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Thread: Modifying my super cub squared wing's tips

  1. #1

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    Modifying my super cub squared wing's tips

    I am about to recover my super cub wing and told the A&P to take off my Xwinds STOL CONCEPT tips and put on Dakota Cub tips. He said he didn't think we could do that as those CONCEPT tips were part of the original wing modification of squaring off the wing and lengthening out the aileron, he thought. Surely I could do that I would think, but how? I really want to keep my squared wing with the longer aileron and then add my Fowler flaps. I think it would be a hecka of an overall good mod and performer. And we could use a few good Piper ribs and where might I find those bad boys? Thanks for any help I can get on this "holding me up" paperwork issue.

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    www.SkupTech.com mike mcs repair's Avatar
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    Modifying my super cub squared wing's tips

    Not ALL parts of an STC mod need to be installed. Up to the installer for/mechanic. For example we had a citabria with a crosswinds stol fences, but no cuff, paper work time at sale cleanup and FAA said that’s fine just log it as part of stc...


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    RaisedByWolves's Avatar
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    You can also extend the flaps inboard. Part of the stc, you don’t have to have the rest installed.


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    I have 40 years of paperwork and we just found an STC that would allow me to do that and put Sullivan tips on. I really would like to go Carbon Concept tips or Dakota Tips. Does anyone know of any paperwork, field approval I guess, that would allow me to go from Sullivan tips to Carbon or Dakota tips?

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    Owner produced part?
    DENNY
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    www.SkupTech.com mike mcs repair's Avatar
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    I think you(your mechanic..) is making this harder than it needs to be....

    I have in the past gotten field approvals to put a dakota style copy tips on when Sullivans were called for(sullivan had a weird multi STC's of THEIRS required thing, my FAA inspector just shook his head about..)... but that was back when it was EASY to get field approvals, I think it's pretty relaxed now, and unnecessary....

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    I have a old set of sullivan tips I will swap ya for the charley center ones. I would call CAC in wasilla and see if they can make you a new set or better yet a carbon fiber set.
    DENNY

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    I had a FSDO inspector tell me one time... "It's OK, we don't care what you do with your wingtips because it doesn't make that much difference.. you can write it in as a minor alteration." When I was a young guy I watched a hangar door come down on a 172 with droop tips. They put an "original style" (pre '72) tip on that side (only tip at the airport) and took it out and flew it.... stalls, etc. The old guy (whom I love, Is long deceased, soloed me, and is a God in my view) said he couldn't tell the difference.
    I dunno, not trying to sell anyone on anything but I do remember those things.
    Also, one of the survey guys I know has a Cub with simply blunt last-rib tips.. that one gets off faster than any of the others I've watched... kind of like an Ag Cat. He didn't waste the weight on any fancy lift-enhancing devices out there.
    The Rutan quote..(I believe) of - " If you let it go and it doesn't rise it's too heavy" applies I think.
    Also that part about whether it lifts it's own weight plus some...
    FWIW, when I put my Cub back together (apart for rust long ago - not bent) it's going to have the original tips - I doubt any of the changes make a sweeter wing.

  9. #9

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    Quote Originally Posted by DENNY View Post
    I have a old set of sullivan tips I will swap ya for the charley center ones. I would call CAC in wasilla and see if they can make you a new set or better yet a carbon fiber set.
    DENNY
    Denny,
    Possibly. I met you up there when I was at the AK. Av meeting in May too. I looked at your plane. Remember me? What is CAC? Do you mean Carbon Concepts? I like his stuff. BUT I may just cap them off; I don't know yet. Those tips I have weigh, I think, about 14 lbs each? I really am not familiar with the Sullivan tip and how it looks and performs next to a Dakota Cub tip. I think, if I could do anything and wanted a tip over just capping it, I would prefer a DC tip made by Randy in carbon fiber.

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    Here's a Dakota tip next to a Sullivan. They are very similar with Dakotas being a little smaller. Don't think it matters much what way you go.Click image for larger version. 

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  11. #11
    www.SkupTech.com mike mcs repair's Avatar
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    CAC and carbon concepts are same family. Different businesses


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    I remember, I would off to buy the tips off you, but I spent all my fun money on a new cam and followers.
    DENNY

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    Quote Originally Posted by DENNY View Post
    Owner produced part?
    DENNY
    Owner produced parts need to comply with the Type Design. He can’t change the design as an owner produced part.


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    Quote Originally Posted by mike mcs repair View Post
    Not ALL parts of an STC mod need to be installed. Up to the installer for/mechanic. For example we had a citabria with a crosswinds stol fences, but no cuff, paper work time at sale cleanup and FAA said that’s fine just log it as part of stc...


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    Only if the STC makes that provision. If an STC doesn’t explicitly say portions can be installed, then the entire STC needs to be installed, or you need an additional approval (Field Approval, DER Approval, one time STC) to install piecemeal.


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    That would have been my guess. One fed told me that a field approval had to be followed exactly, and made me specify a particular brand of hose. I got that changed before block 3 was stamped.

    The strange thing is you can install two different STCs, and no fed has to approve, even if they have differing effects. I learned that when a buddy put micros on a Sportsman leading edge. They just measured from the new leading edge.

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    Denny,
    I would possibly trade my Center tips for your Sullivan tips but I would have to have my A&P OK it as "legal"(so any paperwork you can supply me on your tips would help) and the tips would have to be in pretty good shape as I am putting in all new wing parts and want a first class job (which I am getting and then some). I am trying to knock at least 75 lbs out of this plane so the carbon fiber route is how I would like to go if my A&P can come up with the legal paperwork to do this. Again, also looking at just "capping" the ends which I have never heard of (probably the lightest thing I can do). Like I said before, I have 40 years of paperwork and many "Alaskan" mods for my mechanic to go through and see what all of our options are.

  17. #17
    www.SkupTech.com mike mcs repair's Avatar
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    Quote Originally Posted by dgapilot View Post
    Only if the STC makes that provision. If an STC doesn’t explicitly say portions can be installed, then the entire STC needs to be installed, or you need an additional approval (Field Approval, DER Approval, one time STC) to install piecemeal.


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    not according to our FAA...

  18. #18
    cubpilot2's Avatar
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    I got rid of the plane booster droop tips, extended the ailerons
    and finished it with the existing plywood rib.
    Works great. I did get a field approval at the time.
    You have to end the wing somewhere. It doesn’t have to be “fancy”.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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  19. #19

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    I am having some new tips made by the Airglas people in Anchorage same as the one Carbon Concepts make but far better quality. I have a set of theirs and they just do not lay down to fit right at rib, just a bit too flimsy and warped where screws go on the inboard edge.
    Ones I will have should be complete next week.
    Advise if anyone wants a set. Not priced yet.
    What would a nice quality set be worth? Carbon fiber and light, will see weight next week.
    Going on a Husky, but same as Cub rib.
    John
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    Quote Originally Posted by bob turner View Post
    That would have been my guess. One fed told me that a field approval had to be followed exactly, and made me specify a particular brand of hose. I got that changed before block 3 was stamped.

    The strange thing is you can install two different STCs, and no fed has to approve, even if they have differing effects. I learned that when a buddy put micros on a Sportsman leading edge. They just measured from the new leading edge.
    Every STC has a limitation that says the Installer is responsible to determine that the interrelationship between this STC and any other previously approved modifications will induce unairworthy characteristics. There is even an AC that helps you make that determination.


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    Quote Originally Posted by mike mcs repair View Post
    not according to our FAA...
    There in lies the problem, no standardization between FSDOs, and even between inspectors in the same FSDO


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    Quote Originally Posted by dgapilot View Post
    Only if the STC makes that provision. If an STC doesn’t explicitly say portions can be installed, then the entire STC needs to be installed, or you need an additional approval (Field Approval, DER Approval, one time STC) to install piecemeal.
    That's my understanding also.
    Or at least how it should be interpreted IMHO.
    Installing two different STC's that may interact is NOT the same as installing only part of an STC.
    Cessna Skywagon-- accept no substitute!
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  23. #23

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    Quote Originally Posted by dgapilot View Post
    There in lies the problem, no standardization between FSDOs, and even between inspectors in the same FSDO


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    Truest statement on supercub.org.

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    Quote Originally Posted by dgapilot View Post
    Only if the STC makes that provision. If an STC doesn’t explicitly say portions can be installed, then the entire STC needs to be installed, or you need an additional approval (Field Approval, DER Approval, one time STC) to install piecemeal.


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    I thought I heard through the tundra telegraph that Charlie at Crosswind would issue a deviation from the STC if you only wanted let's say extended inboard flap. I would agree that in my reagion you wouldn’t be able to deviate from the STC without a field approval or deviation from the STC holder.
    Last edited by PA-22/20-160; 10-28-2018 at 12:34 PM.
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    Quote Originally Posted by dgapilot View Post
    There in lies the problem, no standardization between FSDOs, and even between inspectors in the same FSDO


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    that is no problem. Because one mans junk is anothers treasure. I think i said that the right way? were all individuals and if everything was done according to one mind this world would suck.

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    So does this boil down to the fact that if I want to add a wing tip, that isn't in any of my STC paperwork, then it's either a "minor alteration", and A&P determined (and needs no approval) or I have to get a "field approval",by the local FSDO folks? Same with just "squaring the wing off" with no tip at all, which I think is a great idea too and doesn't weigh sicum? I think supercub.org is a fantastic site; I should have been using this more over the years because of the quantity of "experience" out there to help each other figure things out. I like the education part of it and "ideas" (I never thought of that) part of it. Thanks!
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    Click image for larger version. 

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ID:	39510Every time I see Boeing’s latest multi million dollar wing tip . I think , hey they just stole crosswinds design.��
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  28. #28

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    Anyone have an idea for stc’d led replacements on the two wingtip(red and green) tail (white) and belly strobe lights? I believe my PA-12 has original lights (see pictures) and original wingtips.Click image for larger version. 

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  29. #29
    www.SkupTech.com mike mcs repair's Avatar
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    Quote Originally Posted by dgapilot View Post
    There in lies the problem, no standardization between FSDOs, and even between inspectors in the same FSDO


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    yes I remember asking my inspector if i could do something some one else 's fat said they couldn't(same office) and he was like "yes, but don't get me into a debate with the other guys in the office...."

    key thing is to ask for right guidance, then NEVER ask again once you've gotten the right answer you need!

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    Quote Originally Posted by mike mcs repair View Post
    yes I remember asking my inspector if i could do something some one else 's fat said they couldn't(same office) and he was like "yes, but don't get me into a debate with the other guys in the office...."

    key thing is to ask for right guidance, then NEVER ask again once you've gotten the right answer you need!
    And get it in writing or email! I’ve seen lots of times when a violation gets issued, without paper or email from official source, the response will always be “I never said that”!


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    DGA has the idea. Granted, a lot of paperwork never gets looked at - we have really high power approved repair stations that routinely skip ADs on annual. One Mooney went for twenty years without fuel tank or control column AD compliance. Another doesn't do the Champ DMB wheel AD. And I mentioned the Cub muffler AD missed by three different shops (I insisted on an Atlee Dodge muffler - I hate doing that AD on a Super Cub).

    So a fed says "minor" (by the way, modify a wing rib and it is not "minor"). Then change address and IA. On the minuscule chance that your new IA even spots it, you could be in for an expensive "un-modification!

    I really like the less extreme wingtips, shown above. We do have a Super Cub here with those giant droops. Nobody likes them. Dakota makes reasonably good looking tips. I have no idea if modified tips do anything for a Cub. They usually hang them on after 200# of other kitschy mods, so performance is down from the get-go.

  32. #32
    BC12D-4-85's Avatar
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    Charly at Crosswinds told me years ago that his dad Cal started with a flat flare to his wingtips. Then he kept bending the rear down until it helped performance. Finally he needed to add the upper fin to maintain the curved shape under windloads. Someone should confirm that but whatever worked was the bottom line. Great times then to be an experimenter which they both were and are.

    Gary
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    My old tips would need some work for sure. Call Dakota cub and see if they have a STC for their wingtip alone. I would use a Univair rib on the end. It gives you a solid structure for whatever you want to hang on the end.
    DENNY

  34. #34

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    Quote Originally Posted by bob turner View Post
    DGA has the idea. Granted, a lot of paperwork never gets looked at - we have really high power approved repair stations that routinely skip ADs on annual. One Mooney went for twenty years without fuel tank or control column AD compliance. Another doesn't do the Champ DMB wheel AD. And I mentioned the Cub muffler AD missed by three different shops (I insisted on an Atlee Dodge muffler - I hate doing that AD on a Super Cub).

    So a fed says "minor" (by the way, modify a wing rib and it is not "minor"). Then change address and IA. On the minuscule chance that your new IA even spots it, you could be in for an expensive "un-modification!

    I really like the less extreme wingtips, shown above. We do have a Super Cub here with those giant droops. Nobody likes them. Dakota makes reasonably good looking tips. I have no idea if modified tips do anything for a Cub. They usually hang them on after 200# of other kitschy mods, so performance is down from the get-go.
    The statement by the fed was in reference to a cessna wing, with no modifications involved. Simply another shape at the tip. I do believe if you start cutting your Cub wing you will be doing something considered a major alteration and the requisite paperwork would need to be filed.
    The comment about him calling it a "minor" was aimed at the idea of whether or not the particular shapes had much to do with adding performance.
    Again, I don't know, and would love like the next person to find the magic bullet.. but it all seems to come down to weight.
    A friend of mine commented that he wondered if the plane would slip as well without the original tips. That was food for thought for me and enough to decide to keep the nice round blend of original when I finally put mine together again.
    Pure perfomance - my bet would be on the last rib covered with fabric.. but I really dunno and really don't care.. except for gaining knowledge.
    One good reason to file a 337 is to have it for the time the "problem" FSDO guy shows up. Since there is no particular requirement to retain maintenance and minor alterations (other than transponder) records past a year, it's easy to have things not on the books. With a 337 you can show it was agreed to at a certain point in time. That's why I like to file them if I know they will be well-received by my PMI, because then it's on the record, whether needed or not.
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  35. #35
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    Quote Originally Posted by tempdoug View Post
    that is no problem. Because one mans junk is anothers treasure. I think i said that the right way? were all individuals and if everything was done according to one mind this world would suck.
    I agree when it comes to Fords vs Chevvies or blondes vs redheads.
    Disagree when it comes to "the law"....
    anything you can get approved by the Anchorage FSDO should also be approvable by the Seattle FSDO, and vice versa.
    I know a guy who was building a Pacer with a lot of mods--
    he didn't have paperwork or any other approval documentation for some of them.
    He did talk to an IA who said he'd sign them off as minor alterations...
    I told him to think long and hard about going that route,
    he might be have trouble passing muster at annual time someday with a different IA who's more of a stickler..
    Cessna Skywagon-- accept no substitute!
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  36. #36

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    Modifying my super cub squared wing's tips

    Quote Originally Posted by hotrod180 View Post
    I agree when it comes to Fords vs Chevvies or blondes vs redheads.
    Disagree when it comes to "the law"....
    anything you can get approved by the Anchorage FSDO should also be approvable by the Seattle FSDO, and vice versa.
    I know a guy who was building a Pacer with a lot of mods--
    he didn't have paperwork or any other approval documentation for some of them.
    He did talk to an IA who said he'd sign them off as minor alterations...
    I told him to think long and hard about going that route,
    he might be have trouble passing muster at annual time someday with a different IA who's more of a stickler..
    I always tell someone that is planning on making a “minor alteration” determination to follow that up with the decision logic from AC43-210A figure 3-1. If you use the FAAs own guidance, answer the questions truthfully, and document it in the maintenance records, even if someone in the future disagrees, you have documentation to support your decisions. The real question with wing changes (even just tips) how do you support no change to performance or flight characteristics without flight testing? Isn’t the original idea of changing tip to change performance?


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  37. #37
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    My old PMI always used to tell me that he never heard of anyone getting in trouble for filing a 337....but he'd seen a few that did for not filing one.
    John

  38. #38
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    Quote Originally Posted by tbone View Post
    Anyone have an idea for stc’d led replacements on the two wingtip(red and green) tail (white) and belly strobe lights? I believe my PA-12 has original lights (see pictures) and original wingtips.Click image for larger version. 

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    The quick and easy way is to use LED replacement lamps in the same light assemblies.

    Web
    Life's tough . . . wear a cup.
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  39. #39

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    Just filing a 337 doesn't do it. For a major alteration (a wingtip, for instance) you need either a field approval with an FAA stamp in block 3, or an STC, or something that has been determined to be "approved data" for the installer.

    I am with Web on the lights. That's what I did. I figure a lightbulb change barely needs a logbook entry. Barely. (I hate cluttered logbooks; my oil changes go on the hangar wall, to be erased in a year).
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  40. #40

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    You can pretty much erase everything but AD compliance, transponder checks, time-life components (any on a Cub?), and major repairs/alterations within a year if you don't like cluttered logs.
    One AMD inspector suggested I keep a "needed" set of records, and an "archive" set of records. Makes it easier for the inspectors to glean the relevant information, but still allows you to keep a history of your plane. That history is not required by regulation but is desirable for most. I don't like incomplete logs but aside from the aforementioned (unless I forgot one) they are not required.
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