Inter-thermal Speed To Fly [Archive]

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Ken Kochanski (KK)

January 5th 10, 01:51 PM

Morning,

I'm reviewing some STF topics to correct some fallacies that seem to
have crept into my understanding of STF theory and application ... I
though I knew this stuff ... or maybe I forgot ... I am a senior now,
you know ... :-))

So, if I have MC set at 3 ... and I am crusing XC to the next three
knotter ... should I slow in lift and speed up in sink ... or will I
have a faster average speed if I just hold speed steady ... i.e. at
the velocity appropriate for MC = 3 in still air. I see pilots doing
both ...

Also, do all flight computers compute inter-thermal STF with the
formula that does not include a wind component - as identified in
Reichmann's texts, for example.

Anybody have an excel program that will plot polars ... including the
tangent to the shifted origin you get when when you change airmass
sink ... or tail/head winds ..

Gracias, Happy new Year ...
KK

Tuno

January 5th 10, 03:17 PM

KK,

If we're flying in the same contest, my suggestion is to slow down in
the sink and speed up in the lift ;)

Paul Remde has an excellent Excel spreadsheet on his web site that
contains all kinds of nifty polar plotting and manipulation.

My flight computer (LX7007) includes wind component in STF
calculations. I tend to follow its speed suggestions but not too
aggressively. Some pilots believe in flying a constant speed going to
the next thermal but I've never understood why you would want to
continue at an MC=whatever speed if you're in a large area of gnarly
sink. I push my stick forward and get my ass out of that as quick as I
can. Similarly I like to slow down if I find myself in buoyant air and
I think this is what most pilots do.

But more experienced pilots have forgotten more about this topic than
I will ever know -- I think BB has some excellent articles on this at
his web site. John what's the link?

..02NO

Ken Kochanski (KK)

January 5th 10, 03:37 PM

..02NO

Thanks for the direction to the Remde site ...

"My flight computer (LX7007) includes wind component in STF
calculations."

This is interesting ... it uses wind in the Cruise STF calculation?
Reichmann on page 99 of Cross-Country Soaring (1988) says wind is not
used for this calc ... and, I'm thinking speed rings - which were the
first STF 'computers' - do not have any wind input ... but different
people have given me different answers on this ...

Thanks,

KK

January 5th 10, 03:56 PM

On Jan 5, 8:51*am, "Ken Kochanski (KK)" >
wrote:
> Morning,
>
> I'm reviewing some STF topics to correct some fallacies that seem to
> have crept into my understanding of STF theory and application ... I
> though I knew this stuff ... or maybe I forgot ... I am a senior now,
> you know ... :-))
>
> So, if I have MC set at 3 ... and I am crusing XC to the next three
> knotter ... should I slow in lift and speed up in sink ... *or will I
> have a faster average speed if I just hold speed steady ... i.e. at
> the velocity appropriate for MC = 3 in still air. I see pilots doing
> both ...
>
> Also, do all flight computers compute inter-thermal STF with the
> formula that does not include a wind component - as identified in
> Reichmann's texts, for example.
>
> Anybody have an excel program that will plot polars ... including the
> tangent to the shifted origin you get when *when you change airmass
> sink ... or tail/head winds ..
>
> Gracias, Happy new Year ...
> KK

Heretic alert... :-)

My suggestion: understand the theoretical points that Reichmann makes,
then throw that damned book away. But excel spreadsheets are fun to
play with on the laptop in front of the wood stove in January, so
don't let me dissuade you there.

My semi-obvious observations, shared with many others:

1. Achieved XC speed vs cruise speed for all of these speed to fly
models goes through a very broad optimum.
2. The models all ignore transient losses -- your glider is optimized
for 1.0 gee flight
3. Slower than "optimum" cruise speed enhances range, gives better
chance of finding really good thermal for next climb, often results in
higher XC speed.
4. The vario only tells you about where you've been.

Better approach -- my $0.02 -- choose your speed based on what you
anticipate encountering in the next 60 seconds. Fly smooth (IIRC, you
already do). I think of it as STF theory with the sharp edges
polished off. So what if you are "wrong" a lot of the time. See how
you do next to the guy that is chasing needles. And it's more
enjoyable flying this way, too. Basically, I'm providing
justification here for the way a lot of us already fly, consciously or
not.

Arrrrgh. January sucks.

But happy new year just the same.

-Evan Ludeman / T8

Mike the Strike

January 5th 10, 04:35 PM

On Jan 5, 8:56*am, T8 > wrote:
> On Jan 5, 8:51*am, "Ken Kochanski (KK)" >
> wrote:
>
>
>
> > Morning,
>
> > I'm reviewing some STF topics to correct some fallacies that seem to
> > have crept into my understanding of STF theory and application ... I
> > though I knew this stuff ... or maybe I forgot ... I am a senior now,
> > you know ... :-))
>
> > So, if I have MC set at 3 ... and I am crusing XC to the next three
> > knotter ... should I slow in lift and speed up in sink ... *or will I
> > have a faster average speed if I just hold speed steady ... i.e. at
> > the velocity appropriate for MC = 3 in still air. I see pilots doing
> > both ...
>
> > Also, do all flight computers compute inter-thermal STF with the
> > formula that does not include a wind component - as identified in
> > Reichmann's texts, for example.
>
> > Anybody have an excel program that will plot polars ... including the
> > tangent to the shifted origin you get when *when you change airmass
> > sink ... or tail/head winds ..
>
> > Gracias, Happy new Year ...
> > KK
>
> Heretic alert... :-)
>
> My suggestion: understand the theoretical points that Reichmann makes,
> then throw that damned book away. *But excel spreadsheets are fun to
> play with on the laptop in front of the wood stove in January, so
> don't let me dissuade you there.
>
> My semi-obvious observations, shared with many others:
>
> 1. *Achieved XC speed vs cruise speed for all of these speed to fly
> models goes through a very broad optimum.
> 2. *The models all ignore transient losses -- your glider is optimized
> for 1.0 gee flight
> 3. *Slower than "optimum" cruise speed enhances range, gives better
> chance of finding really good thermal for next climb, often results in
> higher XC speed.
> 4. *The vario only tells you about where you've been.
>
> Better approach -- my $0.02 -- choose your speed based on what you
> anticipate encountering in the next 60 seconds. *Fly smooth (IIRC, you
> already do). *I think of it as STF theory with the sharp edges
> polished off. *So what if you are "wrong" a lot of the time. *See how
> you do next to the guy that is chasing needles. *And it's more
> enjoyable flying this way, too. *Basically, I'm providing
> justification here for the way a lot of us already fly, consciously or
> not.
>
> Arrrrgh. *January sucks.
>
> But happy new year just the same.
>
> -Evan Ludeman / T8

You should read some of John Cochrane's analyses on the subject,
especially "Just a little faster, please"

Classic McCready theory is just fine for optimizing speed provided
that the next thermal strength is at least as good as the number you
have dialed in on your ring/computer and that you actually find a
thermal. However, it doesn't make any allowance for the chances of
finding a thermal.

The probability of finding a thermal depends on how far you can fly
and the closer you are to the ground, the smaller this distance is.
Many pilots use a more aggressive McCready setting when high and dial
it back as they get closer to the ground to increase range.

On the question of speed variations on encountering lift and sink
between thermals, you will find all sorts of different practices. I
once flew in the back seat with a good cross-country pilot who
subscribed to the very aggressive "push in sink and zoom in lift" camp
and I was puking in minutes! Not many fly like that any more, as it's
generally agreed that the aerodynamic losses of accelerating and
decelerating outweigh any small gains. I fly at a more-or-less
constant speed, but speed up gently in long runs of sink and slow down
gently in lift - pretty much what Tuno describes.

if the wind speed is constant throughout the airmass you are flying
in, it has little bearing on your overall speed, but will affect your
final glide.

Mike

Andy[_10_]

January 5th 10, 05:29 PM

On Jan 5, 8:35*am, Mike the Strike > wrote:
> On Jan 5, 8:56*am, T8 > wrote:
>
>
>
>
>
> > On Jan 5, 8:51*am, "Ken Kochanski (KK)" >
> > wrote:
>
> > > Morning,
>
> > > I'm reviewing some STF topics to correct some fallacies that seem to
> > > have crept into my understanding of STF theory and application ... I
> > > though I knew this stuff ... or maybe I forgot ... I am a senior now,
> > > you know ... :-))
>
> > > So, if I have MC set at 3 ... and I am crusing XC to the next three
> > > knotter ... should I slow in lift and speed up in sink ... *or will I
> > > have a faster average speed if I just hold speed steady ... i.e. at
> > > the velocity appropriate for MC = 3 in still air. I see pilots doing
> > > both ...
>
> > > Also, do all flight computers compute inter-thermal STF with the
> > > formula that does not include a wind component - as identified in
> > > Reichmann's texts, for example.
>
> > > Anybody have an excel program that will plot polars ... including the
> > > tangent to the shifted origin you get when *when you change airmass
> > > sink ... or tail/head winds ..
>
> > > Gracias, Happy new Year ...
> > > KK
>
> > Heretic alert... :-)
>
> > My suggestion: understand the theoretical points that Reichmann makes,
> > then throw that damned book away. *But excel spreadsheets are fun to
> > play with on the laptop in front of the wood stove in January, so
> > don't let me dissuade you there.
>
> > My semi-obvious observations, shared with many others:
>
> > 1. *Achieved XC speed vs cruise speed for all of these speed to fly
> > models goes through a very broad optimum.
> > 2. *The models all ignore transient losses -- your glider is optimized
> > for 1.0 gee flight
> > 3. *Slower than "optimum" cruise speed enhances range, gives better
> > chance of finding really good thermal for next climb, often results in
> > higher XC speed.
> > 4. *The vario only tells you about where you've been.
>
> > Better approach -- my $0.02 -- choose your speed based on what you
> > anticipate encountering in the next 60 seconds. *Fly smooth (IIRC, you
> > already do). *I think of it as STF theory with the sharp edges
> > polished off. *So what if you are "wrong" a lot of the time. *See how
> > you do next to the guy that is chasing needles. *And it's more
> > enjoyable flying this way, too. *Basically, I'm providing
> > justification here for the way a lot of us already fly, consciously or
> > not.
>
> > Arrrrgh. *January sucks.
>
> > But happy new year just the same.
>
> > -Evan Ludeman / T8
>
> You should read some of John Cochrane's analyses on the subject,
> especially "Just a little faster, please"
>
> Classic McCready theory is just fine for optimizing speed provided
> that the next thermal strength is at least as good as the number you
> have dialed in on your ring/computer and that you actually find a
> thermal. *However, it doesn't make any allowance for the chances of
> finding a thermal.
>
> The probability of finding a thermal depends on how far you can fly
> and the closer you are to the ground, the smaller this distance is.
> Many pilots use a more aggressive McCready setting when high and dial
> it back as they get closer to the ground to increase range.
>
> On the question of speed variations on encountering lift and sink
> between thermals, you will find all sorts of different practices. *I
> once flew in the back seat with a good cross-country pilot who
> subscribed to the very aggressive "push in sink and zoom in lift" camp
> and I was puking in minutes! *Not many fly like that any more, as it's
> generally agreed that the aerodynamic losses of accelerating and
> decelerating outweigh any small gains. *I fly at a more-or-less
> constant speed, but speed up gently in long runs of sink and slow down
> gently in lift - pretty much what Tuno describes.
>
> if the wind speed is constant throughout the airmass you are flying
> in, it has little bearing on your overall speed, but will affect your
> final glide.
>
> Mike

I was looking at this last night - must be January.

What we actually experience in the air tends to diverge considerably
from McCready theory. Take a flight of mine from last season as an
example:

Average climb for the flight was 7.7 knots. Had I dialed this into my
computer it would have told me to cruise (no water) at 113 kts. My
actual average cruise speed was 80 kts. The good lift band on this day
was from 11,000 to 17,000 feet - particularly given some long
stretches of inhospitable terrain and ground elevations of 8,000+
feet. My search range at the McCready speed to fly would have been
around 25 miles at a theoretical L/D of 23:1. At 80 knots my search
range was around 40 miles at the theoretical cruising L/D of 39:1 at
80 knots. In fact, my achieved average L/D was 60:1 and I had 4 glides
of 40 miles or more, two of which ended in thermals of greater than 9
knots average covering a lot of altitude - those fast climbs that
cover a lot of altitude REALLY help your speed.

My McCready cross-country speed for the course should have been 80 mph
had I flown the McCready speed to fly and 73 mph cruising at 80 kts.
My actual speed around the course was 95 mph (taking out the effect of
the final glide made the sustained X-C speed 93 mph according to
SeeYou). So theoretically I should have paid a 10 percent speed
penalty for flying too slow. In fact I got a 16 percent speed benefit
- not all attributable to flying slower - there were clearly some
bands of lift too. On reflection I probably flew 10 knots too slow for
the day - but I hate getting low.

The conclusion I draw from this is that on days where you are likely
to need some search range (most days I fly) to get to the best
thermals, on days with cu marking the thermals you should optimize
your glides around finding the best lift, which usually entails flying
slower to keep your average height higher and extends you search range
by 50 percent or more. Most experienced contest pilots I fly with
cruise 10-20 kts slower than theoretical McCready speed.

In terms of pullups I don't change anything unless I get that
sustained surge that marks a good thermal - typically 4-5 seconds -
but once I've slowed down I'll spend at least a little time trying to
find the core before moving on if I don't hit a solid thermal right
away. Very few pilots do the aggressive pull an push anymore - lift is
generally more spread out than that anyway.

9B

Tuno

January 5th 10, 05:41 PM

The conclusion I draw from this is to follow 9B more often!

Papa3

January 5th 10, 06:08 PM

On Jan 5, 8:51*am, "Ken Kochanski (KK)" >
wrote:
> Morning,
>
> I'm reviewing some STF topics to correct some fallacies that seem to
> have crept into my understanding of STF theory and application ... I
> though I knew this stuff ... or maybe I forgot ... I am a senior now,
> you know ... :-))
>
> So, if I have MC set at 3 ... and I am crusing XC to the next three
> knotter ... should I slow in lift and speed up in sink ... *or will I
> have a faster average speed if I just hold speed steady ... i.e. at
> the velocity appropriate for MC = 3 in still air. I see pilots doing
> both ...
>
> Also, do all flight computers compute inter-thermal STF with the
> formula that does not include a wind component - as identified in
> Reichmann's texts, for example.
>
> Anybody have an excel program that will plot polars ... including the
> tangent to the shifted origin you get when *when you change airmass
> sink ... or tail/head winds ..
>
> Gracias, Happy new Year ...
> KK

Yo KK,

Is this all just theory for you or did you pick up a new chariot?

Anyway, I did a lot of the number crunching and spreadsheet stuff
years ago when I was teaching a lot of XC groundschools. Then, John
Cochrane came along and ruined everything - I mean I can't even spell
"sto-kas-tick"... :-)

So, here's what I've been leaning toward lately. I've adopted a
"high gear", "low gear" approach. For your standard east coast
conditions, I'll set and fly McCready up high (say above 4,000 feet),
which typically will mean cruising around 80kts dry on your 3-4kt day
in my LS8. But, as soon as I get below that, I'll back off by at
least 10-15kts to make sure that I don't have to take a crappy thermal
just to survive.

I've also taken to the "whifferdill" approach when cruising - ie. if I
sense some lift I'll slow up and "explore" to see if I hit a good
pulse, but I'm really trying to avoid the 360 turn unless it really
feels solid. I've flown with CG a few times and watched how much of
the air he explores without doing a full turn - it's pretty amazing.

P3

Sandy Stevenson

January 5th 10, 07:31 PM

On Jan 5, 11:08*am, Papa3 > wrote:
> On Jan 5, 8:51*am, "Ken Kochanski (KK)" >
> wrote:
>
>
>
>
>
> > Morning,
>
> > I'm reviewing some STF topics to correct some fallacies that seem to
> > have crept into my understanding of STF theory and application ... I
> > though I knew this stuff ... or maybe I forgot ... I am a senior now,
> > you know ... :-))
>
> > So, if I have MC set at 3 ... and I am crusing XC to the next three
> > knotter ... should I slow in lift and speed up in sink ... *or will I
> > have a faster average speed if I just hold speed steady ... i.e. at
> > the velocity appropriate for MC = 3 in still air. I see pilots doing
> > both ...
>
> > Also, do all flight computers compute inter-thermal STF with the
> > formula that does not include a wind component - as identified in
> > Reichmann's texts, for example.
>
> > Anybody have an excel program that will plot polars ... including the
> > tangent to the shifted origin you get when *when you change airmass
> > sink ... or tail/head winds ..
>
> > Gracias, Happy new Year ...
> > KK
>
> Yo KK,
>
> Is this all just theory for you or did you pick up a new chariot?
>
> Anyway, *I did a lot of the number crunching and spreadsheet stuff
> years ago when I was teaching a lot of XC groundschools. * Then, John
> Cochrane came along and ruined everything - I mean I can't even spell
> "sto-kas-tick"... *:-)
>
> So, here's what I've been leaning toward lately. * *I've adopted a
> "high gear", "low gear" approach. *For your standard east coast
> conditions, I'll set and fly McCready up high (say above 4,000 feet),
> which typically will mean cruising around 80kts dry on your 3-4kt day
> in my LS8. * But, as soon as I get below that, I'll back off by at
> least 10-15kts to make sure that I don't have to take a crappy thermal
> just to survive.
>
> I've also taken to the "whifferdill" approach when cruising - ie. if I
> sense some lift I'll slow up and "explore" to see if I hit a good
> pulse, but I'm really trying to avoid the 360 turn unless it really
> feels solid. * *I've flown with CG a few times and watched how much of
> the air he explores without doing a full turn - it's pretty amazing.
>
> P3

As someone who is just starting to fly cross country, this is one of
the best discussions I've read here in the last few years.
Thanks for your posts, guys.

Mike the Strike

January 5th 10, 08:09 PM

On Jan 5, 12:31*pm, Sandy Stevenson > wrote:
> On Jan 5, 11:08*am, Papa3 > wrote:
>
>
>
> > On Jan 5, 8:51*am, "Ken Kochanski (KK)" >
> > wrote:
>
> > > Morning,
>
> > > I'm reviewing some STF topics to correct some fallacies that seem to
> > > have crept into my understanding of STF theory and application ... I
> > > though I knew this stuff ... or maybe I forgot ... I am a senior now,
> > > you know ... :-))
>
> > > So, if I have MC set at 3 ... and I am crusing XC to the next three
> > > knotter ... should I slow in lift and speed up in sink ... *or will I
> > > have a faster average speed if I just hold speed steady ... i.e. at
> > > the velocity appropriate for MC = 3 in still air. I see pilots doing
> > > both ...
>
> > > Also, do all flight computers compute inter-thermal STF with the
> > > formula that does not include a wind component - as identified in
> > > Reichmann's texts, for example.
>
> > > Anybody have an excel program that will plot polars ... including the
> > > tangent to the shifted origin you get when *when you change airmass
> > > sink ... or tail/head winds ..
>
> > > Gracias, Happy new Year ...
> > > KK
>
> > Yo KK,
>
> > Is this all just theory for you or did you pick up a new chariot?
>
> > Anyway, *I did a lot of the number crunching and spreadsheet stuff
> > years ago when I was teaching a lot of XC groundschools. * Then, John
> > Cochrane came along and ruined everything - I mean I can't even spell
> > "sto-kas-tick"... *:-)
>
> > So, here's what I've been leaning toward lately. * *I've adopted a
> > "high gear", "low gear" approach. *For your standard east coast
> > conditions, I'll set and fly McCready up high (say above 4,000 feet),
> > which typically will mean cruising around 80kts dry on your 3-4kt day
> > in my LS8. * But, as soon as I get below that, I'll back off by at
> > least 10-15kts to make sure that I don't have to take a crappy thermal
> > just to survive.
>
> > I've also taken to the "whifferdill" approach when cruising - ie. if I
> > sense some lift I'll slow up and "explore" to see if I hit a good
> > pulse, but I'm really trying to avoid the 360 turn unless it really
> > feels solid. * *I've flown with CG a few times and watched how much of
> > the air he explores without doing a full turn - it's pretty amazing.
>
> > P3
>
> As someone who is just starting to fly cross country, this is one of
> the best discussions I've read here in the last few years.
> Thanks for your posts, guys.

I should also add that knowing the theory isn't enough. The ability
to put that knowledge into practice by feeling the air and knowing
when to turn and when to keep going are much more important. I know
the theory inside out and am a competent cross-country pilot, but I
don't have that extra sixth sense that the best pilots have and I am
always a bit slow.

Mike

Uncle Fuzzy

January 5th 10, 08:40 PM

On Jan 5, 11:31*am, Sandy Stevenson > wrote:
> On Jan 5, 11:08*am, Papa3 > wrote:
>
>
>
>
>
> > On Jan 5, 8:51*am, "Ken Kochanski (KK)" >
> > wrote:
>
> > > Morning,
>
> > > I'm reviewing some STF topics to correct some fallacies that seem to
> > > have crept into my understanding of STF theory and application ... I
> > > though I knew this stuff ... or maybe I forgot ... I am a senior now,
> > > you know ... :-))
>
> > > So, if I have MC set at 3 ... and I am crusing XC to the next three
> > > knotter ... should I slow in lift and speed up in sink ... *or will I
> > > have a faster average speed if I just hold speed steady ... i.e. at
> > > the velocity appropriate for MC = 3 in still air. I see pilots doing
> > > both ...
>
> > > Also, do all flight computers compute inter-thermal STF with the
> > > formula that does not include a wind component - as identified in
> > > Reichmann's texts, for example.
>
> > > Anybody have an excel program that will plot polars ... including the
> > > tangent to the shifted origin you get when *when you change airmass
> > > sink ... or tail/head winds ..
>
> > > Gracias, Happy new Year ...
> > > KK
>
> > Yo KK,
>
> > Is this all just theory for you or did you pick up a new chariot?
>
> > Anyway, *I did a lot of the number crunching and spreadsheet stuff
> > years ago when I was teaching a lot of XC groundschools. * Then, John
> > Cochrane came along and ruined everything - I mean I can't even spell
> > "sto-kas-tick"... *:-)
>
> > So, here's what I've been leaning toward lately. * *I've adopted a
> > "high gear", "low gear" approach. *For your standard east coast
> > conditions, I'll set and fly McCready up high (say above 4,000 feet),
> > which typically will mean cruising around 80kts dry on your 3-4kt day
> > in my LS8. * But, as soon as I get below that, I'll back off by at
> > least 10-15kts to make sure that I don't have to take a crappy thermal
> > just to survive.
>
> > I've also taken to the "whifferdill" approach when cruising - ie. if I
> > sense some lift I'll slow up and "explore" to see if I hit a good
> > pulse, but I'm really trying to avoid the 360 turn unless it really
> > feels solid. * *I've flown with CG a few times and watched how much of
> > the air he explores without doing a full turn - it's pretty amazing.
>
> > P3
>
> As someone who is just starting to fly cross country, this is one of
> the best discussions I've read here in the last few years.
> Thanks for your posts, guys.- Hide quoted text -
>
> - Show quoted text -

As someone who has been flailing around at XC for only a few
years..... Thanks!

Andy[_10_]

January 5th 10, 09:48 PM

On Jan 5, 10:08*am, Papa3 > wrote:
>
> I've also taken to the "whifferdill" approach when cruising - ie. if I
> sense some lift I'll slow up and "explore" to see if I hit a good
> pulse, but I'm really trying to avoid the 360 turn unless it really
> feels solid. * *I've flown with CG a few times and watched how much of
> the air he explores without doing a full turn - it's pretty amazing.

A lot of pilots do this - it serves two useful purposes: 1) it keeps
you in rising air longer without ever giving ground by doing a 360,
and 2) It allows you to search for the strong core.

I did some calculations on course deviations versus expected climb
rates - it's junior high school trigonometry. Conclusion: If you have
any good reason to believe that the lift will be stronger - course
deviations of 45 degrees and several miles make perfect sense.

The guys who are really fast on course are the ones who only settle
for the strongest lift along the way. The key skills are 1) being able
to use all available cues to go to where the lift is likely to be best
- in a micro and macro sense - clouds, terrain features, wind
direction and velocity, macro weather patterns, other gliders, etc, 2)
knowing how low to go before lowering you expectations for lift - or
being able to anticipate a change and adjust accordingly.

9B

Tuno

January 5th 10, 10:15 PM

Sandy,

If you are just starting, be sure to spend time at John Cochrane's web
page:

http://faculty.chicagobooth.edu/john.cochrane/research/Papers/#corner

There you will find the "Just a Little Faster, Please" article that
Mike the Strike mentioned. The thing to take away from the article is
that small differences in your ability to pick the best lift have a
far greater impact on your x/c performance than what you do with your
STF decisions.

Or you can do what I do and follow 9B!

2NO

cernauta

January 5th 10, 10:19 PM

On Tue, 5 Jan 2010 05:51:14 -0800 (PST), "Ken Kochanski (KK)"
> wrote:

>Morning,
>
>I'm reviewing some STF topics to correct some fallacies that seem to
>have crept into my understanding..

There's a lot of interesting thinking in Karel Termaat's soaring page
http://home.planet.nl/~kpt9/

in particular, on the topic of how to handle a positive air gust
during the glide: http://home.planet.nl/~kpt9/positive.htm

Aldo Cernezzi

SoaringXCellence

January 5th 10, 11:15 PM

On Jan 5, 2:19*pm, cernauta > wrote:
> On Tue, 5 Jan 2010 05:51:14 -0800 (PST), "Ken Kochanski (KK)"
>
> > wrote:
> >Morning,
>
> >I'm reviewing some STF topics to correct some fallacies that seem to
> >have crept into my understanding..
>
> There's a lot of interesting thinking in Karel Termaat's soaring pagehttp://home.planet.nl/~kpt9/
>
> in particular, on the topic of how *to handle a positive air gust
> during the glide:http://home.planet.nl/~kpt9/positive.htm
>
> Aldo Cernezzi

Another aspect of the best speed is the selection of the line to
follow. Like the comment above on course deviations. In one contest
I offset just 1/4 mile left of track into a real nice lift street
(blue day). The best pilots are integrating all the information from
terrain, clouds and previous climbs. Also looking in all directions to
select their course to fly. I know from previous experience in model
XC soaring that sometimes it all comes together. You look over that
direction and say "The thermal is right THERE!" and it is.

Phillip Wills also said something similar in his book (don't remember
which one). There are days that you fly that you just know where to
go for the lift.

I can't do it all the time but I'm getting better!

Mike

Andreas Maurer

January 6th 10, 04:01 AM

On Tue, 5 Jan 2010 11:31:38 -0800 (PST), Sandy Stevenson
> wrote:

>As someone who is just starting to fly cross country, this is one of
>the best discussions I've read here in the last few years.
>Thanks for your posts, guys.

Better stop reading now, Sandy. ;)

Otherwise I guarantee that you'll be completely puzzled by the variety
of techniques and opinions you are going to read here over the next
week. <vbg>

Here's a method that is very simple yet makes champions. Invented by
Ingo Renner who became three time world gliding champion using it.

First, and most important, set the *correct* McCready setting.
A 3 kt thermal is usually only 2 kts if you count the time you need to
center it, therefore always use a lower McCready setting than the
average climb rate your variometer is showing you.

Between thermals fly a *constant speed* depending on the McCready
setting. Do not adjust speed to the current sink rate, only pull back
and climb into a thermal if it is really strong.
Keep the AoA constant - fly smooooooooth.

Set McCready to half your chosen value once you get below 50 percent
of the cloud base, and only fly with best glide speed if you really
desperately need a thermal in order to avoid an outlanding.

The same method is used by the pilots who have been dominating German
15m class for the last 6 years (... and by the guy writing this
posting). Works like a charm, and is very simple to use.

mattm[_2_]

January 6th 10, 04:41 PM

On Jan 5, 11:01*pm, Andreas Maurer > wrote:
> On Tue, 5 Jan 2010 11:31:38 -0800 (PST), Sandy Stevenson
>
> > wrote:
> >As someone who is just starting to fly cross country, this is one of
> >the best discussions I've read here in the last few years.
> >Thanks for your posts, guys.
>
> Better stop reading now, Sandy. ;)
>
> Otherwise I guarantee that you'll be completely puzzled by the variety
> of techniques and opinions you are going to read here over the next
> week. <vbg>
>
> Here's a method that is very simple yet makes champions. Invented by
> Ingo Renner who became three time world gliding champion using it.
>
> First, and most important, set the *correct* McCready setting.
> A 3 kt thermal is usually only 2 kts if you count the time you need to
> center it, therefore always use a lower McCready setting than the
> average climb rate your variometer is showing you.
>
> Between thermals fly a *constant speed* depending on the McCready
> setting. Do not adjust speed to the current sink rate, only pull back
> and climb into a thermal if it is really strong.
> Keep the AoA constant - fly smooooooooth.
>
> Set McCready to half your chosen value once you get below 50 percent
> of the cloud base, and only fly with best glide speed if you really
> desperately need a thermal in order to avoid an outlanding.
>
> The same method is used by the pilots who have been dominating German
> 15m class for the last 6 years (... and by the guy writing this
> posting). Works like a charm, and is very simple to use.

That sounds about right. The John Cochrane paper suggests a similar
technique. Since he's on the US international team now I guess it
works!

In RL flying I have a PDA that measures the actual climb rate from
when you
start turning to when you leave, so I know my achieved climbs to base
my MC setting.
I set MC on my s2f vario independently from what my PDA suggests
(since my vario
doesn't listen to the PDA anyway) based on how aggressive I feel about
getting to
the next thermal. That feeling is based on the suggested speed to
fly, altitude,
time of day, look of the clouds ahead, whatever. I'll fiddle with it
as I get lower,
down to around MC=1 (Reichmann notes that your glide range at MC=0 and
MC=1
is really very similar, and MC=1 gets you to that thermal more
quickly). For that matter
I almost always fly dry so there's not a lot of difference in speed to
fly at different
settings anyway. I try to find lines of clouds more or less in the
direction of where
I'm going so I can try a bunch before settling on the right thermal.

It was interesting looking at one of my fastest days during contest
flying. I was flying
Sports class and found some amazing thermals that day. If I'd been
able to carry the 1
when adding the task time to my start time I would have flown nearly
60mph on course
(I came in about 10 minutes early so only got 54mph). However, I saw
a certain
standard class plane a couple of times up close. Out of curiosity I
pulled his trace
later on and compared it to my own. Mine had several really good
thermals that day,
but almost ALL of his thermals were really good! That alone is a good
reason he's
on the national team and I'm just cannon fodder.

-- Matt

Papa3

January 6th 10, 05:26 PM

On Jan 5, 4:48*pm, Andy > wrote:
> On Jan 5, 10:08*am, Papa3 > wrote:
>
>> I did some calculations on course deviations versus expected climb
> rates - it's junior high school trigonometry. Conclusion: If you have
> any good reason to believe that the lift will be stronger - course
> deviations of 45 degrees and several miles make perfect sense.
>

>
> 9B

Steve Sliwa wrote his thesis on this topic sometime back in the 1970s
IIRC. He used a bit more than junior high trig, but the conclusions
were similar. The secret was deciding sooner than later that "street
b" would work better than "street a", which is exactly what we see
qualitatively in contests.

Papa3

January 6th 10, 07:02 PM

On Jan 6, 12:26*pm, Papa3 > wrote:
> On Jan 5, 4:48*pm, Andy > wrote:
>
> > On Jan 5, 10:08*am, Papa3 > wrote:
>
> >> I did some calculations on course deviations versus expected climb
> > rates - it's junior high school trigonometry. Conclusion: If you have
> > any good reason to believe that the lift will be stronger - course
> > deviations of 45 degrees and several miles make perfect sense.
>
> > 9B
>
> Steve Sliwa wrote his thesis on this topic sometime back in the 1970s
> IIRC. * *He used a bit more than junior high trig, but the conclusions
> were similar. * The secret was deciding sooner than later that "street
> b" would work better than "street a", which is exactly what we see
> qualitatively in contests.

Turns out the article was published in the April 1981 Soaring
magazine. I have a complete set of Soaring from late 1960s ... with
the exception of .... April 1981??!! Well, it's probably in one of
the "reading rooms" in the house, but don't have the energy to sort
through the stacks right now. If anyone has an electronic copy of
the article I'd love to re-read it; it's been years.

January 6th 10, 08:29 PM