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Thread: PA-12 Jig

  1. #1

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    PA-12 Jig

    Hi everyone! Thanks for a great site and an incredible amount of info.

    A little intro...my history is 21 years of Air Force aircraft maintenance and NDI. Currently taking care of a fleet of Beechcraft King Air 350's. So obviously I have very little experience with small GA aircraft, but have always had an interest, particularly with Cubs when I was stationed at Elmendorf. I had a dream....

    Fast forward about 24 years and I am finally in a position to pursue my dream of rebuilding and flying an airplane--both of which I don't know how to do, so I bought a pa-12. I know most will say foolish but thats what I like to do, so off I go...when I'm done hopefully I'll have a nice airplane to learn to fly in.

    Question 1: Who has a pa-12 fuselage jig in the Midwest? I'm in Oklahoma City. I spoke with Steve Pierce (very helpful and knowledgeable) but I think he is too busy and also not jigged for -12's. Fox aviation in Justin Tx haven't returned any calls.

    Question 2: How exactly (techniques) does a fuselage get "adjusted" back to straight. The tail is bent bad enough to plainly see, although it was flying like this. Will brute force, hairy eyeballs and a few pieces of string get you there? 😳

    Sorry for for the long post but I have exhausted the search function for a solid lead on pa-12 jigs.
    Thanks
    Scott

  2. #2

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    Sandblast frame and punch test tubes to make sure it is worth fixing. If you have a good solid jig!! Bolt in wing fittings, gear fittings, engine mount. and set tail. What you usually find is some of the bolts don't fit and tail is long or short of whatever you book says. Once plane is in jig take you time and figure out what has to move to make it right. Tie ribbon or tape to all bent tubes fittings and call all your friends to look at it. When they spot the stuff you missed tie ribbon or tape to that stuff. Go get some beer and figure out what to move to make it right. Now sleep on it, than go find what you and your friends missed. Once you have a plan start correcting all the bent tubes, get everything straight before you start cutting out bad tubing. On another side note this is a good time to put the tail feathers on and make sure the stabilator has the correct amount of travel. What really matters in flight is that the wings tail and firewall are in proper relation to each other!! If the wings and tail is right but firewall is all jacked up it won't fly well. So now is the time to start replacing bad tubing and extending or shorting nose tubes to get firewall, tail, and top deck incidence, right. Set the tail angles and make sure top deck is square. Gear fittings need attention also heat and portapower works well. Now is also the time to consider how bad the fever of MOREBETTERDISEASE has hit you. All the tabs for belly pods, metal belly, brake lines, battery, hold down rings, ELT, antenna, extended baggage, floats, skis, dash, and seat belts/shoulder harness should be tacked in. Baggage door, seaplane door, big door, cub seat and shooter window, all go in after frame is square. I would keep it in jig for the bigger door stuff. Once it is all straight and everything is correct. Go get some buddys and beer, look it over, take ribbon or tape and mark all the stuff you missed or that needs final weld. If nothing major than pull out of jig and finish welding tabs.

    If you don't have a jig than I would start with simple frame to bolt gear fittings to make sure they are square, flat and true. Than go from there with string, tape, and level (who knows that wing incidence may even end up more like a cubs). Without a jig clamp in a support rod as you cut tubes out. Mike and Steve can might have some tricks for this way of doing it. The nice thing about the fabric pipers is once you are in the ballpark proper rigging will correct for the small sins.

    I am sure I missed some stuff the others can fill in.
    DENNY
    Likes Ericklee liked this post

  3. #3
    www.SkupTech.com mike mcs repair's Avatar
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    you don't "need" a jig.... it just makes it faster

  4. #4

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    Does Univair do repair work?

  5. #5

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    I believe Javron Aviation has a PA-12 jig. Brainerd, MN.

  6. #6
    windy's Avatar
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    Univair sells PA-12 "long" and "short" tail sections. The long tail replaces about 10 ft of tail, up to just behind the cockpit. The short tail section is about half that. Both tails come with the halos that hold the stringers. Univair builds the tails in a jig, but there is still some welding to get it attached straight & square to the front half of the fuselage. Then there's all the morebetterdisease welding. I'm in the process of putting the Univair long tail section on my PA-12. A bonus, the new tail is 4130 chrome moly versus the original mild steel. We didn't use a jig, but made copious use of a level, plumb bob, chalk line, measuring tape, straight edge, square, and the Piper PA-12 drawing.

    It was surprising to set the old cut off tail section next to the new one. Mr. Piper's design is very forgiving, to think that my PA-12 could even fly straight with such a jacked up tail. I probably would have kept flying it that way, but found a big crack in the vertical tail post. There were enough crooked tubes, that for my case, it made sense (cost & schedule) to go ahead & bite the bullet on a new Univair tail. I'd rather be flying than fixing. I'll have to learn to fly all over again with a straight tail!
    Last edited by windy; 11-06-2016 at 06:18 PM.

  7. #7
    Cub junkie's Avatar
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    You may not want to put it in a jig. I second what mcs mike says.

  8. #8
    flybynite's Avatar
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    Write a check to Univair for a new fuselage with the baggage compartment, X brace, Supercub gear, etc. You will be $$$ ahead and HOURS ahead.

    Jay (Javron) has a jig for PA 12s but it will take a long time to turn your plane around. I used Univair's short section on my 12.

    Speaking from experience.

    Wayne

  9. #9

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    I just finished up my 12 a few months back and it seems to fly rite. It was pretty bad when I started and I got in way over my head. I basically just secured everything I could to the floor and checked a few measurements before I ever started cutting. I too used the Univair short fuselage section since I just found too much rusty tubing back there. Ultimately, I incorporated a ton of Alaska mods.
    Everybody that advised me that I would spend way more than the finished product was worth turned out to be right, but I like what I did and it sure turns heads. If you realize this to be true before you get in too deep, I'd sure give some serious consideration to "flybynight" suggestion for a new fuselage to start. You'll have a "new" 1947 airplane when you're done that way.

  10. #10

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    2nd Windy. It took about 7 hours. Plus about another 4 for miscellaneous bits. Looking for a jig will just take up valuable repair time and drag it out. Watch this video
    https://youtu.be/Sd3sw0OppWM
    One bite at a time, or just buy it like she did. Funny thing is, all our original fuses were mild aft of the cabin so the new 4130 tail will make your bird a lot tougher, and make it last through the next 50 years. If you decide to fix what's there you might consider at least replacing the longs, just do it one at a time.

  11. #11

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    I will be ready to fbought a new Unfair fuselage with all my mods already in it my 'new' 12 by June, I had the same concerns and issues you mention. So I shipped my bent old fuselage off to a guy who claimed to have a jig, 2 years later I got it back untouched. Too big of job he said, there was 2 years I would never get back, he was going to fix it and do all the mods for $8k or so, got it home and did hard head scratching and found a guy who thought we could do it labor wise for 5-8, plus materials, and all of my labor, e gads!

    Long story short, i bought a new univair fuselage with all the mods perfectly installed and I couldn't be happier, Jason was great to work with, as ordered and on time. I'M out of the country til Nov. ,15 but would be glad to visit with you after that. Do yourself a favor, buy new and spend your time on other issues you will have
    Doug



    Long story short-

  12. #12
    Gordon Misch's Avatar
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    www.super-12.com Steve makes and repairs -12 fuselages. He has the jig, plenty of experience, and produces superb workmanship. It certainly can't hurt to give him a call - -
    Gordon

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

  13. #13
    www.SkupTech.com mike mcs repair's Avatar
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    Quote Originally Posted by rsrguy3 View Post
    ..all our original fuses were mild aft of the cabin so the new 4130 tail will make your bird a lot tougher, and make it last through the next 50 years...
    not NEAR TRUE at all...

    the old mild steel stuff bends(and can be bent back) and stretches for decades.... the 4130 stuff cracks next to the weld in a couple years of abuse....

  14. #14
    www.SkupTech.com mike mcs repair's Avatar
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    so did univair ever get the -12 fuselage available with a useful big rear baggage area?? when i first seen them(2011?) they only had that useless original bag mount a bout a foot deep behind rear seat....

    ???

  15. #15
    Gordon Misch's Avatar
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    4130 elongation at rupture, 25.5%. Yield tensile strength 63,000 psi. Ultimate tensile strength 97,000 psi. http://asm.matweb.com/search/Specifi...bassnum=m4130r

    1020 elongation at rupture, 15%. Yield tensile strength 50,000 psi. Ultimate tensile strength 61,000 psi. http://www.matweb.com/search/datashe...f1cffbb&ckck=1

    Proper welding process is certainly important - -

    Edit: I didn't find any work-hardening/embrittlement data.
    Gordon

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

  16. #16
    Southern Aero's Avatar
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    Scott

    Like Mike said, you don't necessarily need a jig to repair.......... even for extensive damage. Jigs are best used for new construction. PM me some pics of what you have so I can look at it if you don't find some one closer. I'm in Georgia just south of Atlanta.
    ......... It doesn't cost any more to go first class! You just can't stay as long.

  17. #17

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    Quote Originally Posted by mike mcs repair View Post
    so did univair ever get the -12 fuselage available with a useful big rear baggage area?? when i first seen them(2011?) they only had that useless original bag mount a bout a foot deep behind rear seat....

    ???
    Yes they did, I have Atlee's way too big top and bottom extra baggage. Bottom means changing out the torque tube and bell crank to 18 style, all part of the stc. I also had them add in gross weight increase, sea plane tube, x brace, pa14 be uaggage cathedral, float fittings, 18 gear, belts to the floor, 18 seat, sea plane swing up door, I didn't know about Atlee's squared off door, wish I would have. Again univair was super to work with.

  18. #18
    aktango58's Avatar
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    I don't know where your plane came from, but if it is an original 60 year old frame, it has internal ills.

    Around here if you open your plane up with original tubes, we just pre order longeron material and pray we don't have to do the top, the bottom at the tail post is always bad.

    If you like to build, and that is your passion, consider building your own jig. I have seen a couple of 18 jigs, and they are really not that complicated, and would take less than a few days to tac together once you get the correct measurements. The trick is to have a lay down area large enough that you can secure all parts once you get them square. If you got fancy you could actually put in the gear and wing attach fitting on some type of jack screw so you could attach them to out of square parts and tension them as you heat to square it up.

    Not saying it would be easy, but it might be the same amount of time to build one as drive a few days to pick one up, or drop the frame off, and then drive again after done.

    Glad you have a goal in mind, and look forward to the process. Be aware, there was a 12 project a person was trying to sell on here, and was having trouble because the sum of parts were worth less than his cost. But having your plane, your way is not about cost and time.

    If you do build yourself a jig, I am sure others would want to use it after you are done! So build it sturdy.
    I don't know where you've been me lad, but I see you won first Prize!

  19. #19

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    Another vote for www.super-12.com give Steve a call his work is absolutely beautiful, very, very talented. I have one of his fuselages it is a work of art.

    Dan Borg

  20. #20

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    Wow! Thanks for all the input. I need to do a more thorough assessment first before I go for repairs or buy a new fuselage. My 3 year rebuild goal is going to tough to meet if I don't farm out or buy new. That's ok.
    Certainly good to know that the jig is not an absolute requirement as I would prefer to keep it in house for my own satisfaction.
    Scott

  21. #21

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    Normally I'd repeat the advice Charly Center gave me when I asked him about repairing/modifying my own PA-12 airframe almost 15 years ago. He told me it made less sense to spend money and time on that (then) almost 60 year old mild steel airframe and more sense to buy a new 4130 airframe with all the mods already done. But, if this is your first go a a Cub build and you don't have a Cub builder to steer you? A -12 project is already more difficult than an -18 but when you replace the airframe the -12 becomes a truly custom airplane. Nothing that came out of the old one will fit into the new one. That'll slow you down. At the end of the process I think everyone would rather have the new 4130 airframe.

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