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Thread: New build with lots of mods

  1. #1

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    New build with lots of mods

    Dear friends,

    My name is Ryan. I have been lurking/freeloading on this site for about a year now. Today, I became a member, ponied up and hope to contribute something back by posting some of the details of my build.

    this is my first complete airplane build, first time posting on a forum and I have very limited experience with cub style aircraft, so bear with me.

    I started this project with a tube package from VR3 engineering. They deliver an incredible product; unfortunately, I forgot just how long it takes to weld out something of this size. The fuselage is welded and I am now in the process of tabbing it out.

    Like I said, first time build so criticism is welcome!

    Hopefully I can figure out how to post pics. Stay tuned...
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  2. #2

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    Main landing gear complete! 15Ē of wheel travel (not sure yet if it is all usable) I forget the exact weight; however, it came in about 7 lbs heavier than 3+ gear/cubane V.

    Ryan
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  3. #3
    RVBottomly's Avatar
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    Welcome!

    Now you will have to tell us more about your gear. Like what kind of spring/shocks are those!?

  4. #4

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    Rudder and brake pedals

    Working on rudder and toe brakes now.

    Rudder peddle is pretty much per piper drawing. The only big difference is the bottom tube is 3/4 rather than 5/8 (same as top). This is so I only have to make one size bushing.

    Turned the bushings from delrin rod.

    Modeled toe brakes off of Carbon Cub geometry. I really like the way they feel.

    There are 3 holes drilled on the arm that pushes the master cylinder. This is so I can change the mechanical advantage created by the lever.

    Here is the initial design. Lots of work to do still. Hope they work.

    Ryan
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  5. #5

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    It is a fox air shock with aluminum body and internal reservoir (separates gas and oil). The geometry seems to work out really well. Less wheel scrub and camber change. I built a similar set of gear for a savage cub it performs very well so I stuck with the same concept.

    Thanks, Ryan

    a pic of the savage cub...
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  6. #6
    skywagon8a's Avatar
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    Welcome Ryan!



    This is an interesting gear and shock design. It looks as though it will work well with the vertical loads. When landing on rough terrain much of the landing loads will be in an aft direction. Your design directs those loads to a point under the center of the fuselage, they then transfer to an outward force where the gear attaches to the fuselage rear attach location. That location is designed to accept loads in an upward direction to be further distributed through the fuselage. The center of that rather flat V could fail under compression loads with a high impact landing.

    Another observation is where the front gear legs attach to their center pivot. For maximum strength the load path should be straight to the opposite side of the fuselage. Yours attaches to the rather flat triangle which has nothing to prevent it from pulling down under high landing loads. Look at the picture of your Savage Cub. That lower front tube makes a straight pull to the opposite longeron attach point.

    N1PA
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  7. #7

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    Thank you so much for the feedback. I will definitely take that into consideration.

    Cheers, Ryan







    Sent from my iPad using SuperCub.Org

  8. #8

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    Quote Originally Posted by Ryan Murphy View Post
    Main landing gear complete! 15” of wheel travel (not sure yet if it is all usable) I forget the exact weight; however, it came in about 7 lbs heavier than 3+ gear/cubane V.

    Ryan
    I like the gear, nice to see you are not stuck in a box. Also nice to see from your shop you are clearly able to do the job at hand.
    Regards, Charlie
    Super Coupe E-AB build in process

  9. #9
    RVBottomly's Avatar
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    Quote Originally Posted by Ryan Murphy View Post
    It is a fox air shock with aluminum body and internal reservoir (separates gas and oil). The geometry seems to work out really well. Less wheel scrub and camber change. I built a similar set of gear for a savage cub it performs very well so I stuck with the same concept.

    Thanks, Ryan

    a pic of the savage cub...
    I appreciate Pete's observations, but I still really like your execution. I've sketched this approach out a few times, and have seen other stabs at it. Yours looks well done.

    Another question: why 2 sets of shocks per side instead of one? Is it because of what was available, or load balancing, or what? I was thinking one set at the right shock rating might be a little lighter--fewer bolts, etc.

    I also was thinking maybe 2 sets might give less drag, sort of like what happens when a round tube is flattened. All speculation at this point on my part.

  10. #10

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    My opinion about the shallow Vee selected for this build, it is very similar to what is under a J4. If I were to do something different, I would build the Vee to be integral weldment with the fuselage eliminating the bolt on ends at the longerons which are the week link here.
    Regards, Charlie
    Super Coupe E-AB build in process
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  11. #11
    skywagon8a's Avatar
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    Quote Originally Posted by CharlieN View Post
    My opinion about the shallow Vee selected for this build, it is very similar to what is under a J4. If I were to do something different, I would build the Vee to be integral weldment with the fuselage eliminating the bolt on ends at the longerons which are the week link here.
    Alternatively if he still wants to be able to remove the gear as an assembly, he could close the V with a cross tube tying the ends together.
    N1PA
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  12. #12

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    Tentative landing gear plan

    Thank you all for the comments regarding the gear. The positive ones keep me motivated. The criticism and suggestions inspire change and corrections that prevent bad things from happening.

    I spent some time studying geometry and load resultants; there is definitely room for improvement. Additional bracing, maybe gussets, and I like the idea of closing the V in. One more concern, force created from breaking, with 35s on asphalt. Worst case scenario, unbolt the whole gear assembly, make a coffee table out of it and install a more standard gear. For that reason, as well as potential conflict with floats I decided not to make it an Intercal part of the fuselage.

    To address the question regarding two shocks per gear leg: I have a hole bunch of those shocks. I think fox made them for a military contract. I purchased about 14 of them. Iíve been using them for everything. They are a 2 inch air shock. While one shock was sufficient to hold up the light sport savage cub, it is not sufficient to hold a super cub up at gross weight (especially with the almost 2 to one mechanical advantage created by mounting the shock closer to mid shaft on the gear leg). If I was not restricted by money, I would definitely be using TK1. Those guys are brilliant!



    iím hoping to put the landing gear into solid works and then have a stress analysis run; unfortunately, thatís going to require somebody way smarter than me. In the meantime, as the build progresses and moves into testing, the landing gear assembly and tail wheel assembly will remain unpainted so that modifications may be made.

    Thanks again for the comments. Here are some pics of the gear mounted to the fuselage. Itís just on 31Ē Dessers for now.
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  13. #13

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    I started on the tail wheel suspension. Here it is so far.Click image for larger version. 

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  14. #14

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    For those interested, hereís a pic showing the breakdown of a internal reservoir shock and how the free floating Click image for larger version. 

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ID:	52489piston separates gas and oil. This shock has been shortened and modified to be used for the tail wheel.


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  15. #15

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    Ryan, your tail wheel looks rather similar to mine and I would not change your main gear, fly it first and you decide. Like me your experience is outside the box, do not fall into the damn box, you do not need to be there your engineering is sound, keep going your way.
    Regards, Charlie
    Super Coupe E-AB build in process
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  16. #16

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    I think that is an excellent design. If you have a light onboard air source you could adjust for a low tailwheel on takeoff(better AOA) and high on landing to help absorb shock (great with slats). I would recommend rubber bump stop under tailpost as failsafe.
    DENNY
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  17. #17
    www.SkupTech.com mike mcs repair's Avatar
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    Quote Originally Posted by Ryan Murphy View Post
    I started on the tail wheel suspension. Here it is so far.Click image for larger version. 

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    You need more tubes in tail section. Those bend anyway, before you added shock to the equation. But then again your tail wheel isnít putting force like a spring mount did.....


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  18. #18

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    Ryan, What is your ultimate goal? What mission(s) do you have in mind that common, vetted modifications don’t already resolve?
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  19. #19
    Crash, Jr.'s Avatar
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    Quote Originally Posted by Paul Heinrich View Post
    Ryan, What is your ultimate goal? What mission(s) do you have in mind that common, vetted modifications don’t already resolve?
    I'll echo this. Seems like a lot of "more better" disease. Interesting suspension concept but it's a lot of weight to add that's pretty unnecessary unless you're hell bent on just smashing the plane directly into the earth.

  20. #20
    Gordon Misch's Avatar
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    Best if the line of action of the shock passed through the center of that "x" cluster. Right now it looks like it's imposing bending on the four tubes making up that cluster. But maybe the photo angle is deceiving - - -
    Gordon

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    My SPOT: tinyurl.com/N4328M (case sensitive)

  21. #21

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    Maybe a bump stop on the tail spring to stop it ever striking your rudder
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  22. #22

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    Quote Originally Posted by Ryan Murphy View Post
    I started on the tail wheel suspension. Here it is so far.Click image for larger version. 

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    This is a most excellent design, and a great build in progress. It is nice to see someone actually building and testing new ideas. Please keep posting your progress, and ignore the critics who have never fab'd anything in their life.
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  23. #23

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    Thanks Charlie!

    Do you happen to have any pics of your tail wheel? I would like to see what others have done, especially how tube locations may have been modified or moved.

    Ryan

  24. #24

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    Thank you Denny!
    I like the “on board air source idea”. The tail wheel will be getting a bump stop.
    Cheers, Ryan

  25. #25

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    Mike,

    I am guilty of bending up the tail of an airplane. I will be adding more tubes as well as a couple gussets. Hopefully I can post some pics soon.

    Ryan

  26. #26

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    Quote Originally Posted by Ryan Murphy View Post
    Thanks Charlie!

    Do you happen to have any pics of your tail wheel? I would like to see what others have done, especially how tube locations may have been modified or moved.

    Ryan
    Sure, March of this year,
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    The TW on this is temporary, it is actually a nose wheel from a Long EZ. I have machined a few parts for my TW but not gotten any further.

    My build is here, https://www.supercub.org/forum/showt...-3-14159265359

    More details available.
    Regards, Charlie
    Super Coupe E-AB build in process
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  27. #27

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    Paul and Crash jr,

    The mission is bush flying with my friends, hunting, fishing, camping and traveling, sometimes in some fairly challenging areas. The main gear design worked well enough in my savage cub that I decided to incorporate it into this build. The goal is to build an aircraft that meets this mission and hopefully along the way help others with ideas and decisions. I don’t believe these designs are better than any others out there. The weight penalty is significant; however, for my mission acceptable.

    Cheers, Ryan
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  28. #28

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    Charlie -- Is your tailwheel free castoring inside a delrin/nylon/hdpe bushing? Have any pictures of that assembly?

    I am working in this area on mine and using an acetal crush-plate-type bushing with an AN bolt to compress the stack, but have been dreaming about a simple locked vertical post out of the tailwheel fork that is captured in a mount with an acetal bushing. It looks like that is exactly what you have here...

  29. #29

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    Quote Originally Posted by Gordon Misch View Post
    Best if the line of action of the shock passed through the center of that "x" cluster. Right now it looks like it's imposing bending on the four tubes making up that cluster. But maybe the photo angle is deceiving - - -
    Gordon,
    I agree. I just couldnít get it to work out that way though. There will be another gusset in there to help pick up the load. Stay tuned...

    Ryan

  30. #30

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    Quote Originally Posted by motosix View Post
    This is a most excellent design, and a great build in progress. It is nice to see someone actually building and testing new ideas. Please keep posting your progress, and ignore the critics who have never fab'd anything in their life.
    Thank for the compliment! I will definitely continue to update you all with the build
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  31. #31

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    Charlie,

    very similar indeed. Looking forward to going through your build.

    Thank you,
    Ryan

  32. #32
    skywagon8a's Avatar
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    Ryan, In what part of the World are you located? I can't quite make out your licence plate.

    N1PA

  33. #33

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    Removable rear seat cross bar question

    All,

    I would like to permanently remove the rear seat cross bar. From what I understand, it is required for flight. Anyone have any experience with such a modification?

    the masking tape is my idea for substitute bracing.
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  34. #34

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    N1PA,
    I’m in Prescott,AZ. Need to update my profile.
    Ryan
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  35. #35

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    I’m pretty sure that the upper crossbar is the only thing that keeps the sides from folding in or out. I wouldn’t mess with the geometry of such a critical structure.

    And how would you support the rear seat if you do change it to your suggested geometry?

    Why would you want to permanently remove it anyway?
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  36. #36
    www.SkupTech.com mike mcs repair's Avatar
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    the original cross bar was paper thin folded into a square tube like the compression members in wings early on... not much strength there...

    you are best to just weld in a cross bar, then cut at edges 3/4 through about 1 1/2" or 2" from sides (remember left side has fuel lines behind panel and needs longer stub...) then you weld on a cap to center section, and drill and pin outer stubs... you can weld pins in, or use removable pins....

  37. #37

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    Without the bar in place it is pretty easy to move the side of the fuselage in and out. I have had dogs get under it and lift it up when flying, plane did not fall out of the sky but for rough backcountry work I would want it in place. I don't think bars in place of the tape would really do the job, and they take up a lot of space. While we are on that section of the fuselage, a few questions. Why did you want to remove the bar? It is normally the support for the rear seat back. Are you going flat floor or raised floor? Are you doing extended baggage? Do you plan to sleep in the plane? I would recommend you look at the Willow mountain door mod at airframes. Consider making the bottom of the door flush to the floor for sliding heavy stuff in and out. I don't think I have ever heard anyone say the baggage door was too big.
    DENNY
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  38. #38

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    Thanks guys.

    Yes, flat floor, mounting directly to lower longeron “similar to Willow Mountain”with extended baggage. My hope was to have a sling style rear seat similar to a carbon cub.

    Thanks again for the suggestions

    Ryan

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