Vertical stabilizers

Speaking of below 250 knot aircraft, does it really matter much what shape
they make the vertical stabilizer?

They seem to come in all kinds of shapes... de Havilland favored
elliptical, Cessna favors a swept back trapezoid, Mooney swept forward...
etc.

Aerodynamically speaking, what difference does it's shape make? I guess
sweeping back creates a bit less drag than straight vertical. But other
than that, we're not generating induced drag because it's not generating
lift. It seems like area should be the only consideration.


--
Dallas

On Feb 18, 2:02*pm, Dallas wrote:
Speaking of below 250 knot aircraft, does it really matter much what shape
they make the vertical stabilizer?

They seem to come in all kinds of shapes... de Havilland favored
elliptical, Cessna favors a swept back trapezoid, Mooney swept forward...
etc.

Aerodynamically speaking, what difference does it's shape make? *I guess
sweeping back creates a bit less drag than straight vertical. * But other
than that, we're not generating induced drag because it's not generating
lift. *It seems like area should be the only consideration. *

--
Dallas

I don't know that sweep reduces drag. It just looks faster.
Sometimes it appears swept because it's tapered and the trailing edge
is vertical. And a tapered vertical tail can be made lighter and have
less "tip" drag. Cessna's swept tail supposedly helps hold the nose up
a little in a turn if the rudder is deflected, but it would be a
minimal contribution, I think.

The old rounded tails were easy to make with small steel tubing
and fabric; lots harder with sheet metal. Rounded shapes were popular
in those old days--just look at the cars of the '40s. Angular shapes
were popular in the '60s and '70s, just like the cars of the day, and
airplanes were angular, too. Which mostly means that style sells
airplanes more than functionality.

Dan

Aerodynamically speaking, what difference does it's shape make?

I'm no aerodynamicist, so I can't offer hard numbers, just some thoughts:

As the stabilizer is a wing like any other wing, its shape will matter
as the shape of any wing.

Aerodynamics in coordinated flight is only part of the story.
Particularly spin recovery is crucial, which depends highly on the
airflow on the rudder, which in turn depends on a lot of things, e.g. on
the the shape of the horizontal stabilizer and the horizontal rudder
position.

Aesthetics certainly matters, too.

On Feb 18, 1:02*pm, Dallas wrote:
Speaking of below 250 knot aircraft, does it really matter much what shape
they make the vertical stabilizer?

They seem to come in all kinds of shapes... de Havilland favored
elliptical, Cessna favors a swept back trapezoid, Mooney swept forward...
etc.

Aerodynamically speaking, what difference does it's shape make? *I guess
sweeping back creates a bit less drag than straight vertical. * But other
than that, we're not generating induced drag because it's not generating
lift. *It seems like area should be the only consideration. *

--
Dallas

Obviously the Mooney design is faster.

Robert M. Gary wrote:

Obviously the Mooney design is faster.

I had one owner explain to me that the tail on the Mooney was indeed
faster as the tip vortices ended up comming off the bottom of the
vertical stablizer. The air down there was already churned up by
the fuselage and so less air was disturbed than otherwise would be.

Personally the fastest thing would be to get rid of the vertical stabilizer.
Hmmm, now what kind of a plane would do that....

--
Frank Stutzman
Bonanza N494B "Hula Girl"
Boise, ID

Personally the fastest thing would be to get rid of the vertical stabilizer.
Hmmm, now what kind of a plane would do that....

Horten, for example: http://www.youtube.com/watch?v=GjXr5w3M4mc

"John Smith" wrote in message
...
Personally the fastest thing would be to get rid of the vertical
stabilizer.
Hmmm, now what kind of a plane would do that....

Horten, for example: http://www.youtube.com/watch?v=GjXr5w3M4mc

And, of course, the B2 Spirit: http://www.youtube.com/watch?v=IdbpMOWGYGk

On Sat, 20 Feb 2010 00:46:03 +0000 (UTC), Frank Stutzman wrote:

I had one owner explain to me that the tail on the Mooney was indeed
faster as the tip vortices ended up coming off the bottom of the
vertical stablizer.

But a vertical stabilizer is not going to generate a tip vortice.
(disclaimer: as far as I know)

The vortices are generated by unequal pressure on opposing sides of an
airfoil. A vertical stabilizer in coordinated flight would have equal
pressure on both sides of the surface, thus no vortice.

--
Dallas

Dallas wrote:
A vertical stabilizer in coordinated flight would have equal
pressure on both sides of the surface,


Just askin', but is that always true? In a turn, even if coordinated, is
there not a force against the vertical stab causing it to act as a
keel
to help maintain lateral stability?

On Mon, 22 Feb 2010 17:21:21 -0700, romeomike wrote:

Just askin', but is that always true? In a turn, even if coordinated, is
there not a force against the vertical stab causing it to act as a keel
to help maintain lateral stability?

(Disclaimer: I don't claim to be an aeronautical engineer, but I like the
subject.)

To me, coordinated is coordinated. Sure, there are micro disruptions that
try to produce a yaw that the vertical stabilizer is called upon to resist,
after all, that's why it's there.

But, in a coordinated turn, the goal is to balance the pressure on both
sides of the stabilizer.

Have you ever seen those short strands of yarn some glider pilots tape to
the front of their canopies? The goal is to keep the strand straight down
the centerline during a turn which can only be accomplished if there is
equal airflow on either side of the hull.


--
Dallas