Rutan Ski-gull

Discussion in 'Aircraft Design / Aerodynamics / New Technology' started by lear999wa, Mar 31, 2013.

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  1. May 29, 2013 #21

    BBerson

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    Re: Rutan outa clue ?

    I don't see how a canard lifting the front is any different than an aft tail pushing down in water. In either case the aircraft rotates around the CG. The floats tails would sink in either case.
    But a canard can't really use flaps. Slow speed lift with flaps is nice.
     
  2. May 29, 2013 #22

    DangerZone

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    Re: Rutan outa clue ?

    Well there could be a difference... The tail deflects the control surfaces upwards so it is pushed down. The canard should push the control surfaces down so the air flow would lift it up. Yet, if water gets in the way the canard will have problems getting the nose up...
     
  3. May 29, 2013 #23

    autoreply

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    Re: Rutan outa clue ?

    But by definition (otherwise it'd be a tailsliding deathtrap) considerably above stall speed. That makes your TO run very long...

    Sailplane-like wings are perfectly suitable for an amphibian. It's dihedral and wing clearance that's relevant, not the AR of the wing. Long, slender wings are a bit easier to fold as weld. A folded high-AR wing beats a short stubby wing any time with water operations...
     
  4. May 29, 2013 #24

    DangerZone

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    Re: Rutan outa clue ?

    That's all true, yet the transition between gliding and floating successfully is the biggest obstacle to overcome...

    Unlike land where a glider's wing would merely touch ground or bounce off the little wheel/sliding surface attached underneath the wingtip, water has a 'gluing' element which many people are unaware of. Once the wingtip of this glider would merely touch the water surface it would be held by a tremendous physical force, spinning the aircraft instantly in many unknown and uncontrolled directions.

    When talking about water surface landing, people usually have the idea of perfectly still water, flat, an ideal landing strip like a wide smooth flat concrete runway. In reality, it never is so. It is curvy, bouncy, sticky, moving, sliding in all directions, it is a nightmare for landing if the design lacks a perfect bottom.
     
  5. May 29, 2013 #25

    topspeed100

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    I agree Burt Rutan is pretty objective about future...and on the contrary Al Gore actually scares people to death with his scientist reports claiming about new ice age due to melting of the ice caps...I figure the fact is somewhere in the middle...how much into Rutan or Gore direction ?...God only knows.
     
  6. May 29, 2013 #26

    Daveed'

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    let's out rutan rutan. he likes the boomerang. that could be the planform. my symetrical brainbag like a p38 setup. one more structure. wing panels of 15' and 5' times two=40'. center cab for main floatation, outer booms for skis and motor and steady state floatation. use the ic-gen-propmotor thread . rutan has done this before, on the bipod. put the props to suit your fancy. i like tails and wingtips. tailskis and mainskis. just before TO you're up on 4 skiis. i don't know how to handle rotation except for a canard or retracting tail skiis. tailfeathers to be typical rutan. all foam and glass ala the quickie. cheap and fast and fast to build, and rugged and seaworthy. that's my two cents worth. anybody got a dime? Daveed'
     
  7. May 29, 2013 #27

    autoreply

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    A double-fuselage is almost incompatible with trailerable/fits in a garage, see the BiPod. Can't imagine how to get props that are in a fuselage/boom high enough to clear the water.
     
  8. May 29, 2013 #28

    BBerson

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    Long wings tend to weathercock worse. This is a problem for seaplanes. Even the DHC-2 Beaver, which was designed from the start to be a seaplane, could use more rudder/fin. Long wings require long tails = added weight.
     
  9. May 29, 2013 #29

    captarmour

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    just the other day i was thinking exactly that imagining a see saw and thinking the weight pushing down has to be equal to the weight pushed up to balance, so if i pull up i am accomplishing the same...or am i? what about the weight felt at the pivot. if i were to pull up instead of push down would not the pivot point feel less weight than if i pushed down?

    i tend to think that a sea era type but with high wings and a wider waterwing/lifting body will be ideal for a sailplane like amphib. the wingtip pontoons would not be used except for 'unusual attitude'. another point of view is basically a biplane with lower delta wing with narrow center and wingtip pontoons coupled with a high aspect ratio high wing.
     
  10. May 29, 2013 #30

    Jay Kempf

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    There was a Korean or Vietnam vintage fighter/interceptor that had a wing that could be jacked up to a higher angle of attack for carrier operations. Why don't seaplanes either have massive flaps and or tandem with massive flaps to just fly off level instead of rotating. The B52 is an example of a plane that doesn't rotate on takeoff. With massive flaps and a lowish wing position it seems you could transition from planing boat to WIG to flight. Returning to WIG and then settling for landing makes sense. Of course it takes more distance so it isn't good for a bush plane maybe but other than that?
     
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  11. May 29, 2013 #31

    captarmour

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    with a low wing loading and good design it need not have a long TOR
     
  12. May 29, 2013 #32

    Holden

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    The idea of using long wings to avoid the medical issues is the driving point to Rutan's ski-gull design. I am also looking into it for the same reasons. We all will be without a medical at some time in our lives.

    As some of you may remember, the Sea-Era crashed twice. Both times the wing tip was the "catch all" of the design. The flat faceted hull prevented it from flipping over and being destroyed.

    If you slow-watch the Rutan video you can get a picture of the layout. It did not have a canard. There are two floats lateral for a three hulled design. The center hull has a long nose out front and the shape is...curved...very unlike a Sea-Era.

    Said another way, in a Rutan design you will likely only get one crash...

    Rutan is right, seaplane design is much harder than land airplane design. The ski idea is not new and there are several other airplanes attempting to use them, myself included.

    In short the ski-gull should be interesting. It is, however, not roadable, and therefore will be limited in production and use.

    It is interesting that Rutan gets to the most difficult design after retirement. What if he would have focused on seaplanes first and not wasted time making airport land locked airplanes what his career would have been like. We don't need 20 airplane designs that cannot go into production, we need ONE that works in the real world of life.

    Basically what Rutan has is a seaplane with a long wing, three hulls, T tail in back, lateral twin engines, large flaps behind the props, all mounted on air retractable skis with urethane "roller blade" wheels you can fit in your pocket. The hull is round and the ski comes out and takes the shock of water loads.

    BTW, it is not WIG able.

    Holden
     
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  13. May 29, 2013 #33

    bmcj

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    Re: Rutan outa clue ?

    Have you been to Six Flags Magic Mountain? Lots of kids pay good money to go on rides like you just described! ;)
     
  14. May 29, 2013 #34

    harrisonaero

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    Holden gets the gold star for figuring out the real reason the SkiGull has long wings :)
     
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  15. May 29, 2013 #35

    Jay Kempf

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    Rutan mentioned in the video that the concept was a solution to his loss of medical. So stall speed and overall weight as well as overall complexity started the compromises.

    I watched the video but couldn't really get a good still of any major portion of the screen.
     
  16. May 29, 2013 #36

    harrisonaero

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    Nope, nothing to do with stall speed and complexity. Purely span loading to make it a two-place or less powered glider and a weight under 850 kg. At least that's what can be inferred from the video :)
     
  17. May 29, 2013 #37

    BBerson

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    Re: Rutan outa clue ?

    Are you saying Burt's medical was denied, so he can't fly sport pilot without the medical but can fly a motor glider?
     
  18. May 29, 2013 #38

    harrisonaero

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    I'm not saying anything other than what was inferred in the video which is that it's a powered glider.
     
  19. May 29, 2013 #39

    autoreply

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    Do you recall around which minute/second approximately?
     
  20. May 29, 2013 #40

    Daveed'

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    autoreply..ski gull fits in the garage according to rutan. a craft like this need not be trailerable or even garageable imho, and the outer panels come off. tractor props to be mounted on each rudder,above the fray. and one on each wingtip, for yaw on water.
    . b berson. this should take care of windage and docking, and when unmoored all the way thru TO and beyond. selectable wingtip thrusters of small prop diameters, tied to aileron stick. they are really for roll control after TO. daveed'
     

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