Author Topic: Vertical stabilizers also improve roll stability  (Read 11249 times)

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Ratliff

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Vertical stabilizers also improve roll stability
« on: June 11, 2008, 07:49:29 PM »
The attached discussion illustrates how in a sideslip condition on an aircraft a vertical stabilizer aids roll stability as well as directional stability. A car skidding sideways is equivalent to an aircraft in sideslip.

Offline interested bystander

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Re: Vertical stabilizers also improve roll stability
« Reply #1 on: June 11, 2008, 09:28:56 PM »
Other than takeoff and landing, roll stablization is an annoyance, that should be able to handle with stick and rudder.

Nobody wants their landspeed machune to roll, granted, but DOES ANY OF THIS APPLY DIECTLY TO El Mirage, Maxton, Texas Mile, Bonniville, etc.? or even Interstate 15.

Who inquired about this to warrant your posting this stuff?
5 mph in pit area (clothed)

Offline SPARKY

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Re: Vertical stabilizers also improve roll stability
« Reply #2 on: June 11, 2008, 09:31:55 PM »
have you been sideways at 250??
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Ratliff

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Re: Vertical stabilizers also improve roll stability
« Reply #3 on: June 11, 2008, 09:39:54 PM »
Other than takeoff and landing, roll stablization is an annoyance, that should be able to handle with stick and rudder.

Nobody wants their landspeed machune to roll, granted, but DOES ANY OF THIS APPLY DIECTLY TO El Mirage, Maxton, Texas Mile, Bonniville, etc.? or even Interstate 15.

Who inquired about this to warrant your posting this stuff?

Bluebird, Mark II.

Ratliff

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Re: Vertical stabilizers also improve roll stability
« Reply #4 on: June 11, 2008, 09:43:30 PM »
Other than takeoff and landing, roll stablization is an annoyance, that should be able to handle with stick and rudder.

Nobody wants their landspeed machune to roll, granted, but DOES ANY OF THIS APPLY DIECTLY TO El Mirage, Maxton, Texas Mile, Bonniville, etc.? or even Interstate 15.

Who inquired about this to warrant your posting this stuff?

Spirit of America, 1962.

The year Breedlove didn't set the record.

« Last Edit: June 11, 2008, 09:56:08 PM by Ratliff »

Ratliff

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Re: Vertical stabilizers also improve roll stability
« Reply #5 on: June 11, 2008, 09:55:04 PM »
have you been sideways at 250??

Donald Campbell got sideways at 250 mph.

Bluebird, Mark 1.

Offline Glen

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Re: Vertical stabilizers also improve roll stability
« Reply #6 on: June 11, 2008, 10:03:46 PM »
Ask Ed or Richard of the Danny Boy streamliner. They are believers in the Vert. Stabilizer
Glen
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Offline Stainless1

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Re: Vertical stabilizers also improve roll stability
« Reply #7 on: June 11, 2008, 10:05:06 PM »

Spirit of America, 1962.

The year Breedlove didn't set the record.

 no tail on that one...  :-o
Stainless
Red Hat 228.039, 2001, 65ci, Bockscar Lakester #1000 with a little N2O

Offline aircap

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Re: Vertical stabilizers also improve roll stability
« Reply #8 on: June 12, 2008, 12:11:43 AM »
Quote
Nobody wants their landspeed machune to roll, granted, but DOES ANY OF THIS APPLY DIECTLY TO El Mirage, Maxton, Texas Mile, Bonniville, etc.? or even Interstate 15.

Salt racers aren't putting them on their cars just to get chicks.
"Act your age, not your shoe size". - Prince

Offline Rex Schimmer

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Re: Vertical stabilizers also improve roll stability
« Reply #9 on: June 12, 2008, 01:15:14 PM »
Its all about having the center of pressure behind the center of gravity. If you don't have it that way you are probably going to have some handling problems. Easy fix is a big tail fin, make it right and it will only add a very small drag penalty but a big stability addition.

Rex
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Offline Stainless1

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Re: Vertical stabilizers also improve roll stability
« Reply #10 on: June 12, 2008, 01:38:20 PM »
Most have a fin, don't think its value was disputed before or after the post discussing rolling moment.  On an LSR car, if you have a rolling moment you are already in trouble and the fin won't help.  The fin will help correct a yaw problem, I don't think any ever disputed that.  Most aircraft have ailerons and rudder to correct the problem, haven't see either on an LSR car.
Stainless
Red Hat 228.039, 2001, 65ci, Bockscar Lakester #1000 with a little N2O

Ratliff

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Re: Vertical stabilizers also improve roll stability
« Reply #11 on: June 12, 2008, 03:33:37 PM »
Most have a fin, don't think its value was disputed before or after the post discussing rolling moment.  On an LSR car, if you have a rolling moment you are already in trouble and the fin won't help.  The fin will help correct a yaw problem, I don't think any ever disputed that.  Most aircraft have ailerons and rudder to correct the problem, haven't see either on an LSR car.

Among other factors, including airspeed, the vertical stabilizer has to be of sufficient height so that the side force it generates is far enough above the center of gravity to have the leverage for effective anti-roll. The stubby little tailfins many teams run don't have the height. However, the dynamics are explained in the graphic I included with my original post.

The Danny Boy streamliner and lakester look like they have fins with the height to generate effective anti-roll.

http://www.dannyboystreamliner.com/services1.htm

http://www.dannyboystreamliner.com/streamliner.htm

« Last Edit: June 12, 2008, 03:52:34 PM by Ratliff »

Ratliff

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Re: Vertical stabilizers also improve roll stability
« Reply #12 on: June 12, 2008, 03:35:30 PM »
Its all about having the center of pressure behind the center of gravity. If you don't have it that way you are probably going to have some handling problems. Easy fix is a big tail fin, make it right and it will only add a very small drag penalty but a big stability addition.

Rex

Correct. Until the fin has some angle of attack on it, the drag penalty is very minimal.

Ratliff

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Re: Vertical stabilizers also improve roll stability
« Reply #13 on: June 13, 2008, 10:18:50 AM »
Check out the vertical stab (and the canard wings) on the J-34 jet car Ab Jenkins was proposing in 1950.

Offline Evil Tweety

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Re: Vertical stabilizers also improve roll stability
« Reply #14 on: June 13, 2008, 04:41:13 PM »
Quote
Nobody wants their landspeed machune to roll, granted, but DOES ANY OF THIS APPLY DIECTLY TO El Mirage, Maxton, Texas Mile, Bonniville, etc.? or even Interstate 15.

Salt racers aren't putting them on their cars just to get chicks.

So any truth to the tale about the lakester (wing tank) that always spun out to the left (or maybe it was right - but consistently the same direction) when at speed?

I guess it was a wing tank where they (Airforce) had slight angle to the fin so it would spin away from the plane when ejected . . . hard to see unless you knew to look for it.

Can anyone verify?