It appears that the idea is to minimise structural mass where
wingspan isn't an issue. Not applicable to span limited contest gliders.
No big deal here. The thing isn't tailless - it has two horizontal
stabilisers, one on each wing tip.
The proverse yaw thing is obvious as the tip section is lifting
downwards. Deflecting the aileron up increases the downforce so
increasing the induced drag that side.
I sat in the SB13 about a week before its first flight. I hear it has
handling problems that were never really satisfactorily resolved. One
issue was when they first flew it with forward C of G the low moment
of inertia about the spanwise axis caused it to try to line up with
the relative wind very easily so entering a thermal caused a marked
nose down pitch which the pilot needed to correct. If you've ever
entered a strong thermal in a conventional glider you may have felt
"the thermal lifting the tail". It isn't. It is just the glider
trying to line up with the new relative wind, now coming from below
the horizon. So if you've been taught to fly attitude (ie the false
notion that attitude determines airspeed only true under limited
circumstances) this is when you pull back on the stick. If you do
this too quickly you may stall the glider as the thermal has already
increased the angle of attack.
In 1983 at the Reno SSA Convention Dr Ilan Kroo, an aero professor at
Stanford, gave a talk about possible unconventional glider
configurations. He compared conventional with tailless and canard and
came to the conclusion there was no performance advantage to be had
but that the unconventional configurations would likely have some
handling issues. His one commnet re conventional gliders was that he
thought the tailplanes should be higher aspect ratio.
Mike
At 09:56 PM 7/11/2016, you wrote:
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Hi All
For those that read the article on NASA's Prandtl-D flying wing
model in the July-August edition of 'Gliding International', the
NASA technical paper on the wing span loading is at:
<http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20160003578.pdf>http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20160003578.pdf
The concept of proverse yaw (ie the opposite of adverse yaw) from
the ailerons is fascinating.
Regards
Anthony
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