Winch launch speed versus height gain

Neil wrote:
Ok, I could probably arrange with the winch driver to experiment, but is
there any definitive guidance on getting the greatest height off a winch
launch? (eg. Skylaunch).

i.e. if I'm "driven" at the higher end of the speed range acceptable to my
gliders placarding, will I get higher or lower than a lower speed launch?
I used to consider faster meant higher, but last weekend a most experienced
colleague said you'd end less high, as you spend less time gaining height.
I'm sure there's a set of graphs that would show a polar curve type
trade-off, but is there a simple way of looking at this?

Read the glider's Flight Manual, which should tell you the optimum
speed. For example, mine (an H.201 Libelle) says:

Winch tow: Max. tow speed 65 kts, most agreeable 50-54 kts.

Of course this is relative to the other numbers: stall 36 kts, min sink
42 kts, best glide 52 kts at my usual flying weight. The most agreeable
speed should be 5 or 6 kts faster with water (not being a B series, mine
doesn't carry water).

We have a 240 hp Supacat and usually launches are pretty much on Vwinch.
Usually I'm grateful if the winchie stays below Vwinch at the top so I
don't have to pull off early. A few times I've managed to talk a driver
into slower launches and have been launched at around 55 kts, which
certainly feels a lot nicer. Its not happened enough times for me to
have compared launch heights, though I don't think theres much in it.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |