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Thread: Piper J4A Cub Coupe

  1. #1

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    Piper J4A Cub Coupe

    Hello Folks,

    Are there any other Piper J4A Cub Coupe owners out there?

    Thanks, Tim

  2. #2
    Bushwhacker Air's Avatar
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    I think the guy who owns the J4 that use to sit on the pavement at Key West used to lirk around here.

    I have friends that own a very nice one - great bird.

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    Try training a pilot from zero in one. I am so far not totally successful. It is an awful feeling needing a brake and not having one. So far no damage, but we are only at fifteen hours.

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    Bob, is it safe to assume that this is your J4? It's been 10 years or so since I last flew a tail wheel plane, and that was in the first J4 I owned and sold; I wish I hadn't sold it.

    There differently is a learning curve. I know I'm going to need some duel time with my 'new' one before I feel comfortable again.

    My first one had the old expander tube brakes that at least would hold the plane during run-up. When I got my new J4 it had been converted over to the Grove disc brake system. I'm lucky if I can hold the plane at 1000 rpm's. So far we've found one hose that leaked like a sieve and a fitting that was totally cross threaded. I'm sure the system is full of air. Both disc and pads had fluid on them also, I'm not sure if you can get the brake pads dried out once they get soaked with the fluid.

    Even with the old expander tube brake system under the right conditions it was still possible to stand it on it's nose.

  5. #5
    lov2fly's Avatar
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    I own a 1939 J-4A. It has been in the family since 1947.

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    Tim - my problem is that the instructor's side has no brakes at all! The student has Grove brakes.

    This aircraft has been on its back several times, not by me.

    The latest was by a pilot with over 4000 tailwheel hours. The guy was not familiar with Cubs. The airplane has a starter, and UL of 398 #.

    Grove brakes, properly maintained, are good enough to hold a Cub at full power- as are the stock brakes. The Grove Cub brake is identical to the Mooney 201 brake. The parts interchange! Don't try it, it is illegal.

    Not my airplane, and this is the last student in a J-4. Give me a J-3 any day.

  7. #7
    cubdriver2's Avatar
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    Welcome Tim, at one point we had 7 flying here in NY and 5 or 6 more that are projects, I've got a photo of 4- J4s all on 1320edo's in a loose formation above Bob's island in the upper Hudson, I get about 225 hrs a year on my J4a, 40 on skis, 120 on floats and the rest on 4x25 goodyears, be very carefull of the brakes, they are not your friend, all J4s are very nose heavy, Bob the one you are flying with the starter even more so, compared to the over 2000hrs in a pa11 the J4 is very blind when the tail is down, even worse with the 25'' tires on, but you get used to the bad view and adjust to deal with it, it's a great aircraft but different then a J3/pa11.

    Glenn

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    Cub X's Avatar
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    I have a 41 J4E, a little different than an A model. Cowelled in with starter and generator, metal spar wings etc.
    Kevin

  9. #9
    cubdriver2's Avatar
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    Quote Originally Posted by Cub X
    I have a 41 J4E, a little different than an A model. Cowelled in with starter and generator, metal spar wings etc.
    Just wondering what your baggage lb capacity is, I don't think the E model is as nose heavy as the A's are, the A has a 105lb rear baggage but you don't have the 16gal front tank.

    Glenn

  10. #10
    Cub X's Avatar
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    Front tank is ony 7 gallons and an 18 gallon wing tank. I believe the bagage is around 50lbs. I wouldn't put more than that in that bag anyway.
    Kevin

  11. #11
    cubdriver2's Avatar
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    Quote Originally Posted by Cub X
    Front tank is ony 7 gallons and an 18 gallon wing tank. I believe the bagage is around 50lbs. I wouldn't put more than that in that bag anyway.
    Thanks, made my bag out of that HD mesh that they cover the dump truck loads with and I sat in it ( 205lb ) to test it, has over 100lbs in it almost every weekend, when I recover the fus I'm going to remove the bag and make the baggage go to the floor with a tunnel for the cables, never enough room in a float plane.

    Glenn

  12. #12
    Cub X's Avatar
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    How is your cargo bag fastened. Mine just snaps in with buttons around the cross tube and on the wood trim along the sides. I also get some interference from my battery box underneath on the right side. I am leary of putting to much in there because if it gives way it would interfear with the control cables underneath. I wish i could put mine on floats but it's an E model and the type certificate doesn't allow for them.
    Kevin

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    Quote Originally Posted by cubdriver2
    I've got a photo of 4- J4s all on 1320edo's in a loose formation above Bob's island in the upper Hudson,
    Glenn
    Glenn,
    I'd like to see the pictures, there is a possibility that one of J4's is one I used to own years ago, plus I'm pretty sure I know the Island you're referring too.
    Tim

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    i own a 41 J4E. I've owned it for about 27 yrs

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    cubdriver2's Avatar
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    Quote Originally Posted by timj4a
    Quote Originally Posted by cubdriver2
    I've got a photo of 4- J4s all on 1320edo's in a loose formation above Bob's island in the upper Hudson,
    Glenn
    Glenn,
    I'd like to see the pictures, there is a possibility that one of J4's is one I used to own years ago, plus I'm pretty sure I know the Island you're referring too.
    Tim
    Tim, I'm working on the pix, they are printed but the guy who took them is going to send me some digital ones

    Glenn

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    cubdriver2's Avatar
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    Quote Originally Posted by Cub X
    How is your cargo bag fastened. Mine just snaps in with buttons around the cross tube and on the wood trim along the sides. I also get some interference from my battery box underneath on the right side. I am leary of putting to much in there because if it gives way it would interfear with the control cables underneath. I wish i could put mine on floats but it's an E model and the type certificate doesn't allow for them.
    The bag has a tunnel sewn into the top front and top back of the bag and a 1/4" tube slid the full lenth from side to side, the front is lashed to the cross tube for the top of the seatback, and the back is lashed to the cross tube behind the bottom of the headliner, with 3/16" ply for a floor to help distribute the weight.

    Glenn

  17. #17
    Cub X's Avatar
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    The plywood is a great idea...might help protect my cargo bag from tearing on the battery box corner. Here is a pic of my J4.
    Kevin

  18. #18
    Tim's Avatar
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    here's Glenn's


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    Lov2fly, cubdriver2, Cub X, cubx3. A question to all you long time J4 owners, and anyone else for that matter. My overhead trim crank mechanism works but feels a little 'floppy' when turned, anyone had this problem?
    Tim

  20. #20
    cubdriver2's Avatar
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    Floppy, it feels like it's loose in it's mount ? not sure what you mean, on a side note, if you want to keep the trip cable in tention at all temps remove the left wing root fairing and just above the door opening is a adjustment for the trim cable, if I remember it's a 4-40 threaded stud with a nut that you tighten to adjust to keep it under tention, the other end has a pully that captures the trim cable and pulls it sideways so that it's tight enough to maintain friction on the trim handle pully, if you want to make it work better put a compression spring on the 4-40 stud between the nut and the fuselage bracket that the stud comes through and tighten it down compressing the spring half of it's travel and your trim will have perfect tention ( no slip ) year round.

    Glenn

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    Quote Originally Posted by cubdriver2
    Floppy, it feels like it's loose in it's mount ?
    Glenn
    Glenn, it's the mounting that feels loose. The first J4 I had had the same problem. Back then I just quit using it, on my "new" plane I'd like to fix the problem.
    Tim

  22. #22
    Cub X's Avatar
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    I believe its just a brass bushing that the trim crank goes through. Probably changable... I will have to look at it next time i fly.
    Kevin

  23. #23
    cubdriver2's Avatar
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    I flew last nite, never noticed it before but mine is also very floppy, crank end of handle moves up and down about 1 1/2" seem to work fine, I don't think it's a bushing problem, the handle is held on with a pin if I remember and the holes are most likely egged out.

    Glenn

  24. #24
    Cub X's Avatar
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    Finally took a look at my trim crank. Pin that pulley is mounted on goes through a bushing in the mounting plate. I then have a pipe style spacer, washer and then the crank handle with a cotter pin. There is no up and down play what so ever, just a little wable from wear between the pin and bushing. You may need to add a spacer if your getting up and down movement. Do you have a headliner or sky light?
    Kevin

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    Quote Originally Posted by Cub X
    Finally took a look at my trim crank.
    Kevin, what did you have to do to look at the way the trim crank mechanism is mounted in your plane. I think that the mounting system in mine may have loosened up.
    Tim

  26. #26
    Cub X's Avatar
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    I don't have a headliner, everything is exposed and a sky light above. You can see it from inside and from above.
    Kevin

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    Quote Originally Posted by Cub X
    I don't have a headliner, everything is exposed and a sky light above. You can see it from inside and from above.
    Kevin, I have a headliner and obviously can't see squat as how the trim crank mechanism is attached to the ceiling cross members. Any chance you could take a picture.
    Tim

  28. #28
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    Side view showing trim mounting cross member between V in top structure.

    Top view, a little hard to see but you get the idea.
    Kevin

  29. #29

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    Kevin, thanks for the picture. As you can see from my setup you can't see any thing. ( unfortunately it will take me a while to figure out how to post a picture) I have to admit that when I said the system was floppy I didn't explain it very well. The crank handle itself appears to be pretty solid, but the indicator scale is the thing that’s floppy. Depending on which end of the indicator scale you push up on it moves between 1 to 2 inches up. The scale is only attached to the headliner itself, not anchored to anything, it's just hanging from the headliner. There is a cable that is attached to the pointer on the scale When you turn the crank the pointer moves, but the whole system squeaks and squawks, differently not smooth at all, seems like a very fragile setup. Yours looks a whole lot better.
    Tim

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    Lets see if this works.
    [/img]

  31. #31
    Cub X's Avatar
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    I was under the impression it was your trim crank, the indicator is a different cable comming from the trim tab itself. There isn't much to it, a thin wire like cable that is spring loaded. I just have a piece of rod that is attached across it and slids back and forth over a plate that has graduations on it. There is also a spring in there somewhere. If you look at my last picture, the view through the top window you can see the plate a little ways back from the trim crank. Yours seems to be very close together. I will take a picture of the indicator next time i am down at the hanger.
    Kevin

  32. #32
    Darrel Starr's Avatar
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    I vivited Bob Schefter's shop in Fergus falls, MN last Thursday. There is a very interesting J-4A project Bob is working on. If anyone can help, they desperately need a cowl or any cowl parts for a J-4A -- if you can help, please call Bob at 218-205-0463.
    Thanks, Darrel

    It took an english wheel expert to remake the lower boot cowl!







    One of the most interesting aspects of this project are the original STAINLESS STEEL tail feathers!





    Please help out if you can -- with leads on getting a cowl!!!

  33. #33
    cubdriver2's Avatar
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    As far as I know the J4A's never had SS tail feathers, they were on the J4ES seaplane model if I remember right, also never saw a panel like that in any of the J4's I've seen before, the drop below the panel looks weird and in the way of your knees, but it looks very nice what's been done, I have a complete firewall forward with bright work that I'm saving for my boo boo day, good luck finding a original nose bowl, you could find gold on the moon sooner, just my opinion.

    Glenn

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    Somebody reported that Clyde Smith has a device that allows the data plate stamps to align - may have been the device Piper used in those days. Bumping a cowling is not the most difficult thing in the world - but you need a concrete form. Borrow a cowl, make a concrete form, and find some .032 dash O aluminum. I used 7075-O in 1966, and four thousand hours later it is still in one piece. I had no idea what I was doing, but the aluminum moved for my hammer. Even the edges rolled without splitting even once.

  35. #35

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    j4

    If you take your headliner loose around the pilot's side door frame you will be able to see most of the trim system.I just had mine apart to change the idler pulleys.

  36. #36
    Darrel Starr's Avatar
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    Bob did tell me that he designed and built the lower panel "mantle clock" piece to house the fuel valve.
    Even if we are looking for gold in out-of-the-way places, we live in hope that that perfect "new-old-stock" J-4A cowling will be found in a box in some hangar someplace.
    For example, when I was a 16 yr old I bought a 1937 Ford Cabrolet convertible. It was worth $65 at the time, probably $30K+ now -- too bad I sold it long ago. Anyway, it had dented rear fenders so I went up to my local Ohio small town Ford dealer (in about 195 and asked if he had new fenders for it. They directed me upstairs where they had all kinds of new stuff for 1930s cars. I bought new rear fenders for my car for $5 each, Oh the good old days!
    Darrel

  37. #37
    cubdriver2's Avatar
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    The reason that a J4 cowl is worth it's weight in gold is because you have a VERY nose heavy airplane when flown solo or without baggage or fuel in the rear tank everyone of them has been on it's back ( by by nosebowl ) we had one here that ended up on it's back and a local guy bought it from the insurance co and spent about a $1000 fixing it with used parts and got it back in the air, on it's very first flight he landed a little long ( they float and stall slower then a J3 ) and he got on the brakes a little and put it on it's back again, on it's first flight. My friend spent $6500 on a project just to get the boot cowl and nose bowl for his J4.

    Glenn

    PS, by the way, there are 4 different nosebowls for the J4 if you count the 39/J4 with the cyl exposed and 3 for the closed cowl models

  38. #38
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    Darrel, his workmanship looks flawless, what he built sticks down more then the stock throttle/ fuel valve shelf, if your 5'10" or over there's no room for your knees with the stock setup, get him to put the seat and cushion in and sit in it before he gets to far down the road, I totally removed my fuel valve location and at 6' with a passenger it's pretty tight even with it removed, remember it has sticks so you have to sit bow legged to get full aileron control.

    Glenn

  39. #39
    Darrel Starr's Avatar
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    I'll send Bob Schefter an email and hope that he reads all of your good comments. He is a fine craftsman -- we are very happy with the cover and paint on our SC, N18SY, that Bob did two years ago.
    Darrel

  40. #40

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    Quote Originally Posted by Cub X
    the indicator is a different cable comming from the trim tab itself. There isn't much to it, a thin wire like cable that is spring loaded.
    Kevin,
    If I understand you correctly there are two cables that are connected to the trim system. A heavy cable that actually moves the trim tab and another small cable that is some how slaved off the trim tab that moves the indicator? If you look at the picture I posted you'll see that there are 4 screws that attach the indicator plate to the headliner, and that’s exactly what it feels like they are attached too, the headliner. If you push the plate it moves up and down with the headliner, the plate is not attached top anything solid. I guess that the only way I'll know is to remove the screws. Probably open a can of worms there.
    Tim

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