high efficiency practical airframe

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stanislavz

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As in topic name. I have mentioned in some threads Rutan boomerang as best today airframe for electric conversion. But - for electric one could use contra rotating props/twin motor with idler gear etc. No need for hardcore twin motor.

So my question is - do exist other practical aiframe with performance similar to Rutan boomerang. Single or multi engine.

And please remember - Boomerang was Rutan "daily" plane
 

dog

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There is a cessna 337 hybrid conversion flying in
france, 1 gas motor, 1 big electric, and two small
electrics mounted in the wings in line with the booms.
Not in the same speed range as the boomerang,
but some of the thinking and implimentation might fit the idea you are putting forwards.
 

stanislavz

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Thank you for replay. But this Cessna is type of aircraft which i would like to exclude :)
 

stanislavz

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Why do you want to exclude it?
To draggy/ to slow.

There is highly refined versions like Global Flyer from same Rutan. But is not a "daily driver". And its reassembles twin glider by its design.

Boomerang on the other hand - was Burt Rutan "daily car" . And by making some calculations on napkin using input from Boomerang :

250 mph cruise using 143kw of power,
Empty weight: 2,359 lb (1,070 kg)
Max. takeoff weight: 4,189 lb (1,900 kg)
O-360 installed weight of ~ 350 Lbs.

And info for Tesla battery modules - 55 Lbs per module with cooling and frame with 5.3 kwh capacity and 1C of safe discharge rate

+ 1 kw of continoust electric engine power per 1 lbs. (On safe side, direct driven motor/motors, will take more for few minutes)

Gives following output for 1000lb of cargo: 2359 - 350 - 350 + 150 = 1809 lb empty weigth of airframe with motors. + 1375lb for batteries = 3184lb. + 1000lb cargo.

And we have 132kwh of energy, and ~200 miles range with some reserve. With high speed.

Do same math on Cessna 337 - half range on lower speed (144 mph cruise at X power, more air-frame weight).
 

TFF

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The boomerang was about asymmetric thrust on a lost engine for a twin. It was never totally put to the test as Burt is always off to the next thing. Concept by the concept guy. He is also a showman in that he knows what gets noticed and can pull it off enough to get the publicity.
 

stanislavz

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The boomerang was about asymmetric thrust on a lost engine for a twin. It was never totally put to the test as Burt is always off to the next thing. Concept by the concept guy. He is also a showman in that he knows what gets noticed and can pull it off enough to get the publicity.
I know about assymetry. For electric - it is still wise to put batteries not in a fuselage.

Any source of real boomerang data then ?
 

stanislavz

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Back on topic - this is not about building next tri surface super optimized airplane.

Just - lets call it "wings for the Tesla" . Tesla was build using yesterday battery technology today, not waiting for tommorow one.

And just by using same 100kwh battery - one could get more than 100mph range at decent speed for 700-800lbs load (pilot + three passengers)

Data is 1200lbs for 100kwh pack + 1lbs per 1kw of continous motor power. Question is - how many folks , at which distance it could take. And still be more practical than Rutan global flyer.
 

12notes

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To draggy/ to slow.

There is highly refined versions like Global Flyer from same Rutan. But is not a "daily driver". And its reassembles twin glider by its design.

Boomerang on the other hand - was Burt Rutan "daily car" . And by making some calculations on napkin using input from Boomerang :

250 mph cruise using 143kw of power,
Empty weight: 2,359 lb (1,070 kg)
Max. takeoff weight: 4,189 lb (1,900 kg)
O-360 installed weight of ~ 350 Lbs.

And info for Tesla battery modules - 55 Lbs per module with cooling and frame with 5.3 kwh capacity and 1C of safe discharge rate

+ 1 kw of continoust electric engine power per 1 lbs. (On safe side, direct driven motor/motors, will take more for few minutes)

Gives following output for 1000lb of cargo: 2359 - 350 - 350 + 150 = 1809 lb empty weigth of airframe with motors. + 1375lb for batteries = 3184lb. + 1000lb cargo.

And we have 132kwh of energy, and ~200 miles range with some reserve. With high speed.

Do same math on Cessna 337 - half range on lower speed (144 mph cruise at X power, more air-frame weight).
Unfortunately, you're leaving out a lot of weight. The modules need additional hardware to work and cool properly. The Tesla 85kWh pack using those modules weighs 1054 lbs. Scale that to 132kWh and it would be a 1855 lbs battery pack, reducing useful load to 520lbs. Scale it down to the 1375 lbs you want and it's only 111kWh. Without the resources of Tesla, it's unlikely you'll get the battery modules to scale up as efficiently, and the battery pack would be heavier.

But even assuming you match Tesla's packaging and the finished battery pack is the same density, you are underestimating takeoff and climb power needed. An 8 minute full power climb to 15,500 ft (best cruise altitude @1,900 f/min best climb rate) would use nearly 41kWh, leaving 91kWh for cruise. A single go around using 1 minute of full throttle and 3 minutes of cruise power would consume 12 kWh. Reducing the reserve down to only enough for a single go around, that leaves 79kWh for cruise, or 33 minutes, or a cruise range of 137 miles. Assuming you don't have a death wish, you'd want more reserve than that, and would end up with an electric airplane that can go about 100 miles, which is pretty much where every electric plane is with the current state of batteries. And this assumes you use the 132kWh battery which reduces your useful load to 520 lbs.

If you want 1000 lbs. useful load, and use the 111kWh battery, then you're looking at 24 minutes of cruise, or about 101 miles with the single go around reserve.

Unfortunately, this is where we are with electric planes. Wish it were different, but battery energy density evolves slowly and there isn't a useful airframe, other than motorgliders, that will get you more than about 100 miles of range with reserve.
 

stanislavz

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Unfortunately, you're leaving out a lot of weight. The modules need additional hardware to work and cool properly. The Tesla 85kWh pack using those modules weighs 1054 lbs. Scale that to 132kWh and it would be a 1855 lbs battery pack, reducing useful load to 520lbs. Scale it down to the 1375 lbs you want and it's only 111kWh. Without the resources of Tesla, it's unlikely you'll get the battery modules to scale up as efficiently, and the battery pack would be heavier.

But even assuming you match Tesla's packaging and the finished battery pack is the same density, you are underestimating takeoff and climb power needed. An 8 minute full power climb to 15,500 ft (best cruise altitude @1,900 f/min best climb rate) would use nearly 41kWh, leaving 91kWh for cruise. A single go around using 1 minute of full throttle and 3 minutes of cruise power would consume 12 kWh. Reducing the reserve down to only enough for a single go around, that leaves 79kWh for cruise, or 33 minutes, or a cruise range of 137 miles. Assuming you don't have a death wish, you'd want more reserve than that, and would end up with an electric airplane that can go about 100 miles, which is pretty much where every electric plane is with the current state of batteries. And this assumes you use the 132kWh battery which reduces your useful load to 520 lbs.

If you want 1000 lbs. useful load, and use the 111kWh battery, then you're looking at 24 minutes of cruise, or about 101 miles with the single go around reserve.

Unfortunately, this is where we are with electric planes. Wish it were different, but battery energy density evolves slowly and there isn't a useful airframe, other than motorgliders, that will get you more than about 100 miles of range with reserve.
Thank you for reply. I am using Tesla battery modules, because they have cooling channels and frame already.

But - is it wise to assume - same energy used to climb is saved on descend , except energy loss in drag.

Another example in different mtow category :

1592220229960.png

But - it will be non practical as "daily car" On ther hand - 116 miles per hour using 6.4 kw of energy..
 
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pictsidhe

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If you want efficiency, you must have either span or a lot of speed. You can't cheat the physics. The Tesla model 3 pack is around 1060lb and 75kWh. It has 4 large modules, which apparently are not easy to disassemble.
 

BJC

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The Tesla model 3 pack is around 1060lb and 75kWh. It has 4 large modules, which apparently are not easy to disassemble.
Not difficult for the tenacious to disassemble a Tesla, unless, of course, you want to salvage usable components.

EA71C577-922B-40E0-9383-359D23B27422.jpeg
 

stanislavz

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Not difficult for the tenacious to disassemble a Tesla
Some of mine friends, could even mill extra spaces in connection plates, to make it 48 voltage, in place of 24. (or 44v vs 22 votlage). Diy world is really re-purposing them widely.
 

12notes

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Thank you for reply. I am using Tesla battery modules, because they have cooling channels and frame already.

But - is it wise to assume - same energy used to climb is saved on descend , except energy loss in drag.

Another example in different mtow category :

But - it will be non practical as "daily car" On ther hand - 116 miles per hour using 6.4 kw of energy..
This is missing a key piece of data, what is the climb rate at 40kW? If it's 1000fpm, then it will use 5.33 kW getting to 8000 ft, add enough power for 1 go around and you're down to a total of 5.4 kW left for cruise, which ends up with 94-98 miles powered range. This gets much worse if the climb rate is below 1000 fpm.

It's true a gliding descent would add range, but I did say "other than motorgliders" in my previous post.
 

pictsidhe

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Some of mine friends, could even mill extra spaces in connection plates, to make it 48 voltage, in place of 24. (or 44v vs 22 votlage). Diy world is really re-purposing them widely.
Model 3 cells are potted in epoxy, unlike earlier packs, which are much easier to pull cells from. I really can't see anyone reliably using anything but the sub modules from M3 packs...
 

pictsidhe

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stanislavz

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You'll have more weight with a sturdy mount, BMS, interconnects and charger. The M3 packs use higher energy density cells and includes the above bits
It was only a study. Nissan leaf packs are some better on stored energy efficiency, but they use only passive cooling.
 
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