Re: Gliders to fliers

["Martin Barnett" <martin.barnett3@virgin.net>]

James Cunningham wrote:
> 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.
<snip>

I appreciate that, but with regards to the non-canard adaptations you
mentioned that are at the disposal of aircraft, this is not an option
animals have in mastering flight or if they do it has been ruled out for
birds already.  ie, the stabilising mechanism on the SR71 Blackbird is
almost directly comparable to that fore-limb to hind-limb patagium on
gliding mammals that started this thread - the one birds don't have.  So
given the suggestion I recall that the theory went:  Arboreal with a gliding
tail and then the arms evolved, I would say the wrist to shoulder patagium
would HAVE to be implemented long before if not most of the primary feathers
as well to act as stabiliser for that ridiculously high level of lift coming
from behind coupled with there being none at the front.  This is all about
placement of the fuselage on the wings as (despite the ornithischian hip
arrangement swinging the stomach weight further back) most of the forward
end of the body including chest, sternum (if and when present) and head
would surely provide a tendency towards dropping like a stone from the air -
particularly when thinking this head is NOT keratinous, it is bone and
therefore obviously heavier.  I merely abbreviated the point with my comment
on the shortening of the fuselage/body length of birds.  Perhaps I should
have said that any lengthening made from the natural starting point birds
seem to have would be all fore of the lifting surface (reluctant to call an
animal's tail as a delta wing due to possible confusion incurred, but it
seems to be an apt analogy).  I believe my point still stands that
counteractive measures would have to be made by any animal attempting to
glide on a tail with no help from it's forelimbs, namely reducing the length
of it's body as this would surely alter the amount of weight fore of the
lifting surface.  This might help matters but when I think about it it may
well not help enough.  This would seem to stand in the way of parsimony in
the Tail first then wings theory especially when you think the creature
would instinctively spread it's arms wide enough to catch itself when it
landed anyway (assuming of course that protodromaeosaursinstinctively behave
like every other four-limbed animal when thrown through the air for the
first time, but I THINK I can say that's a given).  What's the grounding (no
pun intended) for the tail first then wings theory anyway?  Is it, tail
developed as display feature to attract mate, while feathers being
cumbersome and in the way were not implemented until proven necessary during
flight?
Yours,
           Samuel Barnett

Nothing like a cat among the pidgeons to prove which ones cannot fly