Rutan Catbird

Discussion in 'Aircraft Design / Aerodynamics / New Technology' started by Rik-, Sep 21, 2019.

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  1. Sep 23, 2019 #41

    Topaz

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    The canards on most of Rutan's designs are fairly highly loaded. Catbird seems to have been the exception. In fact, the story goes that many years ago one side of the canard was damaged at an airshow and they just cut it off and flew the airplane home without it. I believe it actually flew with "half a canard" for some significant amount of time.

    The (rear) horizontal tail contained the primary pitch controls (elevators) and were also the pitch trimming surfaces. As far as I know, the canards on Catbird had no movable parts or surfaces at all.
     
  2. Sep 23, 2019 #42

    Hephaestus

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    I'd never looked close... So what's the canard for then? Just to make it obviously rutan?

    OSH13_Rutan-Catbird_-Evening-Wide-Angle-Right-Front.jpg
    No hingeline no evidence it changes incidence... Dang.
     
  3. Sep 23, 2019 #43

    Topaz

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    It would allow the main wing to be slightly farther aft than it would be otherwise, without increasing trim drag from the aft tail. The canard probably also reduces total trim-related aerodynamic loads on the main wing to zero. A conventional airplane has a horizontal tail that lifts down, adding load to the main wing. On Catbird, the canard lifts up, aft tail lifts down. If the loads are managed correctly, they cancel each other out. This would result in a reduction of induced drag. While minor at cruise compared to lower airspeeds, it's still a drag reduction. The fact that the canard has no movable surfaces would make this effect strongest at one airspeed, probably the design cruise speed.

    There was a brief craze of three-surface designs with very small canards during this period, with the canard included as a "stall fuse" to give an otherwise conventional wing-tail combination some measure of stall resistance. Unfortunately, some of them proved capable of being put into a "deep stall" where the airplane stabilized in a stalled condition and lacked enough pitch control power (with the horizontal tail stalled) to get the nose far enough down to exit the stall. I very much doubt that Catbird is one of these, and I doubt it's trying to get much, if any, stall resistance from the canard itself. The long tailcone holding the horizontal tail should keep it out of the "deep stall" regime. Most of the susceptible designs were rather short-coupled between the main wing and horizontal tail.
     
    Last edited: Sep 23, 2019
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  4. Sep 23, 2019 #44

    Hephaestus

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    And it would dampen horizontal pitching moments I'd imagine. Interesting...
     
  5. Sep 23, 2019 #45

    Topaz

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    Dampen dynamic pitching motions (phugoid), certainly.

    Something that I always wondered about was how it affected stalling behavior, assuming the main wing is actually allowed to stall. The positioning of the canard would make it operate as a big-but-distant "slat", and probably delay root stall on the wing to some degree. You wouldn't want the tip to stall first (always bad), so it seems like the stall break must start just inboard of the canard tips on the main wing. Does that make a roll-off in stall more likely, or stronger than it might otherwise be?

    I don't know. I've never read a pirep on the aircraft.
     
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  6. Sep 23, 2019 #46

    Topaz

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    You can get a better idea of the (small) size of the canard on the Catbird in this picture. I know we have several people here on HBA that worked for Scaled. Any of you during the Catbird era? What was it like, and what was the motivation behind the configuration?

    Cat top by Chris Van Pelt.JPG
     
  7. Sep 23, 2019 #47

    Voidhawk9

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    [QUOTE="Hephaestus, post: 493136, member: 32093"So what's the canard for then? Just to make it obviously rutan?
    [/QUOTE]
    That would be a very un-Rutan thing to do. :D
     
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  8. Sep 23, 2019 #48

    mcrae0104

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    If it didn't have whiskers, it wouldn't be a Catbird, would it?
     
  9. Sep 23, 2019 #49

    Rik-

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    Anyone notice the cooling air seems to enter from below and exit above the cylinders?
     
  10. Sep 23, 2019 #50

    Speedboat100

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    Interesting bird...little slower than Mike Pateys Turbulence but a noble attempt.
     
  11. Sep 23, 2019 #51

    Rik-

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    31% slower with 1/3rd the power
     
  12. Sep 23, 2019 #52

    bmcj

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    Different roles.
     
  13. Sep 23, 2019 #53

    Voidhawk9

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    Different eras!
     
  14. Sep 23, 2019 #54

    Speedboat100

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    Somehow I get the picture that none of the Rutan aeroplanes were really fast..but endurance was his thing.
     
  15. Sep 23, 2019 #55

    TFF

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    Efficiency. Rutan is about Efficiency. He can make you anything if you got the money. Patey built a kit and stuck a big engine on it. Catbird has a Lycoming 360 in it. The Lancair Legacy with a 360 is about the same speed, with three less seats.
     
  16. Sep 23, 2019 #56

    Rik-

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    The catbird, flew 8.5 hrs nonstop from Oshkosh to tehapai. That’s some endurance at 200 knots.

    All due respect to Mike, Mike just stuck a really big engine into a small plane. Rutan likes odd stuff a small engines. The catbird has from 180-210 hp engine (depending upon what generation it was in of its life)

    Oh, Rutan designed and built his own plane.

    He did build a Reno air racer, once again odd as all hell, had it not been for the oddball power it would have been something amazing..
     
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  17. Sep 23, 2019 #57

    Hephaestus

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    download (7).jpeg
    Pond racer is still one of my adolescent dreams ;)
     
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  18. Sep 23, 2019 #58

    BJC

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    Don’t know what the winds were, but most of that flight was at high altitudes, with ground speeds (I think ground speeds) of 200 mph or slightly less for most of the trip. Data from one of the flight trackers,
    IIRC, Rutan did not define the configuration; Mr. Pond did. I have doubts that it would have been successful as an Unlimited category racer back when there were some serious unlimiteds.


    BJC
     
    Last edited: Sep 23, 2019
  19. Sep 23, 2019 #59

    Hephaestus

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    You know... Looking for the pond racer picture.

    Anyone remember this rutan paper design?
    122-01.jpeg

    The "popular mechanics scorpion" ?
     
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  20. Sep 23, 2019 #60

    Rik-

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    It was far ahead of its time. Had they not insisted upon the V6 Nissian motors it would have succeeded I feel.

    Of course today unlimited racers are a static display as it’s priced itself out of reality with the limited engine parts available and the limited aircraft supply they simply can’t afford to risk a 2mil plane at a under paying race event.
     

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