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Re: Gliders to fliers
Martin Barnett wrote:
> .....according to Sankar Chatterjee..... Have there been any bird flight
> mechanics and evolution publications post 1997 that dispute this claim?
>
Yes.
> As an abstract thought, the only way delta-wing aircraft get away with having
> no cannards is
> by having a shorter fuselage so as not to need minor front-end lift.
>
That's not the purpose of the canard. Most aircraft achieve stability
by using a wing airfoil with a nose-down pitching moment. Conventional
aircraft resist this moment by using an aft tail to create an additional
download which is carried by the wings in addition to the weight of the
aircraft. The tail download multiplied by the distance between the
centers of lift of the two surfaces serves to create the nose-up moment
required to counteract the nose-down moment created by the wing
airfoil. Canard aircraft carry the secondary surface in front, creating
lift, plus the nose-up moment. This has the side effect of reducing the
load carried by the main wings so that it is less than the weight of the
aircraft. Delta wing aircraft that do not use a canard achieve the
ability to do so by using either an airfoil with a reflexed trailing
edge that has a reduced pitching moment, or by using large elevon
surfaces and/or leading edge devices, or all three. Fuselage length is
not particularly relevant (placement of the fuselage on the wings is, as
is the length and location of the main landing gear). In animal flight,
the fossil evidence indicates a general progression in the direction of
reduced longitudinal stability as the animals' neural systems evolved
to handle dynamic flight requirements.
As most of you know, I tend to lean toward trees-down for pterosaurs and
ground-up for birds, but I don't think the issue is resolved for
pterosaurs yet. The largest, latest ones appear to have been
constructed for launch from the ground.
Best wishes,
Jim