On Wed, 26 Jun 2013 09:58:47 -0700, Bill D wrote:

YouTube videos show a difference between UK practice and German
practice. German ground rolls are pretty consistent at two seconds
indicating 1G acceleration. By contrast, I've seen videos of very
wobbly UK ground rolls taking as much as 15 seconds but that's an
exception - most are 3 - 4 seconds.

In the UK a lot of emphasis is put on having at least 50 kts *and
accelerating* before you rotate into a full climb.

I don't recall any specific comments about acceleration rates, though in
the past I've used a stopwatch and timed consistent launches as taking 5
secs from first movement until the glider started to rotate into full
climb, which I assumed meant the glider was accelerating through 50 kts.
This corresponds to roughly 0.5G on average.

This was on our club's Supacat winch with a 240 hp diesel V8 powering it.
The huge majority of the launches I've had on this winch have been like
that. I've also had a couple of launches on a Skylaunch (350hp+ V8
burning LPG), which provides a noticeably higher initial acceleration
than our V8 Supacat. I'm happy with both.

OTOH, I recently had a few much more sluggish launches with longer ground
rolls and that subjectively seemed to take forever to accelerate past 50
kts. I didn't like these at all and have promised myself that if I get
another I'll be having a discussion with the winch driver.

I'm with you on this Bill: brisk acceleration on the winch is good.


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martin@ | Martin Gregorie
gregorie. | Essex, UK
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