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Thread: limitations on 13 rib wings

  1. #1

    limitations on 13 rib wings

    is there any limitatins on 13 rib wings as far as hp is concerned? 150hp or 160hp.

  2. #2

    13 rib

    No such limitations on HP 150/160 with 13's
    There is a lower VNE limit with the 13's
    I fly 13's
    VNE limit on a cub, there you go

  3. #3

    13 rib wings

    How about gross weight limitations?

  4. #4
    I'm a 1750 Gross with 13 all legal begal
    30.5 Dodge tank is OK too

    I think it's just a VNE thing

    Anyone else out there please respond

    PA19guy

  5. #5

    Re: 13 rib wings

    Quote Originally Posted by mikombs
    How about gross weight limitations?
    Does anyone know if the 13 rib wings are legal on the 2000 lb gross weight STC?
    The most important aspect of this signature line is that you don't realize it doesn't say anything significant until you are done reading it & then it is too late to stop reading it....

  6. #6
    Yes the 13 rib wing is legal for the 2000# GW STC from Wip.

    Frank

  7. #7
    Just to add a little more info. . . The early Ag models with the same wing had a gross of over 2,000 lbs. But, of course in the restricted category.
    Larry C.

  8. #8
    I'm a 1750 Gross with 13 all legal begal
    How did you get your 13 rib wings legal. Are your wings field approved?? As far as I know, all 150 horse factory cubs had 15 rib wings. I am putting together a cub out of parts now and the owner bought a set of newly covered 13 rib wings to put on his modified 18A-150 airframe. Any info you have would be appreciated to get his legal without having to add two ribs to his wings, otherwise we would have to take the knife out.

  9. #9
    What is the VNE for a 13 and 16 rib wing? doug

  10. #10
    Is your plane a actual PA18A-150? If so you will need the 16 rib wings. If its a earlier PA18A converted to a 150 engine you can use the 13 rib wings with a 1750 gross weight per Roger Borers STC.

    The reason you would need 16 rib wings with a PA18A-150 is because thats what they had at the factory and why the VNE and flap speeds are higher. You will have 2 extra ribs in the flap bay area making the flap false spar stronger so the flap speed is 85 instead of 80.

  11. #11
    Quote Originally Posted by tempdoug
    What is the VNE for a 13 and 16 rib wing? doug
    13 rib is 138. Not sure on the 16, but it's around 150, I think.
    Volunteer, in charge of Political Correctness

  12. #12
    Are there any more structural differences with the 18A-150?

  13. #13
    Is your plane a actual PA18A-150?
    Unfortunately it is. I told him to make sure he gets the right wings...
    Looks like I need to get the knife out

    Thanks.

  14. #14
    We are just finishing up a set of wings that were 13-rib and are now 16-rib wings. There sure is a lot more to it than just adding two ribs!

    Every single rib was relocated although the compression members and wires remain in the same locations.

    We replaced the leading edge and false spars because they had large cut-outs for the previous ribs and the newly located ribs would have required more cut-outs. These extra cut-outs would have very much reduced the attachment strength, thus allowing the wing to be excessively flexible and "warp."

    The folks at Dakota Cub and Northern Piper (Dakota Cub dealer) were extremely helpful, we purchased their parts and Dakota 23-gallon tanks. Everything fit very well, and they were very helpful with the common problem areas. Northern Piper (907) 561-0430.

    A DER in Anchorage is working with me on getting the paperwork right.

    Have fun, be patient and plan on replacing those phillips head screwdriver insert bits several times throughout the project! Vickie

  15. #15
    Have you tried to get a FA to drop the VNE and flap speeds? I think this is the way I would approach it instead of butchering a perfectly good set of wings. Use one of the STC's that bring the 13 rib wing to 1750# standard cat and the TC as supporting data.

  16. #16
    I have changed 13 rib to 16 rib before, last time was on uncovered wings though. Right now we are trying a paperwork approach to get legal.
    Fun, Fun......

  17. #17
    Quote Originally Posted by Frank T
    Yes the 13 rib wing is legal for the 2000# GW STC from Wip.

    Frank
    Since it was brought up...It is my impression that the Wipline PA-18 2,000 lb gross weight upgrade kit can only be installed on a stock wing. No slotted leading edge or extended wings. Am I correct in this or has anyone had one approved on modified wings? Crash
    "The fear of God is the beginning of wisdom". Psalm 111:10

  18. #18
    Crash

    That one I don't have an answer for. Next time I run into Wip I'll ask him. I do know that they only did static testing on the stock wing.

    Frank

  19. #19
    Another Question,

    Is there any advantage of the 16 Rib as opposed to the 13 Rib stock wings besides VNE?

    David.

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