What do you think about "e-soaring"?

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Aviator168

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Randall Fishman is selling an electric-powered ultralight (103). The battery can last for 2hrs. I think we use it as a glider.

 
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John.Roo

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Hello Aviator,
yes, I know ultralight Song - another nice Czech construction (producer is company Gramex from Zbraslavice).
What is your opinion – are batteries for 2 hour flight included in EW 120 kg? J
Best regards!
Martin
 

Aircar

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Mitja - if you check your diagram the one marked WRONG you will see that it actually is RIGHT -- provided the direction of rotation is reversed and each blade is rotated anti clockwise in pitch in the case of a tractor (it would be better to have much lower RPMs and gear up to a dynamo but the lift vector and camber and twist are OK ) stopping a prop to feather can be a bit difficult for the reason of windmilling .
 

ultralajt

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Mitja - if you check your diagram the one marked WRONG you will see that it actually is RIGHT -- provided the direction of rotation is reversed and each blade is rotated anti clockwise in pitch in the case of a tractor (it would be better to have much lower RPMs and gear up to a dynamo but the lift vector and camber and twist are OK ) stopping a prop to feather can be a bit difficult for the reason of windmilling .
prop-windmill-dellusion.jpg
Are you sure? Are you really sure? Are you really, really sure? If so, then think again please! Draw speed vectors for yourself!

The midle sketch I drawn is prop blade rotated for 90° as Henryk said. Such propeller could be used as windmilling object, but it is way wrong regarding twist distribution along the blade. Compare it with sketch on the far right!
This one is proper as it has proper twist, meaning that each blade section has proper angle of attack. Just in this case you can expect some efficiency, othervise just a portion of blade work at proper ange of attack and rest of it work wrong... as matter a fact it even act as a brake against rotation at certain speeds.

The easiest way to convert propeller from tractor to windmill is just stay at current prop blade (as Martin suggest), but using simetric airfoil and accept lower than perfect efficiency.


PROP00.jpg
Above: from left to right... more "plastic" presentation of my drawing above, commented by Aircar.

PROP01.jpg
Above: each prop blade section make the same forward distance at each propeller turn, hence high angle of attack at root and small at the tip.

PROP02.jpg
Above: path of each blade section. Note that pitch angle is lower at the tip, than at the root.

PROP04.jpg
Above: if we just rotate blade for 90° each blade section is oriented wrong to be effective at windmilling. Red traces are each section angle "theoreticlal path", while it should be where silver lines are drawn.

PROP05.jpg
Above: this is a proper pitch distribution. Each section travel the same forward path at each prop revolution.

PROP06.jpg
Above: close view on the proper pitch distribution of the windmilling propeller.

I hope I was clear enough... I am not willing to loose much time explaining myself endlessing....

Regards!
Mitja
 
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henryk

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http://www.ivoprop.com/images/inflightpartspic.jpg

http://www.rotaryforum.com/forum/attachment.php?attachmentid=50127&d=1223275450

Both models utilize the same carbon / graphite fiber blades with stainless steel leading edges. The blades are capable of pitch change 3 to 17 degrees on the tips or inches of helix advancement from 18" to 52".

=sum attitude =circa 20 degrees...
"Controllable-pitch three-bladed propeller with regeneration potential has patented blades"

=Windward = I think,similar to IVOPROP...
 

John.Roo

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Not at all dear Mitja J
I am very glad that we are discussing and of course part of discussion are different opinions.
By the way… you have beautiful design ideas in thread “Rigid glider with performance like paraglider”.
Very good job! As I wrote before - I really hope to have once possibility to test fly your Kanja glider.

I was looking (also with no success so far) for more info about “Etlantic” patented propeller.
Well maybe they will present some ideas on AERO Friedrichshafen.


By the way…
Dear friends if some of you are planning to visit AERO Friedrichshafen 2014 please make stop in Foyer West (E-Flight EXPO).
I will be there with PhoEnix and for sure I will have with me some Czech beer
J


And beside our stand we will have boys with Crossover project (
http://www.eurosportaircraft.com/) – also interesting design and new ideas.
For me is especially interesting their “range extender” system.


Best regards!

Martin
 

autoreply

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Good to hear, I'll definitely walk by as well. I was curious about the Crossover project, but didn't learn much last year, let's see if this year I'll succeed.
 

autoreply

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There have been some articles. Can't recall where, Aerokurier and Cafeblog? There was also the range-extender opposite to Lange and DG, but forgot their name.
 

saini flyer

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There have been some articles. Can't recall where, Aerokurier and Cafeblog? There was also the range-extender opposite to Lange and DG, but forgot their name.
Thanks Jarno, I found a mention in may 2013 article in cafe on 90lbs genset so I think we are looking at <20KW unit...maybe even lower as the engiro is about that weight for the 20KW.

When do they plan on selling these and how will these be certified... twin engine/single engine with twin motors.... It was already too much for FAA to look at eflight and now this with twin electric motors ..:gig:
 

Aircar

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Sorry Mitja -this thread is a bit off the mainstream for me (belongs in "new technology' perhaps) I wasn't shunning you . Naturally the inner part of the prop is not going to be optimum if simply reversed but with the camber facing aft it will work as a windmill (just take a prop on a shaft and walk out into a strong wind --I would envisage though it gearing up so as to turn much slower revs and hence better matching the ideal pitch. I used to do target towing with a windmill powered RAF WW2 winch (and 4000 ft of steel cable --that was our "insurance" ) --the prop was 'feathered' when not in use by rotating end on into the airstream .

The rotation of the (prop) blades may need to be more than 90degrees -- we used Bolly carbon fibre props on the Cobra and on their own they could be rotated (in pitch) as far as wanted --they would windmill (just on the hub, not on the aircraft) but that is not taking any power out of course, just playing around .

Even a desk fan will show that the fan can work in reverse --try it in some wind or take one in a car . 'Working' is not the same as being ideal -- I did preliminary design of a 15 metre diameter wind turbine in 1980 for the solar energy council here and have some of the 'bibles' on wind turbine design --we even made one with no twist at all that nearly flew apart from centrifugal force .

BTW what is the 'range extender" ? I posted a link to the Crossover on HBA quite a while ago --the wing position looks a bit odd --not pylon nor high but inbetween and looking draggy to my eye , the retraction of the motor pylons takes out a lot of fuselage structure and causes some concern for that --the threat from debris going from the wheels into the props is also a worry ( I flew on the first flight of the SV 10 Tardis in 1983 -it had two Fuji Robin 250cc engines mounted just aft of the wing and a spring landing gear of similar type to the crossover --we chipped a prop by about the third landing from a stone thrown up .)
 

JenDAG

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I'm not convinced that range extender (genset of IC engine and generator) is good idea for aircraft. It brings to many compromises and extra weight.
Especially for sailplane when main distance of flight can be done unpowered. For car it could make sense in mean time when waiting for better accumulators.
I like more energy regeneration idea, it makes more sense to me.
 

John.Roo

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Hello friends!
Saini Flyer is right – configuration with two electric motors is very difficult for certification.
But on Crossover team web (I thing latest info is on Facebook
https://www.facebook.com/Eurosportaircraft?fref=ts) you can see already different configuration with motor in the fin (like e-Genius).


Range extender is system used in some electric cars for example.
You have a pure electric car but to extend range you can use small combustible engine/generator in trunk or in trailer (
http://www.eptender.com/).
For electric airplanes would be enough power of +-20kW = small combustible engine.
I thing that Silence airplane (
http://silence-aircraft.de/en/aircraft/) had version with electric motor and removable range extender below fuselage. Maybe was only concept… it is long time ago…

Pipistrel and Diamond are working on hybrid solution so we will see more on AERO I hope
J

My opinion?
Electric airplanes are actually perfect for glider pilots. With acceptable L/D pilot needs only power for takeoff and then some reserve for safe flight back home…
For real cruiser is much better to have combustible engine. Simple refueling and long range is result of high power density of petrol in compare with energy density of batteries.
It is a pitty that due to difficult certification is not easy to transfer car engines technology to airplanes. You have cars with 100kW power and fuel consumption 8 l/h and even less. Automotive engines are far away ahead and I don´t think so they are significantly less safe. It is even more difficult to understand why airplane is synonym for enormous fuel consumption, because in airplane during cruise you can let engine run on optimal rpm – without necessity to change gear.

Coming back to “electric solutions”…
Question is – do we need to compare electric airplanes with combustible airplanes? When I discuss on airshow with “normal” pilots interested in electric airplanes I always hear the same – I like the idea, but I need to fly 500 km (1 000 km, 1 500 km…. however) distance. When this will be possible I will buy it because I want to decrease petrol costs. My question is – how often do you fly 500 km (1 000 km…. however) distance? When I visit most of airfields, I see pilots flying 30 min to 1 hour (mostly above the airfield or nearby) and then 2-3 hours discussing with other pilots drinking coffee
J This is situation in Czech Republic please don´t take it like fact valid worldwide, for example in USA pilots take airplane more like car flying often super long cross-country flights.

Typical glider pilot request? Give me enough power for 2x takeoff to 600 m (or 1x to 1 000 m) and possibility to use the rest of available power for 150 km flight coming back home. That sounds reasonable
J


So as a summary…
All special systems (range extenders, hybrids) are destroying idea of “simple” flying. If you have combination of fuel and batteries you have system much more complicated then only electric / only combustible system. And complicated = expensive, difficult for maintenance and with higher possibility of failure. When we started PhoEnix project idea was to produce electric motorglider with costs below of Rotax 912 version. Actually I have to say that electric motor, controller, batteries and chargers are about the same cost. With 8kWh capacity you have already mentioned 45-60 min. flight endurance = add you own opinion about comparison with Rotax 912 J My expectations for future? As with everything new… cost of electric solution will go down.

But nothing from above written is solving my biggest problem…

Like every “big boy” I like to play with “new and expensive toys” and electric airplanes are really great “playground” of possible development J

Best regards!
Martin
 

JenDAG

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Coming back to “electric solutions”…
Question is – do we need to compare electric airplanes with combustible airplanes? When I discuss on airshow with “normal” pilots interested in electric airplanes I always hear the same – I like the idea, but I need to fly 500 km (1 000 km, 1 500 km…. however) distance. When this will be possible I will buy it because I want to decrease petrol costs. My question is – how often do you fly 500 km (1 000 km…. however) distance? When I visit most of airfields, I see pilots flying 30 min to 1 hour (mostly above the airfield or nearby) and then 2-3 hours discussing with other pilots drinking coffee
J This is situation in Czech Republic please don´t take it like fact valid worldwide, for example in USA pilots take airplane more like car flying often super long cross-country flights.

Typical glider pilot request? Give me enough power for 2x takeoff to 600 m (or 1x to 1 000 m) and possibility to use the rest of available power for 150 km flight coming back home. That sounds reasonable
J

Martin, you nailed it! :)


-today,thanks HCCI technology it is possible to big reduce of the fuel consumption,
Henryk, HCCI technology is not matured enough at the moment and you can't run engine with fixed compresion ratio on petrol(gasoline) (or petrol like fuel) at all loads what you need only in CI regime.
 
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