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

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stanislavz

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Sad and angry. Again you have to think different in e world.

As in best ant safet airplane for me - pazmany pl2 - place batteries in wing tips. Not in wing spar, nor in bucket under you seat. Or in front of you.

If it will burn - you want stop it or have any chance, except of full eject seat.
 

Speedboat100

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One thing is for sure...Lazair excels as it uses only 3 KW of electricity in level flight...in cruise. This concept could take you a long way..unless the pilot wasn't hanging underneath the wing and causing a tramendous drag.

So a light weight plane with some sorta aerodynamic pod/hull for the pilot could possibly increase the speed by 100 %...and then 2 hrs flying time would yield 300-400 km distance.
 

stanislavz

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Not only cooling. Cells are not identical. Some is weaker, some is stronger. Most bms do limit upper charge - so all cells behave as weak one. And going into deep discharge - may over discharge some cells and gradually form metallic lithium crystal, which reaps its way through separator. And you have fire.
 

Hephaestus

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I still like the battery pod concept, off the wing or fuselage like a long-ez style baggage pod. Run fire protection style fusible links so there's an automatic x° mechanical release, and physical seperation from structure if release fails. Mount it on CG so when it sheds you drop the weight and are otherwise unaffected.only problem is the Anderson plugs likely would hold the pack, needs to be some kind of breakaway battery contact that I don't currently see in existence yet.

Even with billions invested even Tesla still has issues. All the electric ev's have had battery fires for one reason or another.

It's all about risk mitigation.
 

Aerowerx

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A direct drive motor is going to be much heavier than a geared motor.
Why?

You still need the same power delivered to the prop. The reason for a PSRU is to match the power curve of a gasoline engine to the power required at the prop. A brushless DC motor can be (theoretically, anyway) designed to provide just about any RPM at any HP desired. No need for a PSRU.

If you have a non-optimum brushless dc motor and then add a PSRU, you are loosing power between the motor shaft and the prop. And how much will both of them together weigh?

Disclaimer: I am not a motor expert. This is just from what I have read about brushless motors.
 

Speedboat100

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Why?

You still need the same power delivered to the prop. The reason for a PSRU is to match the power curve of a gasoline engine to the power required at the prop. A brushless DC motor can be (theoretically, anyway) designed to provide just about any RPM at any HP desired. No need for a PSRU.

If you have a non-optimum brushless dc motor and then add a PSRU, you are loosing power between the motor shaft and the prop. And how much will both of them together weigh?

Disclaimer: I am not a motor expert. This is just from what I have read about brushless motors.
The benefit ought to be more than the loss for the PRSU gearing.
 

12notes

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One thing is for sure...Lazair excels as it uses only 3 KW of electricity in level flight...in cruise.
This number is unsubstantiated, but you keep claiming it for some reason. It should be using a lot more than 3kW (4HP) , 11% of maximum power, while in cruise. Do you have any evidence to back this number up?
 

stanislavz

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Just my opinion :



And for 1 to 12 glide ratio, it will give you maximum weight of airplane of 12 * 16 ~ 200 kg. This is just an example, it is only static thrust, and it will decrease with speed - so as required power. Just an fast example.
 

Speedboat100

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This number is unsubstantiated, but you keep claiming it for some reason. It should be using a lot more than 3kW (4HP) , 11% of maximum power, while in cruise. Do you have any evidence to back this number up?

They claim it is 3 KW and also their batteries and their endurance vs weight confirms it. Might be a tad higher with more batteries.

HPAs only use 250 watts continuous.
 

Speedboat100

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Just my opinion :



And for 1 to 12 glide ratio, it will give you maximum weight of airplane of 12 * 16 ~ 200 kg. This is just an example, it is only static thrust, and it will decrease with speed - so as required power. Just an fast example.

Better glideratio certainly helps alot. Heavy sailplanes can climb with just 20 kg of static thrust.
 

stanislavz

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Better glideratio certainly helps alot. Heavy sailplanes can climb with just 20 kg of static thrust.
I do take 1 to 12 glide ratio from wiki for lazair. So far, for me it is just mathematical optimisation - for any wanted parameter, as maximum range or speed or endurance.

Henryk posted some time ago, a german flying wing with enclosed pod for pilot with 1 to 25 glide ratio... So it should cruise with 1.5 kw of power..
 

pictsidhe

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All still goes to power / cooling surface. You cant put more than 1.2 Tesla in iron core before saturation. Independant of shape.

And pancake shape will provide way much cooling area, than more compact shape. Plus automaticly will make less rpm and more torque.
The torque of a motor and resistive power loss is set by it's size. The speed is set by how fast it can spin before it comes apart. Running far slower than it can safely run will result in far less power than it is capable of. yes, higher speed means more iron losses. But low loss cores and a little derating takes care of that. Double the RPM, you get nearly double the power

Long life gearboxes have been built for over a century. I suspect that RC gearbox builders aren't aiming for long life...

25:1 glide ratio at how slow?
 

12notes

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They claim it is 3 KW and also their batteries and their endurance vs weight confirms it. Might be a tad higher with more batteries.

HPAs only use 250 watts continuous.
Lazair has made no such claim, you have not substantiated this any time you've mentioned it. Their endurance for the e-Lazair on their website is about an hour, their endurance doesn't agree with your claim.
 

henryk

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I do take 1 to 12 glide ratio from wiki for lazair. So far, for me it is just mathematical optimisation - for any wanted parameter, as maximum range or speed or endurance.

Henryk posted some time ago, a german flying wing with enclosed pod for pilot with 1 to 25 glide ratio... So it should cruise with 1.5 kw of power..
40 (wing) + 30 (fuselage with motor) +100 (pilot+gas)=170 kg

170/25=7 kG thrust...

70 N x 30 m/s=2100 W= circa 2 kW !
 
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