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Enalpria

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Apr 20, 2020
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Has anyone built either a J1-B Don Quiote, or J2 Polonez in the US or better yet Texas?
I'm working on an electric powered ultralight version that is actually more similar to Janowski's J3 Eagle, but would love to talk to anyone that has actually built and flown one of his aircraft.
 

BJC

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I like the Janowski designs, especially the J-6, J-5 and J-1B. Circa 1992, my hangar mate had a J-5.

What weight, HP, and battery capacity are you targeting?


BJC
 

Enalpria

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Apr 20, 2020
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BBC,

I'm looking at a 22-25KW motor with 72v with 35-40ah batteries.
I'm looking to have the airframe come in at about 185-200lbs max before the power system requirements.
 

BJC

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That leaves only 54 to 69 pounds for battery, wiring, controller, motor and propeller.


BJC
 

Enalpria

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Apr 20, 2020
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Yes.....the motor is about 8 lbs, and I'm still trying to get the weight of the batteries. I'm budgeting 40 lbs for those, so it will be close.
I may have to have less flight time due to battery weight to make the 254 lb weight limit😐
I hope the FAA makes a concession for electric powered ultralight to have extra weight due to gas ones having an extra 30 lbs or so of fuel....
 

Enalpria

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Apr 20, 2020
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So it looks like the battery is @33lbs, motor 8-9lbs, prop, about 2lbs, and esc/motor controller probably 1-2 lbs, wiring and throttle switch???? Props spinner????
I think budgeting for 50-60 lbs total for the complete power system.
 

rv7charlie

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Nov 17, 2014
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672
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Jackson
This brings up an interesting legal hair-split question. The regs allow 254 lbs, empty weight, and they allow 5 gal of gas, *which isn't included in the 254 lb empty weight*.

If you built a 254 lb electric ultralite that includes a battery rack, how much 'fuel' (battery capacity) is allowed? The equivalent energy (flight duration) of 5 gal of fuel? I've never heard of the FAA violating a 350 lb *operator* of a legal ultralite, for being 'over gross'; I've never seen any legally defined gross weight limit for an ultralite. Perhaps you could back into a number, using wing area & the legal max stall speed, but I've never seen it defined.

(Yes, this question ignores the *engineering* side of the equation; how much extra weight can the airframe handle.)

Charlie
 

cluttonfred

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As I understand it, the FAA has refused to exclude batteries from the Part 103 empty weight when that specific request has been made. If it were me, I'd install your 33 lb of batteries in a removable container, paint it red and put a big "FUEL" sticker on it and don't ask any questions. In the extremely unlikely case of being called on it by the FAA, you can honestly say that you made a good faith effort to follow the regs written for gasoline engines with your electric engine which is not covered.
 

Luke Warmwater

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Dec 3, 2015
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Cabo San Lucas, Baja California Sur, Mexico
As I understand it, the FAA has refused to exclude batteries from the Part 103 empty weight when that specific request has been made. If it were me, I'd install your 33 lb of batteries in a removable container, paint it red and put a big "FUEL" sticker on it and don't ask any questions. In the extremely unlikely case of being called on it by the FAA, you can honestly say that you made a good faith effort to follow the regs written for gasoline engines with your electric engine which is not covered.
aHA! Just put the batteries in a backpack.....
 

Enalpria

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Apr 20, 2020
Messages
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All good points. You know, that might actually be a legal loophole to label the batteries as fuel. They do serve the same purpose.
If I remember a previous on-line discussion about this the FAA wouldn't go for it because gasoline is a consumable fuel(weight-wise).
And the fact of making sure the capacity wad equal to the energy in 5 gallons of gasoline.
I REALLY like the idea of a red battery pack that says fuel on it!
 
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