Front Electric Sustainer

On Nov 1, 2:49*pm, "vaughn"
wrote:
"Andy" wrote in message

...

*This still
leaves total climb capability a bit over 4,500 feet so the straight
cruise must get more out of the motor than a sawtooth, though I am not
clear why this would be true.

One good reason is because the whole electrical system, especially the
battery itself, is more efficient when operated at lower currents. *At
higher power outputs, a greater percentage of the battery's precious stored
energy turns into waste heat, so less of the battery's stored energy is
available to actually propel your aircraft..

Vaughn

True - though I was under the impression that a sawtooth profile is
more efficient for the overall glider-motor system. I'm at a loss as
to why the cruise mode for this system would produce nearly twice the
range of the sawtooth - at least according to math on the various
specs quoted.. The electric motor would have to REALLY hate being run
full out.

9B

I was wondering when someone would use the motor and folding prop used
on the Radian RC sailplane on a full scale ship. Nice, motor weight in
nose is balanced with battery weight aft and only 77 pounds total. I
figure 75 miles at low power or 5700 foot climb at full power. Heat
from running motor could warm your feet on a cold winter day! Any idea
on retrofit price and availability?
JJ

On Nov 1, 1:49*am, LimaZulu wrote:
First flight of Front Electric Sustainer - FES

http://www.front-electric-sustainer.com

http://www.youtube.com/watch?v=TNOKq6PKIvM

Regards,

Luka Znidarsic

I've got an empty engine bay in my Apis, always thought an electric
motor would be a nice thing to put in there. The doors for the prop
can handle a 46" dia. blade.

Brad

This looks like a natural for a single blade prop, folding flush into
a contoured recess in the bottom of the nose.

I like it!

Kirk

On Sun, 01 Nov 2009 09:51:45 -0800, kirk.stant wrote:

This looks like a natural for a single blade prop, folding flush into a
contoured recess in the bottom of the nose.

That would be nice to see from a propeller efficiency point of view too,
because the prop could be bigger while absorbing the same power. The
bigger the prop the more efficient it is. Propeller ground clearance
would be irrelevant for a sustainer system.

I remember seeing an Antares 20E and an ASW-22ble launch within 10
minutes of each other, so the ground and air conditions were very
similar. The ASW-22 has 49hp (36 kW) and (I think) a 0.9m diameter prop
while the Antares swings a 2m prop with a 47 kW motor. The Antares was
off the ground in about 1/3 the run the '22 needed and climbed out at
least twice as fast. I don't know how the takeoff weights would compare,
but if they're not too different the additional 30% power output in the
Antares wouldn't account for the takeoff and climb out difference I saw,
but the different props could easily do it. A two blade prop is rather
more efficient than a 5 or 6 blade unit and the almost 5:1 difference in
swept area would make a big difference to drive efficiency, especially at
low speeds.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

kirk.stant wrote:
This looks like a natural for a single blade prop, folding flush into
a contoured recess in the bottom of the nose.

I like it!

Kirk

Another good idea from the model world :-). Needs a hefty counterweight
at those dimensions of spinner (small) and prop (large) though.

/AndersP