I need help Comparing and Calculating final glide performance

[Udo]

Here are the data points for glider A:
starts at exactly 13 minutes and 42 seconds.
at 2349 ft with a speed of 50 kt

arrives at 20:22 at the finish line with an
altitude of 121 ft at 95 kt, a distance covered of 12.7 miles.

Glider B
starts at nearly the same location ( within 100 ft) at 13:56
at an altitude 2400 ft at 57 kt

arrives precisely at the same finish line at 20:02
at an altitude of 62 feet with a speed of 103 kt also covered the same
distance of 12.7 miles.

The condition are the same but for the second glider leaving 14
seconds later and arriving 20 seconds early. The flight pass was
nearly identical but for the second glider passing the first
hal ways

What is the true difference between the two. It is clear there is not
much difference.

Thanks in advance for shedding light on this for me.
Udo

[Tim Taylor]

On Oct 31, 4:20*pm, Udo > wrote:
> Here are the data points for glider A:
> starts at exactly 13 minutes and 42 seconds.
> at 2349 ft with a speed of 50 kt
>
> arrives at 20:22 at the finish line with an
> altitude of 121 ft at 95 kt, a distance covered of 12.7 miles.
>
> Glider B
> starts at nearly the same location ( within 100 ft) at 13:56
> at an altitude 2400 ft at 57 kt
>
> arrives precisely at the same finish line at 20:02
> at an altitude of 62 feet with a speed of 103 kt also covered the same
> distance of 12.7 miles.
>
> *The condition are the *same but for the second glider leaving 14
> seconds later and arriving 20 seconds *early. The flight pass was
> nearly identical but for the second glider passing the first
> hal ways
>
> What is the true difference between the two. It is clear there is not
> much difference.
>
> Thanks in advance for shedding light on this for me.
> Udo

Udo,

Assuming (OK, we know what that means) that both gliders are at the
same weight and the same performance. If they were not that could be
a big difference.

Glider B had 3.77% more energy expended than glider A from the start
to finish just in a total energy balance but this does not account for
all the 9.29% better speed. About 5.5% of the better speed has to be
accounted for from picking a better line, flying at better speeds at
the right time, better performance of the glider, and weight
difference.

[Andy[_10_]]

On Oct 31, 2:20*pm, Udo > wrote:
> Here are the data points for glider A:
> starts at exactly 13 minutes and 42 seconds.
> at 2349 ft with a speed of 50 kt
>
> arrives at 20:22 at the finish line with an
> altitude of 121 ft at 95 kt, a distance covered of 12.7 miles.
>
> Glider B
> starts at nearly the same location ( within 100 ft) at 13:56
> at an altitude 2400 ft at 57 kt
>
> arrives precisely at the same finish line at 20:02
> at an altitude of 62 feet with a speed of 103 kt also covered the same
> distance of 12.7 miles.
>
> *The condition are the *same but for the second glider leaving 14
> seconds later and arriving 20 seconds *early. The flight pass was
> nearly identical but for the second glider passing the first
> hal ways
>
> What is the true difference between the two. It is clear there is not
> much difference.
>
> Thanks in advance for shedding light on this for me.
> Udo

Udo,

I'm assuming the distance is quoted in statute miles and that the
gliders accelerated to their average speed over the distance at the
start of the glide and slowed to the finish speed at the end of the
glide. Glider A averaged 99.3 kts. Glider B averaged 108.6 kts.

The difference between starting and finishing energy for Glider A was
292 feet and for Glider B was 330 feet. If we subtract this energy
from the altitude difference for each over the glide we get 1,936 and
2,008 feet and L/D's of 34.6 and 33.4 respectively for Glider A and
Glider B. For a current generation 15M glider this is about the
performance you'd expect with zero wind and half a load of water.

The main anomaly is that for the same glider at the same wing loading
you'd expect 4-5 points lower L/D for the higher cruise speed versus
the 1.2 points in your example. This would indicate that either
Glider B was a higher performance design, was at a higher wing loading
or found more favorable conditions on the glide.

I'm not sure what you're trying to figure out, but that's how the
rough calculations come out for me.

9B

[Udo]

The 57 kt versus 50 kt can be explained by the fact, that the second
glider was a little higher before it went through the same point in
space as glider A. Glider A had a wingloading of 8 lb/ft^2 Glider B
8.3 lb/ft^2. It was heavier by 3.6%

[Andy[_10_]]

On Nov 1, 1:41*pm, Udo > wrote:
> The 57 kt versus 50 kt can be explained by the fact, that the second
> glider was a little higher before it went through the same point in
> space as glider A. *Glider A had a wingloading of 8 lb/ft^2 Glider B
> 8.3 lb/ft^2. It was heavier by 3.6%

Were they the same glider model? It's not clear what point you are
trying to make or understand. Two gliders flying the same distance at
different speeds will have different performance, particularly if they
are not the same glider type and they fly even slightly different
courses. The difference in starting speed between the two gliders
doesn't matter. The only things that really matter in this example are
the cruise speeds and the difference between starting energy and
finishing energy - and of course the altitude loss over the prescribed
distance.

I'm dying to know the question behind your question. Is there a lesson
in this for all of us?

9B

[Andy[_10_]]

On Nov 1, 2:08*pm, Andy > wrote:
> On Nov 1, 1:41*pm, Udo > wrote:
>
> > The 57 kt versus 50 kt can be explained by the fact, that the second
> > glider was a little higher before it went through the same point in
> > space as glider A. *Glider A had a wingloading of 8 lb/ft^2 Glider B
> > 8.3 lb/ft^2. It was heavier by 3.6%
>
> Were they the same glider model? *It's not clear what point you are
> trying to make or understand. *Two gliders flying the same distance at
> different speeds will have different performance, particularly if they
> are not the same glider type and they fly even slightly different
> courses. The difference in starting speed between the two gliders
> doesn't matter. The only things that really matter in this example are
> the cruise speeds and the difference between starting energy and
> finishing energy - and of course the altitude loss over the prescribed
> distance.
>
> I'm dying to know the question behind your question. Is there a lesson
> in this for all of us?
>
> 9B

The difference in wingloading explains 1 additional L/D point for
Glider B. So you still have only half the expected difference in L/D -
2.2 points versus and expected 3 or 4. My only explanation is that
Glider B must've been better by 5-7% or flew through air that was an
equivalent amount better.

9B

[Udo]

Andy,
It was between an ASW27B and my modifyded HP18.
I have a bit of time to reflect on my past.
If you wish you can review the flight log your self on the Schreder
website.
http://www.soaridaho.com/Schreder/Stories/Contests/2003_Seniors/2003_Seniors.htm
Udo



On Nov 1, 5:17*pm, Andy > wrote:
> On Nov 1, 2:08*pm, Andy > wrote:

>
> > On Nov 1, 1:41*pm, Udo > wrote:
>
> > > The 57 kt versus 50 kt can be explained by the fact, that the second
> > > glider was a little higher before it went through the same point in
> > > space as glider A. *Glider A had a wingloading of 8 lb/ft^2 Glider B
> > > 8.3 lb/ft^2. It was heavier by 3.6%
>
> > Were they the same glider model? *It's not clear what point you are
> > trying to make or understand. *Two gliders flying the same distance at
> > different speeds will have different performance, particularly if they
> > are not the same glider type and they fly even slightly different
> > courses. The difference in starting speed between the two gliders
> > doesn't matter. The only things that really matter in this example are
> > the cruise speeds and the difference between starting energy and
> > finishing energy - and of course the altitude loss over the prescribed
> > distance.
>
> > I'm dying to know the question behind your question. Is there a lesson
> > in this for all of us?
>
> > 9B
>
> The difference in wingloading explains 1 additional L/D point for
> Glider B. So you still have only half the expected difference in L/D -
> 2.2 points versus and expected 3 or 4. My only explanation is that
> Glider B must've been better by 5-7% or flew through air that was an
> equivalent amount better.
>
> 9B- Hide quoted text -
>
> - Show quoted text -

[Tim Taylor]

On Nov 1, 4:11*pm, Udo > wrote:
> Andy,
> It was between an ASW27B and my modifyded HP18.
> *I have a bit of time to reflect on my past.
> If you wish you can review the flight log your self on the Schreder
> website.http://www.soaridaho.com/Schreder/Stories/Contests/2003_Seniors/2003_...
> Udo
>
> On Nov 1, 5:17*pm, Andy > wrote:
>
>
>
> > On Nov 1, 2:08*pm, Andy > wrote:
>
> > > On Nov 1, 1:41*pm, Udo > wrote:
>
> > > > The 57 kt versus 50 kt can be explained by the fact, that the second
> > > > glider was a little higher before it went through the same point in
> > > > space as glider A. *Glider A had a wingloading of 8 lb/ft^2 Glider B
> > > > 8.3 lb/ft^2. It was heavier by 3.6%
>
> > > Were they the same glider model? *It's not clear what point you are
> > > trying to make or understand. *Two gliders flying the same distance at
> > > different speeds will have different performance, particularly if they
> > > are not the same glider type and they fly even slightly different
> > > courses. The difference in starting speed between the two gliders
> > > doesn't matter. The only things that really matter in this example are
> > > the cruise speeds and the difference between starting energy and
> > > finishing energy - and of course the altitude loss over the prescribed
> > > distance.
>
> > > I'm dying to know the question behind your question. Is there a lesson
> > > in this for all of us?
>
> > > 9B
>
> > The difference in wingloading explains 1 additional L/D point for
> > Glider B. So you still have only half the expected difference in L/D -
> > 2.2 points versus and expected 3 or 4. My only explanation is that
> > Glider B must've been better by 5-7% or flew through air that was an
> > equivalent amount better.
>
> > 9B- Hide quoted text -
>
> > - Show quoted text -

Udo,

I think I have the answer for you. The difference in your loggers
gives you an additional 187 feet of altitude so you actually had 13.4%
more energy to expend to achieve the 9% faster speed. Look at the
altitudes after you each land.

[Udo]

Hi Tim
After careful study here are my revised data points.

The difference is 187 ft when stationary on the ground

After reviewing the altitudes of both gliders at the same finish
line, time stamp 20:26 the difference is 40 ft
.. Glider A dove 40 ft lower at the finish at time stamp 20:22 altitude
131 ft
B finished at the same finish point at 20:02 altitude -16 ft -187 ft
= 171 ft real altitude.

At the start, B has the advantage on the the time mark of 14:00 of
plus 187 ft

Restating the data points
A at point 13:46 had a speed of 52 kt and an altitude of 2333 ft
B at the nearly the same point at 14:00 had aspeed of 62 kt at an
altitued of 2297 ft plus the 187 logger differencial fo a total of
2484
for B a 151 ft advantage

The total advantage for B was 111 ft. ( 151 ft -40 ft) plus carring
10 kt more energy at the start and finishing also with a 5 kt higher
speed
but B also flew faster by 34 seconds.

Udo

> Udo,
>
> I think I have the answer for you. *The difference in your loggers
> gives you an additional 187 feet of altitude so you actually had 13.4%
> more energy to expend to achieve the 9% faster speed. *Look at the
> altitudes after you each land.- Hide quoted text -
>
> - Show quoted text -