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John.Roo

Well-Known Member
Joined
Oct 8, 2013
Messages
468
Location
Letohrad / Czech Republic
Hi.
I am trying to build a motor glider and looking for an Engine .
What is the price for an Electric engine?
Hello!
It depends on details like - Empty Weight, Max. TakeOff Weight, L/D, place of propulsion system (pusher, tractor, retractable), possible diameter of prop...

If it is new design and you have no experience with electric propulsion than I recommend you to start with "known"combustion engine, test real flight characteristics and than install electric propulsion :)
 

Bille Floyd

Well-Known Member
Joined
Sep 26, 2019
Messages
338
...

Coming back to eSoaring, I'm looking at the ATOS Wing, and I think it's the closest thing to home buildable. The wing structure is not something I've seen before, where the covering seems to be a rigid sail cloth of some kind, like you'd find in a wind-surfing board. But it's really easy to source that kind of material, and it's not inordinately pricey for the surface needed.

What isn't great about the ATOS Wing is the seating position. It puts the pilot above and behind the wing, blocking all visibility. This might be to fit the tall landing gear and keep battery cables short, but that seems sub-optimal.

So if I were considering a home-build version, I'd think about how to build that style wing with a Birdy pusher tail, so that the human and the battery would be reversed.
I wouldn't be able to deal, with the seating position of that
Atos motor-glider either ! Perhaps if the pilot were on top
of the wing, and a motor arrangement, like on your AC-5M ?
Now picture a light E-motor , on the end of that retractable pylon !
Battery's could be back a bit ; pushing the pilot forward, for
a better view.

As far as fabric goes --- 3,2oz Dacron seams to have the longest
life span for a Hang glider ; i'd stay away from that clear stuff with
the Technora , because it doesn't last many years .

Bille
 

opcod

Well-Known Member
Joined
Aug 28, 2010
Messages
77
Location
Canada
To reply to the question.. a proper 20kw to takeoff an ulm or real glider is around 4k and 1.5 for the controller. You can get a ctrl way cheaper with no function and no monitoring for 500 and weight about 4time the previous one. It will also drain the batt pack like crazy. Overall you will not save anything in the medium run. And a chinise motor rated at 45kw is mean to run at 40kw for few sec, and after it melt and burn or sometime catch fire. few minutes run can be acheived at 18kw. Overall, you save 2k on the engine, but to have it way too heavy and underperformance. But as a sustainer, that can work or to show off on the ground it look great.
 

ypsilon

Well-Known Member
Joined
Mar 1, 2016
Messages
278
Location
Austria
You would need a fairly high performance
sailplane , to stay with an Atos ,
From my experience the ATOS doesn't handle light conditions very well. Even a Grunau Baby would outperform it in light and narrow thermals. I guess that's because the Atos is creating a lot of drag with its spoilers when circling.
 

ypsilon

Well-Known Member
Joined
Mar 1, 2016
Messages
278
Location
Austria
With l/d of ten, you flight time will be equal to batteries time only..
Are you aware that paragliders with an L/D of about 10 do 300 km FAI triangles regularly these days? (And more than 500 km free distance). Sorability doesn't have to do with L/D as much as you think. An Airbus A-320 comes in at an L/D of about 17. Good luck with thermalling it :)
 

stanislavz

Well-Known Member
HBA Supporter
Joined
Aug 21, 2016
Messages
773
Location
Lt
Are you aware that paragliders with an L/D of about 10 do 300 km FAI triangles regularly these days? (And more than 500 km free distance). Sorability doesn't have to do with L/D as much as you think. An Airbus A-320 comes in at an L/D of about 17. Good luck with thermalling it :)
Agree. L/D and surface load :)
 

Bille Floyd

Well-Known Member
Joined
Sep 26, 2019
Messages
338
From my experience the ATOS doesn't handle light conditions very well. Even a Grunau Baby would outperform it in light and narrow thermals. I guess that's because the Atos is creating a lot of drag with its spoilers when circling.
From Wikipedia :
Schneider Grunau Baby was a single-seat sailplane first built in Germany in 1931, with ... Winch launch speed: 80 km/h (49.7 mph; 43.2 kn); Maximum glide ratio: 17 at 60 km/h (37.3 mph; 32.4 kn); Rate of sink: 0.85 m/s (167 ft/min) at 55 ...

The Atos is a bit better than your G-Baby , in all parameters ; and
it turns Way tighter , so staying in a thermals core is easier ---



Bille
 
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