On Sun, 17 Jun 2018 09:19:33 -0700, moshe.braner wrote:

If the launch requires 200KW and the supply is 20KW then most of the
launch power is coming from the batteries. That means that you could
supply it with less power and it will still work, although it may need a
longer time to charge between launches? E.g., if a launch uses 100 KW
on the average and takes 1 minute (1.6 KWH) and you do one every 20
minutes (not ideal) then you need a supply of 100/20 = 5 KW.

From experience with Supacat and Skylaunch twin drum winches, the actual
launch takes around 35-40 secs in normal conditions, but then theres a
fair amount of throttle applied to pull the cable down before it drifts
too far, so 1 minute of run-time per launch seems reasonable.

On our field (1000m cable run, twin drum winch) the best launch rate we
ever achieved was 18 an hour - and apart from the winch driver and launch
marshal that required 3-4 extra full-time helpers, i.e. one guy in the
cable truck and at least two extra people retrieving landed gliders,
moving the launch queues up to the twin launch points, AND for no
briefing delays and other fannying about at the head of the queue.

A bunch of us, all recent solos and flying the club's SZD Juniors used to
get stuck in while waiting for a Junior to land, and no matter how we
tried we couldn't top 18 launches an hour. It didn't need much in the way
of long landings, and briefings etc to drop that rate quite a bit.

BTW 5 KW of solar panels is only about $5,000 these days. That would do
about 3 launches per hour.

We routinely do more than that - 100 launches isn't unusual for a decent
day.

And you don't need fancy vaporware batteries, any type
will do, since they stay on the ground.

Agreed - wet lead acid would be fine, particularly as it all helps to
hold the winch down.

However, as I said, we went to other way and have two winches - both are
7-8 litre V-8s running on LPG and using Spectra cables. One is a Skylaunch
and the other is a Tost which was rebuilt by Skylaunch. Since we operate
7 days a week, mostly winched flying from the start of April to the end
of September, we've found that having only one winch loses a bit too much
time on servicing etc, so we got the second one. This lets us alternate
them so the offline one can be serviced etc.


--
Martin | martin at
Gregorie | gregorie dot org