[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Fw: Archie a non-flyer? (was:Re: origin of bats/reply 2 to TMK)



Oops, I sent this off list to Roberto because his ms. to me was not directed to the dino list -- but, he did send a copy to the list, so I am as well.
JimC


----- Original Message ----- From: "jrc" <jrccea@bellsouth.net>
To: "Roberto Takata" <rmtakata@gmail.com>
Sent: Tuesday, June 24, 2008 8:08 PM
Subject: Re: Archie a non-flyer? (was:Re: origin of bats/reply 2 to TMK)



Offlist

----- Original Message ----- From: "Roberto Takata" <rmtakata@gmail.com>
To: "jrc" <jrccea@bellsouth.net>
Sent: Tuesday, June 24, 2008 2:51 PM
Subject: Re: Archie a non-flyer? (was:Re: origin of bats/reply 2 to TMK)



Not across the feather, but behind the feather.

You could test it with a paper sheet. Hold it horizontally with your
fingertips at midline. Push the sheet through the air. The front
middle will curl creating a turbulent airflow that cause the drag -
you will feel the air resistance to the paper motion.

Then hold the paper more proximally to the front - say, half an inch
to the front border. Now the paper will cut the air with less
drag/resistance then before.

But, the flow is turbulent in both cases, both across and behind the wing.
It's not laminar.  You may be thinking about the difference between
turbulent attached and turbulent seperated flow.

(By the way, many people say that the plane wing cross section shape
create lift, but it is not true, it just reduces drag. What create
lift is the angle of attack, if the shape of the wing was responsible
for the lift, then planes could not fly upside down.)

Actually, the camber does extend the critical angle of attack slightly, from
roughly 11 degrees for a non-cambered, flat wing up to approximately 18 for
a cambered wing. And depending upon the amount of camber, the zero lift
angle of attack goes from zero degrees to approximately a negative 3 or 4
degrees. For example, my Cherokee uses a 65sub2-415 airfoil and normally
cruises at a lift coefficient between 0.2 and 0.3, at an angle of attack of
about a negative one degree (slightly nose down). What people ignore is
that the stagnation line normally does not match the intersection of the
camberline with the leading edge.