Rutan Ski-gull

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

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  1. Nov 24, 2015 #141

    harrisonaero

    harrisonaero

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    First flight was from a runway.

    No maximum speed test for first flight- lots more testing before it gets there. ["Gradatim Ferociter": in honor of another <much higher> first flight that also took place yesterday.]

    Engine is a 912iS for now for simplicity. Turbo comes later. Flew for about 1.8 hours and burned just over 3 gallons of Swift fuel. Amazing engine.
     
  2. Nov 25, 2015 #142

    max_burke

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  3. Nov 25, 2015 #143

    MaverickSawyer

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    Broken image link. Comes back with a message of "Unauthorized". But yeah, there is a tailwheels of sorts, and given the short-field performance of the design, those little wheels are all you need.
     
  4. Nov 25, 2015 #144

    max_burke

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    Apologies, I should have re-hosted it. Here is the picture to which I was referring:

    [​IMG]
     
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  5. Nov 25, 2015 #145

    harrisonaero

    harrisonaero

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    Credit for that shot needs to go to Scott B of Antenna Films (also did Black Sky). We had the window in the C182 wide open (up against the wing) and were freezing our tails off for the photos :) Tom Hamilton was flying and did a fantastic job of keeping "down" with the SkiGull since much of the flying was really slow and quite a bit below the stall speed of his loaded C182. The stall horn was going off for a large portion of the flight and Tom still did very controlled s-turns to keep us in chase formation. Pretty much everything Tom does he does with excellence.

    Check out the Kickstarter page if you haven't already- the film is going to be great. Scott and Sandy have lots and lots of footage that will be really interesting to anyone that loves innovation and aircraft technology.

    https://www.kickstarter.com/project...-up-way-up-the-burt-rutan-story/posts/1424377

    Looking Up, Way Up! | The Burt Rutan Story
     
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  6. Nov 25, 2015 #146

    harrisonaero

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    Ok, Tonya just posted this so I think I can now share here...

    ++++++
    The Good, the Bad and the Beautiful by Burt Rutan

    I have been waiting a long time to provide this update - the 47th new type of Manned Aircraft, designed by me or produced by one of my companies, has now flown! Just in time, since we got our first North Idaho snow just hours after the flight.

    While I do plan to continue designing new airplanes, the SkiGull is the very last airplane that I will be personally involved in building. I built SkiGull in my garage starting 20 months ago and it was a grueling exercise for an old guy in his 70s.

    While I will finish the modifications and testing needed to find if SkiGull can reach the goal of being able to handle rough water, ocean swells, beaching on ocean coasts and operating from snowfields, I will not again expose myself of the challenge of laying up sticky composites, sanding foam and carbon fiber, staying up at night to monitor oven cures, etc. I plan to enjoy this new airplane in retirement, including its unique capabilities that combine STOL from all surfaces with ocean crossing range. It has a huge baggage compartment, so Tonya and I might even load it up for golf trips (I had quit golf 2 years ago to build SkiGull).
    I have claimed that the Most Fun anyone can have at an airport is to watch the first flight of a new type. Yesterday our test team* preflight briefed the first flight, took off from runway 06 at KCOE, flew for 1.8 hours and landed back on 06. The aggressive test card** included all the basic stability and control flight tests with the cruise configuration and with flap down and skis extended. All maneuvers on the card were performed on this First Flight. Speeds for first flight were limited to less than 80 knots and altitude to less than 8,000 ft.

    * Test pilot, Glen Smith: Tonya’s instructor for her seaplane rating - a very experienced pilot who used to fly airshows in a PT-17 and now makes his living teaching seaplane flying.

    Chase One - Test Director, me, along with Pilot Mike Kincaid (Former Alaska State Trouper, film stunt pilot and flight examiner who awarded Tonya her seaplane Private rating) in his Super Cub on amphib floats.

    Chase Two - A Cessna 182 piloted by Aerocet’s CEO, Tom Hamilton carrying key SkiGull designer/builder of SkiGull systems Brent Regan, aero developer/DER Joa Harrison, and videographer Scot B of Antenna Films (the Black Sky Producer).

    Ground support including KCOE Airport Manager Greg Delavan, Photographer and aviation writer Mike Satren, SkiGull builder Dan Woodward, SkiGull follow-on developer Dale Martin, wife and health/happiness provider Tonya, photographer Kyle Woodward and Don Ekhoff, CEO of SeagullSolutions and water-ski record holder.

    ** Here is the test card for flight one, all the indicated maneuvers were completed in the 1.8-hour flight. The card started with a “Runway-flight with Option to go” A common maneuver at RAF and Scaled wherein the pilot plans only a short hop down the runway, and can go ahead and power up for a real flight if he is happy with what he finds on the short hop. Glen quickly concluded he had a safe airplane and he then powered up to go for altitude:

    Summary of the flight results:

    The Good News:

    Except as described below in Bad News, the SkiGull proved to have excellent Flying Qualities with no need to fix any flaw. Glen reported the airplane flew straight, perfectly in Roll/Yaw trim with hands-off. The pitch axis has light forces without PIO tendencies and excellent trim (rolling-wheel variable anti-servo tab on the all-flying stabilizer like a Cherokee).

    Three-axis static stability is good and pitch/Dutch-Roll dynamic damping are typical for any certified light plane. Phugoid damping is positive and spiral stability is neutral-to-positive. Speed stability and Maneuvering stability are excellent.

    Trim changes due to flap and skis are light and easy to control, in fact the small ski-down change is offset by the small flap change, so converting to landing configuration requires no re-trimming. Trim change due to power are less than one pound stick force.

    Stall-speed - while we wanted to be able to see the wing tufts from the Cub chase, the Cub had to do s-turns to keep from overtaking the SkiGull’s low speed testing. Clearly the SkiGull stall was lower than the Cub’s stall. Cub was 2-place with about 3 hours fuel and Skill was single place with 5 hours fuel. Its a preliminary conclusion, but having this low stall speed should give SkiGull its predicted STOL capability.

    Fuel use, for the 1.8 hours of mostly low-speed testing was less than 3 gallons! The Rotax 912iS, using the new Swift 94 MON avgas, has incredible fuel efficiency of about 0.33 lb/hp.hr at cruise power. We had no data on the engine's efficiency below 50% power, but it now looks like we still get incredible SFCs at the lower power settings. I now have even more confidence that the SkiGull will have its predicted range of over 2,300 nautical miles.

    Seat comfort noise level and visibility are excellent, particularly the forward nose down view - good view of the horizon, even at stall attitude.

    The Bad News:

    Stall characteristics, as you might expect for a low-drag, natural-laminal flow wing are not acceptable. No stall-warning buffet was observed and the first indication of stall was a roll drop-off to the right. We did not get a look at the tufts since the skigull stalled slower than the Super Cub chase, so we do not know what part of the wing caused the roll-off. This will require addition of the typical add-ons, like stall strips, vortilons or a leading edge cuff.

    During the chase airspeed calibrations, we saw relatively high Vpc errors in the pitot-static probe at low speeds due to the probe being in a suction area on the top of the nose (note in the photos, that tie-down cleat doubles as a pitot-static probe). I will have to move the probe to the wing or wing strut, outboard of the propeller wash. There is no place on the fuselage or sponson side that can be free from water ingestion.
    Even though Glenn made a smooth landing, the right ski had a de-lamination near where it was previously repaired. It is clear that I will have to make new, autoclaved skis. Glen was able to taxi clear of the active runway on one good ski and one soft ski.
     
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  7. Nov 28, 2015 #147

    harrisonaero

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    Nice detailed article about first taxi taxi tests and flight.


    Burt Rutan
     
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  8. Nov 28, 2015 #148

    cowlove

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    Any idea where the docking/auxiliary electric motors are to be mounted? I assume out on the wings? Any info other than "12hp, 27 inch folding prop, 9 minutes?"
     
  9. Nov 28, 2015 #149

    smoothwaterman

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  10. Nov 29, 2015 #150

    Doggzilla

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    No he did not...:roll:
     
  11. Nov 29, 2015 #151

    Sockmonkey

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    I still think they would have done well to use a retractable water prop.
     
  12. Dec 18, 2015 #152

    justifidejoe

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    Just thought I'd post a few photos found on EAA's website.

    It's interesting to me to see how much those fiberglass skis flex when fully loaded.
    You can see the ski delamination that occurred in the 2nd photo.

    [​IMG]

    [​IMG]

    [​IMG]
     
  13. Dec 18, 2015 #153

    Doggzilla

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    Cars have been using fiberglass springs for ages. Definitely not something new. Hes just open minded enough to make use of it.
     
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  14. Dec 18, 2015 #154

    smoothwaterman

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    One of the best things is he doesn't mind if something breaks during testing.
     
  15. Dec 18, 2015 #155

    MaverickSawyer

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    Well, isn't that the point of testing a new design? To find out what the limits of it are?
     
  16. Dec 19, 2015 #156

    harrisonaero

    harrisonaero

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    Carbon skis, not glass. The break was at a repaired area because he knew the chance of a re-design was high so didn't want to take the cost/effort to build a whole new set of skis. The next set will have a full FEA and an autoclave cure.

    One of the biggest things I've learned from working with Burt is that for prototyping unproven ideas you need to make engineering decisions based on risk/benefit. Only focus on the essentials that contribute to the immediate goal. Refinement is for later.
     
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  17. Dec 29, 2015 #157
  18. Dec 29, 2015 #158

    Tiger Tim

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    It seems that on all of Rutan's famous designs that every little element serves a purpose. Based on that could anyone comment on why the SkiGull has gull wings, how that balance at the bottom of the rudder does more good than harm (looks like it would have divergent tendencies as a water rudder), and what's going on with those weird wing tips?
     
  19. Dec 29, 2015 #159

    bmcj

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    First off, I'm only guessing here, so this may only be worth what you paid for it...

    Gull wings - I don't know. Maybe he had no choice because it was named Ski-Gull. :gig:
    It may have been done to reduce the chance of a wingtip catching the water if the wings dip, while still allowing a straight center section.

    Rudder balance - I doubt of the whole understructure moves... there is a dark area in the photo that may mark a separation between moving and fixed portions. Also, if you draw an imaginary line downward extending the hinge line, it looks like there may be just as much submerged area aft of the line as there is ahead of it.

    Wingtips - His Oshkosh presentation didn't show the bent up wingtips. Perhaps he decided he needed a little more dihedral effect and that was the simplest way to do it, plus it might give him the benefits that come from winglets.
     
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  20. Jan 1, 2016 #160

    cheapracer

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