Old vs New Cessna Vertical Stabalizers???

Discussion in 'General Experimental Aviation Questions' started by Southron, Jun 17, 2012.

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  1. Jun 17, 2012 #1

    Southron

    Southron

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    Way back in the 1950's Cessna 140's and some of the early 150's came with a a fairly conventional (for the times) vertical stabilizer. Then sometimes in the early 1960's Cessna started putting "Swept Back" vertical stabilizers on their airplanes-kinda like a much smaller version of the vertical stabilizer found on the then new Boeing 707 Jetliners.

    SO MY QUESTION IS: Does the "Swept Back" vertical stabilizers on Cessna's have any practical, AERODYNAMIC VALUE?

    From a purely practical point of view, WHICH IS BETTER, the "old fashioned" vertical stabilizers found on the 1950's Cessna's OR the more recent "Swept Back" vertical stabilizers?

    Inquiring Minds would like to know!

    THANKS!!!!!
     
  2. Jun 17, 2012 #2

    aviast

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    I've read a bunch of articles about the history of the 172 and they always said the tail was swept for marketing purposes. Call me old-fashioned, but personally I prefer the unswept tail and straight back!

    Here's an article: http://www.greencavedesigns.com/elsethhomepage/skyhi/Reviews/Cessna 172 Jan 2002.pdf

     
  3. Jun 17, 2012 #3

    Max Torque

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    No aerodynamic value.
    I have a fair amount of time in both and the"straight tail" (unswept) Cessnas have more rudder authority and they don’t have what I call “nose arching” with rudder inputs like the swept tails. Hop out of one right into another, and it's definitely noticeable. After several different planes, I bought an old straighttail 172, put a Sportsman STOL kit & baggage door on it, re-configured/upgraded the panel, and never looked back. Building a two-seat tandem bush plane now, but that's to compliment the 172 & for bush work, not to replace it.
    Tom
     
    Last edited: Jun 17, 2012
  4. Jun 17, 2012 #4

    wsimpso1

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    According to the textbooks and research pubs, sweeping subsonic surface reduces its effectiveness and lowers its stall AOA.
    When Cessna swept the tails on 152's, 172's, and 182's, they enlarged the tails to makeup for the sweep, so you got more area (more drag) to approach the same effectiveness... Then there are the many people who have flown both. Every one of them I have heard talk about it, have acknowledged that rudder response and yaw damping is superior with the straight tails.

    In our subsonic airplanes, straight (not swept) is the way to put on wings, canards, and tails.

    Billski
     
    Last edited: Jun 24, 2012
  5. Jun 17, 2012 #5

    autoreply

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    On top of Billski's comment, search for tail sweep on HBA for a lot more discussion. Swept fins are notoriously lousy in spin behavior...
     
  6. Jun 17, 2012 #6

    TFF

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    The straight back straight tales are faster with the same engine than the swept greenhouse back. The greenhouse actually does the hurting of performance although, the straight tail has a hair more control. There is a one year 172 with the straight back with the swept tail and that is the fastest 172 made before all the modern ones with the big engines.
     
  7. Jun 17, 2012 #7

    Detego

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    I've always preferred the Stinson over the Cessna 120/140/150 (fast back), but do like the round tails on both models.

    Stinson 120
    05sanbp.JPG

    Cessna 120
    ce120-03.jpg


    Cessna 140
    cessna140_nc89109_airportda_kp.jpg


    Cessna 150 - In 1966 Cessna redesigned the tail to sweep back.
    1977.gif
     
    Last edited: Jun 18, 2012
  8. Jun 17, 2012 #8

    Battson

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    I understand that those who are really working to the limits (backcountry) prefer straight tail because you get more control authority, compared to swept...
     
  9. Jun 18, 2012 #9

    Southron

    Southron

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    THANKS EVERYONE FOR YOUR REPLIES!!!!

    While I have flown a Lot of Cessna 150's and 172's with the "Swept Back" vertical stabilizers, but I have never had the chance to fly an earlier "Straight Tail" Cessna. I had a sneaking suspicion all along that the Swept Back Tail was more for "Marketing purposes" than aerodynamics. Too bad Cessna doesn't offer a "Straight Tail" Option on their new models!!!
     
  10. Jun 18, 2012 #10

    Dan Thomas

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    That's a 120 or 140. This is a Stinson 108:

    1299-paulaswiftN8299K-2.jpg

    Dan
     
  11. Jun 18, 2012 #11

    Detego

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    Thx Dan.


    1947 Stinson 108-2 ;)

    Stinson 108.jpg
     
  12. Jun 18, 2012 #12

    Detego

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    Aero Commander 100 Darter took the tail to the opposite extreme; ala Mooney.

    1967_Aero_Commander_Darter_100_433400842a8175405385_7.jpg
     
    Last edited: Jun 18, 2012
  13. Jun 18, 2012 #13

    bmcj

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    I've seen some Darters with swept tails too, so Cessna must not be the only company to sacrifice good design to marketing demands.
     
  14. Jun 19, 2012 #14

    Nickathome

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    The club I used to belong to had a 1956 straight backed, straight tailed 172, and also a straight backed, swept tail, and I can't recall any difference in rudder auithority in either one to be honest.

    The swept tail was definitely a marketing ploy, especially in the 150. It was meant to make it appear sleaker/faster. I personally prefer the look of the swept tail over the straight tail birds. To me a 150 with straight tail just doesn't look right.....
     
  15. Jun 19, 2012 #15

    Norman

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    I don't think a swept forward 1/4 chord tail is a sacrifice at all. sweep back makes the lift curve per alpha shallower and the spar may need to be a bit heavier but swept forward doesn't have those effects because the spar can be 90 degrees to the fuselage and the aerodynamic sweep effect is dependent on leading edge sweep not 1/4c. If you compare two tail fins of the same height and area, one constant chord and the other tapered the tapered one has a lower bending moment (which translates to lower torque on the aft fuselage) and a thicker root (assuming that it has the same airfoil section at both ends) which means either a lighter or sturdier tail. Mooney got it right!
     
  16. Jun 19, 2012 #16

    BBerson

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    Sweep does increase the tail moment arm, doesn't it?
    BB
     
  17. Jun 19, 2012 #17

    Detego

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  18. Jun 19, 2012 #18

    bmcj

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    Sorry... should have made my statement more definitive. I meant that I've seen Darters with rearward sweep on the fin/rudder.
     
  19. Jun 19, 2012 #19

    Norman

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    Well that would be a sacrifice to style. The tragedy is that somehow most designers seem to think that Mooney has a trademark on the forward swept fin.
     
  20. Jun 19, 2012 #20

    autoreply

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    I'm admittedly nitpicking, but wouldn't that be the quarter chord point?
    Yes, but if you do the math (for a Cressna), it's really infinitesimal if you figure in taper and decreased dCl/dAlpha for a typical SEP. For a T-tail it makes a lot of sense though, since you displace the complete H-stab. For twins (and thus also airliners), it's a much bigger effect since you need so much more fin area.
     

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