Eric, regarding the rough air speed - I thought you
flew an ASH 26? If so the BGA datasheet (quoting the
'FAA Web') lists the rough air speed as 99 knots i.e
the same as the manoeuvring speed. For my 2005 Discus
2cT the speeds are both 103 knots. I think all gliders
have a rough air speed limit for conditions such as
'wave rotor, thunderclouds, visible whirlwinds or when
crossing mountain ridges' to quote my manual.

http://www.gliding.co.uk/bgainfo/tec...eets/ash26.pdf

Bagmaker - you seem analytically minded so have a look
at John Cochrane's excellent paper 'Just a Little Faster
Please'. The link won't post but if you Google +'john
cochrane' +soaring you will get his site.

John Galloway

At 06:36 11 March 2006, Eric Greenwell wrote:
bagmaker wrote:
Newbie help required!
Lets suppose I am on a shallow final glide, 60k out
in my 40:1 ship,
cruising at 60 knots. Recent thermals have been at
least 5 knots and I
am coming into some big lift. For the discussion rough
air Vne is 100
knots.

Best not to confuse 'rough air' speeds with Vne, which
is the 'never
exceed' speed. The 'rough air' limit (I'm not sure
this is used any more
- only my very old gliders had it) is quite a bit lower,
and the newer
gliders don't have it, but do state 'maneuvering speed',
lower yet.

And, practically speaking, you certainly don't want
to be going Vne when
there are thermals bigger than 5 knots in your way!
If the glider hangs
together, it will be a very rough ride.

What strength thermal should I take to increase finishing
speed to Vne

You need your gilder's polar to determine what strength
thermal is
needed for any McCready speed determination - nothing
else needed.

and how much (if any) time will this save me?

It will save you time, but without the polar, your
altitude above the
finish, and the distance to the finish, we can't give
you a number.

How do I estimate this at the time?

You don't have to estimate it. A chart of speed vs
McCready settings is
made up ahead of time. The less thinking you have to
do while flying,
the more time you can spend flying the glider.

What is the latest point on track
to take such a thermal?

I'm guessing, but I'd say about where you need to stay
in the thermal at
least one full turn to get high enough to use the 100
knot speed. Any
closer, and you'd waste time getting unneeded altitude.


--
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Eric Greenwell - Washington State, USA

www.motorglider.org - Download 'A Guide to Self-launching
Sailplane
Operation'