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 <> 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 *
> tel:   07 4635 5784     overseas: int+61-7-4635 5784
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