thanks On Tue, Sep 20, 2016 at 7:13 PM, Matthew Gage <[email protected]> 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 <[email protected]> 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 < > [email protected]> 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 >> >> _______________________________________________ >> Aus-soaring mailing list >> [email protected] >> http://lists.base64.com.au/listinfo/aus-soaring >> >> > _______________________________________________ > Aus-soaring mailing list > [email protected] > http://lists.base64.com.au/listinfo/aus-soaring > > > > _______________________________________________ > Aus-soaring mailing list > [email protected] > http://lists.base64.com.au/listinfo/aus-soaring > >
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