Inter-thermal cruise speeds?

[Frank[_1_]]

I'm curious what others are using for inter-thermal cruise speeds for
modern 15m (and 18m I guess) gliders like the Ventus 2bx, Ventus 2cx,
ASW-27, ASG-29, Diana 2, etc (add models as necessary).

Here in the U.S. we have been moving toward cruise speeds much lower
than would normally be dictated by using straight McReady settings,
but how low is too low?

I've also been flying a V2bx & V2cxt in Condor a lot, and cruise
speeds there are all over the map, from 90kt to 125kt (fully
ballasted) in the same race/weather conditions, with varying results.

Any thoughts?

TIA,

Frank (TA)

[[email protected]]

On Feb 7, 10:50 am, Frank > wrote:
> I'm curious what others are using for inter-thermal cruise speeds for
> modern 15m (and 18m I guess) gliders like the Ventus 2bx, Ventus 2cx,
> ASW-27, ASG-29, Diana 2, etc (add models as necessary).
>
> Here in the U.S. we have been moving toward cruise speeds much lower
> than would normally be dictated by using straight McReady settings,
> but how low is too low?
>
> I've also been flying a V2bx & V2cxt in Condor a lot, and cruise
> speeds there are all over the map, from 90kt to 125kt (fully
> ballasted) in the same race/weather conditions, with varying results.

It would seem to depend on a lot on the conditions of the day, right?
How far apart are thermals? How large is the working altitude band?
How strong are the thermals?

I don't fly nearly as high a performance ship, but on a good day with
reasonably well marked 8-12 knot thermals that go to 15,000 feet and
beyond, I'll easily fly 10-15 knots faster between them than on a blue
day when I'm having less luck getting the lift.

Jeremy

[Cats]

On Feb 7, 6:50*pm, Frank > wrote:
> I'm curious what others are using for inter-thermal cruise speeds for
> modern 15m (and 18m I guess) gliders like the Ventus 2bx, Ventus 2cx,
> ASW-27, ASG-29, Diana 2, etc (add models as necessary).
>
> Here in the U.S. we have been moving toward cruise speeds much lower
> than would normally be dictated by using straight McReady settings,
> but how low is too low?
>
<snip>

Surely too slow is when people flying faster than you make better
progress....

[Tim Taylor]

On Feb 7, 11:50 am, Frank > wrote:
> I'm curious what others are using for inter-thermal cruise speeds for
> modern 15m (and 18m I guess) gliders like the Ventus 2bx, Ventus 2cx,
> ASW-27, ASG-29, Diana 2, etc (add models as necessary).
>
> Here in the U.S. we have been moving toward cruise speeds much lower
> than would normally be dictated by using straight McReady settings,
> but how low is too low?
>
> I've also been flying a V2bx & V2cxt in Condor a lot, and cruise
> speeds there are all over the map, from 90kt to 125kt (fully
> ballasted) in the same race/weather conditions, with varying results.
>
> Any thoughts?
>
> TIA,
>
> Frank (TA)

Frank,

In the west I have found the opposite to be true. I have found most
are flying at MC to 5 knots faster than would be dictated under
classical assumptions. The biggest change has been to try and
minimize time circling as much as possible by flying energy bands.

A great text:

Competing in Gliders - Winning With Your Mind
Authors: Leo and Ricky Brigliadori

the book has an excellent chapter on speeds under different
conditions. The only time to fly less than MC is if you have to cross
large gaps were there is not likely to find lift.

MC is always based on the "expected next climb". Also during setting
MC it is critical to use the real number, not what someone sees on the
vario or even the averager. I use the average thermal value in
WinPilot to give me a real number while on task.

[alex8735]

I usually do what my speed to fly indicator tells me. The hard part is
really getting the right MC setting. If you have a nice thermal
hitting 3m/sec on your averager, the real average on the complete
thermal will probably be below 2m/sec...taking into account the time
needed to center the theraml and weaker conditions at the top and
bottom of the thermal. Flying a bit to slow is usually less damaging
than flying a bit to fast. You also have to take into account that you
have a higher range flying slower...which in turn gives you a better
pick of good thermals. Regarding all these implications I set my MC to
about 1m/s when the averager shows thermals of 3m/sec. If conditions
ahead look good I go up a few points...if they look bad tend to be
more conservative and slow down to MC 0,5.

When flying the LS8 full of water a MC of 1m/s dictates speeds in a
range of 140km/h to 180km/h. I think that is more or less fast
enough;-)

If you want to do better on your averade speed then optimizing cruise
speed probably won't give you the desired effect. You lose most time
(and speed) thermaling so the trick ist to thermal as seldomly as
possible an when it's necessary only picking the best thermals
around;-)

[Peter Thomas]

For most UK European and international comps IGC files
are posted, grab as many files of the top 3 places
and stick them in you flight analysis software and
start analysing

the consensus of most articles from top comp pilots
i have read is the climb rate is more important than
the cruise speed, so cruise at sensible speeds to have
the range to find better thermals

the maths i have seen says reducing your cruise speed
for a given climb rate only has a small effect on your
theoretical xc speed, which can easily be made up if
you pick better themals

I fly club class non competition in the UK, 3000 -
4500 2-4kt would cover most xc days, thermals might
go 2kt 2kt 4kt, you go go faster by reaching the 4kt,
to fast and your groveling or in a field

there also seems to be a drift towards stable cruise
speeds rather than chasing M/C

Pete

At 18:54 07 February 2008, Frank wrote:
>I'm curious what others are using for inter-thermal
>cruise speeds for
>modern 15m (and 18m I guess) gliders like the Ventus
>2bx, Ventus 2cx,
>ASW-27, ASG-29, Diana 2, etc (add models as necessary).
>
>Here in the U.S. we have been moving toward cruise
>speeds much lower
>than would normally be dictated by using straight McReady
>settings,
>but how low is too low?
>
>I've also been flying a V2bx & V2cxt in Condor a lot,
>and cruise
>speeds there are all over the map, from 90kt to 125kt
>(fully
>ballasted) in the same race/weather conditions, with
>varying results.
>
>Any thoughts?
>
>TIA,
>
>Frank (TA)
>

[Shawn[_5_]]

Peter Thomas wrote:
> For most UK European and international comps IGC files
> are posted, grab as many files of the top 3 places
> and stick them in you flight analysis software and
> start analysing
>
> the consensus of most articles from top comp pilots
> i have read is the climb rate is more important than
> the cruise speed, so cruise at sensible speeds to have
> the range to find better thermals
>
> the maths i have seen says reducing your cruise speed
> for a given climb rate only has a small effect on your
> theoretical xc speed, which can easily be made up if
> you pick better themals
>
> I fly club class non competition in the UK, 3000 -
> 4500 2-4kt would cover most xc days, thermals might
> go 2kt 2kt 4kt, you go go faster by reaching the 4kt,
> to fast and your groveling or in a field
>
> there also seems to be a drift towards stable cruise
> speeds rather than chasing M/C

This discussion reinforces what I've found in the real world. Cruise at
70 kts on weak days, 80 or 85 kts on strong days, and fly the MacCready
settings only on Condor :-)



Shawn

[Mike the Strike]

Frank:

One thing that classic MacCready theory doesn't take into account is
the depth of the working height band.

It would be a foolish pilot who set his computer/ring to MacCready 5
on a day with 5 knot thermals that topped out at 1,500 feet AGL, but
with cloudbases at 15,000 feet you could probably set it at 6 or
higher. Several pilots I know set their ring almost as a function of
height rather than thermal strength.

The chance of you hooking up with a good thermal increases with the
top of the lift and you can increase your speed accordingly. When you
get low, you need to slow down. There have been some good articles on
this if you search the databases.

Mike


On Feb 7, 11:50 am, Frank > wrote:
> I'm curious what others are using for inter-thermal cruise speeds for
> modern 15m (and 18m I guess) gliders like the Ventus 2bx, Ventus 2cx,
> ASW-27, ASG-29, Diana 2, etc (add models as necessary).
>
> Here in the U.S. we have been moving toward cruise speeds much lower
> than would normally be dictated by using straight McReady settings,
> but how low is too low?
>
> I've also been flying a V2bx & V2cxt in Condor a lot, and cruise
> speeds there are all over the map, from 90kt to 125kt (fully
> ballasted) in the same race/weather conditions, with varying results.
>
> Any thoughts?
>
> TIA,
>
> Frank (TA)

[Tim Taylor]

On Feb 7, 5:00 pm, Mike the Strike > wrote:
> Frank:
>
> One thing that classic MacCready theory doesn't take into account is
> the depth of the working height band.
>
> It would be a foolish pilot who set his computer/ring to MacCready 5
> on a day with 5 knot thermals that topped out at 1,500 feet AGL, but
> with cloudbases at 15,000 feet you could probably set it at 6 or
> higher. Several pilots I know set their ring almost as a function of
> height rather than thermal strength.
>
> The chance of you hooking up with a good thermal increases with the
> top of the lift and you can increase your speed accordingly. When you
> get low, you need to slow down. There have been some good articles on
> this if you search the databases.
>
> Mike
>

Mike,

Working the bands is very common and I think of it as setting the MC
to the strength of the next thermal "I am willing to take". The day
average may be 6 knots, but if I am low and willing to accept a 3 knot
thermal I will set the MC to that. As I get lower the odds of finding
a good thermal are reduced and I am willing to take a weaker thermal
to get back up in the band or at least get the range to hopefully
reach a better thermal.

In the Western US there are many summer days where dropping below the
mountain height can cost you dearly in time to get back up. In the
14-18 K range I tend to fly MC+5, 12-14K MC for the average thermal
strength I am expecting still to find, 10-12 K I dial back to extend
range, 8 to 10K back further and below 8 back to zero. This is with
base elevation about 5,000 in the valleys.

[Frank[_1_]]

On Feb 7, 3:31*pm, Tim Taylor > wrote:
> On Feb 7, 11:50 am, Frank > wrote:
> A great text:
>
> Competing in Gliders - Winning With Your Mind
> Authors: *Leo and Ricky Brigliadori
>

Yep, I have it and have read through it a number of times. The speed
discussions are very good, and maybe someday I'll be able to actually
understand it all ;-)

Frank(TA)

[Rick Culbertson]

Frank & all,

Great subject, it's my favorite and the essence of the "go faster"
game we all like to play. I certainly agree with Tim. Competing in
Gliders - Winning With Your Mind by Leo and Ricky Brigliadori is the
latest and greatest must have book in your soaring Library for the
"just a little bit faster please" (nod to BB) type pilot.

Here's the really interesting part concerning the answers (so far) to
your questions, every one of the comments are generally correct. The
theory of how and what to set your MC for inter-thermal runs and final
glides are generally known, the fact that most are setting MC slightly
less than the actual average achieved climb rate is well known, not
speed chasing the vario is a given today, height band evaluation,
adjusting for the conditions or obstacles ahead and long glides
chasing lift bands followed by climbing in only the strongest thermals
of the day all equate to faster XC speeds and the list goes on and on.
So you toss all that info in a blender then go flying and see what's
working today, be creative by varying the techniques.

So the real key and IMHO the most enjoyable part of what we do is when
we're tapping into our creative side. This is the side that quietly
informs us when to apply a little, slightly in advance of the obvious
gear shifting, creative wondering in lift bands or perhaps making that
90 degree turn and then finding just what you're looking for when
perhaps none of this was obvious to our right side of the brain. The
numbers side of the game, as I see it is really only a checklist
guideline, to be applied as an appropriate and important rule of
thumb. However the rewards are often found on the edges or perhaps
somewhat outside of the numbers. I doubt if many have won the day or
got around a 1,000k by just following the numbers. Having said that
somewhere between 70kts and 110kts sounds about right to me ;-)
21

[Stephen[_2_]]

Mike the Strike wrote:
>
> It would be a foolish pilot who set his computer/ring to MacCready 5
> on a day with 5 knot thermals that topped out at 1,500 feet AGL, but
> with cloudbases at 15,000 feet you could probably set it at 6 or
> higher. Several pilots I know set their ring almost as a function of
> height rather than thermal strength.
>

My understanding of the theory is that you will ALWAYS be worse off if
you set a MC higher than the thermal strength and therefore fly faster
than optimum. Flying slower however does have several advantages, as
others have described.

Stephen

[Mike the Strike]

Stephen:

That is true if all thermals have the same strength. In reality,
thermals have a strength (and size) distribution. On a day with a 5-
knot average thermal strength you will find thermals as strong as 8
knots or as weak as 3 knots. More working altitude enables you to
pick the strongest thermals and maintain an effective MacCready higher
than the average thermal strength. The fastest pilots (which doesn't
include me) seem to be rather good at this.

Knowing when you can step up the speed and when to slow down is the
key to winning.

Mike

> My understanding of the theory is that you will ALWAYS be worse off if
> you set a MC higher than the thermal strength and therefore fly faster
> than optimum. Flying slower however does have several advantages, as
> others have described.
>
> Stephen

[Bill Daniels]

I really liked John Cochrane's paper "A little Faster Please".

The message I took from that was that the MacCready setting can be used as a
general "optimism setting". I tend to set MacCready with a "gut check"
about how I feel conditions will be ahead.

If you are bumping along above 17,000 feet, there's no thermal that's worth
stopping for since you don't want to go any higher so M could be infinity.
On the other hand, if you are low in tiger country, you'll take any thermal
(M=0). There's a sliding scale in between.

I use GPS_LOG which can average the last three thermals and automatically
set M. That almost always gives me a M setting higher than my gut says I
should use. Maybe that's why I fly slow.

Bill D


"Mike the Strike" > wrote in message
...
> Stephen:
>
> That is true if all thermals have the same strength. In reality,
> thermals have a strength (and size) distribution. On a day with a 5-
> knot average thermal strength you will find thermals as strong as 8
> knots or as weak as 3 knots. More working altitude enables you to
> pick the strongest thermals and maintain an effective MacCready higher
> than the average thermal strength. The fastest pilots (which doesn't
> include me) seem to be rather good at this.
>
> Knowing when you can step up the speed and when to slow down is the
> key to winning.
>
> Mike
>
>> My understanding of the theory is that you will ALWAYS be worse off if
>> you set a MC higher than the thermal strength and therefore fly faster
>> than optimum. Flying slower however does have several advantages, as
>> others have described.
>>
>> Stephen
>

[Andy[_1_]]

On Feb 7, 11:50*am, Frank > wrote:
>
> Any thoughts?

I'm late to the thread but I have read the other posts. So far no one
has mentioned:

TAS effect (the advantage of better ground speed at high altitude)
Polar knees (the sharp fall off in performance at high speed seen in
some modern gliders).
Streeting
Wind shift with altitude.

Simple MC theory does not deal with any of this very well, or if it
does I missed understanding it.

Years ago I thought the only way to fly fast was to push forward on
the stick. I used to landout a lot. Over the years I got to fly with
many excellent pilots and was impressed by how slow many of them flew
and how seldom they stopped to thermal.


Andy

[[email protected]]

On Feb 7, 1:50*pm, Frank > wrote:
> I'm curious what others are using for inter-thermal cruise speeds for
> modern 15m (and 18m I guess) gliders like the Ventus 2bx, Ventus 2cx,
> ASW-27, ASG-29, Diana 2, etc (add models as necessary).
>
> Here in the U.S. we have been moving toward cruise speeds much lower
> than would normally be dictated by using straight McReady settings,
> but how low is too low?
>
> I've also been flying a V2bx & V2cxt in Condor a lot, and cruise
> speeds there are all over the map, from 90kt to 125kt (fully
> ballasted) in the same race/weather conditions, with varying results.
>
> Any thoughts?
>
> TIA,
>
> Frank (TA)

The speed that gets you to the next acceptable thermal without hitting
the ground. Seems obvious
but each day we have to find a rythym that accomplishes this very
basic element.
I don't see the best pilots making drastic changes in how fast they
fly. This takes too much attention better applied to where to fly.
UH

[[email protected]]

Anyone else here see Carl Herolds talk at the convention a couple
years ago titled, If you fly Mcdready you will lose"? Actually, he
said that was a title just to get attention but that the real title
was Fly Slower to Fly Faster, or something like that. It was
fascinating to see all this graphs and flight traces. It was very
convincing to see his data that indicated staying high and not
circling was ultimately faster. I think there may be a threshold L/D
value particular to specific conditions in which his technique
worked. Regardless, I now circle as little as possible.

MM

[bobcaldwell]

On Feb 7, 5:00 pm, Mike the Strike > wrote:
> Frank:
>
> One thing that classic MacCready theory doesn't take into account is
> the depth of the working height band.
>
> It would be a foolish pilot who set his computer/ring to MacCready 5
> on a day with 5 knot thermals that topped out at 1,500 feet AGL, but
> with cloudbases at 15,000 feet you could probably set it at 6 or
> higher. Several pilots I know set their ring almost as a function of
> height rather than thermal strength.
>
> The chance of you hooking up with a good thermal increases with the
> top of the lift and you can increase your speed accordingly. When you
> get low, you need to slow down. There have been some good articles on
> this if you search the databases.
>
> Mike
>
> On Feb 7, 11:50 am, Frank > wrote:
>
> > I'm curious what others are using for inter-thermal cruise speeds for
> > modern 15m (and 18m I guess) gliders like the Ventus 2bx, Ventus 2cx,
> > ASW-27, ASG-29, Diana 2, etc (add models as necessary).
>
> > Here in the U.S. we have been moving toward cruise speeds much lower
> > than would normally be dictated by using straight McReady settings,
> > but how low is too low?
>
> > I've also been flying a V2bx & V2cxt in Condor a lot, and cruise
> > speeds there are all over the map, from 90kt to 125kt (fully
> > ballasted) in the same race/weather conditions, with varying results.
>
> > Any thoughts?
>
> > TIA,
>
> > Frank (TA)


I have also found John Cochrane's (BB) work in this area to be most
enlightening. Here is the link to the paper.

http://faculty.chicagogsb.edu/john.cochrane/research/Papers/newmcred.pdf

It gets pretty technical but the gist is that he blends MC theory with
probability (of reaching the next thermal of a certain strength)
theory and proves it mathematically. A little calculus for those cold
winter months.....

Bob

[[email protected]]

On Feb 8, 8:45*pm, wrote:
> Anyone else here see Carl Herolds talk at the convention a couple
> years ago titled, If you fly Mcdready you will lose"? *Actually, he
> said that was a title just to get attention but that the real title
> was Fly Slower to Fly Faster, or something like that. *It was
> fascinating to see all this graphs and flight traces. *It was very
> convincing to see his data that indicated staying high and not
> circling was ultimately faster. *I think there may be a threshold L/D
> value particular to specific conditions in which his technique
> worked. *Regardless, I now circle as little as possible.
>
> MM

As had been already mentioned, there are a bunch of reasons why flying
slower than McCready theory makes sense. Some are consistent across
flying conditions, others are situation-specific.

Fist, in my experience, your perceived climb rate may not be your
actual climb rate - even using you vario or computer averager,
depending on how it calculates average. I consistently find average
climb rates looking at SeeYou to be a knot or more slower than was my
perception in the air. This is mostly because pilots (and perhaps some
instruments) don't adequately count the time centering a thermal with
no climb or include "trys", thermals that don't pan out. These two
effects reduce your realistic expected climb rate. Maybe your computer
properly adjusts for this maybe it doesn't, only some experimentation
can tell you for sure.

Flying slower keeps you higher, which has a number of direct and
indirect benefits that I've tried to quantify through the following
example. Imagine a flight where the lift band is 10,000' to 17,500',
the average (achieved) climb is 5 knots, the distance between climbs
is 35 miles and there are cu present. For my glider the theory gives
an expected cruise speed of 98 knots (dry) and an altitude loss
between thermals of 7,100'. If I slow down and fly 15 knots slower
(83 knots) instead, I end up with an altitude loss between thermals of
5,600' and an average achieved cross-country speed that is about 1.7
mph slower. So why fly slower? By staying higher my average cruise
altitude is 14,700 rather than 13,900 so I gain back about 1.5 mph in
true airspeed difference. You only need to find a 0.04 knot better
climb to close the remaining cross-country speed gap, or a 0.4 knot
faster climb if you ignore the TAS effect. Since we are flying higher
on average it is reasonable to expect you'll be able to do this under
the described conditions for several reasons. You will be closer to
the clouds and will have a slightly better change of aligining on them
to find lift. You will also be higher in the lift band so less likely
to fall into weaker lift or will be less inclined to accept weaker
lift as you get lower. You will have a greater search distance to find
better lift. If I fly McCready in this scenario I can go about 35
miles between thermals before I get out of the lift band. If I fly 15
knots slower I can fly 45 miles for the same altitude range. Lastly, I
have found that I have a somewhat harder time sensing and successfully
pulling up into and quickly centering thermals if I am cruising at 100
knots versus 85 knots. In the extreme case, flying faster ups you risk
of getting stuck down low and having to take a sub-standard thermal to
get back up or even landing out. Individual flying style will
determine which of these effects matters most for any individual
pilot.

How you think about this varies with the conditions of the day. If it
is blue with a very wide lift band, large, closely-spaced thermals
with very consistent thermal strengths you won't get as much benefit
from slowing down. The TAS effect is also reduced for lower altitude
lift bands. If the thermal strengths are lower overall, you actually
have to find a thermal that is more significanly above average (on a %
basis) to make up the cruise speed difference.

If I change the example to flying 20 or 25 knots slower than McCready
it gets harder to see the benefits because the incremental climb rate
you need to achieve to make up for the sub-optimal cruise speed goes
up substantially.

9B

[[email protected]]

On 9 fév, 12:54, wrote:
> On Feb 8, 8:45*pm, wrote:
>
> > Anyone else here see Carl Herolds talk at the convention a couple
> > years ago titled, If you fly Mcdready you will lose"? *Actually, he
> > said that was a title just to get attention but that the real title
> > was Fly Slower to Fly Faster, or something like that. *It was
> > fascinating to see all this graphs and flight traces. *It was very
> > convincing to see his data that indicated staying high and not
> > circling was ultimately faster. *I think there may be a threshold L/D
> > value particular to specific conditions in which his technique
> > worked. *Regardless, I now circle as little as possible.
>
> > MM
>
> As had been already mentioned, there are a bunch of reasons why flying
> slower than McCready theory makes sense. Some are consistent across
> flying conditions, others are situation-specific.
>
> Fist, in my experience, your perceived climb rate may not be your
> actual climb rate - even using you vario or computer averager,
> depending on how it calculates average. I consistently find average
> climb rates looking at SeeYou to be a knot or more slower than was my
> perception in the air. This is mostly because pilots (and perhaps some
> instruments) don't adequately count the time centering a thermal with
> no climb or include "trys", thermals that don't pan out. These two
> effects reduce your realistic expected climb rate. Maybe your computer
> properly adjusts for this maybe it doesn't, only some experimentation
> can tell you for sure.
>
> Flying slower keeps you higher, which has a number of direct and
> indirect benefits that I've tried to quantify through the following
> example. *Imagine a flight where the lift band is 10,000' to 17,500',
> the average (achieved) climb is 5 knots, the distance between climbs
> is 35 miles and there are cu present. For my glider the theory gives
> an expected cruise speed of 98 knots (dry) and an altitude loss
> between thermals of 7,100'. *If I slow down and fly 15 knots slower
> (83 knots) instead, I end up with an altitude loss between thermals of
> 5,600' and an average achieved cross-country speed that is about 1.7
> mph slower. So why fly slower? *By staying higher my average cruise
> altitude is 14,700 rather than 13,900 so I gain back about 1.5 mph in
> true airspeed difference. *You only need to find a 0.04 knot better
> climb to close the remaining cross-country speed gap, or a 0.4 knot
> faster climb if you ignore the TAS effect. Since we are flying higher
> on average it is reasonable to expect you'll be able to do this under
> the described conditions for several reasons. *You will be closer to
> the clouds and will have a slightly better change of aligining on them
> to find lift. You will also be higher in the lift band so less likely
> to fall into weaker lift or will be less inclined to accept weaker
> lift as you get lower. You will have a greater search distance to find
> better lift. If I fly McCready in this scenario I can go about 35
> miles between thermals before I get out of the lift band. If I fly 15
> knots slower I can fly 45 miles for the same altitude range. Lastly, I
> have found that I have a somewhat harder time sensing and successfully
> pulling up into and quickly centering thermals if I am cruising at 100
> knots versus 85 knots. In the extreme case, flying faster ups you risk
> of getting stuck down low and having to take a sub-standard thermal to
> get back up or even landing out. Individual flying style will
> determine which of these effects matters most for any individual
> pilot.
>
> How you think about this varies with the conditions of the day. If it
> is blue with a very wide lift band, large, closely-spaced thermals
> with very consistent thermal strengths you won't get as much benefit
> from slowing down. The TAS effect is also reduced for lower altitude
> lift bands. If the thermal strengths are lower overall, you actually
> have to find a thermal that is more significanly above average (on a %
> basis) to make up the cruise speed difference.
>
> If I change the example to flying 20 or 25 knots slower than McCready
> it gets harder to see the benefits because the incremental climb rate
> you need to achieve to make up for the sub-optimal cruise speed goes
> up substantially.
>
> 9B



Hi,
Here's Ingo Renner rules to achieve fast x/c speed flying a Duo-
Discus.

-Ignore MaCready and fly one of three speed;
55 for thermaling, 70-80 kts for low weaker condition
90-110 kts for strong condition
-Fly straight to your goal with very minor deviation for lift.
-Slow down gently in lift and centre thermal in one circle or keep
going,
no second chance
-Leave as soon as climb falls off,
-Fly carefully with smooth control movement, no abrupt pull up or push
over.
-Always fly with the yaw string straight and centered.

Taken from a text entitle "Soaring with the master", by Ian Sutcliffe
in Free Flight,the Canadian magazine on soaring.
S6

[[email protected]]

On Feb 10, 5:35*am, wrote:
> On 9 fév, 12:54, wrote:
>
>
>
>
>
> > On Feb 8, 8:45*pm, wrote:
>
> > > Anyone else here see Carl Herolds talk at the convention a couple
> > > years ago titled, If you fly Mcdready you will lose"? *Actually, he
> > > said that was a title just to get attention but that the real title
> > > was Fly Slower to Fly Faster, or something like that. *It was
> > > fascinating to see all this graphs and flight traces. *It was very
> > > convincing to see his data that indicated staying high and not
> > > circling was ultimately faster. *I think there may be a threshold L/D
> > > value particular to specific conditions in which his technique
> > > worked. *Regardless, I now circle as little as possible.
>
> > > MM
>
> > As had been already mentioned, there are a bunch of reasons why flying
> > slower than McCready theory makes sense. Some are consistent across
> > flying conditions, others are situation-specific.
>
> > Fist, in my experience, your perceived climb rate may not be your
> > actual climb rate - even using you vario or computer averager,
> > depending on how it calculates average. I consistently find average
> > climb rates looking at SeeYou to be a knot or more slower than was my
> > perception in the air. This is mostly because pilots (and perhaps some
> > instruments) don't adequately count the time centering a thermal with
> > no climb or include "trys", thermals that don't pan out. These two
> > effects reduce your realistic expected climb rate. Maybe your computer
> > properly adjusts for this maybe it doesn't, only some experimentation
> > can tell you for sure.
>
> > Flying slower keeps you higher, which has a number of direct and
> > indirect benefits that I've tried to quantify through the following
> > example. *Imagine a flight where the lift band is 10,000' to 17,500',
> > the average (achieved) climb is 5 knots, the distance between climbs
> > is 35 miles and there are cu present. For my glider the theory gives
> > an expected cruise speed of 98 knots (dry) and an altitude loss
> > between thermals of 7,100'. *If I slow down and fly 15 knots slower
> > (83 knots) instead, I end up with an altitude loss between thermals of
> > 5,600' and an average achieved cross-country speed that is about 1.7
> > mph slower. So why fly slower? *By staying higher my average cruise
> > altitude is 14,700 rather than 13,900 so I gain back about 1.5 mph in
> > true airspeed difference. *You only need to find a 0.04 knot better
> > climb to close the remaining cross-country speed gap, or a 0.4 knot
> > faster climb if you ignore the TAS effect. Since we are flying higher
> > on average it is reasonable to expect you'll be able to do this under
> > the described conditions for several reasons. *You will be closer to
> > the clouds and will have a slightly better change of aligining on them
> > to find lift. You will also be higher in the lift band so less likely
> > to fall into weaker lift or will be less inclined to accept weaker
> > lift as you get lower. You will have a greater search distance to find
> > better lift. If I fly McCready in this scenario I can go about 35
> > miles between thermals before I get out of the lift band. If I fly 15
> > knots slower I can fly 45 miles for the same altitude range. Lastly, I
> > have found that I have a somewhat harder time sensing and successfully
> > pulling up into and quickly centering thermals if I am cruising at 100
> > knots versus 85 knots. In the extreme case, flying faster ups you risk
> > of getting stuck down low and having to take a sub-standard thermal to
> > get back up or even landing out. Individual flying style will
> > determine which of these effects matters most for any individual
> > pilot.
>
> > How you think about this varies with the conditions of the day. If it
> > is blue with a very wide lift band, large, closely-spaced thermals
> > with very consistent thermal strengths you won't get as much benefit
> > from slowing down. The TAS effect is also reduced for lower altitude
> > lift bands. If the thermal strengths are lower overall, you actually
> > have to find a thermal that is more significanly above average (on a %
> > basis) to make up the cruise speed difference.
>
> > If I change the example to flying 20 or 25 knots slower than McCready
> > it gets harder to see the benefits because the incremental climb rate
> > you need to achieve to make up for the sub-optimal cruise speed goes
> > up substantially.
>
> > 9B
>
> Hi,
> Here's Ingo Renner rules to achieve fast x/c speed flying a Duo-
> Discus.
>
> -Ignore MaCready and fly one of three speed;
> 55 for thermaling, 70-80 kts for low weaker condition
> 90-110 kts for strong condition
> -Fly straight to your goal with very minor deviation for lift.
> -Slow down gently in lift and centre thermal in one circle or keep
> going,
> no second chance
> -Leave as soon as climb falls off,
> -Fly carefully with smooth control movement, no abrupt pull up or push
> over.
> -Always fly with the yaw string straight and centered.
>
> Taken from a text entitle "Soaring with the master", by Ian Sutcliffe
> in Free Flight,the Canadian magazine on soaring.
> S6- Hide quoted text -
>
> - Show quoted text -

Ingo is a great pilot so I wouldn't quibble that his technique works
for him in the conditions he was thinking of when he gave this advice.

That said, I can say from personal experience that I have seen world-
class pilots pursue very different strategies with great success under
conditions that may or may not be similar to what Ingo was thinking
of. In particular I see a lot of very good pilots in the high desert
of the western US make significant deviations from courseline to seek
out lift. This may have something to do with the topography of the
site and the lift distribution on any given day.

With respect to speeds, it all depends on what Ingo means by "low and
weak" versus "strong". His speed ranges cover the gamut and in the end
the basic idea is right - don't fly the speed director.

9B

[Tony Verhulst]

Frank wrote:
> I'm curious what others are using for inter-thermal cruise speeds for
> modern 15m (and 18m I guess) gliders like the Ventus 2bx, Ventus 2cx,
> ASW-27, ASG-29, Diana 2, etc (add models as necessary).

According to a fellow club member (Discus 2), if the day is booming, fly
80 kts, if the day is good, fly 70 kts, if the day is so so, fly 60 kts.
YMMV.

Tony V.

[[email protected]]

On Feb 12, 8:01*pm, Tony Verhulst > wrote:
> Frank wrote:
> > I'm curious what others are using for inter-thermal cruise speeds for
> > modern 15m (and 18m I guess) gliders like the Ventus 2bx, Ventus 2cx,
> > ASW-27, ASG-29, Diana 2, etc (add models as necessary).
>
> According to a fellow club member (Discus 2), if the day is booming, fly
> 80 kts, if the day is good, fly 70 kts, if the day is so so, fly 60 kts.
> YMMV.
>
> Tony

Those sound like east coast conditions with no water. They correspond
to 2.5, 1 and 0 knot McCready settings on my ASW 27 - a D2 wouldn't be
too far off.

It would have to be a truly weak day for me to fly best L/D (60 kts)
all the time.

Andy

[N5]

On Feb 7, 6:50 pm, Frank > wrote:
> I'm curious what others are using for inter-thermal cruise speeds for
> modern 15m (and 18m I guess) gliders like the Ventus 2bx, Ventus 2cx,
> ASW-27, ASG-29, Diana 2, etc (add models as necessary).
>
> Here in the U.S. we have been moving toward cruise speeds much lower
> than would normally be dictated by using straight McReady settings,
> but how low is too low?
>
> I've also been flying a V2bx & V2cxt in Condor a lot, and cruise
> speeds there are all over the map, from 90kt to 125kt (fully
> ballasted) in the same race/weather conditions, with varying results.
>
> Any thoughts?
>
> TIA,
>
> Frank (TA)

As someone who changed from an LS4 to an ASW27 last year I did wonder
about this quite a bit and how best to learn to fly in a different
speed range. I like the idea of 3 speeds as mentioned by some other
writers, tip-toeing (best glide), normal (75-80 kts) and flat-out
(90+kts), because it's easy to do. I like setting Macready and just
using it as guidance, because it's easy to do. I like paying attention
to other gliders around me and seeing how they're getting on, because
it's easy to do.

All that leaves you with plenty of capacity for the important jobs -
picking the right pieces of sky, making an excellent job of climbing
if you choose to stop, and changing to Plan B if you get the first 2
jobs wrong. After several beery evenings analysing flight traces, it
seems I perform best late in the afternoon when you either correctly
find, reach and use the few large thermals that are left or you don't
get home before the bar closes. If only I could apply that selection
process at other times of the day I'd be getting somewhere.

And I think I go faster on Condor because if you get it wrong you can
just hit restart.

For those of you who enjoy other's mistakes, see if you can spot an
example of Plan B taking it's time to kick in ...
http://www.bgaladder.co.uk/dnload.asp?DSN=77TC3IR1.igc

Martin (UK)

[Eric Greenwell]

Mike the Strike wrote:
>> Stephen wrote:
>> My understanding of the theory is that you will ALWAYS be worse off if
>> you set a MC higher than the thermal strength and therefore fly faster
>> than optimum. Flying slower however does have several advantages, as
>> others have described.

> That is true if all thermals have the same strength. In reality,
> thermals have a strength (and size) distribution. On a day with a 5-
> knot average thermal strength you will find thermals as strong as 8
> knots or as weak as 3 knots.

McCready theory is based on what *you* get for thermal strength, not
what a random sampling of the thermals in the area would produce, so I
have to agree with Stephen. Set your MC higher than the thermals you are
encounter will slow you down. Of course, we're assuming you are flying a
classic thermal flight, and not convergence, wave, ridges, etc.

Probably no one reading this thread anymore - I was traveling and got
here late!
--
Eric Greenwell - Washington State, USA
* Change "netto" to "net" to email me directly

* Updated! "Transponders in Sailplanes" http://tinyurl.com/y739x4
* New Jan '08 - sections on Mode S, TPAS, ADS-B, Flarm, more

* "A Guide to Self-launching Sailplane Operation" at www.motorglider.org

[Eric Greenwell]

Bill Daniels wrote:
> I really liked John Cochrane's paper "A little Faster Please".
>
> The message I took from that was that the MacCready setting can be used as a
> general "optimism setting". I tend to set MacCready with a "gut check"
> about how I feel conditions will be ahead.
>
> If you are bumping along above 17,000 feet, there's no thermal that's worth
> stopping for since you don't want to go any higher so M could be infinity.
> On the other hand, if you are low in tiger country, you'll take any thermal
> (M=0). There's a sliding scale in between.
>
> I use GPS_LOG which can average the last three thermals and automatically
> set M. That almost always gives me a M setting higher than my gut says I
> should use. Maybe that's why I fly slow.

Maybe, but probably not - I think a lot of good pilots do the same. My
experience is, if I use a MC setting the same as the average climbs I'm
making, two things usually happen:

1) My speed director tells me to fly scary fast in medium or stronger
sink (like 110-120 knots), and

2) I get low frequently!

So, I usually set it as high as I can without getting stuck low
somewhere, and that's generally around one-third of the climb average. I
flew contests for many years, and the really good pilots weren't flying
much faster, if any, than I was, but they sure chose better places to
go, and they knew when to shift gears sooner than I did.

--
Eric Greenwell - Washington State, USA
* Change "netto" to "net" to email me directly

* Updated! "Transponders in Sailplanes" http://tinyurl.com/y739x4
* New Jan '08 - sections on Mode S, TPAS, ADS-B, Flarm, more

* "A Guide to Self-launching Sailplane Operation" at www.motorglider.org