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Re: WING FEATHER ATTACHMENT




Michael Bruce Habib wrote:

> Firstly: Would having a discontinuous wing surface provide
> enough resistance to make any difference?

It would make some difference, but it would appear that there are flight modes
that would compensate to a large degree.

>  If the only gliding surface we are considering is distal wing elements,
> I don't see how it would make any difference.

Why not?

>  If anything, the arms would be forced back towards the shoulders,

Why?

> and the animal would twirl around.

Again, why?

> Modern gliders all use broad surfaces across all four limbs, so that the 
> braking
> force
> is applied across most of the animal and a broad membrane.

Are you referring to parachuting rather than gliding?

> Otherwise, the creature just spins.

??

>  The aim is not so much to travel a long distance but to land
> > with greater precision

Not necessarily.  The 'aim' may be something else entirely....

> Absolutely.  Gliding is not unpowered flight, it is slowed
> falling.

Er uh, I wouldn't tell a sailplane pilot that.

>  Modern gliders slow their rate of descent such
> that they have time to steer,

Modern gliders often deliberately increase their rate of descent, since it can
increase their airspeed by the same amount.  This is why racing sailplanes carry
water ballast to increase their weight and wingloading.

> are going slow enough to
> steer,

Steering force production increases with higher speeds.

> and (most importantly) don't break themselves upon
> landing.

Yup.

>  Gliding possums, squirrels, and others all show
> this same technique.  All of these gliders have very low
> terminal velocities in free-fall, thanks to the gliding
> surface.

Good gliding surfaces don't inherently produce low terminal velocity.

> That is, while it going forward more than down, the animal must land lower 
> than
> it
> takes off.

That depends entirely upon local atmospheric lift conditions.  It is quite
possible for a good glider to land higher than the takeoff, depending upon how
much energy is extracted from the atmosphere during the flight.  On some days 
even
a crappy glider can accomplish it.

> The distances are determined by the launching force and
> available vertical drop distance, not by how fast the
> animal glides.

I'd phrase this as 'determined by launching force, atmospheric lift conditions,
and available vertical drop distance, with the distance being very dependent 
upon
how fast the animal glides, with speeds diverging in either direction from the
optimum being counterproductive'. This latter is because profile and 
interference
drag increase with increasing flight speed while induced drag decreases with
increasing flight speed.

Jim