Inter-thermal cruise speeds?

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)

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

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....

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.

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;-)

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)

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

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)

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.

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)