On Sat, 06 Feb 2021 18:05:35 -0800, 2G wrote:

On Saturday, February 6, 2021 at 5:18:16 PM UTC-8, kinsell wrote:
On 2/6/21 8:05 AM, Mark Mocho wrote:
Sorry, but I disagree that electrics will turn "pure" sailplanes into
a fringe activity. I personally like pure sailplanes over
motorgliders and sustainers. Probably comes from 28 years of hang
gliding and 20 years of gliding (45 years total). I played around
with powered ultralights, but never really wanted one. I have a self
launch endorsement in gliders (as well as two turbojet Type Ratings
in jet powered two-seat gliders), but I prefer unpowered flight for
the challenge, as well as lower complexity and lower insurance costs.
Sure, I am forced to depend on tows, but you can pay for a LOT of
tows with the differential in the price of a motorglider. As far as
propulsion type, I don't particularly care for the limited battery
capacity due to poor energy density compared to fuel. And don't kid
yourself that batteries are completely safe. Any energy storage
system has risks of 'dumping' that energy in an enthusiastic manner.
Everybody screeching about getting rid of oil & gas had better do
some research on what it takes to produce a wind turbine. (Hint: They
don't grow from magic beans.) And you might not have noticed, but
there are NO solar-powered solar cell factories. And the Tesla S 100
kWh battery (1,375 lbs.) stores the energy equivalent of 2.1 gallons
of AvGas.

Perfect solution would be a battery-powered winch. Hook a bunch of
batteries up to a motor, hook the motor up to a drum. How hard could
that be? No folding props to deal with, no certification, no annual
inspections, no insurance, no skilled labor required to run it. Plus
you don't have to carry a load of undumpable ballast around with you
all the time.

I ran into a guy (who's name I can't remember) at the 2016 Reno
Convention who's club was in the process of designing an electric winch
using direct DC drive. It is a non-trivial task.

My club looked at it. The German Startwinde winch is basically a big
brushless motor and an aluminium shell stuffed with truck batteries. Its
designed to run off mains power with the batteries acting as a buffer
between the steady mains feed (7-20kW) and the 200kW brushless electric
motor.

Consequently you need to run HD cables to the various points on the
airfield where you position the winch depending on the wind direction. As
I said, we looked in to it but the cable costs made it unattractive
because there are four places were we set up our winch depending on the
wind, only two of them are near the clubhouse and its mains supply: the
other two are about 1km away in different directions. So, we ended up
getting a Skylaunch winch with a big V8 running off LPG instead.

That said, you could also run an electric winch off an 8-12kW builder's
trailer generator parked alongside it, but I have no idea of the
economics of that compared with either wiring the airfield or running a
Skylaunch or similar winch.



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Martin | martin at
Gregorie | gregorie dot org