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Thread: The DoubleEnder

  1. #1
    KenyaCub's Avatar
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    The DoubleEnder

    I promised to post something about the DoubleEnder prototype, so here it is:
    This idea started to go on paper about 3 years ago. To come up with the actual concept took several years of imagination and research prior to that. The concept originated from several ideas. I've been flying cubs for a long time and like what you can do with them, but what can be improved upon? Performance, handling, visibility and safety were some of the driving factors.

    The visibility idea came from another airplane, the Partenavia P68 Observer. It's a twin engine six seater and has a bubble canopy up front. Flying in it is a lot of fun due to the extreme visibility. Visibility in a cub is such an important factor for landing off airport. Then add the performance you can get with slats at high angles of attack, but that you cannot use practically in a cub since you can't see where you're going ... and all of a sudden the bubble canopy starts to make a lot of sense. Other than the usefulness in landing and taxiing off airport, it is also a thrill to be able to see so much, right down to between your feet. It's a whole different perspective.

    The need for safety is quite obvious. One of the biggest contributing factors to accidents in a cub is a low to the ground stall/spin. The slats increase that safety margin by a lot, and give it the low speed maneouverability that is just not available without it. There's also many places I like to fly over (low), where no matter how quickly you may react, if that engine quits it's going to be an ugly day. Sometimes on long cross country's I end up taking detours just to be able to keep a safe landing spot below (highways, avoiding long stretches of water etc.) Wouldn't it be nice not to have to worry about such things? Wouldn't it be nice to be able to lose an engine, and have it be a non event where you just add some power and keep going to your destination. Wouldn't it be nice to be able to just push the direct button on the gps and fly straight to where you're going without concern of the terrain below. Hence the need for twin engine. The other safety requirement is to have a good "crash cell" around you in case of a mishap. The fuselage and engine mounts were designed to withstand some pretty strong impacts. We also incorporated a front crush cell in case of frontal impact, in order to have some buffer before getting into the main structure.

    I was hoping to have something that could fly with a cub and perform somewhat like it. It wasn't designed to be a hot-rod airplane in the first place, but somewhere along the line it ended up in that category. I like the way a cub "feels", and I was hoping to somewhat retain that. The wings and tail surfaces were left identical to a cub, and even the relative positions remained the same. The gear and wing struts are also off a cub, and in the same relative position. You could swap wings, tail-feathers, gear, and struts with a cub and it would fit right on. This was also done for ease of parts availability. I incorporated a cg that was further aft than a cub, since a cub flies better with some weight in the back, and you're able to get on the brakes a lot harder. The neat part is when you have a passenger there is almost no effect on cg since the seat is located very close to the center of cg.
    The performance comes from a combination of wing mods, cg, lots of power, and the fact that you are able to use high angles of attack and still see where you're going.
    The push-pull setup came from the requirement of control at very slow speeds with a single engine failure. This airplane can fly in the 20's when hanging on the slat, and an engine failure with a standard configuration twin would just make the airplane yaw and lose control at those low speeds. Add to that the places where this airplane is meant to fly and land, and a slight deviation off course could end up real bad in certain scenarios.

    The project came to completion with basically a three man team. I initially came up with the design and concept. I then linked up with Doug Keller (ksecub on this site), who did all the structural engineering and analysis, as well as the canopy, in 3D CAD. Doug has a lot of experience building experimental cubs and was the man behind the Husky Cub, the Carbon Cub prototype, and his current hot-rod cub (which is a hell of a performer). He's also done engineering work in the past for Sherpa and Cubcrafters. The blueprints were then handed over to Eric Lewis who built it. Eric used to work for Sherpa and was Byron Root's right hand man. He built some of the Sherpa prototypes.
    A few years later, the DoubleEnder was finally ready to fly (that was in March 2010). I got to be the test pilot, and I'll spare you all the details, but there's been some very exciting times at first! Since then, we've been constantly tweaking and modifying certain things on it.
    It flies really well. It actually exceeded my expectations as far as performance and feel. The performance is right up there with some of the lightweight or hot-rod cubs. And it still "feels" similar to a cub. If you're used to a cub, you'd feel right at home in this thing. Also all the control placements in the cockpit were kept identical to a cub in order to maintain that familiar feel we all like. It was a pleasant finding to have relatively no negative aerodynamic issues. Most of the problems we encountered came from the powerplants (such as engine cooling issues, fuel system, proper exhaust configuration etc). Even though we are still fighting some of those issues, it's easier to tackle than aerodynamic problems.

    This airplane is far from being close to its final form. It was meant to be a proof of concept, and now that we know it works well, we are refining it, and going the extra length to make the design even better. We still have a lot of things in the works.

    Here's some of the features of this airplane as it is today:
    - 2 Rotax 914 (turbocharged 115hp each) (no mixture or carb heat controls needed) (premium or avgas)
    - Custom built exhaust and relocated turbo on the front engine
    - Independant fuel system for each engine
    - Warpdrive 72 inch 3 blade propellers (ground adjustable)
    - 12 inch heavy duty extended gear
    - soon to have a set of extra long and reinforced AOSS's
    - 35 inch Bushwheels + tailwheel
    - Dakota cub squared off wings
    - Cubcrafters 2300 lb wing reinforcements
    - 25 gallon fuel tanks
    - Heavy Duty Wing Struts
    - Equal length flaps and ailerons, both with 2 inch extended chord
    - Wayne Mackey's slat and selectable drooping aileron system
    - VG's located behind the slat
    - Roll control spoilers linked to the aileron, located behind the slat, similar to a Helio Courrier
    - 3 inch extended elevator and rudder

    Of course, none of this would of been possible without our used car salesman Mike Olson. He gave us the redneck influence and support that was required throughout. Mike has been nominated our exclusive dealer and is in charge of providing information and sales. Please contact him directly for further information, he'll be glad to be of assistance.

    Here's a few pictures, there's some more in my gallery ...






  2. #2
    180Marty's Avatar
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    Love that last picture.

  3. #3
    StewartB
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    It takes guts to step out of the box and innovate. Congratulations on the plane.

    SB

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    Alec-----Awesome, what was the empty weight? Harold K.

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    tcraft128's Avatar
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    Any videos, that is awesome!!!

  6. #6
    www.SkupTech.com mike mcs repair's Avatar
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    neat, i gotta admit it was weird looking at first in that other thread!

  7. #7
    Roger Peterson's Avatar
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    I love it, but I bet it is hell to hand prop. Keep the picts and progress coming.
    Roger
    Based at O8XS. Sweeny Texas (Winter)
    Finlayson Lake, Ontario (Summer)
    I plan on living forever.......so far, so good !!!

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    VERY INTERESTING

  9. #9
    Bugs66's Avatar
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    Wow, what an incredible project! I sure love the view, that must have put a huge smile on your face! Video would be great!

    Also, can you provide the empty weight and some performance numbers? Thanks for sharing.

  10. #10
    Iflylower's Avatar
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    Love it. Can't wait to see it compete and perform!



    If you're lucky enough to fly, you're lucky enough

    "There are three things in life that people like to stare at: a flowing stream, a crackling fire and a Zamboni clearing the ice." Charlie Brown

  11. #11
    Dave Calkins's Avatar
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    Alec, thanks for the description and background. A beautiful execution of the concept.

    Any photos of the roll-spoilers? control system for them and the droopy ailerons?

    Wing-incidence?

    Tail feathers "oversized"? how much?

    VG's?

    12" extended gear? is that enough? I'm sure the slat will have that wing flying with the nose pointed straight up!

    AOSS? good!

    Again, a beautiful a/c, in my opinion. Thank You. DAVE

  12. #12

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    Hey Taucho I have a board meeting in the am then I will college the deposit process Sold two side by side one tandum the deposites will be wired to Loni's bank by the weekend Mikeo (Head Redneck)

  13. #13
    dave's Avatar
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    That last photo speaks volumes. While the rest of the Cub community is resigned to limited foreward visibility, your concept opens up a whole new world. I wouldn't be surprised to see this plane influencing future bush plane design. I hope we see build photos one day.

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    NO panel space, that's is a real money and weight saver right there! What a great innovative design, that thing probably climbs like a raped ape with those TWO 914's, awesome, lets see some vids?

  15. #15

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    Taucho doesn't need panel space this airplane has the latest heads up display with forward vision plus lots lots more unique features Mikeo

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    Quote Originally Posted by mikeo
    Taucho doesn't need panel space this airplane has the latest heads up display with forward vision plus lots lots more unique features Mikeo
    Even better!
    I too refer to my plane in the third person, "Honey likes to fly low".........

  17. #17
    KenyaCub's Avatar
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    Thanks for the comments.
    The empty weight ended up around 1400. Weight savings were not on the priority list since this is a proof of concept, and it did not justify spending more time and money in order to lighten it up. When I started this project, I did not know whether the design would end up flying well ... now that it has been proven, we can go the extra length to make it lighter. We know we can save a LOT of weight on the next one. Even at that weight it still performs well, and it's only going to get better!

    Dave,
    The wing incidence is about 2 degrees (there was no reason to add more incidence since we're not limited with visibility).
    The roll control spoiler uses a separate cable than the aileron, so you have two cables running up the strut. (I don't seem to have any good pictures of this).
    Tailfeathers are oversized by 3 inches.
    VG's are located behind the slat as per Wayne's recommendations.
    The airplane can fly at a much higher angle of attack than the 12 inch gear can provide, but there is a practical limit as far a structural loads, weight and drag is concerned.

    It approaches with good control at 30mph. I can slow it up even more to about 26, but the control suffers and it is not practical to use in the bush.
    It cruises at 97 mph at sea level. As mentioned earlier this is still a work in progress and these will not be the final numbers. I don't have any good video of it yet.

    PS: I hear Mike Olson has a special promotional deal going on this week: the first five DoubleEnder customers will get a brand new Dodge truck for FREE. If you place your order now, you should get your airplane around the same time as Sherpa starts delivering theirs.

  18. #18
    SJ's Avatar
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    Alec,

    Very cool! Thanks for posting about it!

    sj

    P.S. How is the heater?
    "Often Mistaken, but Never in Doubt"
    ------------------------------------------

  19. #19
    Dave Calkins's Avatar
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    Quote Originally Posted by KenyaCub
    Dave,
    The wing incidence is about 2 degrees (there was no reason to add more incidence since we're not limited with visibility).
    The airplane can fly at a much higher angle of attack than the 12 inch gear can provide, but there is a practical limit as far a structural loads, weight and drag is concerned.

    The reason for greater wing incidence.

    ...Just wondered what you went with. Thanks.

  20. #20
    Dave Calkins's Avatar
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    PS...I really appreciate your candid responses and willingness to share this project with us. You have created a "monster" for sure, and it is as interesting as any yet!! And Paul K. told me it performs well.

    Quote Originally Posted by KenyaCub
    It approaches with good control at 30mph. I can slow it up even more to about 26, but the control suffers and it is not practical to use in the bush.
    .........which 'control' "suffers" below 26?

    What is your spoiler blade width? What is maximum extension above the wing? How far aft of the Slat does the spoiler blade exit the top of the wing? Does it maintain roll authority at very, very, very high AOA?

    Droopy ailerons? How much aileron droop? Any differential in the ails. while drooped?

    How do you compare the DoublenDer's thrust to weight ratio to MikeO's Redneck Thrusteight??

    Thanks again. DAVE

    Oh....fuselage length close to stock? Does Doug think a long one like his would do any good?

    Lots of cool factor here!!!!

  21. #21
    Cubus Maximus's Avatar
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    Nice work Alec! This really is a fantastic design idea!

    Brad

    (You know...hmmm... unless you go all the way over - accidentally putting this airplane on its nose ((you name the reason)) isn't going to cause anything more than a little scratched lexan/plexi/whatever, less if you mount a skeg under the chin.)

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    That is wild! How long can you stay aloft?

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    Taucho (Alec) Redneck in Training , the truck promo worked like you said it would ! The question is how soon will the kit be available ! I'm referring all interested to Doug Keller (Wingnut) Oh your gear parts are on the way to Kenya. Mikeo Head Redneck

  24. #24
    KenyaCub's Avatar
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    Steve, heater? Do you know how a solar cooker works? This airplane uses the same principle.

    Dave, if you want more info about the spoilers, contact Doug. He engineered them. The spoilers are small, smaller than they should be, but this was a test just to see if they would work. The spoilers help, it's the fastest rolling "cub" I've flown, but no, it still does not have enough roll response when flying slow at very high angles of attack. I have my ailerons drooped to 30 degrees, and that doesn't help either for roll. No differential in the aileron droop, why would you want some?
    Below a certain speed (around 26), it's too far behind the power curve and you need gobs of power to arrest sink rates. It becomes harder to hit the spot. It's fine for showing off on a long runway, but not practical to use in the bush.
    The fuselage length is stock. With the current configuration, I don't see the need to extend the tail. We might have to do it later depending on what other wing mods we incorporate.
    Mikeo's Redneck cub would have a better thrust to weight ratio, if only he figured out how to make the nitrous work and how to keep the pistons from shooting out the engine case.

    Kevin, with the fuel in the wings it can fly for just over 4 hours at maximum cruise. A lot longer if you throttle back.

  25. #25
    Dave Calkins's Avatar
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    Alec. The spoilers I did are about 29 inches in span and they deploy about 3 inches above the wing surface about 4 inches behind the front spar. They work great.........as much roll (and yaw) as you would want. ........They only deploy when the flaps are down and ailerons are drooped.......never in cruise.

    Droop Aileron differential.....the idea is that when they are fully drooped and the pilot puts the joystick full-over.....the 'down' aileron doesn't go any further down...but the "up" aileron does go up......It works well when coupled with a roll spoiler. Without differential, adverse yaw would be crazy........especially with 30 degrees of droop and then the "down" aileron going down further with an aileron command.....YIkes.

    The longer tail was a question really more in comparison to Dougs latest Cub and if your flap/wing is blanking the tailfeathers, or if that problem is solved with the long tail......or if that is a problem at all? etc.

    Thanks once again for your response. Your airplane is an exciting piece of work. DAVE

    PS. I like the idea of a "nose skeg" for tip-over resistance.

  26. #26
    www.SkupTech.com mike mcs repair's Avatar
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    don't have to worry about shooting the prop.....

  27. #27
    Iflylower's Avatar
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    Yah, looks like it'd make a really good coyote hunter!
    If you're lucky enough to fly, you're lucky enough

    "There are three things in life that people like to stare at: a flowing stream, a crackling fire and a Zamboni clearing the ice." Charlie Brown

  28. #28
    slowmover's Avatar
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    I am impressed and applaud your ingenuity and innovative mentality. That airplane looks BAD ASS!

  29. #29
    Ruidoso Ron's Avatar
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    Is that bubble canopy one-piece? Must have been quite a challenge to fabricate.

  30. #30
    Marty57's Avatar
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    This popped up on the Home Built Airplanes site. Seems this was built from a Breeze with PA 11 wings and a Bell47 bubble back in the 90's.




    Here's a link to the info: http://www.homebuiltairplanes.com/fo...bbleplane.html

    Marty 57
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    Psalm 36:7 "High and low among men find refuge in the shadow of His wing"
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  31. #31
    eaglepilot's Avatar
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    Hi All,

    I listen faithfully to Uncontrolled Airspace podcast, and I sent them a note, pointing to this thread and mentioning that this might be a topic they could discuss. Lo and Behold, they talked about it last week, and I attach the link below. They start talking about the Double Ender at about minute 56 in the podcast.

    http://uncontrolledairspace.com/wiki...php?id=ucap220

    If you haven't followed/listened to Uncontrolled Airspace, it's a great aviaton podcast, entertaining and informative. It's a must listen for me.

    BTW, they also talk about a new TV series about Alaska flying at about minute 60, and about Alaska in general.
    Last edited by eaglepilot; 01-28-2011 at 02:24 PM.

  32. #32
    EI-Guy Mathew Sharp's Avatar
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    How about a panel shot of that there DoubleEnder?

    Matt
    Electronics International Inc.
    Sales/Support
    http://www.buy-ei.com

  33. #33

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    No offence intended but that things almost as ugly as I am, looks like the secret love child of a polish Wilga and an A-10 warthog. But I'm sure it works brilliantly.

  34. #34
    Bill Rusk's Avatar
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    I had a chance to see it today on a PDX overnight (in the company of DW). Very interesting, some very creative ideas on this thing. It would be a hoot to fly.

    Bill

  35. #35
    Steve Pierce's Avatar
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    Quote Originally Posted by Marty57 View Post
    This popped up on the Home Built Airplanes site. Seems this was built from a Breeze with PA 11 wings and a Bell47 bubble back in the 90's.




    Here's a link to the info: http://www.homebuiltairplanes.com/fo...bbleplane.html

    Marty 57
    Built by a retired Ag pilot who invented the Boss Hoss motorcycle in Dyersburg, TN.
    Steve Pierce

    "When everything seems to be going against you, remember that the airplane takes off against the wind, not with it."
    Henry Ford

  36. #36

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    Any updates/progress on the D.E?? Sure would love to see some get produced and flyin'.....Herman.

  37. #37

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    have a look at these http://www.seabirdaviation.com.au/

    A
    mate of mine is the test pilot for this mob,,,went for a blat in VH-SUA a few weeks back, they sell them for power line work ,shark spotting any low n slow stuff
    cheers Mat

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