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So... max. power is not really a parameter I am looking for :)
For me more important is:
- max. continuous power (power I able use keeping temp. of motor, controller and batteries in reasonable temp. range)
- efficiency during cruise power settings (this is affecting endurance and in this "power setting" is motor runnig most of time - so I need best possible efficiency).
I totally agree with this and what I can say is that although every component is important, the most important factor designing an aircraft - and especially one with electric propulsion that has, lets say - specific energy challenges, the most important factor is the aerodynamic performance. This is where 'rubber meets the road' If one aircraft has improved aerodynamics so it is able to cruise at 20kW vs. another that needs 40kW for cruising at the same weight, speed and altitude, the first one has double the range and endurance, considering that all other parameters are equal.

From the aerodynamics perspective mostly everything reduces to cruise L/D and that is dependent mostly on span - larger the better, and wetted area - lower the better; and also on producing efficiently thrust, the most important is the propeller design - its size depends on aircraft cruise speed, larger is not necessarily better. Improving the propeller efficiency by - let say 5%, e.g. from 80% to 85% has the same result as improving the motor efficiency from 96% to 100.9% which is impossible. Improving on the 'weaker link' is always more effective and has larger benefits overall, not mentioning that is most likely easier too.
 

jedi

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I totally agree with this and what I can say is that although every component is important, the most important factor designing an aircraft - and especially one with electric propulsion that has, lets say - specific energy challenges, the most important factor is the aerodynamic performance. This is where 'rubber meets the road' If one aircraft has improved aerodynamics so it is able to cruise at 20kW vs. another that needs 40kW for cruising at the same weight, speed and altitude, the first one has double the range and endurance, considering that all other parameters are equal.

From the aerodynamics perspective mostly everything reduces to cruise L/D and that is dependent mostly on span - larger the better, and wetted area - lower the better; and also on producing efficiently thrust, the most important is the propeller design - its size depends on aircraft cruise speed, larger is not necessarily better. Improving the propeller efficiency by - let say 5%, e.g. from 80% to 85% has the same result as improving the motor efficiency from 96% to 100.9% which is impossible. Improving on the 'weaker link' is always more effective and has larger benefits overall, not mentioning that is most likely easier too.
Close but not really.

You are assuming that the object is to go from A to B. You only need enough range to get there. If the 40 kW aircraft is twice as fast it would be superior in most instances. (Yes, you did say at the same speed but many do not want to go that slow. Most private pilots cruise at well over max L/D speed)

Range is not always the limiting factor. If you are flying for fun endurance may be a higher priority than max range. In that case minimum power is more important than max L/D.

In many military missions loiter time is the dominant specification.

If the aircraft is designed for both long and short distances you may want a lower max L/D but a very broad speed range for good L/D so that the speed may be adjusted to arrive arrive at B in the shortest time with the battery nearly discharged.

This thread is "e-soaring". Most likely range under power is not the dominant design parameter for an e-soaring pilot.

Yes, airplane design is a basket full of compromise.
 
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John.Roo

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Close but not really.

You are assuming that the object is to go from A to B. You only need enough range to get there. If the 40 kW aircraft is twice as fast it would be superior in most instances. (Yes, you did say at the same speed but many do not want to go that slow. Most private pilots cruise at well over max L/D speed)

Range is not always the limiting factor. If you are flying for fun endurance may be a higher priority than max range. In that case minimum power is more important than max L/D.

In many military missions loiter time is the dominant specification.

If the aircraft is designed for both long and short distances you may want a lower max L/D but a very broad speed range for good L/D so that the speed may be adjusted to arrive arrive at B in the shortest time with the battery nearly discharged.

This thread is "e-soaring". Most likely range under power is not the dominant design parameter for an e-soaring pilot.

Yes, airplane design is a basket full of compromise.
You are right - e-soaring is not that much about the speed or fast cruising.
True is that I also prefer to fly Phoenix with long wings. However would be interesting to compare energy consumption with short and long winglets. For example same power settings vs achieved speed etc.
vs
 

Dusan

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However would be interesting to compare energy consumption with short and long winglets
Not sure for the exact results for the Phoenix, but the theory is simple: There is always more induced drag with shorter wingspan. The theory also states that the minimum drag is at the speed where induced and parasite drag are equal, and here the answer is not so simple: A shorter wingspan aircraft could have less total drag at higher speed, the parasite drag could be lower as the wet-area is lower, but there are a lot of other factors involved.
 

John.Roo

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Not sure for the exact results for the Phoenix, but the theory is simple: There is always more induced drag with shorter wingspan. The theory also states that the minimum drag is at the speed where induced and parasite drag are equal, and here the answer is not so simple: A shorter wingspan aircraft could have less total drag at higher speed, the parasite drag could be lower as the wet-area is lower, but there are a lot of other factors involved.
Therefore is good idea to test both configurations on the same airplane, with the same propulsion system settings and ideally during the same day with the same weather conditions :)
 

John.Roo

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henryk

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how these generators really work

=SR Generator (NO permanent magnets !)

"High-speed switched reluctance generators directly coupled with gas or steam turbines provide an ideal source of electric power due to their higher efficiency and power density, better fault tolerance and reliable operation. "


=today and tomorrow...
 
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John.Roo

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AERO 2021 Summer edition is cancelled.
Well... probably is better to cancel it instead of to realize the exhibition at this stage of anti-COVID vaccination. I can understand that for organizators of AERO is not easy, but they are responsible and taking care of exhibitors and visitors safety.
I hope that situation will be better in year 2022.
 

John.Roo

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=today many aircrafts are E-driven...

=this night (accus loading) one of A123 LiOn prismatic cell was exploded with after-fire !
Bogdan is alive,but worry ...
Honestly... I really suggest to do not use metal sleeves arround cells. Remember issue with Samsung Note few years ago - they had problem because place for battery in phone was too "exact". Cells need space arround or at least some foam (insulation) in between.
 

EzyBuildWing

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Shouldn't we all be flying electric-planes and driving electric cars?
Bill Gates drives an electric car, and his Jet burns green-plant Ethanol.....very interesting recent 60-Minutes Bill Gates interview:
 

John.Roo

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Awesom spring day :) My friend asked me to tow him up with his Discus glider. Then I released the tow rope during a low pass over airfield and after climbing back to 600 m AGL I turned off the Rotax engine, feathered propeller and enjoyed more than 90 minutes of soaring flight near LKUO and LKZM. Could be much longer soaring, but it was not good idea to drink coffee before flight.... :)
 
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