"Jim Vincent" wrote in message
...
In my experience, one drum is pretty adequate.

Most fields in the US are limited in length, so the launch height is
usually
just enough for a pattern. I find with one drum I can launch a ship,
retrieve
the chute, and have be back at the launch point just as the glider lands.
We
turn the glider around (usually lands cross wind), and we're ready to go
with
another. We achieve about 6-7 launches per hour this way at my
field..until
two or three other people turn up (with little experience but they're
BS'ed the
membership into thinking they know what they're doing) and our rate goes
down
to about 3 an hour.

Jim Vincent
CFIG
N483SZ
illspam

Jim, with one glider, one drum works fine. The length of the field doesn't
matter since with a longer field, the glider goes higher and stays up longer
so the wire is still back at the launch site in time for the glider landing
if the retrieve driver hustles. If you are launching from grass, all those
wire retrieves are sure tearing up the turf.

My most recent winching is with 5000 feet of wire and 2000 feet AGL is a
common release height. If there are any thermals, the glider will contact
one 3 out of 4 launches and soar away. In the western US there are many
runways 7000 feet or longer where winching is possible. You're talking
3000' AGL launches with that much room.

With a gaggle of gliders waiting to be launched you need the efficiency of
multiple drums or multiple winches. The real issue is often not how many
launches you can make in a day, it's how fast can you get everybody launched
when the thermals start. I've read of several winch operations that achieve
a sustained launch rate of one every two minutes.

Bill Daniels