A wing 3 ft above the CG will give excessive roll stability; to
get an acceptable roll rate there will have to be substantial
anhedral. It will be at least look peculiar but there may be
other detractions.
I do not remember if the Slingsby T 21 was too stable
but that might be an attraction in a trainer.

John F



At 21:17 05 February 2014, Bob Kuykendall wrote:
From the perspective of an inveterate pragmatist:

I think it comes down to operationality. Yes, the autoconnects add
complexi=
ty. Yes, placing the wing panel separation at the station of maximum
bendin=
g moment adds weight.=20

But what you get in return is a system of parts that allows for easy
storag=
e and transport, rapid assembly, and high reliability. That system has
been=
proven to result in good soaring performance at the lowest possible cost
i=
n terms of operator fatigue. And that makes for a more enjoyable soaring
ex=
perience. And when it comes down to it, quality of experience is what we
sh=
ould be trying to maximize here, not necessarily quality of performance.

It is easy to conceive of this or that adaptation that might result in
grea=
ter performance for a no-holds-barred competition machine. However, all
too=
often the result is a less robust machine that requires more work to
assem=
ble and prepare for operation. That's great if all you want to do is win
pr=
estigious contests and are prepared to either do or pay for the extra
work
=
required to campaign such an aircraft. It's less great for everyone else,
a=
nd especially for those who buy such aircraft on the used market and find
o=
ut what a pain it can be.

Thanks, Bob K.
https://www.facebook.com/pages/HP-24...t/200931354951

On Wednesday, February 5, 2014 1:29:19 AM UTC-8, J. Nieuwenhuize wrote:
Op dinsdag 4 februari 2014 22:53:33 UTC+1 schreef :
=20
It seems it would make the structure more complex and heavier. I
would
=
guess it also would cost more to build a pylon wing glider.
=20
I would expect the exact opposite. Looking at all the parts, easily a
qua=
rter of all the parts of a normal 15M sailplane are in the wing-fuselage
in=
tersection and the spar roots are a pretty beefy (and heavy) part since
you=
have a joint at the highest loaded part of the whole structure. I don't
ha=
ve a weight breakdown at hand, but some earlier number-crunching yielded
ar=
ound 15 kg weight saved by carrying on the wing (and have 2 lighter
joints
=
outboard)
=20
All those automatic connections add a lot of complexity and weight too
an=
d you can reduce their number by half. Not to mention spoilers (drag
brakes=
) that can be in the middle of the wing since you're outside the
fuselages
=
"blocked zone" reducing the number of parts further.
=20
=20
=20
One of the interesting things about glider design is that, even for
ope=
n class, it's not really a free for all. The design has to comply with
nati=
onal airworthiness requirements and have acceptable flying
characteristics
=
for the average pilot. Compare this to an Unlimited Reno racer for
example.=
I remember what Gerhard Waibel said about the ASW-12 in hindsight. It
was
=
something about learning how all new, hot gliders will become older
gliders=
flown by less than top rank pilots eventually and you have to take that
in=
to consideration even when you're trying to make a world championship
conte=
nder.
=20
=20
=20
An excellent point. Yet, not certifying and having a homebuilt,
developme=
nt cost could be drastically less, though it'd still be wise to meet
every
=
requirement from CS22. Save France, to the best of my knowledge you can
fly=
homebuilt sailplanes in most soaring-minded countries.
=20
=20
=20
One. You need a fair pylon height to avoid interference drag in the
gap=
=20
=20
between the top of the fuselage and the wing's lower surface. I'd
say=
=20
=20
interference drag is relatively high on the Sunseeker shown he
=20
=20
=20
http://www.solar-flight.com/
=20
=20
=20
However I'm not an aerodynamics expert and have no idea what the
optimu=
m=20
=20
height sound be except that its unlikely to be less than 10-15% of
the=
=20
=20
wing chord, think of the Wien for this pylon height, and that its
one=
=20
=20
problem the Ku-4 Austria didn't suffer from.
=20
=20
=20
martin@ | Martin Gregorie
=20
gregorie. | Essex, UK
=20
org |
=20
=20
=20
A bit of number-crunching suggests something like 0.5-1 root chord, so
1-=
2 feet for a typical single-seater.