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Thread: PA 18 wood stringers

  1. #1

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    PA 18 wood stringers

    I am looking for the exact dimensions of all the PA18 wooden stringers.
    Does anybody have them ?
    Are there improved versions ?
    What are they made of ?

  2. #2
    Steve Pierce's Avatar
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    Univair has aluminum ones. Shipping will eat you alive.

    Steve

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    Exactly what do you mean by stringers? If you are speaking of the stringers that hold the fabric away from the turtle deck and the fuselage on a cub you can get them from Univair. www.univair.com Assuming that is what you are talking about I believe that most folks replace all of them except possibly on the sides with either 1/2 or 3/8 inch thin wall steel tubing welded to the tabs for the stringers on the fuselage and turtle deck and also on the bottom of the fuselage. You can see this done in the some of the photos of my project. http://home.earthlink.net/~djfraudma.../supercub.html

  4. #4

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    I have contacted :
    SPRUCE - UNIVAIR - WAG AERO and others !, they are unable to give me the dimensions of the original Piper PA 18 wooden stringers for the fuselage.

    the exact dimensions I need are the following :

    PART NUM. DISCRIPTION HEIGHT WIDTH LENGTH
    14978-00 Botom stringer
    14983-03 Top stringer
    14984-02 Top LH & RH stringer
    14979-00 Sid LH & RH stringer

    Also, can someone confirme that these stingers were originaly made in SPRUCE

  5. #5
    Clay Hammond's Avatar
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    Contact Clyde Smith, old Piper employee and Cub guru. Now labors to keep old Cubs flying on. His number is somewhere in this forum.

  6. #6
    Steve Pierce's Avatar
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    My Super Cub project has wood stringers I will measure them and get back to you.

    Steve

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    Many thanks in advance for those measurments !!!

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    SuperCub MD's Avatar
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    Sorry, missed this question before, I would highly recomend the Univair aluminum stringers to anyone, but they will probably cost more than the plane by the time you ship them to France. The originals were made of spruce, and here are the dimensions for the part numbers you asked for.

    P/N 14978-00 3/8" X 7/8" X 162"
    P/N 14983-03 3/8" X 7/8" X 120"
    P/N 14984-02 3/8" X 7/8" X 109"
    P/N 14979-00 1/4" X 1/2" X 157"

    Radius two corners round and smooth, (the edges that touch the fabric). Also, try to get the spruce quarter sawen, it will be stronger and not warp as much.

  9. #9
    Steve Pierce's Avatar
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    Thanks Mark. You saved me a trip thru the mud to the storage hanger. You lost me on the quarter sawn though. I'll ask my brother the carpenter.

    Steve

  10. #10

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    Many thanks to all of you for your help !

    Come and see our PA 19 being restored here in Paris France.

    Our airfield is juste North of Paris ( LFPA ).

    Thanks again ...

    Marc André

  11. #11
    kiwicubber's Avatar
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    I have wooden stringers on our project Super Cub, is there any specification for the string to attach them? They have wax string wound around the ends to stop them splitting.

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    cheers Bill
    Bill and Neroli.
    www.supercub.co.nz

  12. #12
    Stew's Avatar
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    Univair Aluminium Stringers

    I needed a new set of stringers for a PA18-150 and ordered the aluminium ones from Univair.

    The shipping and customs costs to the UK, as mentioned above, were horrendous so I asked how many items they could get in the cardboard shipping tube for the same shipping cost and the answer was two sets so I went ahead and ordered two sets.

    It is possible that the spare set could become available but would have to check with another interested party.

    Kind regards

    Stew

  13. #13
    Steve Pierce's Avatar
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    I like the aluminum after seeing would crack, split and crack over time. They use safety ware to install.
    Steve Pierce

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    Will Rogers
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  14. #14

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    I used Douglas Fir in 1969. No holes drilled for safety wire. Two cover jobs later still dead-straight. Ceconite puts lots less stress on them than did Grade A. My originals were seriously bowed, as were some of my longerons.

    I used 3/4" for the turtleback instead of 7/8". I was in the Navy and making $92/mo. at the time, and just had the lumber yard rip a 1x8.
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  15. #15
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    Quote Originally Posted by bob turner View Post
    I used Douglas Fir in 1969. No holes drilled for safety wire. Two cover jobs later still dead-straight. Ceconite puts lots less stress on them than did Grade A. My originals were seriously bowed, as were some of my longerons.

    I used 3/4" for the turtleback instead of 7/8". I was in the Navy and making $92/mo. at the time, and just had the lumber yard rip a 1x8.
    When I first saw this thread I was wondering if anyone had tried Doug Fir. I have a nice 10 foot piece of VG fir rough cut as a 2X10 that I was thinking of using.
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  16. #16
    RaisedByWolves's Avatar
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    Saw a pacer with wood and they were bowed really bad. Looked horrible.


    Sent from my iPhone using Tapatalk
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  17. #17

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    I got tired of paying the high freight costs years ago, custom made a machine for routing and shaping wood stringers and it works great. I start with 3/4 X 3/4 Sq. fir good quality clear door stop material. I run fifty or sixty pcs. at a time, let them sit for a few weeks, a small percentage will twist and warp. If they are still straight after a few weeks they will be straight for ever.
    I prefer wood over aluminum. If you are struggling to move your cub in deep snow, and accidentally push on the side and bend an aluminum stringer it is almost impossible to straighten it. If it is wood it might crack or break but you can get inside and splice it, and from the outside will never know it was damaged. The profile of the ones I make are like a mushroom and are slightly stronger. Also when I am installing the fus. fabric with the seam down the back, I can use map tacks to hold the seam to the stringer while the glue dries. It helps keep every thing straight. I have used wood stringers for over 25 years and the aircraft that I used them on are still as straight as the day I installed them.
    I would take a sample of the original to a local company that specialize in wood working and get a price on having them make/ copy them. Have them make some extras in case of fitting mistakes or warpage.
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  18. #18
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    Quote Originally Posted by Leo12 View Post
    I got tired of paying the high freight costs years ago, custom made a machine for routing and shaping wood stringers and it works great. I start with 3/4 X 3/4 Sq. fir good quality clear door stop material. I run fifty or sixty pcs. at a time, let them sit for a few weeks, a small percentage will twist and warp. If they are still straight after a few weeks they will be straight for ever.
    I prefer wood over aluminum. If you are struggling to move your cub in deep snow, and accidentally push on the side and bend an aluminum stringer it is almost impossible to straighten it. If it is wood it might crack or break but you can get inside and splice it, and from the outside will never know it was damaged. The profile of the ones I make are like a mushroom and are slightly stronger. Also when I am installing the fus. fabric with the seam down the back, I can use map tacks to hold the seam to the stringer while the glue dries. It helps keep every thing straight. I have used wood stringers for over 25 years and the aircraft that I used them on are still as straight as the day I installed them.
    I would take a sample of the original to a local company that specialize in wood working and get a price on having them make/ copy them. Have them make some extras in case of fitting mistakes or warpage.
    Just letting you know, I’m filing your name in my book for if/when I need to recover my airplane.
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  19. #19
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    Thanks Leo, is there a special string that you use for attaching the wooden stringers to the fittings?

    cheers Bill
    Bill and Neroli.
    www.supercub.co.nz

  20. #20

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    The top arches have weld on clips with teeth that bite into the side of the wood stringer to hold it in place. The side stringers (two) and top (three) are attached at the front, and fit in to and behind channels. Left hand channel is attached to the rear boot cowl sub panel support former and is attached with .020 or .025 SS lock wire. The right hand stringer is shorter and fits into a similar channel behind the cabin door frame and is also lock wired. These front attachment channels sides, top and bottom are drilled in two places on the side of the channels to accept the lock wire, so the lock wire is not proud of the outer surface of the stringer.

    Down the side and bottom of the fuselage, where the stringer is going to contact any of the tubes, the tubes should be protected with hockey tape to protect the tube from abrasion, from the stringer, and the lock wire that is going to hold the stringer in place. I drill a hole (small .020 or .025) about halfway across the stringer, using this hole to lock wire the stringer to each tube it comes in contact with. Do the same for the belly stringer. I have never seen string used to hold the stringers on. Also the two side stringers should be lightly pulled and tied together in the last most rearward bay so as not to leave a large bump on the out side of the fabric. Lock wire can be used for this also. This also goes for the two top side stringers. PS --If you are going to abrasion clean your fuselage, DO NOT USE SAND. Make sure that you take it to some one that can glass bead it.
    Good luck with your project.
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  21. #21
    kiwicubber's Avatar
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    Thanks Leo, that’s a very good and clear explanation. Do you know if there a drawing that shows the attachment method?

    cheers Bill
    Bill and Neroli.
    www.supercub.co.nz

  22. #22

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    I just epoxied the turtle deck stringers. Only 49 years later still stuck. I wired the side stringers, but found out later that you can glue them too - fabric cement is enough, because once the fabric is shrunk and doped, they are not going any where, ever.
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  23. #23

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    The drawing I have found so far are for the PA-12 drawing 24056AO. It shows that the original attachment method used .032 brass locking wire and a cloth tape called friction tape. Don't substitute the cloth tape for electricians tape as it traps moisture and can case corrosion. I believe all of the cub models used the same attachment method. I am not sure if you can still buy brass locking wire? I am sure that some place I have the PA-18 stringer installation drawing, I will keep looking, but I am sure it shows the same method of attachment. Are you looking for approved data that will satisfy the civil aviation people? Hope this info helps.
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  24. #24
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    Drawing 21621

    Drawing 21621 is on the Northland CD and is relevant all Cub wood stringers and shows Revision "L" on 8th Sep 1948 to include PA17/18/19/20/21. Not seen anything yet about installation.

    Have attached copy but site upload limitation means that reproduction is not very good.

    Have cleaned it up a bit, just PM me with your email if you want a copy sent to you.

    Kind regards

    Stew
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  25. #25
    kiwicubber's Avatar
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    Thanks Leo and Stew, I have the drawing 21621 and also the fuselage drawing 12183, but as you say Stew, nothing about installation. We are rebuilding a certified Super Cub so must keep to the original as much as possible, within the limitations of current materials etc, and what has been done to the aeroplane since 1957. When we got it the stringers were attached with string, which I have also seen on another cub of similar vintage, but our other cub, a 100 hp one, had the wooden stringers replaced by steel u tube. Sometimes we can and have to be practical in the rebuild process.

    cheers Bill
    Bill and Neroli.
    www.supercub.co.nz

  26. #26

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    Hi Bill
    We have just fitted the top 3 stringers to our fuse and used epoxy and also the wax string. I will find out where to get the string from and let you know. Failing that I will send you some.
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  27. #27

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    I have found the two PA-18 drawings that show how the stringers were attached. Piper drawing 14486 Jan 23 ,1957and Drawing 139595 Rev. s April 5,1974. both use SS safety wire
    Hopes this helps
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  28. #28
    kiwicubber's Avatar
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    Thanks Leo, would you be able to send a copy by PM please?

    cheers Bill
    Bill and Neroli.
    www.supercub.co.nz

  29. #29
    Steve Pierce's Avatar
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    I have the 14486 drawing but Drawing 139595 Rev. s seems to have to many numbers but I can't find anything close. Can you email me a copy as well. steve@pierceaero.com
    Steve Pierce

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  30. #30
    Stew's Avatar
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    Piper drawing 14486 Jan 23 1957 and Drawing 139595 Rev. s April 1974.

    Much appreciate a copy of these drawings as well, fixing my stringers this very week.

    Kind regards

    Stew

    sd_edwards@hotmail.com

  31. #31

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    Sorry my mistake, Its drawing 13959. I found and left the drawings at my satellite office, and it is a fair distance from me at this time. I should be back there in a few weeks and will bring them back with me. I did take cell phone photos of the title blocks and stringer info, that I will post hopefully later to day. Thanks again
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  32. #32
    Captain Ron's Avatar
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    The same information (I assume!) is shown in Figures 2 through 6 on drawing 13388 which is available through Christian's excellent site (http://www.supercubproject.com/drawi...s/A3250023.pdf).

  33. #33

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    PA 18 wood stringers

    Quote Originally Posted by Leo12 View Post
    Sorry my mistake, Its drawing 13959. I found and left the drawings at my satellite office, and it is a fair distance from me at this time. I should be back there in a few weeks and will bring them back with me. I did take cell phone photos of the title blocks and stringer info, that I will post hopefully later to day. Thanks again

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