Increased life expectancy for Antares drive battery

On Dec 11, 11:53*am, wrote:
I like the planform. A little retro, a little contemporary - plus you
gotta have forward sweep unless you want the back seater to sit on the
spar. The Duo planform is similar, with the tips swept back. The Arcus
seems a bit more radical in the sweep changes, but that could just be
due to a narrower chord, which it appears to have.

9B

Agreed, although I'm not sure I find it aesthetically pleasing (says
the man with a Russia AC-4 for sale!)... I'm betting the change in
wing-sweep on the outboard sections is to reduce twist loads and
improve the behavior/control-authority at the stall - but that's just
a guess from an amateur aerodynamics enthusiast. :-P Also, I'm
betting it would be weird to try to fit winglets onto a tip that is
swept forward.

Very cool, though! The future is now...

--Noel
(who is betting that electric prop-jobs will be much easier to qualify
and get insured than Jets, for the foreseeable future; at least in the
USA)

On 11 Dec, 16:32, Greg Arnold wrote:
Andreas Maurer wrote:
On Thu, 11 Dec 2008 09:16:01 -0600, "Paul Remde"
wrote:

Cool!

A very kind r.a.s. friend sent me a PDF with drawings of the Arcus. It looks
great!

Beauty is in the eye of the beholder... I still cannot get used to
this wing planform.

A 3-side view can befound he
http://ukjuniors.blogspot.com/2008/12/new-duo.html

... although I don't know if it's already an official drawing.

Bye
Andreas

Is there a higher resolution drawing out there?

Interesting that the first announcement of a new SH product appears on
the Lange webpage.

Two friends of mine, one in Scotland and one in the US, have received
notification about the Arcus direct from the Schemmp-Hirth factory
saying that it would be available in pure glider, turbo, self
launching (I presume conventional engine) and electric self-launcher
versions. So the Lange website wasn't entirely the first
announcement.

What interests me is not the wing planform (which I like) but whether
they use a Ventus-type aerofoil section or do they have a new flapped
section - something that could lead to a new version of the Ventus???

John Galloway

Andreas Maurer wrote:

Beauty is in the eye of the beholder... I still cannot get used to
this wing planform.

Form follows function, I would hope.

I think it looks nice, here is hoping if handles as nice as a Duo
(good for it's size) ...

If I had one on order I'd definitely let my friends fly it. And I hope
the person with one order I know thinks same way :-)

Darryl

On Dec 11, 12:00*pm, "noel.wade" wrote:
...I'm betting the change in
wing-sweep on the outboard sections is to reduce twist loads and
improve the behavior/control-authority at the stall - but that's just
a guess from an amateur aerodynamics enthusiast. :-P

There are many possible reasons for the tip treatment. One possible
reason is aeroelastic as forward sweep can lead to unpleasant flutter
characteristics due to a positive relationship between wing bending
and AOA - though it doesn't seem to cover enough of the span to do
much. Another possibility is to influence spanwise flow at the tip and
reduce vortex losses. Thene there may be weight and balance and/or
handling reasons as you mention. Or maybe they though it looked cool.

9B

On 12 Dec, 17:31, wrote:
On Dec 11, 12:00*pm, "noel.wade" wrote:

...I'm betting the change in
wing-sweep on the outboard sections is to reduce twist loads and
improve the behavior/control-authority at the stall - but that's just
a guess from an amateur aerodynamics enthusiast. :-P

There are many possible reasons for the tip treatment. One possible
reason is aeroelastic as forward sweep can lead to unpleasant flutter
characteristics due to a positive relationship between wing bending
and AOA - though it doesn't seem to cover enough of the span to do
much. Another possibility is to influence spanwise flow at the tip and
reduce vortex losses. Thene there may be weight and balance and/or
handling reasons as you mention. *Or maybe they though it looked cool.

9B

All SH gliders since the Discus have had swept back outer wing
planforms - following Will Scheumann's deduction that it would reduce
induced drag ( on his cut down ASW 12 wings). The heart-warming thing
about that was that he worked this out logically, but non-
mathematically, from consideration of the likely relative pressures at
adjacent spanwise stations - and had the courage of his convictions to
modify his glider accordingly to prove it.

.... but for me the most important reason for having the sweep backs is
that, from some viewpoints, a wing with a step change in dihedral
gives the illusion of there being a aesthetically clumsy sweep-forward
if there is not a sweep-back at that point. Walk round a DG 1000 to
see this effect at the near-tip dihedral

http://www.dg-flugzeugbau.de/Data/dg1000-6.jpg

Once the designer has got the planform as close to ellipticaI as is
practical there are extra induced drag gains to be made from going out
of plane with progressive dihedral change. Add to that the Scheumann
effect and the aesthetic desirability of sweep back and the modern SH
wing emerges.

John Galloway

On Dec 12, 9:31*am, wrote:

There are many possible reasons for the tip treatment. One possible
reason is aeroelastic as forward sweep can lead to unpleasant flutter
characteristics due to a positive relationship between wing bending
and AOA - though it doesn't seem to cover enough of the span to do
much. Another possibility is to influence spanwise flow at the tip and
reduce vortex losses. Thene there may be weight and balance and/or
handling reasons as you mention. *Or maybe they though it looked cool.

9B

While we're having fun with speculation: I've helped Brad and Bob a
bit on a few of the HP/Glidiar bits; and Brad and I have gone through
a few design processes on potential glider projects in the future
(think something between an Apis and an LS-8, with provisions for
non-2-stroke-motor self-launching systems)... Bottom-line: I'm an
amateur, but I've studied a lot of the basic aerodynamics and design
stuff out there, and have some hands-on experience with laying up
composites molds and molded parts.

I've looked at the manufacturing complexities involved in a multi-
segement or "bent" main spar (with wings that have multiple taper-
breaks and thus a different chordwise airfoil thick-points where the
spar would tend to be placed), and it seems to me that you need to
have a really good reason, before you start introducing all of those
extra calculations and production hassles. Plus, at each bend in the
spar you have the potential for stress-concentrations as the loads
have to be taken a slightly different direction - and the lift forces
being places on the spars at different angles to each other can induce
torsional effects that you have to take into account... You could
design your system with this in mind - for example to induce wing-
twist at different speeds - but again you're increasing the complexity
of the system, so there had better be a good pay-off! Obviously top-
end racing machines are going to be trying to squeeze every last % of
performance they can, but you still have to look at return-on-
investment; and influencing spanwise-flow / wingtip vortices can be
done more simply with airfoil selection, simpler taper-changes, and
simple well-desiged winglets. And in regards to CG - couldn't you
just take a couple of degress of sweep out of the whole wing to adjust
that, rather than mess with the outboard wing panels and all of the
issues mentioned above?

Whatever the reason, its certainly an interesting development!

Take care,

--Noel

On Fri, 12 Dec 2008 09:31:19 -0800, ablackburn6 wrote:

Or maybe they though it looked cool.

The Duo and the Arcus 3-view both look very like a gannet in flight. I
mean the sea bird, not the Fleet Air Arm turboprop toy.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

All SH gliders since the Discus have had swept back outer wing
planforms - following Will Scheumann's deduction that it would reduce
induced drag

As this thread started with the Antares: Somewhere on their homepage,
Lange claims that theoretically the best wing shape is a super-ellipsis.
And that's what the Antares got. Incidentally, the Disci (single and
duo) wings come pretty close.

Read more about the ARCUS E option he
http://lange-aviation.com/htm/englis...e/arcus_e.html
/Lars