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Vertical stabilizers



 
 
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  #1  
Old February 18th 10, 10:02 PM posted to rec.aviation.piloting
Dallas
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Posts: 541
Default 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
  #2  
Old February 19th 10, 03:00 AM posted to rec.aviation.piloting
[email protected]
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Posts: 1,130
Default Vertical stabilizers

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
  #3  
Old February 19th 10, 03:46 AM posted to rec.aviation.piloting
[email protected]
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Posts: 1,130
Default Vertical stabilizers

On Feb 18, 7:42*pm, "Morgans" wrote:


* * *I agree, at the speeds involved, sweep is all for style, not function.

That said, I have heard many people say that their old straight tail Cessnas
were faster than the later ones with the swept tail, even with the later
ones having bigger engines. *So is it the tail, or some other changes? *I
don't know, but it makes you wonder.
--
Jim in NC


Those old Cessna were faster before they stuck the back window into
the mix. The fairly sharp drop behind the cabin caused some drag,
especially on the 150. Without the window the top of the fuselage was
much straighter.

Dan
  #4  
Old February 19th 10, 09:40 AM posted to rec.aviation.piloting
John Smith
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Posts: 195
Default Vertical stabilizers

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.
  #5  
Old February 19th 10, 08:21 PM posted to rec.aviation.piloting
Robert M. Gary
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Posts: 2,767
Default Vertical stabilizers

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.
  #6  
Old February 20th 10, 01:46 AM posted to rec.aviation.piloting
Frank Stutzman[_3_]
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Posts: 29
Default Vertical stabilizers

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

  #7  
Old February 20th 10, 02:08 AM posted to rec.aviation.piloting
John Smith
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Posts: 195
Default Vertical stabilizers

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
  #8  
Old February 20th 10, 04:15 AM posted to rec.aviation.piloting
Peter Dohm
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Posts: 1,754
Default Vertical stabilizers

"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



  #9  
Old February 21st 10, 08:22 AM posted to rec.aviation.piloting
Dallas
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Posts: 541
Default Vertical stabilizers

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
  #10  
Old February 23rd 10, 01:21 AM posted to rec.aviation.piloting
romeomike
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Posts: 51
Default Vertical stabilizers

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?
 




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