Electric Duct Fan (EDF) Self-Launch Glider?

On 1/18/2011 3:56 AM, Mike the Strike wrote:

One technique to launch underpowered self-launchers is to auto-tow the
ship until it is airborne and then climb under power. The
acceleration and ground roll can be a significant problem at high
altitudes or on soft fields and the auto-tow is cheap and simple.

Bungee launch without the hill! That would enable you to launch
unassisted: stretch the bungey out the runway, climb in, trigger the
release of the bungee, and WHHoommp! You are going 45 knots and off the
runway.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
email me)

On 1/18/2011 9:09 AM, CLewis95 wrote:

Evan .. some have missed a few of the parameters I stated up front.
The "model" EDF unit I am refering to advertises 38lbs Static
Thrust ... I can cluster and raise/retract this "cluster" into the
large bay of the Genesis 2 area that was designed to house a BRS
system. (though I would experiment with fixed mount first if I ever
actually tried this)

Can you give a link to the EDF you are considering?

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
email me)

On Jan 18, 6:42*pm, Eric Greenwell wrote:
On 1/18/2011 9:09 AM, CLewis95 wrote:

Evan .. some have missed a few of the parameters I stated up front.
The "model" EDF unit I am refering to advertises 38lbs Static
Thrust ... I can cluster and raise/retract this "cluster" into the
large bay of the Genesis 2 area that was designed to house a BRS
system. *(though I would experiment with fixed mount first if I ever
actually tried this)

Can you give a link to the EDF you are considering?

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
email me)

These are (2) units that I have been watching for ~ 2 years now..
hoping next generation would be stronger:

TF 8000 (28lbs Max Thrust)
http://www.ductedfans.com/TF_8000.html

DS 94 HST (22lbs Max Thrust)
http://www.ductedfans.com/Schuebeler...ed%20Fans.html

I just noticed in reviewing these links that the Max Thrust is stated
as 28lbs on TF 8000 ... I was using 20lbs for assumptions x 3 =
60lbs. In a previous reply I incorrectly said "3 x 38 = 108 rated max
thrust" .. I should have said "3 x 28 = 84 rated max thrust" ... again
I am using 60lbs for assumed thrust.

There are a number of purpose built electronic speed controllers for
these units.

Curt - 95

On Jan 18, 7:43*pm, CLewis95 wrote:
On Jan 18, 6:42*pm, Eric Greenwell wrote:

On 1/18/2011 9:09 AM, CLewis95 wrote:

Evan .. some have missed a few of the parameters I stated up front.
The "model" EDF unit I am refering to advertises 38lbs Static
Thrust ... I can cluster and raise/retract this "cluster" into the
large bay of the Genesis 2 area that was designed to house a BRS
system. *(though I would experiment with fixed mount first if I ever
actually tried this)

Can you give a link to the EDF you are considering?

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
email me)

These are (2) units that I have been watching for ~ 2 years now..
hoping next generation would be stronger:

TF 8000 (28lbs Max Thrust)http://www.ductedfans.com/TF_8000.html

DS 94 HST (22lbs Max Thrust)http://www.ductedfans.com/Schuebeler...ed%20Fans.html

I just noticed in reviewing these links that the Max Thrust is stated
as 28lbs on TF 8000 ... I was using 20lbs for assumptions x 3 =
60lbs. *In a previous reply I incorrectly said "3 x 38 = 108 rated max
thrust" .. I should have said "3 x 28 = 84 rated max thrust" ... again
I am using 60lbs for assumed thrust.

There are a number of purpose built electronic speed controllers for
these units.

Curt - 95

How about downsizing the fans a little and using them as combined air
extractor and boundary layer suction/boundary layer control devices
which give some thrust. They could blow air along each side of the
fuselage tail across the lower part of the rudder and suck air from
the intake vents and possibly from small slots cut into the top wing
skin. Not a sustainer but it might increase the L/D by a fair
amount.

On Jan 18, 5:43*pm, CLewis95 wrote:
On Jan 18, 6:42*pm, Eric Greenwell wrote:

On 1/18/2011 9:09 AM, CLewis95 wrote:

Evan .. some have missed a few of the parameters I stated up front.
The "model" EDF unit I am refering to advertises 38lbs Static
Thrust ... I can cluster and raise/retract this "cluster" into the
large bay of the Genesis 2 area that was designed to house a BRS
system. *(though I would experiment with fixed mount first if I ever
actually tried this)

Can you give a link to the EDF you are considering?

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
email me)

These are (2) units that I have been watching for ~ 2 years now..
hoping next generation would be stronger:

TF 8000 (28lbs Max Thrust)http://www.ductedfans.com/TF_8000.html

DS 94 HST (22lbs Max Thrust)http://www.ductedfans.com/Schuebeler...ed%20Fans.html

I just noticed in reviewing these links that the Max Thrust is stated
as 28lbs on TF 8000 ... I was using 20lbs for assumptions x 3 =
60lbs. *In a previous reply I incorrectly said "3 x 38 = 108 rated max
thrust" .. I should have said "3 x 28 = 84 rated max thrust" ... again
I am using 60lbs for assumed thrust.

There are a number of purpose built electronic speed controllers for
these units.

Curt - 95

The second one looks like it pulls 180 Amps - 10 KW which puts it at
the very high end of the modeling spectrum.
Probably somewhere in the 30,000 to 40,000 rpm range.

yeah, 40KW and you are getting there.

On Jan 17, 11:53*am, CLewis95 wrote:
Electric Duct Fan (EDF) Self-Launch Glider?

I have pondered this for some time now. *Electric Duct Fan (EDF)
propulsion systems have been making strides in the RC model jet world
and are challenging the use of mini turbine jet engines (now used on a
number of full scale SL sailplanes) *Battery technology regarding
power density and safety continues to improve at a rapid pace. (auto
engineer recently stated that within 5 years batteries will approach
the power density of gasoline ... hard to believe but ?? ) *EDF
systems do not have the tremendously high exhaust temperature (~700°C)
and decibel level issues. (Though not as loud, the EDF systems sound
very similar)

Assuming:
- L/D 40:1 850 pound Sailplane (in my case Genesis 2)
- Cluster of (3) currently available EDF Units producing combined ~60
pounds STATIC THRUST (AFTER taking into account loss of efficiency do
to close clustering of intake ducts)
- Battery capacity for ~10 minutes full power .. no reserve
- 2,500ft Paved Runway .. No Tailwind
- Sailplane pre-positioned on runway (not taxied to runway)
- Goal altitude of ~1,500ft AGL

As a "sustainer" I am fairly confident this would yield some
success .. if only buying you ~10 miles *What I would like to hear
from the hobby-physicists out there are comments on these questions:

1 - How detrimental is the loss of efficiency/performance when
clustering duct fan intakes in very close proximity?
2 - With sailplane starting from rest, how long would it take to
accelerate to flying speed? i.e. Would I need 3 miles of paved runway?
and/or .. Would the batteries be dead before the glider left the
ground?

I certainly am not proposing a "replacement" for jet turbines .. only
curious if the above scenario is at all feasible.

Thanks for comments!

Curt Lewis - 95
Genesis 2
Loves Park, IL USA

I don't think a ducted fan is the way to go, but I could get excited
about an electric sustainer in the nose if available for say10K with
folding prop, controller and battery. Nose weight of the motor is
counter balanced with battery in aft fuselage, but they wont 25K for
the one installed on a LAK-17.
JJ

On 1/20/2011 6:41 AM, JJ Sinclair wrote:


I don't think a ducted fan is the way to go, but I could get excited
about an electric sustainer in the nose if available for say10K with
folding prop, controller and battery. Nose weight of the motor is
counter balanced with battery in aft fuselage, but they wont 25K for
the one installed on a LAK-17.

Possibly, a folding propeller design like the Carat uses would make
installation a lot easier. The battery, controller, motor, and propeller
might be available for $10K total, but you need a battery/motor guy to
complement your composite construction skills. Any Genesis owners like that?

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
email me)