Front Electric Sustainer

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 |

On Sun, 01 Nov 2009 11:51:45 -0800, LimaZulu wrote:

-LAK17a has front tow hook placed bellow instrument panel -95% is
efficiency of motor+controler. Motor have good cooling, and it not looks
that heating will be a problem. It is just warm and controler is rated
for much higher power and is not even warm.

I noticed your web site comments about eliminating the drag from the
pylon and engine, but didn't mention the effect that the pylon would have
on propeller efficiency. Since your prop is a similar size to a
conventional sustainer prop, have you calculated effect on prop
efficiency of moving it from the pylon to the nose?


--
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

On Nov 1, 7:07*am, Darryl Ramm wrote:
On Nov 1, 4:29*am, Andy wrote:





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

If I read the specs right you can operate at full power for 14.4
minutes over which time you can climb a bit over 4,300 feet. *How's
that compare to other sustainers? *This seems simpler than most other
configurations which is nice.

9B

It would be interestingly they claim level flight for 120km which is
greater distance than a 4,300' climb will normally allow you to glide.
Just plucking numbers out of thin air of 50 knots for optimal climb
and cruise speeds (I expect climb would be slower) and an L/D of 50:1.
You would travel 22 km in the climb and glide 65km for a total of
87km. It would require a L/D 74 to match the straight cruise. The
exact optimal speeds and the profile of the climb as battery power
diminishes likely affects all this.

Looks like nice packaging. I am curious as well what happens to the
forward air cockpit air vent, nose pitot tube, nose tow hook, and
where cooling air for the engine comes from (presumably the nose
hole). At 95% efficiency the 15kW motor will generate 750W.

Darryl

I mis-read the projected climb as 1.5 m/s instead of 1.6. 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.

9B

"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

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

Andy wrote:
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


If I go bike-riding, it is a lot easier to go around the hills than to
go over them. If I am driving a car, my gas mileage is better when I go
around hills rather than over them.

What is it about sustainer gliders that causes them to be different? Of
course, the sustainers that we have now have engines that run too fast
for sustained cruising, have a pylon creating a lot of drag, etc. But
eliminate those problems, and isn't it more efficient to cruise at a
constant altitude?

On Nov 1, 6:56*pm, Greg Arnold wrote:
Andy wrote:
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

If I go bike-riding, it is a lot easier to go around the hills than to
go over them. *If I am driving a car, my gas mileage is better when I go
around hills rather than over them.

What is it about sustainer gliders that causes them to be different? *Of
course, the sustainers that we have now have engines that run too fast
for sustained cruising, have a pylon creating a lot of drag, etc. *But
eliminate those problems, and isn't it more efficient to cruise at a
constant altitude?

There will always be drag/inefficiency from the prop itself. But how
significant that is needs a back of the bigger envelope than I have
handy.

In addition to what you already mentioned, most sustainers and some
self launchers run two stroke engines. They have a noticeable
powerband, so you run them in that band and climb (if you are
lucky..). They often just wont run reliably at lower RPM, will oil up
plugs etc.

The electrics are a whole different kettle of fish. The sustainer here
has the advantages of electrics (being able to run at reduced power)
and prop optimization for sustainer use only (the prop does not need
to handle self launch).

The electrics have the benefit of not having to worry about mixture
settings at altitude, somethign many self launchers or sustainers
cannot deal with except by adjustment on the ground. I hope the people
making this produce some performance data for high density altitudes
(~10,000'). Around mountains 'out-west' most sustainers are next to
useless.

Darryl

On Sun, 01 Nov 2009 19:14:52 -0800, Darryl Ramm wrote:

The electrics have the benefit of not having to worry about mixture
settings at altitude, somethign many self launchers or sustainers
cannot deal with except by adjustment on the ground. I hope the people
making this produce some performance data for high density altitudes
(~10,000'). Around mountains 'out-west' most sustainers are next to
useless.

Judging from the performance of free flight models at Denver vs the same
models at Sacramento, the FES should be better than an IC sustainer. Its
noticable that power models lose performance big-time at Denver while
rubber powered models are much less affected. Now doubt this is due to
the way an IC engine loses power with altitude while electric or rubber
motors are unaffected.


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

On Nov 2, 2:36*pm, Martin Gregorie
wrote:
On Sun, 01 Nov 2009 19:14:52 -0800, Darryl Ramm wrote:
The electrics have the benefit of not having to worry about mixture
settings at altitude, somethign many self launchers or sustainers
cannot deal with except by adjustment on the ground. I hope the people
making this produce some performance data for high density altitudes
(~10,000'). Around mountains 'out-west' most sustainers are next to
useless.

Judging from the performance of free flight models at Denver vs the same
models at Sacramento, the FES should be better than an IC sustainer. Its
noticable that power models lose performance big-time at Denver while
rubber powered models are much less affected. Now doubt this is due to
the way an IC engine loses power with altitude while electric or rubber
motors are unaffected.

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

Really good point - I believe it's true that most of the power loss
with altitude is from loss of power produced by the engine, not prop
efficiency. Electric motors don't have this power loss because they
don't depend on combustion.

9B