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
