Best Overall Motorglider available today?

For all you non-believers and skeptics that did not believe the JS1 had
been measured by the Idafleig at 63:1 please see the latest posting on the

Jonkers website regarding the JS2. Your really not as smart as you think
you
are.

On Thursday, November 19, 2020 at 6:15:11 AM UTC-6, Paul T wrote:
For all you non-believers and skeptics that did not believe the JS1 had
been measured by the Idafleig at 63:1 please see the latest posting on the

Jonkers website regarding the JS2. Your really not as smart as you think
you
are.
Paul, no dog in this fight for me but I don't see anything on the JS website mentioning Idafleig, can you post a link to what you are looking at?

Paul T wrote on 11/19/2020 4:13 AM:
For all you non-believers and skeptics that did not believe the JS1 had
been measured by the Idafleig at 63:1 please see the latest posting on the

Jonkers website regarding the JS2. Your really not as smart as you think
you
are.

How odd the 63:1 only occurs at the high wing loading in 21M, and not at the minimum wing
loading, where the L/D is essentially the same for the 18M and 21M wings.


--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorg...ad-the-guide-1

On Thursday, November 19, 2020 at 7:35:55 AM UTC-6, Eric Greenwell wrote:
Paul T wrote on 11/19/2020 4:13 AM:
For all you non-believers and skeptics that did not believe the JS1 had
been measured by the Idafleig at 63:1 please see the latest posting on the

Jonkers website regarding the JS2. Your really not as smart as you think
you
are.
How odd the 63:1 only occurs at the high wing loading in 21M, and not at the minimum wing
loading, where the L/D is essentially the same for the 18M and 21M wings.
--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorg...ad-the-guide-1
I noticed the same thing. So there is essentially no reason to fly it in 21m dry configuration? And almost no situation where you would fly it dry in either configuration anyway?

On Thursday, November 19, 2020 at 7:58:23 AM UTC-6, Me wrote:
On Thursday, November 19, 2020 at 7:35:55 AM UTC-6, Eric Greenwell wrote:
Paul T wrote on 11/19/2020 4:13 AM:
For all you non-believers and skeptics that did not believe the JS1 had
been measured by the Idafleig at 63:1 please see the latest posting on the

Jonkers website regarding the JS2. Your really not as smart as you think
you
are.
How odd the 63:1 only occurs at the high wing loading in 21M, and not at the minimum wing
loading, where the L/D is essentially the same for the 18M and 21M wings.
--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorg...ad-the-guide-1
I noticed the same thing. So there is essentially no reason to fly it in 21m dry configuration? And almost no situation where you would fly it dry in either configuration anyway?
The minimum wing loading in the table does not match minimum wing loading in the polar graph. I'm confused...

On 11/19/2020 8:35 AM, Eric Greenwell wrote:
How odd the 63:1 only occurs at the high wing loading in 21M, and not at
the minimum wing loading, where the L/D is essentially the same for the
18M and 21M wings.

Not odd at all. Reynolds number changes make a big difference especially
with tiny chord. IIRC the original Ventus 15m increased LD 2 points with
ballast, and could not change wingloading as much as modern gliders.

Reynolds numbers do make a difference, but it would be a *very* unusual airfoil that changed that much over such a small change in Re. The Jonkers published polar is peculiar in many ways.

I did reach out to both Ideflug and Jonkers about any data they had on tests, got acknowledgment of the requests but no response from either.

On Thursday, November 19, 2020 at 6:59:29 AM UTC-8, wrote:
On 11/19/2020 8:35 AM, Eric Greenwell wrote:
How odd the 63:1 only occurs at the high wing loading in 21M, and not at
the minimum wing loading, where the L/D is essentially the same for the
18M and 21M wings.
Not odd at all. Reynolds number changes make a big difference especially
with tiny chord. IIRC the original Ventus 15m increased LD 2 points with
ballast, and could not change wingloading as much as modern gliders.

Dave Nadler wrote on 11/19/2020 6:59 AM:
On 11/19/2020 8:35 AM, Eric Greenwell wrote:
How odd the 63:1 only occurs at the high wing loading in 21M, and not at the minimum wing
loading, where the L/D is essentially the same for the 18M and 21M wings.

Not odd at all. Reynolds number changes make a big difference especially with tiny chord. IIRC
the original Ventus 15m increased LD 2 points with ballast, and could not change wingloading as
much as modern gliders.


This does not seem to be about wing loading, as the chart shows the 18/21 versions at the same
wing loading, so I repeat: It's still odd that adding 10' to the span does not significantly
change the performance at any speed except in the lowest few knots of the polar.

If it's Reynolds number that's important: Shouldn't the 21 M wing have more feet of wider chord
than the 18M wing, and shouldn't we expect it to do better, just based on that?

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorg...ad-the-guide-1

On Thu, 19 Nov 2020 08:23:43 -0800, Eric Greenwell wrote:

Dave Nadler wrote on 11/19/2020 6:59 AM:
On 11/19/2020 8:35 AM, Eric Greenwell wrote:
How odd the 63:1 only occurs at the high wing loading in 21M, and not
at the minimum wing loading, where the L/D is essentially the same for
the 18M and 21M wings.

Not odd at all. Reynolds number changes make a big difference
especially with tiny chord. IIRC the original Ventus 15m increased LD 2
points with ballast, and could not change wingloading as much as modern
gliders.


This does not seem to be about wing loading, as the chart shows the
18/21 versions at the same wing loading, so I repeat: It's still odd
that adding 10' to the span does not significantly change the
performance at any speed except in the lowest few knots of the polar.

If it's Reynolds number that's important: Shouldn't the 21 M wing have
more feet of wider chord than the 18M wing, and shouldn't we expect it
to do better, just based on that?

Aspect ratio is also beneficial and will increase the overall L/D ratio
at a given airspeed if the wing section and wing loading are unchanged.


--
--
Martin | martin at
Gregorie | gregorie dot org

Martin Gregorie wrote on 11/19/2020 9:01 AM:
On Thu, 19 Nov 2020 08:23:43 -0800, Eric Greenwell wrote:

Dave Nadler wrote on 11/19/2020 6:59 AM:
On 11/19/2020 8:35 AM, Eric Greenwell wrote:
How odd the 63:1 only occurs at the high wing loading in 21M, and not
at the minimum wing loading, where the L/D is essentially the same for
the 18M and 21M wings.

Not odd at all. Reynolds number changes make a big difference
especially with tiny chord. IIRC the original Ventus 15m increased LD 2
points with ballast, and could not change wingloading as much as modern
gliders.


This does not seem to be about wing loading, as the chart shows the
18/21 versions at the same wing loading, so I repeat: It's still odd
that adding 10' to the span does not significantly change the
performance at any speed except in the lowest few knots of the polar.

If it's Reynolds number that's important: Shouldn't the 21 M wing have
more feet of wider chord than the 18M wing, and shouldn't we expect it
to do better, just based on that?

Aspect ratio is also beneficial and will increase the overall L/D ratio
at a given airspeed if the wing section and wing loading are unchanged.

Exactly! And yet, despite an aspect ratio of 36 (21 M) vs 29 (18 M), the 21 M performance is
almost identical, according to the chart. How can that be?

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorg...ad-the-guide-1