Page 1 of 2 12 LastLast
Results 1 to 40 of 50

Thread: DoubleEnder Update 2013

  1. #1
    KenyaCub's Avatar
    Join Date
    Oct 2004
    Location
    Kenya, Africa
    Posts
    182
    Post Thanks / Like

    DoubleEnder Update 2013

    Click image for larger version. 

Name:	DoubleEnder_4.jpg 
Views:	363 
Size:	259.7 KB 
ID:	13527

    It’s been a few years since I’ve written an update on the DoubleEnder Project and a lot has happened since. The project had started in 2007, and it first flew in 2010. It demonstrated early on that it had good potential to meet its design goals, so the idea was then to tackle each area that could be improved upon.

    Engine cooling has been tricky, but we’ve finally gotten there. It’s actually quite amazing the amount of effort that went into designing the cooling for the engines. We’ve made many changes to scoop sizes, cooler sizes, locations and shapes. The changes not only allowed the engines to run cool under any condition but also reduced drag and enhanced aerodynamics.

    Finding the right balance of wing modifications has also been a fun challenge. I was interested to see where we could get to with today’s modern technology and design tools. After all, a cub wing was designed in the early 20th century and was meant for a different mission than what some of us use it for.
    At the end of the 2010 trip to Alaska, I had in mind to tackle the flaps. I decided to design a double slotted flap system for the cub airfoil. Doug Keller took care of engineering the flaps to be able to fit them onto a cub wing. At that point I did not know what to expect, weather or not these flaps would work on the cub airfoil. The gap, overlap, size and airfoil could all have an impact on the performance, so in order to minimize the risk and get the best chances of success from the beginning I decided to approach an aerodynamic company known for its work in the STOL domain.

    Many months were spent using Computational Fluid Dynamics software analyzing a stock supercub wing, and the modifications it had at that time (such as Mackey’s slats, extended chord flaps etc). We even hooked up a data acquisition module, with an alpha/beta boom and had a professional test pilot gather accurate data. We needed a baseline in order to compare all future modifications from.
    Then they analyzed the double slotted flaps in CFD as we had made them for the cub wing. It showed a decent improvement in CL max. The engineers doing the aerodynamic studies led us to believe that a lot more performance could be attainable, and so they proposed a different airfoil, flap, aileron, spoiler and slat which would have a CL max considerably higher than the cub wing.
    The CFD results on the CL max of this new wing were quite promising: almost twice the amount of lift that the modified cub wing generated.
    It has 70% span fixed vane double slotted flaps, with a huge fowler motion. The ailerons are 30% span and very deep chord. The airfoil is custom, and is derived from the LS416. The spoilers are located at the trailing edge and span 20% of the wing. The slats are fully retractable and automatically operated by airflow.

    Click image for larger version. 

Name:	doubleender_pictures_13.jpg 
Views:	383 
Size:	209.0 KB 
ID:	13529

    We had big hopes for this wing. To my knowledge it is the most complex and aerodynamically advanced wing that has ever been tested on such a light aircraft. I decided to pursue this new wing instead of the double slotted flaps. Doug decided to complete them, and made them available as a retrofit to stock cub wings via his company Performance STOL (www.performancestol.com). I’m glad he finished the project as they work very well, and they are now in use on the current DoubleEnder wing.
    We spent an entire two years analyzing and building the new wing. A lot of time, work, money, hopes and dreams went into this wing. The complexity was way more than what I would of liked, but the idea was to reach the limits of where modern aerodynamics could take us, and we would work on simplifying the mechanism and design later, if it worked out as hoped. The wing finally got completed in 2013, and the first test flight took place in March. It is a work of art. Gorgeous! A credit to Eric Lewis and Pete Anderson who built it.

    As with many things in life, it’s a compromise and some things worked and others didn’t.
    - The airfoil worked well. It was designed to have no more drag than the USA35B, while having a much thicker aspect ratio lending itself better to our application. It achieved its design goals.

    - The flaps did not work as expected, and this was probably the biggest disappointment. While the increase in lift could be felt, there was a lack of drag. You’d expect that with such a large flap the drag would be considerable, but there was actually less drag than what a cub’s plain flap generates. The landing and takeoff speeds were about matched with our previous wing. When flying with the flaps down at about 50 mph it was like hitting a wall of air, with tons of drag, but once slowed up to below 40mph the drag would disappear and would make it difficult to slow down even further. My personal conclusion is that these flaps are more adapted for faster airplanes. We will eventually redesign a new flap for this airfoil.

    - The ailerons worked beautifully. For such a short span it had good roll control, even at slower speeds. It still lacked a bit of authority if it were to be on its own, but combined with the right spoiler this aileron is very effective for such a small span.

    - The spoiler did not meet the design criteria. Although it was effective with the flaps deployed, it didn’t have much effectiveness when the flaps were retracted. We have been more successful with other types of spoilers we have designed over the years, and will eventually modify this wing to accommodate those.

    - While the slats did enable the airplane to fly at high angles of attack when open, and considerably reduced the drag when closed, they did not consistently operate how we wanted them to. We’ve already designed and tested a new slat mechanism, which works well and is considerably lighter, and will eventually adapt it to this wing.

    Concurrently to developing this new wing, I have also been trying different modifications to the cub airfoil.
    The wing that is on it now, is the USA35B airfoil with an automatic slat, the double slotted flaps (75% wingspan), short span and deep chord Frieze ailerons (25% wingspan), and roll control spoilers (25% wingspan). The roll is almost entirely done by spoilers as the ailerons are still quite ineffective. So far, out of all the wings we have tried, this has proved to be the best performer. But we’re not done with its design either. We are currently designing a new aileron for it, and refining our slat mechanism. The new slat system, compared to the original one, allows the slat to fully close in the cruise position. This substantially reduces the drag, enables you to cruise faster and burn less fuel.

    In the meantime we have also been testing several different horizontal tail configurations, as well as different vertical stabilizers and rudders. We’ve tried about 5 different horizontal tail configurations. They all have their strong and weaker points, the best tail we have tried is super effective and light on the controls but it weighs a lot, the lightweight tails we have tried are heavier on the controls and less effective. The key is to find the right balance between it all. To tell you the truth, all of the configurations we have tried would fly just fine if you didn’t know any different, but why settle for something that works, when you can achieve something that works better? That’s basically been the philosophy behind the entire DoubleEnder project.

    We have managed to considerably increase single engine performance and cruise speed, while also lowering the fuel burn. This was primarily done by reducing drag in several areas of the plane. We modelled the entire airplane in CFD, and analyzed the airframe as a whole in order to quantify the amount of drag that each element creates. This helped us understand where the drag is coming from and narrow down the areas that could be improved upon. At the same power setting we used to cruise at 95 mph, we are now cruising at 108 mph.

    Single engine performance, and safety in general, was always a crucial point in the design of this airplane. I did not want to end up with a twin engine that had marginal performance when one engine was lost. That defeats the purpose of having the redundancy of both engines. If it could not keep going under most circumstances on one engine then a single engine design is safer, so this was a crucial design goal.
    As of today the DoubleEnder can climb at around 300 ft/min at sea level, and can maintain altitude at 10,000 feet on one engine. These results are at a weight of 2300 lbs (800 lb of load), at lighter weights it performs considerably better.

    In order to enhance the single engine performance even further, we have designed a fuel dump system. There is now a fuel dump mechanism on the belly pod that enables the pilot to pull a lever in the cabin, which dumps over 300 lbs of fuel in just a few seconds. This was done so that gross weight is set by structural limits and not by single engine performance (as so many certified twins are). Being able to dump the fuel via the belly pod in the event of an engine failure, allowed me to set the gross weight at 2,500 lbs, and know that even if the engine failed at 10,000 feet, I would still be able to maintain altitude. The heaviest condition you could ever find yourself once the fuel is dumped is under 2,200 lbs. It is rare to fly at gross weight (1000 lb of load), so in most scenarios, the fuel dump will allow the pilot to substantially reduce the weight of the airplane and get better single engine performance, should he require it. Care would have to be taken not to dump over a populated area, but then again it might be better to have fuel come down, rather than an entire airplane. This was really designed as a last resort solution to increase single engine performance, but in most cases it would not be necessary as it already does pretty well even with all the fuel in it.

    The belly pod, which incorporates the fuel dump mechanism, is also unique. It is entirely constructed in carbon fibre, and envelops the cabane vee and part of the suspension system. It was designed to reduce the drag caused by this area. It can hold 55 gallons of fuel, and has a small cargo section in the front.

    We still have a few things we are testing to increase the single engine performance even further than what it already is. You can never have too much safety. Between the wing slats that make this aircraft stall at a much higher angle of attack than a normal airplane would, and the performance still available when one engine quits, the DoubleEnder is able to tackle two of the most common safety issues in a cub. That has always been one of the important design goals of this project.

    We used Oratex fabric on our last two sets of wings and might use it again on the next wings. This fabric has promise. It seems durable, but I have not put it through the test of time yet, and seeing how often we uncover and rebuild wings, I might not get to test the longevity of it for quite a while. The finish is not as shiny as what I am used to, but the weight savings are certainly there. We weighed both fabric processes and concluded that you could save about half the weight if you were to cover an entire Cub or DoubleEnder with Oratex. Basically saving about 20 to 25 lbs on the entire airplane.

    In July 2013, I took the DoubleEnder back to Alaska for another round of real world testing. The airplane as it was then weighed about 1500 lbs. and did not have all of our latest wing mods. It was still using the Mackey slats, and a standard aileron profile so mostly relying on the spoilers for roll. It was flying side by side and landing in the same places as the lightweight cubs. It’s performance is no longer comparable to what a cub would do at the same weight, it is a different animal all together. It is rewarding for me to experience that after so many years of development. It gives me the motivation to keep evolving the project even further.

    Here is a link to the new DoubleEnder website:

    http://www.bushplanedesign.com

    It’s been a relentless few years, with failures and successes, but in the meantime we have gained a lot of experience and are better equipped for our future plans. And above all, we’ve been having a hell of a lot of fun.

    Click image for larger version. 

Name:	DoubleEnder_6.jpg 
Views:	490 
Size:	425.6 KB 
ID:	13528
    Last edited by SJ; 03-25-2014 at 05:12 PM. Reason: Poster requested content edit

  2. #2

    Join Date
    Nov 2007
    Posts
    101
    Post Thanks / Like
    Alec,

    Thanks for the update. I love seeing the airplane perform and the evolution of design. I feel it is the biggest leap forward in bush plane design that I have ever seen. Plus, the view out of the pilot's seat is amazing. Please keep the updates, photos, and videos coming.

    Joe

  3. #3
    mike mcs repair's Avatar
    Join Date
    Aug 2004
    Location
    chugiak AK
    Posts
    11,773
    Post Thanks / Like
    thanks for taking the time to write that all up and share!

  4. #4
    180Marty's Avatar
    Join Date
    May 2004
    Location
    Paullina, Ia
    Posts
    2,078
    Post Thanks / Like
    I really like that last picture.

  5. #5
    16-bravo's Avatar
    Join Date
    Feb 2007
    Location
    wasilla, ak
    Posts
    417
    Post Thanks / Like
    Wow, thats great Alec. I cant wait to see it in person someday.

  6. #6
    8856Charlie's Avatar
    Join Date
    Jun 2008
    Posts
    87
    Post Thanks / Like
    Alec, thanks for the update!! What you are doing keeps me up at night thinking about cubs and what else could be done and keeps me in my shop creating and trying new things. Thank you for the inspiration!!! And like 16 Bravo I would love to see it one day.

    Randy

  7. #7

    Join Date
    Mar 2003
    Posts
    495
    Post Thanks / Like
    Taucho You are a real Redneck in training !!! Great update , did Doug narrate the update article ? Mikeo

  8. #8
    SJ's Avatar
    Join Date
    Jan 2002
    Location
    Kansas City, USA
    Posts
    15,363
    Post Thanks / Like
    Very interesting!

    sj
    "Often Mistaken, but Never in Doubt"
    ------------------------------------------

  9. #9
    Olibuilt's Avatar
    Join Date
    Nov 2009
    Location
    Montreal, Canada
    Posts
    890
    Post Thanks / Like
    I think this plane is really an engineering work of art to my eyes. It makes the ''ordinary'' exp cub look so simple and easy to built. I'm really jealous of talents and resources needed to built something like this. Even the pics are just awesome.

  10. #10
    SpainCub's Avatar
    Join Date
    Feb 2009
    Posts
    612
    Post Thanks / Like
    Alec, Amazing stuff you guys have been working on.Thank you for the detail information and I am green with envy of those guys around you putting this plane together. To me, it would highly satisfactory just to be able to walk around it! And touch it!!!

    BTW, what is the airfoil you guys based your modified airfoil? I can't seem to find it? LS416 At first I thought it looked like an SG 6040... or even
    Is this what you mean by LS 416?

    Attachment 13551the Langley... LNF-0416 is a great performing airfoil. Hats off to you guys!!!

  11. #11
    KenyaCub's Avatar
    Join Date
    Oct 2004
    Location
    Kenya, Africa
    Posts
    182
    Post Thanks / Like
    Thanks for all the comments.

    SpainCub, the airfoil we use is called LF417. It is derived from the NACA airfoils LS 416 and 417. They were developed for high lift applications.
    Last edited by KenyaCub; 10-22-2013 at 03:23 PM.

  12. #12
    mountainflier's Avatar
    Join Date
    Jun 2011
    Posts
    58
    Post Thanks / Like
    KenyaCub, thank you for the update on some of challenges on building and designing and the test flying results to make the Doublender a better airplane! I am interested on how slow will the Doublender fly at with a light load with the current wing it has on it?

  13. #13

    Join Date
    Apr 2012
    Location
    King Salmon, AK
    Posts
    113
    Post Thanks / Like
    Wow, what a project!

  14. #14
    KenyaCub's Avatar
    Join Date
    Oct 2004
    Location
    Kenya, Africa
    Posts
    182
    Post Thanks / Like
    mountainflier wrote: I am interested on how slow will the Doublender fly at with a light load with the current wing it has on it?
    It will approach a landing spot at about the same speed as a lightweight or modified cub. The magic is, that it is able to do this with an additional 400 lbs.
    At some point I plan to put all the technology I have derived from the DoubleEnder and apply it onto a lightweight cub-style airplane. It would be interesting to see what can be achieved. The DoubleEnder will stall slower than a cub because of the slats.

  15. #15
    SpainCub's Avatar
    Join Date
    Feb 2009
    Posts
    612
    Post Thanks / Like
    Thanks Alec,one of the cool things you should be able to achieve with your "WING" design (in my mind... something very useful) is been able to set an attitude on a cub-like plane with full flaps extended as achieve a very low decent rate without power. You can almost parachute down in case of engine failure... that is something that I find very attractive with the fowler+slat flap and the slats on your wing. I am sure this is something you have though of, so I am asking what that is like on the double-ender?

  16. #16
    KenyaCub's Avatar
    Join Date
    Oct 2004
    Location
    Kenya, Africa
    Posts
    182
    Post Thanks / Like
    Hi SpainCub, you would develop very high sink rates doing what you describe,and it would not be practical for use, or safe to land that way. Just like in a cub, you need enough forward momentum and built up energy to be able to flare before touchdown (with no power).

  17. #17
    mike mcs repair's Avatar
    Join Date
    Aug 2004
    Location
    chugiak AK
    Posts
    11,773
    Post Thanks / Like

  18. #18
    skywagon8a's Avatar
    Join Date
    Mar 2008
    Location
    SE Mass
    Posts
    11,082
    Post Thanks / Like
    Check out the February 2014 issue of Sport Aviation cover and good article.
    N1PA

  19. #19
    DW's Avatar
    Join Date
    Dec 2002
    Location
    pacific northwest
    Posts
    2,067
    Post Thanks / Like
    Hey Alec what ever happened to the guy from France that flew with us about a year ago did he ever get an article in his magazine on the doublender and cub flying.

    DW

  20. #20
    Patrol Guy's Avatar
    Join Date
    Aug 2007
    Location
    east of the river
    Posts
    1,664
    Post Thanks / Like
    DW - we had a guy from France write a 10 page article with a lot of pictures about our Ohio gang. He sent a couple magazines, but none of us can read French??

  21. #21
    DW's Avatar
    Join Date
    Dec 2002
    Location
    pacific northwest
    Posts
    2,067
    Post Thanks / Like
    Sounds like it might be the same guy...he was going to send me some copies but never heard from him...nice guy he flew with us for two days.

  22. #22
    SchulerJL's Avatar
    Join Date
    Aug 2009
    Location
    Peoria, Illinois
    Posts
    584
    Post Thanks / Like
    Click image for larger version. 

Name:	Doublender.jpg 
Views:	235 
Size:	141.5 KB 
ID:	14755 Great Article!

  23. #23
    knucles's Avatar
    Join Date
    Apr 2011
    Location
    nevada
    Posts
    126
    Post Thanks / Like
    COOL AIRPLANE , good work ....

  24. #24
    KenyaCub's Avatar
    Join Date
    Oct 2004
    Location
    Kenya, Africa
    Posts
    182
    Post Thanks / Like
    Quote Originally Posted by DW View Post
    Hey Alec what ever happened to the guy from France that flew with us about a year ago did he ever get an article in his magazine on the doublender and cub flying.

    DW
    Hey DW, the article came out a few months ago. He did a nice job. We were described as the Mad Max of aviation. There's even a picture with you in there. I'll scan it and upload when I get a chance. See you in a couple months. Take care, Alec
    PS: you can view the EAA article here: http://www.sportaviationonline.org
    Last edited by KenyaCub; 02-08-2014 at 07:59 AM. Reason: Added link

  25. #25
    SteveE's Avatar
    Join Date
    Feb 2006
    Location
    Jenks, OK
    Posts
    4,249
    Post Thanks / Like
    Alec,, thats a great article in the Sport Aviation.

  26. #26

    Join Date
    Mar 2003
    Posts
    495
    Post Thanks / Like
    "MAD MAX OF AVIATION" Frenchmen always understate the obvious!!! mikeo

  27. #27

    Join Date
    Mar 2003
    Posts
    495
    Post Thanks / Like
    Big F still waiting wor your address!! mikeo
    E

  28. #28
    SpainCub's Avatar
    Join Date
    Feb 2009
    Posts
    612
    Post Thanks / Like
    Quote Originally Posted by KenyaCub View Post
    Hi SpainCub, you would develop very high sink rates doing what you describe,and it would not be practical for use, or safe to land that way. Just like in a cub, you need enough forward momentum and built up energy to be able to flare before touchdown (with no power).

    Great article Alec, BTW I missed your reply, but I was talking about emergency situation, engine failure and in terrain that you can't find a spot to land on I have seen some Ultralights (LSA in the US) have this safety feature and testing it (basically you turn the engine off full pitch up and pull on the flaps) and the sink rate in very slow, in the 200 ft/pm, I don't recall the angle of glide for this but it came out to impact bellow 20 mp/h.

  29. #29
    SpainCub's Avatar
    Join Date
    Feb 2009
    Posts
    612
    Post Thanks / Like
    BTW, someone you sent me a heads up and it looks like what I was commenting is in the Denali, go to 3:36 and see what I was talking about.

  30. #30
    Dave Calkins's Avatar
    Join Date
    Jul 2002
    Location
    Anchorage, Alaska
    Posts
    5,486
    Post Thanks / Like
    Quote Originally Posted by SpainCub View Post
    BTW, someone you sent me a heads up and it looks like what I was commenting is in the Denali, go to 3:36 and see what I was talking about.
    SpainCub....a 300fpm descent at 60 mph.....and called a parachute-like maneuver........as demonstrated in that "Denali" video? I am not impressed!

    .........surely that is not what you meant when you talked about a parachutage-type descent in an engine out situation and landing prospects into very rough terrain.?!?

    What you said before is possible in the HotRod's with big flaps, wings, slats, etc....but it takes some power to hold the nose up in many of the HotRod Experimental Cubs I have flown....actually, it takes power in ALL of them to hold the nose high and parachute in a descent.


    Alec, congratulations on the article in S A, there are some beautiful photos there also.
    Thanks j3doc thanked for this post

  31. #31

    Join Date
    May 2012
    Location
    SE Montana
    Posts
    351
    Post Thanks / Like
    Any new info about the double ender? Haven't heard anything for a while.

  32. #32

    Join Date
    Dec 2012
    Location
    Portersville, PA
    Posts
    54
    Post Thanks / Like

  33. #33

    Join Date
    May 2012
    Location
    SE Montana
    Posts
    351
    Post Thanks / Like
    What ever happened to the double ender? Have they continued developing it?

  34. #34

    Join Date
    Dec 2012
    Location
    Portersville, PA
    Posts
    54
    Post Thanks / Like
    Comment a month ago from Youtube:

    zachary lewis1 month ago
    my dad built it in his garage, they have it stored in a hangar at the Aurora airport in Oregon

    http://registry.faa.gov/aircraftinqu...umbertxt=989LW
    Last edited by garyl; 05-02-2017 at 11:46 PM.

  35. #35

    Join Date
    Oct 2018
    Posts
    2
    Post Thanks / Like
    Soo... is this no longer a thing? I sent an email on their website and haven’t heard anything. Does anyone have a POC?

    Thanks!

  36. #36
    mike mcs repair's Avatar
    Join Date
    Aug 2004
    Location
    chugiak AK
    Posts
    11,773
    Post Thanks / Like
    Quote Originally Posted by Northeast_birddog View Post
    Soo... is this no longer a thing? I sent an email on their website and haven’t heard anything. Does anyone have a POC?

    Thanks!
    not sure on specifics... wings ended up on a single engine pusher version.... that ended up in a lake in alaska... and was shipped back south in a container for work.....???

  37. #37

    Join Date
    Oct 2018
    Posts
    2
    Post Thanks / Like
    You wouldn’t happen to know how to contact the company besides email would you?

  38. #38
    Randy's Avatar
    Join Date
    Feb 2002
    Location
    S.Dakota
    Posts
    440
    Post Thanks / Like
    Its been a long cold spell here, been "hangar flying" on the internet, and it dawned on me that I haven't heard much about the Double Ender Cub.
    Seemed like an interesting concept....but haven't seen much more about it.
    Is anything still going on with it?
    http://www.bushplanedesign.com/news--updates.html
    https://www.youtube.com/watch?v=PMxR3q7u6r8

  39. #39
    Farmboy's Avatar
    Join Date
    Jan 2016
    Location
    Glens Falls, NY
    Posts
    2,625
    Post Thanks / Like
    Long gone from the news. The Ascender was built, two place side by side single engine, and just as awesome, but had an incident in an Alaskan lake. Recovered but I’ve heard no news since sadly. Perhaps someone here knows.


    Sent from my iPhone using SuperCub.Org

  40. #40

    Join Date
    May 2012
    Location
    SE Montana
    Posts
    351
    Post Thanks / Like
    I heard from someone that supposedly knows sometbing, that it's in a hanger at an undisclised location, being rebuilt...

    I'd like to see it with a pair of 300hp Apex motors strapped to it's back....

Similar Threads

  1. First Ski flight 2013
    By cubdriver2 in forum Ski Flying Forum
    Replies: 155
    Last Post: 12-19-2013, 05:41 PM
  2. Sun 'n Fun 2013
    By Bobby Breeden in forum Cafe Supercub
    Replies: 16
    Last Post: 05-05-2013, 01:36 PM
  3. Replies: 0
    Last Post: 11-19-2012, 08:00 AM
  4. 2013 Calendar Campaign Video Update Number 1
    By SJ in forum Cafe Supercub
    Replies: 16
    Last Post: 09-26-2012, 05:06 PM
  5. The DoubleEnder
    By KenyaCub in forum Experimental Cubs
    Replies: 36
    Last Post: 10-04-2011, 06:31 AM

Bookmarks

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •