Best option for electric self starting glider

GP are getting their act together and increasing their manufacturing footprint.
We should finally see GP's coming out of the factory door.

Even if there is a little bit more complexity with a pylon mounted motor, there are clear advantages over the FES solution.
- more powerful motor
- better cooling
- better prop efficiency
- no prop strike risk
Another advantage of GP with large batteries is that, beside the larger energy capacity, the cells are discharged at lower amps rating and therefore run cooler.

The climb performance seems to be in line with flight test results.
As discussed before the published climb perf are without WB. Therefore TOM 320-330 kg. Even when flying empty, the typical WL will be ~42 kg/m2 which is already nice.
GP has made some good choices:
- light weight to allow very good electric climb performance (climb rate and altitude gain)
- high aspect ratio/low wing surface to achieve high L/D and higher WL. Maybe Max L/D will be a little bit less than 18m like ASH26 or DG800, but the L/D above 150 km/h should be better.

BTW, you need to add fixed ballast to get to 525 kg MTOM.

Regards,
JL

jld wrote on 4/10/2020 4:48 PM:
GP are getting their act together and increasing their manufacturing footprint.
We should finally see GP's coming out of the factory door.

Even if there is a little bit more complexity with a pylon mounted motor, there are clear advantages over the FES solution.
- more powerful motor
- better cooling
- better prop efficiency
- no prop strike risk
Another advantage of GP with large batteries is that, beside the larger energy capacity, the cells are discharged at lower amps rating and therefore run cooler.

The climb performance seems to be in line with flight test results.
As discussed before the published climb perf are without WB. Therefore TOM 320-330 kg. Even when flying empty, the typical WL will be ~42 kg/m2 which is already nice.
GP has made some good choices:
- light weight to allow very good electric climb performance (climb rate and altitude gain)
- high aspect ratio/low wing surface to achieve high L/D and higher WL. Maybe Max L/D will be a little bit less than 18m like ASH26 or DG800, but the L/D above 150 km/h should be better.

BTW, you need to add fixed ballast to get to 525 kg MTOM.

Regards,
JL

It's not clear going to a 525kg/7.78m2 = 67 kg/m2 (13.75 lb/ft2) wing loading is a
good idea, even in very strong conditions! That aside, the wing loading without
fixed ballast depends on the battery size, because the batteries take up space in
the wing that could be used for water. You can put in 130 L if you get the small
battery; but only 85 L using the big battery. I estimate I can go to 12 lb/ft2
with my weight (165 lb), the large battery, and 85 L of water. That should be
adequate, even in Nevada.

The minimum wing loading you can achieve depends mostly on the battery size you
select, as the large battery is 21 kg heavier than the small battery. That's a
2.7kg/m2 difference (about 0.6 lb/ft2).

Note that pilot weight is just the pilot - no parachute - as the glider has it's
own parachute.


--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorg...ad-the-guide-1