thanks

On Tue, Sep 20, 2016 at 7:13 PM, Matthew Gage <m...@knightschallenge.com>
wrote:

> The pylon raises from the back of the bay. The motor pivots on the pylon
> so the thrust axis is always horizontal.
>
> See https://www.facebook.com/gpgliders/videos for a number of clips of
> the motor in action.
>
>
> On 20 Sep 2016, at 19:04 , Peter Champness <plchampn...@gmail.com> wrote:
>
> Any  good links?
> I found a schematic diagram which indicates that the motor has a pusher
> folding prop.  Not sure how it retracts and fits in the fuselage with the
> blades sticking up?
>
> On Tue, Sep 20, 2016 at 6:46 PM, Mike Borgelt <
> mborg...@borgeltinstruments.com> wrote:
>
>> Yes, Matt.
>>
>> Mainly that the limited diameter of the prop limits prop efficiency. In
>> the chain Battery->motor->prop-> useful thrust,  prop efficiency is the
>> single largest loss. You'll get around 50% at the power/diameter/airspeeds
>> we are dealing with here. More blades aren't necessarily better.
>> I'm no fan of sustainers. For a little extra trouble make the damn thing
>> self launching.
>> I am a little surprised at the willingness of glider pilots to accept ANY
>> performance loss from the FES though. BTW a TE probe typically causes about
>> 0.7% of the drag at 100 KIAS on a 400 Kg modern glider.
>>
>> The Peszke GP glider designer has his views on the matter and has made it
>> clear where he stands as the GP series self launchers have retractable
>> propulsion units. Having seen video of it in action I wouldn't expect any
>> trouble. Seems to take about 4 seconds to extend and retract. Given the
>> number of manufacturers making linear actuators in all sorts of sizes I
>> doubt there is a generic problem with them. Seems to be that both Peszke
>> and FES get their motor/controller/battery tech from the same source.
>> Yes there is a drag penalty for the extended engine on a pylon. With
>> proper design it can be minimised (I'd close the doors with the engine
>> extended). The FES drag penalty in powered flight is more subtle. To
>> produce thrust the air has to be accelerated through the prop. Now VERY
>> APPROXIMATELY we are talking around 1.4 times the flight velocity which
>> gives twice the drag and this air passes over the entire fuselage, wing
>> root, fin and probably part of the tailplane, though at reduced velocity
>> for the latter. With the retractable pusher of the Peszke system, only over
>> the fin and tailplane.
>> Interestingly both the Peszke designer and the FES designers come from a
>> model aircraft R/C glider background. As does the electric propulsion tech.
>>
>> A few other considerations:
>>
>> The system appears to weigh 40 Kg. Better have motor glider or turbo
>> wings on the glider as it is all non lifting parts. Probably not an issue
>> with recent gliders as I suspect all of them are built with the stronger
>> wings to prevent embarrassing mistakes. They do seem to have learned about
>> Murphy's Law since the Libelle aileron drives were designed.
>>
>> You can bet some idle idiot will try to unfold a prop blade on the
>> ground.  Will this be OK or will it cause a problem? The TOP certainly
>> could have a problem if ONE of the three blades was manually opened. Two
>> simultaneously was OK.
>>
>> What happened to the Australia required nose release? Only self launch on
>> lightweight gliders so you'll need a tow.
>>
>> From the website: "Cell manufacturer claims that at discharging with 1C
>> rating (horizontal flight) life expectancy of batteries is around 1500
>> cycles. After that the battery will still have 80% of the original
>> capacity" . At full power they are pulling 200 amps, around 5C., not 1C.
>>
>> DO remove the batteries for charging and put them where the house/hangar
>> etc won't burn down if things go wrong. The R/C people have burned down a
>> few houses and I heard of one near new VW Transporter carrying models where
>> batteries were being charged and it had to stop, be abandoned and burned to
>> the ground.
>>
>>
>> I do agree with Richard Frawley that outlanding sucks for many reasons.
>> After 62 real ones in farmers' fields I've had enough. Mr Lycoming willing,
>> there won't be any more. Besides with the consolidation of agribusinesses,
>> agricultural quarantines (remember the foot and mouth outbreak in the UK
>> where cross country gliding was banned for a season?), foreign ownership
>> and contamination issues with GM crops you may find that the "social
>> licence" for outlanding will go away(as much as I hate that term).
>>
>> Mike
>>
>>
>> At 09:31 PM 9/19/2016, you wrote:
>>
>> I think what Mike was referring to was not the drag of the blades in
>> gliding flight but the efficiency of the nose-mounted propellor in climb.
>> Reliability through simplicity is definitely a factor, but the FES is not
>> much good if you want to self-launch (prop clearance).
>>
>> *Borgelt Instruments* -
>> *design & manufacture of quality soaring instrumentation since 1978 *
>> www.borgeltinstruments.com
>> tel:   07 4635 5784     overseas: int+61-7-4635 5784
>> mob: 042835 5784                 :  int+61-42835 5784
>> P O Box 4607, Toowoomba East, QLD 4350, Australia
>>
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