Sharing a thermal

Try your flavor.

http://www.soarcsa.org/thinking_page...urn_radius_cal
culator.htm


Frank, the CSA website is truly impressive! Well done to you and your team.
Question though, where is the link to the Thinking Pages section? TIA.

Jim Vincent
N483SZ
illspam

Nyal Williams wrote:
How much of this depends on the reaction time of the
vario?

I'm sure that textbooks from 40 years ago said to tighten
up in sink and open out in lift. As a matter of fact,
I believe this is one of the methods described by Reichmann.


By the way, it is what i have been learnt to do, and it seems
to work :-)



--

Michel TALON

At 8000' 50kts IAS = 58kts TAS, so 27 seconds would
correspond to a 40 degree bank angle. Wing loading
is only relegant to the degree that it affects stall
speed. The only relevant variables for turn radius
are ture airspeed and bank angle - assuming you are
flying in an unaccelerated condition.

Of course you can make a real fast circle if you spin
it...

9B


At 23:30 18 October 2004, F.L. Whiteley wrote:

'Eric Greenwell' wrote in message
...
Bill Daniels wrote:


Most vario's have a time constant of about 2-3 seconds
or more. I put a
bunch of different varios on a test bench last winter
and found some
were as
bad as 11 seconds. The average 45 degree bank thermalling
turn takes
about
13 - 14 seconds

Yikes! I don't know what you are flying, but it takes
my ASH 26 about 27
seconds to make one turn (50 kts IAS, 8000' msl, 8.2
lb/sq ft wing
loading). That's measured from a flight trace. My
ASW 20 was a little
quicker, flying at 7.5 lb/sq ft, but nothing like
14 seconds.

Should be 17secs.

Try your flavor.
http://www.soarcsa.org/thinking_page...adius/turn_rad
ius_calculator.htm

Frank Whiteley

Wow, I really appreciate all the comments on thermalling. It is
amazing how much thought and calculations go into this sport although
not all agree on the solution. Reminds me of all the advice I got on
take-off. It was all good but also different.

It would seem logical if you are in a close circle with another glider
that reducing the bank angle is the safer technique. That said if you
are not in danger of conflict then increasing the bank angle seems to
follow what I was taught and what I have read.

The last flight of this year I tried water and that brought out a lot
of flaws in my termalling technique. Controlling speed and flying
through thermals were a problem. It was like learning all over again,
although when I looked at the trace after the flight I was impressed
with my average speed. I think using smoother and less abrupt changes
is something I need to work on and some of the techniques mentioned
here seem to enforce that.

Actual SeeYou measurements

ASW-27B dry (8.2 lbs/sf)
Altitude 13,000 ft
TAS/IAS: 71/53 mph
Measured radius: ~350 ft
Implied bank angle: 43.5 degrees
Stall speed (calculated): ~51 mph

ASW-27B wet (11.5 lbs/sf) -- prior day
Altitude 13,500 ft
TAS/IAS: 84/61 mph
Measured radius: ~515 ft
Implied bank angle: 42.5 degrees
Stall speed (calculated): ~57 mph

9B


At 03:06 20 October 2004, Eric Greenwell wrote:
Bill Daniels wrote:
OK, this is going to get good.

Eric thinks wide fast turns work best for him.

'Fast' is relative: at 8.2 lb/sq ft, going a slower
is
counterproductive. I can slow down to 45 knots from
the usual 50, but
the glider isn't very steady, feels 'draggy', and it
doesn't climb any
better, even in very smooth thermals (this measurement
done when
circling with other gliders). In anything but very
smooth thermals, the
50-52 knots is needed to have decent control, anyway.

I think 45 degree turns are
best on average with steeper turns useful in small
cores. If fly as slow as
I can without risking a stall.

This may be appropriate for the Nimbus 2, but not for
the ASH 26, where
the stall is noticeably lower than minimum sink. Waibel
told me once
that he considers this a safety feature.


Lets have a poll. Tell us how you thermal.

And what, and where. These are likely important reasons
for your bank
angle and speed preferences.


Bill Daniels



--
Change 'netto' to 'net' to email me directly

Eric Greenwell
Washington State
USA

Won't SeeYou underestimate the thermalling speed because it is
calculating speed based on the straightline distance between different
points on a circle?


Andy Blackburn wrote:
Actual SeeYou measurements

ASW-27B dry (8.2 lbs/sf)
Altitude 13,000 ft
TAS/IAS: 71/53 mph
Measured radius: ~350 ft
Implied bank angle: 43.5 degrees
Stall speed (calculated): ~51 mph

ASW-27B wet (11.5 lbs/sf) -- prior day
Altitude 13,500 ft
TAS/IAS: 84/61 mph
Measured radius: ~515 ft
Implied bank angle: 42.5 degrees
Stall speed (calculated): ~57 mph

9B

Greg Arnold wrote in message news:0imdd.50323$hj.44614@fed1read07...
Won't SeeYou underestimate the thermalling speed because it is
calculating speed based on the straightline distance between different
points on a circle?

I was unable to duplicate SeeYou's calculations of thermaling speed. I
tried straight line between two points, fitting a circle through three
points, and calculating circumference based on a rough diameter.

I was trying to reconcile indicated airspeed I recalled from the
flight with SeeYou's numbers. But even after correcting for true
airspeed, I was still off. I finally gave up. Does anyone know how
SeeYou calculates speed in a thermal?

Chip Bearden
ASW 24 "JB"

Dnia 10/20/04 5:16 PM, U¿ytkownik Chip Bearden napisa³:

I was trying to reconcile indicated airspeed I recalled from the
flight with SeeYou's numbers. But even after correcting for true
airspeed, I was still off. I finally gave up. Does anyone know how
SeeYou calculates speed in a thermal?
Ground speed (as well as vertival speed) is an average calculated with a
few last readings. Check Options-Flight menu and values named "ground
speed filter" and "vertical speed filter".

--
Wojtus'.net __|__
FidoNet: 2:484/47 `--------o--------'

I'm at a pretty high sampling rate - 2 seconds I think.
At least my circles look pretty round. I don't know
how SeeYou calculates ground speed, but it stands to
reason that if you only had, say, 2 samples per circle
that might lead to an error - unless SeeYou somehow
assumes a circle through the points (seems doubtful).

The answer is pretty consistent with the bank angles
I thought I was flying based on aligning the diagonal
screws securing my instruments.

9B

At 05:24 20 October 2004, Greg Arnold wrote:
Won't SeeYou underestimate the thermalling speed because
it is
calculating speed based on the straightline distance
between different
points on a circle?


Andy Blackburn wrote:
Actual SeeYou measurements

ASW-27B dry (8.2 lbs/sf)
Altitude 13,000 ft
TAS/IAS: 71/53 mph
Measured radius: ~350 ft
Implied bank angle: 43.5 degrees
Stall speed (calculated): ~51 mph

ASW-27B wet (11.5 lbs/sf) -- prior day
Altitude 13,500 ft
TAS/IAS: 84/61 mph
Measured radius: ~515 ft
Implied bank angle: 42.5 degrees
Stall speed (calculated): ~57 mph

9B