best self-launcher propulsion system?

I know of no actual measurement of drag with the FES (i.e. with prop
folded) but there was some report of comparison flying in a comp with
a similar glider of another make (Ventus?). Can’t recall the link now,
but it would have been either in Lak’s website or Luka’s (the designer/
developer).

For my money, any slight increase in drag is not only imperceptible
to me, but is (a tiny) part of a price I am willing to pay for its
advantages in my particular compromise – getting home without a
retrieve crew if a cross country does not pan out, and getting away
from virtually any launch if it is at all soarable, etc.

Chris N.

Hi Gang
I have had a DG800B and a Stemme S10VT for many years and currently
have a Phoenix so I have some experience with self launchers. I almost
purchased an Antares a couple of years ago but discovered a gotcha
that for me was a show stopper. And that gotcha? Lithium batteries
cannot exceed fairly modest temperatures before they have to be
shutdown meaning if I left an Antares in the hot midday sun in Nevada
for a couple of hours I might not even be able to reach 1,000 feet
before the electric system would automatically shut down. This might
be OK in cooler climates but not at Minden.
The vibration problems of the DG require almost constant monitoring
of the engine and its supports for wear and tear. The Wankel engine of
the 26 is apparently much less prone to vibration problems. Anything
using the Rotax engine is reliable. The Stemme had maintenance
problems but the Rotax 914 engine was reliable.
So if you want the highest performance single place self launcher I
would recommend the Ventus or the 26. For a 2 place self launcher the
Stemme is hard to beat with its much better ground handling compared
to a 25 although the performance of the 25 is a little better.
For a little old guy like me who has completed all the 6 hour XC
flights he ever wants to do in the DG800B and the Stemme you might
want to consider a touring motorgllider and there is one that clearly
stands above the rest and that is the Phoenix. It is the first that
allows the outer wing panels to be removed in less than a minute
reducing the wing span from 15 meters to 11 meters thereby allowing
the Phoenix to be parked in a regular hanger. In the short wing
configuration it is a superb LSA power plane and in the long wing
configuration it is a medium performance motorglider. It is registered
as a LSA glider even though in the short wing configuration it is
clearly a standard LSA power plane. The FAA had never considered this
a possibility and a registered aircraft cannot have 2 certifications.
That suits me.
Dave

At the lower cost end of the spectrum, I can say that the rotax
installation of the Apis is very well thought out and has performed
for me over 4 seasons without fail for air restarts. It runs cool and
usually requires less than a minute at idle before stowing. The engine
is rev limited to about 6000 rpm and I don't always get that.

It is relatively idiot proof, (witness I am still here writing). This
particular installation is no longer available as AMS bit the dust.
The glider is still being built by Pipistrelle with a different
engine.

The Apis is not a state of the art high aspect glider but capable of
long cross country, have done 300k here in Oregon. The wing area is
large, keeping the loading down, and while I get only 5-600 fpm at sea
level, I still get a positive rate at 10k.

Vibration is unpleasant, and I am constantly looking for the smoothest
rpm range for the altitude, sometimes 100 rpm makes a huge
difference. Nothing has shaken off the bird yet and I constantly tell
myself, that it is at least as pleasant as flying around on tow.

Not sure what Pipistrelle is asking but I got in for about 1/2 what a
German machine would cost, including the trailer.

Mark

On Wednesday, January 11, 2012 1:24:33 PM UTC-5, kd6veb wrote:
... I almost
purchased an Antares a couple of years ago but discovered a gotcha
that for me was a show stopper. And that gotcha? Lithium batteries
cannot exceed fairly modest temperatures before they have to be
shutdown meaning if I left an Antares in the hot midday sun in Nevada
for a couple of hours I might not even be able to reach 1,000 feet
before the electric system would automatically shut down. This might
be OK in cooler climates but not at Minden.

Huh ?

I regularly self-launch at Uvalde, Hobbs, etc.
Not exactly locations I need the Sorel boots.

Battery heating is the third power of current.
Thus, reducing from max power shortly after
take-off reduces heating enough that this has
never been an issue for me in actual operation
over many seasons (including multiple contests
at Hobbs and Uvalde, launching on HOT days with
full water ballast).

Hope that's clear !
Best Regards, Dave "YO electric"

On Jan 11, 12:19*pm, Dave Nadler wrote:

Battery heating is the third power of current.


Really? Assuming no external heater is enabled isn't the power that
heats the batteries the product of the internal resistance and the
current and the current? ( I squared R, rather than I cubed R)

Andy

On Jan 10, 7:48*pm, key wrote:
I am curious what group members with experience with self-launchers
regard as the best propulsion system (currently) in terms of in-flight
restart reliability, maintenance, safety, and other operational
factors (e.g., vibration). *Of course the electric Antares might win
on all counts except for range, but it is out of my price league.

thanks,

Key

NEW:
Silent 2 ELECTRO FESL
Front Electric Self Launch
ease of operation and peace of mind

greater reliability when compared with any internal combustion engine
secure and instant start-up; the motor requires no warm-up prior to
application of full power
absence of vibration; the only moving parts are the propeller and the
rotor
maintenance is essentially unnecessary
nose-mounted motor is on the fuselage center-line and thus has no
forward pitching moment
to create take-off difficulties as is typical of pylon mounted
propellers
no loss of motor power as a function of altitude; performance is
unvaried with respect to atmospheric conditions
motor use is extremely simple; no raising of a pylon, simply turn on
the master and apply power
absence of aerodynamic resistance (engine pylon, etc.) and
consequently better flight performance
simplicity and uncomplicated use of the entire system, when compared
to solutions with a retractable
no change to the aerodynamics when using the motor
no change to the center of gravity when changing between powered and
unpowered flight.
prop located in front of the cockpit and safely visible to the pilot
at all times
availability of extra electric energy for even the most well-equipped
instrument panel
lowest price for a new glider
can fly more then an hour level

http://www.alisport.com/eu/eng/silent2electro.htm

I WANT ONE!!!!!

Seems like not much clearance between the prop and the runway. Probably
pretty expensive if you hit the runway with the prop.



On 1/11/2012 12:16 PM, silentpilot wrote:
On Jan 10, 7:48 pm, wrote:
I am curious what group members with experience with self-launchers
regard as the best propulsion system (currently) in terms of in-flight
restart reliability, maintenance, safety, and other operational
factors (e.g., vibration). Of course the electric Antares might win
on all counts except for range, but it is out of my price league.

thanks,

Key

NEW:
Silent 2 ELECTRO FESL
Front Electric Self Launch
ease of operation and peace of mind

greater reliability when compared with any internal combustion engine
secure and instant start-up; the motor requires no warm-up prior to
application of full power
absence of vibration; the only moving parts are the propeller and the
rotor
maintenance is essentially unnecessary
nose-mounted motor is on the fuselage center-line and thus has no
forward pitching moment
to create take-off difficulties as is typical of pylon mounted
propellers
no loss of motor power as a function of altitude; performance is
unvaried with respect to atmospheric conditions
motor use is extremely simple; no raising of a pylon, simply turn on
the master and apply power
absence of aerodynamic resistance (engine pylon, etc.) and
consequently better flight performance
simplicity and uncomplicated use of the entire system, when compared
to solutions with a retractable
no change to the aerodynamics when using the motor
no change to the center of gravity when changing between powered and
unpowered flight.
prop located in front of the cockpit and safely visible to the pilot
at all times
availability of extra electric energy for even the most well-equipped
instrument panel
lowest price for a new glider
can fly more then an hour level

http://www.alisport.com/eu/eng/silent2electro.htm

I WANT ONE!!!!!

On 1/11/2012 1:33 PM, Greg Arnold wrote: (referring to the Alisport Silent 2
Electro)
Seems like not much clearance between the prop and the runway. Probably pretty
expensive if you hit the runway with the prop.


Mercy!!! Pretty much true of all self-launching prop planes with which I'm
familiar...

YMMV,
Bob W.

That's what I would have guessed, but its
a bit more complicated than that...

On Jan 11, 3:33*pm, Greg Arnold wrote:
Seems like not much clearance between the prop and the runway. *Probably
pretty expensive if you hit the runway with the prop.


new prop 2 grands????
not much clearance between the prop and the runway during the
first 11 seconds, then the Silent is off the ground..........
I would hold the stick full back..
And never taxi.