Haak effect blijft nog even haken....
Even een oud draadje oprakelen. Ik las van de week in de nieuwe RCSD (1-2014) dat een elliptisch liftverdeling wel theoretisch de ideale is, maar ook bij uitslaande ailerons een haakeffect veroorzaakt. Een liftverdeling die dat niet doet, is een klokvormige liftverdeling.
http://www.rcsoaringdigest.com/pdfs/RCSD-2014/RCSD-2014-01.pdf
Citaat:
produce adverse yaw with aileron deflection. But things are different
if span constraints are relieved and a bell-shaped distribution can
be used; the wing twist can then be tailored to reduce induced drag
and produce either neutral or proverse yaw with aileron deflection.
This was shown by Ludwig Prandtl (and Robert T. Jones using a
different methodology).
Back in 2002 and 2003 we wrote a series of "On the ʼWing..." articles
dedicated to twist distributions for swept wings. Our primary source
of information on the subject was Al Bowers, Associate Director
for Research, NASA Dryden Flight Research Center. A few days
ago, Al wrote a message through the nurflugel Yahoo! group about
PRANDTL-D, a student project carried out at NASA Dryden FRC.
Al provided a link to a YouTube video, "Proving Prandtl - With A Twist"
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The Prandtl name is actually an acronym for Preliminary Research
for AerodyNamic Design To Lower Drag -or– PRANDTL-D. The wing
twist on the PRANDTL-D follows the Horten sin^2.5 approximation.
Onboard data logging is through ArduPilot with an additional card
to handle some analog inputs. Launches in the video are via old
fashioned hi-start with 45 pounds pull for the 15 lbs. airframe.
While critics have argued the Prandtl and Jones solutions lead to
a "point" design, the PRANDTL-D wing has proven to be just the
opposite. Proverse yaw is consistent over a wide range of elevon
deflections and coefficients of lift.
Is het nu misschien zo dat door de neergaande flap verder dan de aileron te laten lopen er een (grove) klokvormige liftverdeling gecreëerd wordt? En daar mee inverse Yaw? En daarmee het voordeel dat de Franse manier zou kunnen brengen?
Misschien??
.
