Glenn
19 to 1 is not a very good L/D, the best gliders are up to 60 : 1 now.
The glider boys have a mantra " TINSFOS!" there's no substitute for
span, and a 60/1 glider has a span of around 30 metres.
Induced drag is a function of the downwash angle, and lift is a function
of downward momentum change. Lift equals mass of air deflected (by the
wing) X velocity downwards squared. Not quite as simple as that but I
hope that illustrates the point? The wing deflects a cylinder
(elliptical section) of air and the bigger the cylinder the less the
angle you need to deflect it. Trouble with tandem wings is that the
following wing has to use air already deflected by the leading wing so
it doubles the deflection and therefore doubles the induced drag.
Now, canards are not unstallable. Very stall resistant but if you do
have a stall it will be very resistant to unstalling. Known as a deep
stall, not enough pitch authority to unstall the wing. Burt's microlite
canard was very nice to fly but it was possible for a gust to stall both
wings and nearly impossible to recover. Mike Melville did recover (from
a spin) but lost around 7000 feet doing it. This is why our leader Burt
gave up on canards.
Graham
glenn crowder wrote:
> This is an incredible concept that has not been utilized IMO. The
> joined wing concept is the most efficient per NASA studies
> http://www.aoe.vt.edu/design/ikelos/ as it eliminates the draggy tip
> vortices that plague all other designs. The Stratos has
> an L/D of 19/1 and the original needed flaps to degrade the glide
> enough to allow a steeper landing approach. You have
> effective sailplane efficiency in a very compact planform. In
> addition the wings can be made much lighter as the joined wing
> at the tips adds great strength. The lower wing is totally flat with
> no dihedral making it easy to build. The upper wing needs
> no twist and uses 2 deg dihedral. Other advantages are much stronger
> pilot/passengers protection due to the cage type construction,
> wide tolerance of CG changes and greater tolerance for gusty
> conditions due to the short wings.
>
> On the sim it is possible to take off with the stick full back, just
> wait for rotation and the a/c will just climb away bobbing its
> nose with full roll and yaw control. Fully aerobatic too but pitch
> sensitivity is a little much for landing in this mode, easily
> corrected with a pitch limiter for landing. Don't see why the concept
> couldn't work for crowd killers as well as the short wings
> should allow twice as many gates at the terminal.
>
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