At 04:12 08 October 2020, 2G wrote:
On Tuesday, October 6, 2020 at 1:58:06 PM UTC-7, Eric Greenwell
wrote:
The JS website says it's 60 for the JS1C/21M; 63 for the JS2/21M.

jfitch wrote on 10/6/2020 1:37 PM:
Link? Google produces zero results.
On Tuesday, October 6, 2020 at 1
1:00:06 AM UTC-7, Paul T wrote:
At 15:39 06 October 2020, jfitch wrote:
They are claiming 63:1, that is 7 points higher than AS claim of
56:1. I
th=
ink it is best explained by a mistake in their math. I'd be
interested in
s=
eeing the test data proving it.=20

On Tuesday, October 6, 2020 at 12:53:25 AM UTC-7, Carlo
Orsini
wrote:
Thank you for your first hand infos, those are good news for
me (I
don't
=
understand why they advertise these dimensions in a different
way).
JS2
see=
ms to be a nice project overall. Hard to me to understand
where they
strech=
ed out those +4 points of efficency in 21m, according to their
calculated
p=
olars, compared to ASH31 (yes I know that '31 profiles are a
bit
superseede=
d and the aspect ratio is a factor too but 4 points are a huge
amount!!).
Those two dimensions for the JS2 and the ASH31 are
clearly not
be
compa=
rable - one internal cockpit rim and one external I guess. The
525mm
should=
er width for the JS2 is exactly the same as the quoted figure
for the
JS1
(=
and JS3) and the JS1 cockpit roominess is fully equal to the
ASH26/31
from
=
which it was derived. I have 4 years in a JS1 followed by 2 in
the
ASH
26e
=
and they are so similar that it would be hard to know which
cockpit I
was
i=
n with my eyes closed. Looking at the JS2 cockpit photographs
it
obvious
th=
at its structural cockpit rim design is the same as the 31, 26
and
JS1.
JS
=
do not make small cockpits.
I believe the Idafleig measured a JS1C at 63:1......so the JS2
witH
its
few improvements on the JS1C should achieve 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.../download-the-
guide-1

Someone might ask them how they came up with these L/D figures
because I
understand that they aren't from actual flight tests.

Tom


THE JS1C TO MY KNOWLEDGE HAS BEEN MEASURED AT 63:1 BY THE
IDAFLEIG IN ITS FLIGHT TESTS- PROBABLY THE MOST RELIABLE WAY
OF MEASURING A GLIDERS POLAR. (I THINK THE JONKERS BOYS
WHERE SUPRISED BY THAT FIGURE AS IT IS RARE FOR A GLIDER TO
EXCEED ITS THEOROTICAL FIGURE -BUT IT DOES HAPPEN.) ALL
MANUFACTURERS FIGURES ARE AT BEST 'THEORETICAL' UNTIL
MEASURED.................. SOME ARE WILDLY OPTIMISTIC - BUT BEST L/D
DOESNT MEAN MUCH THESE DAYS REALLY................. ITS NOT AS
THOUFGH THIS AIRCRAFT AS NOT PROVED ITSELF IN THE CONTEST
ARENA IS IT.......