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Thread: US35b Full size print out

  1. #1
    tcraft128's Avatar
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    US35b Full size print out

    Anyone have a full size print file for the US35b? I need to make a rib repair jig and it would be nice to start with the correct shape.

    Turning money into noise since 1996

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    Would the Wag-Aero 2+2 wing work?

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    Bugs66's Avatar
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    Drawing 13814 on my web site should be it.

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    tcraft128's Avatar
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    I think the 2+2 will work. I am looking for something that I can print actual size and I am not savoy enough to do it from a pdf. Is there an option to print it scale?
    Turning money into noise since 1996

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    Bugs66's Avatar
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    The drawing is 36x24 or so. Take the PDF on a flash drive to Kinkos or maybe you have a friend with a plotter.

    Edit: was just looking at 13814, the scale is half (6in = 1ft) so yeah, you would need to enlarge.
    Last edited by Bugs66; 03-09-2011 at 07:43 PM.

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    D.A.'s Avatar
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    Quote Originally Posted by tcraft128 View Post
    ...I think the 2+2 will work...
    You probably already know this but the Wag Aero airfoil is different than the Piper airfoil. You are correct, the Wag airfoil is the US35b, while the Piper is "Modified".

    Your project is awesome!

    D.A.

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    www.SkupTech.com mike mcs repair's Avatar
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    Quote Originally Posted by tcraft128 View Post
    ..... I need to make a rib repair jig and it would be nice to start with the correct shape.

    and WHICH version of piper rib sizes/shapes do you HAVE to repair?

    bothering to make a print that's 3/8" different from your ribs you got might not be to useful for you.....

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    D.A.'s Avatar
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    Quote Originally Posted by tcraft128 View Post
    ...I need to make a rib repair jig and it would be nice to start with the correct shape...
    That's why I bought a Dakota rib. Nice crisp line to lay the jig airfoil out with. I had an original Piper rib for the trussing.

  9. #9
    tcraft128's Avatar
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    I have a mix of Super Cub and Pawnee. I did not know there was a difference.

    Thanks for keeping me straight!

    Bugs drawing and Kinko's sounds like the best bet. The engineers here have a plotter, but they are kinda hard to talk to....
    Turning money into noise since 1996

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    Bugs66's Avatar
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    I was able to scale the rib drawing full size using Photoshop. I attached here but will put a copy in my drawings site soon. The drawing size is now 36x72 so you will need a plotter for sure. Make sure you turn off any scaling when printing this PDF. If anyone prints this let me know if the dimensions are ok. As far as I know they are.

    13814_rib_full.pdf

  11. #11
    D.A.'s Avatar
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    Quote Originally Posted by Bugs66 View Post
    The drawing is 36x24 or so. Take the PDF on a flash drive to
    I did the exact thing Bugs. I attached the 12183 drawing from your website to an email and sent it to our local OfficeMax. I called them, asked them to print it on their 36" printer and it was done when I got there. Thanks for having the resource available!

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    You're really heading off in the wrong direction. Never scale off drawings. That is a hard and fast rule from those of us from the pre-CAD age.

    Bugs' drawing has the co-ordinates on it. Plot that out on the piece of board or whatever you're using for your rib jig. If you can't do that, buy a rib from Dakota or Univair and build your jig around it. That's all I did with a good Piper rib.

    Seriously if even if the Piper draughtsmen drew that profile out accurately and without error, the scanning will have distorted it for sure, no matter what machine was used.

    I hope that helps.

    Cheers,
    Andrew.

  13. #13
    Bugs66's Avatar
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    You can easily measure the printed drawing to verify if accurate. If a CAD wizard wants to contribue a fresh drawing that would be welcome! I will host it on my site.

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    Is there and advantage to having the "Modified" airfoil over the US35b?

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    Dave Calkins's Avatar
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    I like the straight '35B better, I think.

    Would love to hear what the smart-guys have to say about the "advantages" of the "modified".

    .....? DAVE

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    D.A.'s Avatar
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    Quote Originally Posted by canopyflier View Post
    Is there and advantage to having the "Modified" airfoil over the US35b?
    I'm not an expert by any means, but I don't think there is a standout advantage to either airfoil. Here's a link to the thread where I compared them one on top of the other:
    http://www.supercub.org/forum/showth...ighlight=chris

    If anything, with the higher camber, I'd say the Wag airfoil is probably a higher lift airfoil. The airfoils are very close, but they're "Just different enough" that you can't mix and match them. Chris and I went with the Piper version because of all the research and support and ready replacement parts that are available. Other than that, I wouldn't think there would be much difference. Just my 37 cents worth.......

  17. #17
    SpainCub's Avatar
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    Hi,

    Here is a files I picked up somewhere (I can´t recall where) but it was nicely drawn by Keri-Ann Price.

    I will be emailing her soon to see if she could come up with the 613.5 Airfoil fully drawn as this file...

    BTW Bugs file measures out if you print, but this file will give you better lines to work from.

    http://www.j3-cub.com/forum/attachme...14-airfoil.pdf

    Ok, so I could not find the file on this computer, but I did find the link where I had gotten it.

    http://www.j3-cub.com/forum/f88/some...6/index12.html

    We should try to get her to build a PA-18 or a Wag Areo 2+2, she could be very resourceful.

    All the best,

  18. #18
    fobjob's Avatar
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    I thought the upper ordinates were increased by 4 %, not .4%.... what would be the point of changing them only .4%???

    ...unless it was a mechanical fit issue...??
    Last edited by fobjob; 01-20-2013 at 05:18 PM.

  19. #19
    Darrel Starr's Avatar
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    Here are some great references to airfoils. Covers just about every plane built.
    http://www.ae.illinois.edu/m-selig/ads/aircraft.html
    http://www.ae.illinois.edu/m-selig/a...atabase.html#T
    The web site has the USA35B but not the "Modified USA35B" as used in Pipers.
    http://www.ae.illinois.edu/m-selig/a...ots/usa35b.gif
    http://www.ae.illinois.edu/m-selig/ads/coord/usa35b.dat

  20. #20
    fobjob's Avatar
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    Here's the wind tunnel data, anyway.. http://www.supercub.org/photopost/sh...sa-35b&cat=500

  21. #21
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    Quote Originally Posted by fobjob View Post
    Here's the wind tunnel data, anyway.. http://www.supercub.org/photopost/sh...sa-35b&cat=500
    This is very interesting. It shows that the stall angle is just below 20 degrees. I would not have suspected that it would have been that high. My guess was that it would have been nearer to 16 degrees. I think that I shall make a angle of attack indicator on a pole mounted on the wing. Perhaps I'll also fit a floating pitot tube to the same pole? The results should get us into some interesting conversation.
    N1PA

  22. #22
    fobjob's Avatar
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    Probably more with the VG's on.....

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    The AOA of the USA35b and USA35bMod were referenced to the bottom of the wing, not the chord line as is done now. That's the reason for the seemingly high stall angle.

    The coordinates of the USA35b are screwed up at the leading edge radius. There are also discrepancies between different Piper rib drawings (false rib and full rib noses are shown different -- they aren't). There are quite a few mistakes in the Piper wing drawings.
    Last edited by JimC; 03-16-2013 at 06:00 PM.

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    Quote Originally Posted by JimC View Post
    The AOA of the USA35b and USA35bMod were referenced to the bottom of the wing, not the chord line as is done now. That's the reason for the seemingly high stall angle.

    The coordinates of the USA35b are screwed up at the leading edge radius. There are also discrepancies between different Piper rib drawings (false rib and full rib noses are shown different -- they aren't). There are quite a few mistakes in the Piper wing drawings.
    Any chance of naming those errors or at least the ones you remember?

  25. #25
    SpainCub's Avatar
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    Quote Originally Posted by JimC View Post
    The AOA of the USA35b and USA35bMod were referenced to the bottom of the wing, not the chord line as is done now. That's the reason for the seemingly high stall angle.
    The coordinates of the USA35b are screwed up at the leading edge radius. There are also discrepancies between different Piper rib drawings (false rib and full rib noses are shown different -- they aren't). There are quite a few mistakes in the Piper wing drawings.

    Please share which drawings you are referring to and what errors you have found? I am reviewing and redrawing some of the wing parts based on both Piper and Wag Areo drawings, so your feedback would be greatly appreciated.

    I think that one of the many issues with the Piper drawings are the revisions, they are not all there... what I am trying to do is get the latest rev, then used that as a base for parametric relationship of the parts, ad you stated the false rib is something I was looking into.

    BTW, can you clarify your comment of high AOA? I am not following you there... (I know it's me... so can you be so kind to please explain this further with a bit more detail? )

    Quote Originally Posted by qsmx440 View Post
    Any chance of naming those errors or at least the ones you remember?
    +1 Caught me typing and walked away thinking I had posted, then saw your post!!!

  26. #26

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    OK 25 posts of people giving their best guess. Let's go to "the" source, Clyde Smith, Jr. - The Cub Doctor. Quoting from the Sept/Oct 2005 Cub Clues newsletter A Study of Piper Ribs Clyde says in part:

    "All fabric Piper ribs employed one airfoil design, the USA 35B, but were modified by increasing the upper coordinates by 4%. Thus the terminology "USA 35B Modified" was the typical description of the Piper rib and the chord was 63 inches. All the ribs were similar from the J2 through the PA-25 Pawnee.
    ...
    In my weekend siminars, I divide the wings into two classes, the "Cruiser Wing" and the "Cub Wing". The Cruiser wing was used on the J4, J5, PA-12 and PA-14. The Cub wing was used on the J3, PA-11, PA-18, PA-25 and all the short wingers. The differences here were that the Cruiser wing had the "S" or "Sloped" type of false spar and had a stamped nose plate rivited into the leading edge or nose section of each rib, rather than the individual truss type bracing.
    ...
    The Cruiser wing panels did not have the short nose rib sections between each main rib either
    ...
    The Cub type wing had the concave type false spar and the nose of each rib had the individual brace members. These wings also utilized the short nose rib sections, forward of the main spar, between tha main ribs."

    John Scott

  27. #27
    behindpropellers's Avatar
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    I would be interested in milling out some jigs for you guys.

    I'm not sure what the demand is but if people wanted 10 or so Jigs built I would do it.

    Thanks

    Tim

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    I'm installing tile in the washroom today. Will get back in more detail later. In the meantime, as just one example, on different Piper drawings, the leading edge radius varies between 1.00 and 1.39 inches, and the radius point moves around. Just aft of the radius point on the top surface there are mistakes in the listed coordinates that make the upper front surface too flat. This has adverse effects on the stall characteristics of airfoils built to the coordinates shown (Piper didn't always build to the drawings).
    fro
    Note the zero reference line in Post #20. In modern wind tunnel work, the aoa is referenced to the chord line (a straight line drawn through the trailing edge and the radius point of the leading edge radius). In older airfoils like the 35b and 35b Mod, it was referenced to a straight line drawn from the trailing edge tangent to the lower surface of the wing. That makes the stall aoa of these older airfoils seem to be several degrees higher than it would be in modern usage. just subtract the angular difference between the two reference lines to adjust the old wind tunnel data to modern usage.
    Last edited by JimC; 03-17-2013 at 10:21 AM.

  29. #29

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    Quote Originally Posted by JimC View Post
    I'm installing tile in the washroom today. Will get back in more detail later. In the meantime, as just one example, on different Piper drawings, the leading edge radius varies between 1.00 and 1.39 inches, and the radius point moves around. Just aft of the radius point on the top surface there are mistakes in the listed coordinates that make the upper front surface too flat. This has adverse effects on the stall characteristics of airfoils built to the coordinates shown (Piper didn't always build to the drawings).
    fro
    Note the zero reference line in Post #20. In modern wind tunnel work, the aoa is referenced to the chord line (a straight line drawn through the trailing edge and the radius point of the leading edge radius). In older airfoils like the 35b and 35b Mod, it was referenced to a straight line drawn from the trailing edge tangent to the lower surface of the wing. That makes the stall aoa of these older airfoils seem to be several degrees higher than it would be in modern usage. just subtract the angular difference between the two reference lines to adjust the old wind tunnel data to modern usage.
    Thank you Jim. Probably 20 people looked at your original post and twenty different worries came up. In my case I was worried that some hole location in the spar was off or a bracket was called out in the wrong place or missing. The thread is about rib design and I forgot that for a moment. There are so many types of builders from "order a kit" to Marty 2+2 (the only thing he didn't do was chop the trees down and brew the glue). We draw from various sources and are willing to spend different amounts on "plans" and parts. For some reason I'm determined to use strictly the free plans from Buggs site so those are the ones I worry about. I finally bought my ribs from Dakota after the pedigree of my "garage sale but new ribs" came into question.

  30. #30
    SpainCub's Avatar
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    Jim, thank you, that does make alot of cense to me now!

    Regards,

    JM

  31. #31
    SpainCub's Avatar
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    Quote Originally Posted by Longwinglover View Post
    OK 25 posts of people giving their best guess. Let's go to "the" source, Clyde Smith, Jr. - The Cub Doctor. Quoting from the Sept/Oct 2005 Cub Clues newsletter A Study of Piper Ribs Clyde says in part:

    "All fabric Piper ribs employed one airfoil design, the USA 35B, but were modified by increasing the upper coordinates by 4%. Thus the terminology "USA 35B Modified" was the typical description of the Piper rib and the chord was 63 inches. All the ribs were similar from the J2 through the PA-25 Pawnee.
    ...
    In my weekend siminars, I divide the wings into two classes, the "Cruiser Wing" and the "Cub Wing". The Cruiser wing was used on the J4, J5, PA-12 and PA-14. The Cub wing was used on the J3, PA-11, PA-18, PA-25 and all the short wingers. The differences here were that the Cruiser wing had the "S" or "Sloped" type of false spar and had a stamped nose plate rivited into the leading edge or nose section of each rib, rather than the individual truss type bracing.
    ...
    The Cruiser wing panels did not have the short nose rib sections between each main rib either
    ...
    The Cub type wing had the concave type false spar and the nose of each rib had the individual brace members. These wings also utilized the short nose rib sections, forward of the main spar, between tha main ribs."

    John Scott
    John, missed your post, looking for that quote now. Thank you!

    If it weren't for the fact that I have two J3 cub ribs and a 12 and 14 rib, I would have never considered this, however the two j3 line up pretty good as do the 12 and 14, but the 14 and 12 are slightly larger at the cord that the j3, however they don´t perfectly line up to the original piper drawing as the j3 is slightly small and the 14 is slightly larger cord. Only the 12 lines up the closes to the drawing... I guess this is all has to do because of the jig differences... 4% is very subtle expect at stations where the cord is thickest at station 18.9... right now from my notes, j3 is 7.53 and 7.56 inches and the 12 is 7.68 inches and the 14 is 7.74 inches... :/

  32. #32
    www.SkupTech.com mike mcs repair's Avatar
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    Quote Originally Posted by SpainCub View Post
    ...
    ....I have two J3 cub ribs and a 12 and 14 rib, ....
    the -18 (j3 too???) is longer or shorter behind rear spar in aileron bay by about 1/8" than a -12/-14....

  33. #33

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    By cord, are you referring to the chord (the distance between the leading edge and the trailing edge)?
    Is it different between the 3 and 12 ?

  34. #34
    SpainCub's Avatar
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    Hi JimC, By cord thickens I was referring to camber thickness on the airfoil. Click image for larger version. 

Name:	Aerodynamic_camber.jpg 
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    To answer your question, yes there are differences hence my questioning if the j3 and the 12/14 weren't different, the old USB 35B and USB 35B Modified, it's hard for me to gestimate as the difference is slightly more then half of what it should be in modified vs standard 35B camber thickness. 7.74 - 7.53 = 0.21 inch vs the +0.308 inch where the standard 35B should have 7.392 inches the modified is 7.7 inches, and non of the ribs measure on or the other...


    Mike, these are full ribs, and their cord length is almost identical only thing that makes them different is slight bends along the entire rib and it is less than 0.067 of an inch when I convert form millimeters :P and I pace a heavy DM board on them to measure.

    These are supposed to be all original Piper ribs, but been in Europe, I'm almost certain that some repairs where made that could have change the ribs all together, all airplane where wrecked at one time or another and surplus parts where used to spring them back to life.
    Last edited by SpainCub; 03-18-2013 at 03:13 AM. Reason: goofed on the decimals!!!

  35. #35

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    I overlaid an AutoCad drawing of the leading edge skin (from printed dimensions on the Piper Drawing) over the photo of the nose rib that was posted above. Both had issues and neither matched the Piper Drawing.

    The PDF print of that was 153 megabytes, so I can't post it here. So, I just took a photo of the screen. It may be too large to post as well.

    The three small green circles near the upper surface represent one problem area. The Piper drawing called for that ordinate to be 4.036" (the bottom circle). It should have been 5.036 (the top circle). The Piper draftsman drew it as the middle circle (and the nose rib appears to match the error in the drawing, giving a concave upper surface near that point- oops). When drawn by dimensions, the height of the nose radius point is also off by a little over a tenth of an inch.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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    Last edited by JimC; 03-18-2013 at 08:04 AM.

  36. #36

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    That's not a Piper nose rib; it's Dakota Cub. Who does a Piper nose rib match the drawing?

    John Scott

  37. #37

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    I was well aware that it is a Dakota rib. I used it because it was also used earlier in this thread and because it is wrong.
    I haven't been out to the airport to pick up a Piper rib to compare it to the drawing (which contains inconsistencies as well) -- the coordinates and dimensions listed on the Piper leading edge skin drawing don't match the drawing linework and don't match the Piper rib drawing. These drawings are all typical of our drafting tolerances and shortcuts in the days before we had Cad software.

    My hunch is that Piper was building to jigs, not drawings.
    Last edited by JimC; 03-18-2013 at 09:11 AM.

  38. #38
    www.SkupTech.com mike mcs repair's Avatar
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    Quote Originally Posted by JimC View Post
    I....

    My hunch is that Piper was building to jigs, not drawings.
    Yup theres a video on youtube showing the ribs being made

  39. #39
    www.SkupTech.com mike mcs repair's Avatar
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    Quote Originally Posted by mike mcs repair View Post
    Yup theres a video on youtube showing the ribs being made
    at about 11:00 mark


  40. #40

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    Thanks Mike. I never seem to tire of watching that. After some new phase in building I go back and look at it again and learn something new in the details that I had missed before I tried making a part.

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