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Thread: PA-12 wings on a PA-18 fuselage

  1. #1

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    PA-12 wings on a PA-18 fuselage

    Will PA-12 wings bolt on to a PA-18 fuselage? I know the angle of incidence is different, but is the difference in the wing or in the mounting points on the fuse. Iím contemplating an experimental project and have access to a set of PA-12 wings with flaps.

    Thanks,

    Dan

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    Here we go again- Crash Jr is probably getting tired of this question. I just had a customer inquiring about the same thing. Short version is theyíll bolt right up but youíll have to figure out what to do with the aileron cables- totally different routing on a -12 vs -18. Hopefully heíll give a few more details, as he was involved in modifying at least one -18 fuselage to accommodate -12 routing.
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  3. #3

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    Look at every Backcountry Cub out there. Modified PA-12 wings on modified Cub airframes.
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  4. #4
    www.SkupTech.com mike mcs repair's Avatar
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    Yes they will bolt on. The buss cable will probably work on either. But you need to modify fuselage (add pulleys) to route main aileron cables as in a -12 or better yet -14


    Sent from my iPhone using SuperCub.Org

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    So, does that mean I get the angle of incidence of the -18 or the -12? I’m not wanting to have to change the tail plane angle and/or give up the short field performance if I can help it. Sounds like a good case for going with ball bearing pulleys as well.

  6. #6

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    AOI is a product of the airframe.

    FWIW? The best performing PA-12 I've observed belongs to Trail Ridge Air in Anchorage. Modified AOI and PA-18 wings.
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    skywagon8a's Avatar
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    Quote Originally Posted by Dnh98221 View Post
    Sounds like a good case for going with ball bearing pulleys as well.
    Do it. You will appreciate the smooth action.
    N1PA

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    I put 18 wings on a 12. The wing root attach points bolt on. The fuselage requires significant work to make everything else work. Even if you have free wings and are doing all the work yourself, itís going to cost you too much.

    And if you do this dispose of the 12 tanks before you even contemplate this conversion.

    And if you have 12 tanks in your 12 throw them away before your next flight.

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    Sorry, guys, I don’t know where you are getting your data, but it’s wrong.

    12 wings CANNOT just be bolted onto an 18 fuselage.

    The angle of the lift strut attachment brackets on both the fuselage and the wing are not the same on 12s and 18s.

  10. #10
    Anchorage14
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    Having put 18 wings on and experimental 12 and 14, the lift struts do present a problem. The length of the struts is not the same and the forward strut has a different width lug that enters attach fitting at the wing. The 12 wings have a different design strut attach fitting. 18 wings on a 14 fuselage worked using 12/14 length struts and removing the washer shaped reinforcement on one side of forward lift strut fitting on the 18 wing. Not sure if the opposite would work in your case, maybe using 18 struts would work adding a washer at the forward attach fitting.
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  11. #11

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    I know everyone wants to improve performance while also saving money, but sometimes reinventing the wheel comes at too great a cost.

    Piper probably had dozens, if not hundreds, of trained aerodynamic engineers working on the design and development of these airplanes. I’m pretty sure they didn’t just say, “Let’s sell airplanes made up of disparate spare parts,” hoping that the finished product “might“ be airworthy enough that they didn’t crash and kill all of their customers.

    I suppose if you’re an engineer and know enough to think all these things out, you can get away with it. But I doubt few, if any, of the members here have the knowledge base necessary to do that type of analysis. I’m certainly not.
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  12. #12

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    I wanted to put -12 wings on an -18 airframe to get the -18 AOI and the -12 ailerons. As it turns out that's pretty much what I have with the backcountry. Internal cables, -12 style ailerons, and increased AOI. If a guy's got the will to make the changes on a plane? Why not?
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  13. #13
    skywagon8a's Avatar
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    If you were to take a detailed look at all of Piper's tube and fabric airplanes, you would be surprised at how much alike they are with interchangeability of parts.

  14. #14

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    Adding horsepower and bigger control surfaces is one thing. Guessing at changes that might be caused by changing the aoi to the overall flight envelope and parameters is another. Stewart could have just been lucky that the changes he did worked.

    Where would he have been if the changes didn’t work out so well? A lot of money, time, and effort would have been down the drain. Who can afford that?

    just saying....if you want SuberCub performance, buy or build a SuperCub.

  15. #15
    Steve Pierce's Avatar
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    Pacer wi gs will bolt on as well. Piper didn't change the big parts. FX3/X Cub ailerons are the cats ass.
    Steve Pierce

    Everybody is ignorant, only on different subjects.
    Will Rogers
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  16. #16
    cubdriver2's Avatar
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    Quote Originally Posted by stewartb View Post
    I wanted to put -12 wings on an -18 airframe to get the -18 AOI and the -12 ailerons. As it turns out that's pretty much what I have with the backcountry. Internal cables, -12 style ailerons, and increased AOI. If a guy's got the will to make the changes on a plane? Why not?
    J4E wings, 16 rib also

    Glenn
    "Optimism is going after Moby Dick in a rowboat and taking the tartar sauce with you!"
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  17. #17
    cubdriver2's Avatar
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    Quote Originally Posted by Paul Heinrich View Post
    I’m pretty sure they didn’t just say, “Let’s sell airplanes made up of disparate spare parts,” hoping that the finished product “might“ be airworthy enough that they didn’t crash and kill all of their customers.
    That's exactly what happened in 1947/48 with the small airplane market in the toilet. Bill Piper and Dave Long Designed the " ninety day wonder" from napkin drawing to first flight from material scraps at Piper. Pa15 Vagabond, my first plane and a delight to fly. Under 650 lbsBe thankful for what they did, because the small sales that the Vag generated kept the bankers from closing Piper and allowed them to survive to play another day. Or....... none of you would have a Super Cub or maybe even all the clones. The lowly Vagabond is the working Mom that made the rest possible

    Glenn
    Last edited by cubdriver2; 10-21-2020 at 07:34 PM.
    "Optimism is going after Moby Dick in a rowboat and taking the tartar sauce with you!"
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  18. #18

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    Quote Originally Posted by stewartb View Post
    I wanted to put -12 wings on an -18 airframe to get the -18 AOI and the -12 ailerons. As it turns out that's pretty much what I have with the backcountry. Internal cables, -12 style ailerons, and increased AOI. If a guy's got the will to make the changes on a plane? Why not?

    I don’t know about the clone kits but the angle of incidence difference between a
    12 and an 18 is arrived at by different locations of the wing root fittings. I suppose and I’ve heard that the aoi can be changed by changing the location of the wing root spar attach fittings. That is only part of the equation. The angle of the tail plane must be changed to correspond to the angle of incidence change. That tail plain change is required to keep the proper trim range. The wing and the tail fly the plane. The rest of the fuselage is just along for the ride.

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    Gordon Misch's Avatar
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    Quote Originally Posted by Paul Heinrich View Post
    Sorry, guys, I donít know where you are getting your data, but itís wrong.

    12 wings CANNOT just be bolted onto an 18 fuselage.

    The angle of the lift strut attachment brackets on both the fuselage and the wing are not the same on 12s and 18s.
    Jury struts are also problematic.
    Gordon

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    Quote Originally Posted by Dnh98221 View Post
    Will PA-12 wings bolt on to a PA-18 fuselage? I know the angle of incidence is different, but is the difference in the wing or in the mounting points on the fuse. I’m contemplating an experimental project and have access to a set of PA-12 wings with flaps.

    Thanks,

    Dan
    If you have skills to make the changes, your labor and the wings are free. it is worth it. It all depends on the mission!! Do you fly heavy, big winds, floats, or just on clear days. Yes it can be done and should be a good flying plane. IS IT WORTH IT. is the question and only you can give the answer.
    DENNY

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    Quote Originally Posted by Paul Heinrich View Post
    Sorry, guys, I don’t know where you are getting your data, but it’s wrong.

    12 wings CANNOT just be bolted onto an 18 fuselage.

    The angle of the lift strut attachment brackets on both the fuselage and the wing are not the same on 12s and 18s.
    The strut brackets are parallel to the spar brackets in both cases, so I don't think that would be an issue.
    After Monday and Tuesday, even the calendar says WTF !

  22. #22

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    Quote Originally Posted by Dnh98221 View Post
    So, does that mean I get the angle of incidence of the -18 or the -12? I’m not wanting to have to change the tail plane angle and/or give up the short field performance if I can help it. Sounds like a good case for going with ball bearing pulleys as well.
    You can’t change the angle of incidence without changing the tail plain angle if you want any reasonable range of trim. The tail needs to be in the proper relationship to the wing for the system to function properly.

    I don’t know how bad it would be if you increased or decreased angle of attack of the wing without changing the angle of the tail to correspond appropriately but it could range from minimal to no trim at least in one direction to uncontrollable.

    The primary reason the 12 is faster than the 18 is that as the wing flys through the air based on the tails control, the fuselage moves through the air at less of an angle with less drag. The reason that the 18 gets off shorter is more angle of incidence which due to the tails control of the wing, The fuselage moves through the air at more of an angle creating more drag, hence less speed but shorter takeoff.
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  23. #23

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    Looking at a -12 vs -18 in flight I'd say the -18 has less airframe drag. Mod a -12 to include Cub gear, Cub tail, etc and the cruise speed is pretty equal to a Cub.

    I know three guys who've changed -12/-14 AOI to match a Cub. None ever mentioned modifying the tail. That doesn't mean they didn't but I'd think they'd have mentioned it to me. Where's Dace Caulkins? He had adjustable spar attach fittings on a plane and moved the AOI with it. I don't recall any chatter about the tail.

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    Every discussion I've followed about increasing AOA on a 12 did include raising the jackscrew. Regardless, it seems like too much hassle. For mine I installed 31"ABW's, 3" extended gear and took out half the wash (at rebuild/ pre-fuel tank installation) and called it good. Kept it light (1095) and it flys great.
    After Monday and Tuesday, even the calendar says WTF !
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  25. #25
    Gordon Misch's Avatar
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    Quote Originally Posted by PerryB View Post
    Every discussion I've followed about increasing AOA on a 12 did include raising the jackscrew. Regardless, it seems like too much hassle. For mine I installed 31"ABW's, 3" extended gear and took out half the wash (at rebuild/ pre-fuel tank installation) and called it good. Kept it light (1095) and it flys great.
    Yup - been about 2 years now since riding with you, and your plane is a dandy.

    Now then, about that Ford pickup .... Oh wait, that's politics.
    Last edited by Gordon Misch; 10-22-2020 at 10:58 PM.
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    Quote Originally Posted by PerryB View Post
    Every discussion I've followed about increasing AOA on a 12 did include raising the jackscrew.
    Do tell. My -12's yoke travel up and down was restricted by tubes, not screw threads. How do you move the jackscrew?

  27. #27
    Gordon Misch's Avatar
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    Good point - I've been wondering that also. I guess just raise the jackscrew tower. A comparison of TCDS stab limits between 12 and 18 might be revealing, but I haven't made the comparison.
    Gordon

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    AkPA/18's Avatar
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    Quote Originally Posted by Gordon Misch View Post
    Good point - I've been wondering that also. I guess just raise the jackscrew tower. A comparison of TCDS stab limits between 12 and 18 might be revealing, but I haven't made the comparison.
    Approximately 1 degree positive up over wing angle.
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  29. #29
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    Quote Originally Posted by Gordon Misch View Post

    Now then, about that Ford pickup .... Oh wait, that's politics.
    I may be looking at a Dodge next time. The truck you rode in (F150) has been great but the F350/6.7 diesel just coughed up an engine. There went my new LyCon motor.
    After Monday and Tuesday, even the calendar says WTF !

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    Quote Originally Posted by stewartb View Post
    Do tell. My -12's yoke travel up and down was restricted by tubes, not screw threads. How do you move the jackscrew?

    You change the whole angle of the tail section of the fuselage. Look down the top longeron of an 18 from the front and you will see a downward turn of the longeron at the back of the fuselage in the area of the jack screw. Not a simple change to make and knowing how much to droop the aft end of the fuselage is the real challenge.

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    2*? Relocating the aft stab attach would be what needs to happen to do that. I think my own -12 had that much surplus trim available. No matter, I was talked out of the mod by a guy who knows a lot more about -12s than me. And that's part of why I thought -12 wings on an -18 airframe would be a fun E-AB project. But now, 10 or 12 years later? I'd just buy a 3-place Cub airframe or an SQ-12 if I needed a 2-place rear seat. I built the Rev instead. The baggage door makes a wider seat unimportant to me.

  32. #32

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    If you put the 12 wings on a 18 fuselage the tail will be correct to start with so not an issue. If you increase the incidence with top deck changes/ adjustable spar ends. Then you may need to adjust the tail, It can be done a few different ways. Pretty easy when uncovered.
    DENNY
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