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Thread: US35b Full size print out

  1. #41

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    Quote Originally Posted by JimC View Post
    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.
    The Piper ribs have the same "discrepancy" as the Dakota rib shown in Jim's picture. I am elbow deep in new Piper rib nose repair sections and second hand ribs at the moment and they are all like that with that concave appearing section along the top. I purchased a Univair nose rib and it is different again.

    I have chosen not to worry about it too much: Before the internet and everyone chatting about these sorts of discoveries and the Northland CD I just used to rebuild the aeroplane with the parts to hand and go out and fly it and it flew like a Cub. A jig was made by selecting the best looking Piper rib and drawing around it with a pencil. So, I have decided not to fret too much and just get on with it.

    Andrew.

  2. #42
    skywagon8a's Avatar
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    Quote Originally Posted by JimC View Post
    My hunch is that Piper was building to jigs, not drawings.
    I agree with JimC,
    It is not unusual, in prototype construction, to make the drawing from the first part. Then sometimes the engineers refine the drawing. Yet they still build subsequent parts from the original fixture. Thus the parts really never match the drawing. This may not be so likely to happen now in the computer age, but back then things were different.
    N1PA

  3. #43
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    Quote Originally Posted by MainlandCub View Post
    A jig was made by selecting the best looking Piper rib and drawing around it with a pencil. So, I have decided not to fret too much and just get on with it.

    Andrew.
    My point exactly, there was debate, but when I took measurements the discrepancies where all over the map, thus the conclusion that moving from jig to jig changed some of the ribs in less than 2% of the chamber thickness all together.

  4. #44

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    I found the Piper error of 4.036 vs 5.036 at the location of the concavity to be the most interesting. That goof did actually hurt the performance of the wing.
    Last edited by JimC; 03-21-2013 at 10:35 AM.

  5. #45
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    Hi Jim, are you referring to a station between station 44.100 and 50.40? I am not following the station you are referring to? changing 4.036 to 5.036 or vise versa only affects upper camber profile of the air foil, would it not? Sorry I think I need some coffee...

  6. #46

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    I'm referring to the upper surface ordinate at Station (abscissa) 3.15
    The draftsman mislabeled that ordinate as 4.036 when it should have been 5.036
    He drew the ordinate at 4.81, and that is what the Dakota rib is built to.

    Kerri-Ann's upper surface ordinate at Sta 3.15 is 5.040 (a difference of 0.004), which is good 'nuff fer guvm't work.
    Last edited by JimC; 03-22-2013 at 11:27 AM.

  7. #47
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    Cool, got it!!! What I sis when I drew it up was make ordinates according to the 104%, so I took the 35B airfoil and added the 104% to that, which is what should have been intended (I believed) and I come up with 4.92 (4.731 * 1.04.) I did not catch that on Kari-Ann's drawing. Probably why I did not have to add another ordinance to smooth the curve out, but who know. I will send you my DWG if you like... or send me the picture of the dakota rib and I can line it up. I have not been out to the hangar to get my ribs out and take some reference pictures with a ruler but I will try that ASAP and compare it using original piper ribs.

  8. #48

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    Check my post #35 for a photo of a photo of the Dakota Rib laid over Kerri-Ann's drawing and with my copy of the leading edge skin done from coordinates from Piper DWG # 10631 (and another drawing whose number I don't recall). For Station 3.15, the lower small green circle is where 4.036 would fall, the upper small green circle is at 5.036, and the intermediate small green circle is at 4.81 (which is what the Dakota Rib is built to).

    I've also tried to attach here, a copy of part of DWG # 10631 with the bad coordinate outlined by a black rectangle. That coordinate should be 5.036 instead of 4.036. However, I couldn't do so, because the upload software won't do anything larger than 620x280, and I can't fit the bitmap drawing into that aspect ratio. I was able to attach it as a jpeg.

    E-mail me at jrccea1 at gmail.com
    and I will send you a copy.

    I would like a copy of your drawing as well. A DXF file would probably be most likely to be compatible.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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    Last edited by JimC; 03-22-2013 at 07:49 PM.

  9. #49

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    I would like to edit my previous post, but can't. Piper Leading Edge Skin Drawing# 10630 has some good coordinates. Sta 3.150 upper surface is called out as 4.936", but only 4.990" will fit (this is in lieu of the 5.036 that I used instead of 4.036" as taken from another Piper drawing in my previous post). Most of the rest of 10630 looks pretty good, but the leading edge radius is 1.5436" instead of the 1.125" and 1.000" that Keri-Ann or I used previously. More to come.
    Last edited by JimC; 03-23-2013 at 10:14 PM.

  10. #50
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    Here is a comparison of the Wag Aero 2+2 vs the data from JimC and myself. Jim's is in blue and the ordinates come from the image above, I took the 35B data and added 4% to that and is in yellow.



    Well, as you can see JimC's data is closer to Wag-Areo and as soon as I can get some volunteer to send in pictures of Piper Ribs or Dakotas or D&E (am I forgetting anyone) that have been take as parallel as possible to the and have a ruler in the picture, I can line them up and see how they differ. Also, if someone has their J3 drawings form Wag Areo and they care to take a picture of the nose rib drawing with a ruler under it, that would help. My set of plans is in a box I currently can get to... had a friend invade my hangar and I don´t have access to a lot of my stuff at the moment.
    Regards,

  11. #51

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    The Pioer drawing doesn't specify the leading edge radius. I like yours better than mine, so changed my nose radius to match yours.

  12. #52

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    What do you guys with autocad plots think happens behind the Rib STA 18.900 upper ordinate? I know the Rib STA 25.200 upper ordinate is lower, but the tracing I have of a Piper rib shows and upper curve increasing past the Rib STA 18.900 upper ordinate before descending down towards the Rib STA 25.200 ordinate.

    However the best fit through the known ordinates from Piper drawing 13814 with a loose piece of cap strip doesn't follow the tracing of the Piper rib. I don't think I will be following the tracing of the Piper rib, but I was curious what your plots showed.

    I am looking at Piper drawing 13814 when quoting the Rib stations.

    Thanks,
    Andrew.

  13. #53

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    The digital copy of 13814 that I have is 'warped' with mid-chord being roughly 0.15 inch too high relative to the leading and trailing edge so that neither the upper or lower surface can be constructed by tracing. Consequently, it would need to be reconstructed from the printed stations and ordinates. I would do that, but not all of them are legible on my drawing. Anyone have a list of them?

    For example, the ordinate at 12.600 is 7.3?0. What is the ? digit?

    The ordinate at 25.200 is 7.4?0. What is the ? digit?

    The ordinate at 37.880 is 5.7??. What are the last two digits?

    I don't have the ordinate for Sta 50.400 or any of the stations and ordinates aft of there.

    With those in hand, it would take me a couple of hours to accurately reconstruct the drawing and extract the high point.

    As an aside, the station called out as 9.45 on this drawing is called out as 9.4375 on other Piper drawings.
    Last edited by JimC; 05-23-2013 at 09:58 AM.

  14. #54
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    Quote Originally Posted by Bugs66 View Post
    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.
    Fyi... The DWG was provided to me by a fellow member (thanks!) and is posted on my site in links page:
    http://www.supercubproject.com/links.aspx

  15. #55

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    I've already measured enough of 13814 in AutoCad this morning to tell you that it is NOT accurate.

    BTW, the drawing labled as 13814 on the link site is NOT 13814. It is one of Kerri-Ann's rib drawings overlaid with a leading edge skin drawn by me based on Piper Leading Edge Skin Drawing # 10630.

    The high point on the link drawing is at Sta 19.019 and the ordinate is 7.852.
    I wouldn't put much faith in either number.
    Last edited by JimC; 05-23-2013 at 10:30 AM.

  16. #56
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    Quote Originally Posted by JimC View Post
    The digital copy of 13814 that I have is 'warped' with mid-chord being roughly 0.15 inch too high relative to the leading and trailing edge so that neither the upper or lower surface can be constructed by tracing. Consequently, it would need to be reconstructed from the printed stations and ordinates. I would do that, but not all of them are legible on my drawing. Anyone have a list of them?

    For example, the ordinate at 12.600 is 7.3?0. What is the ? digit?

    The ordinate at 25.200 is 7.4?0. What is the ? digit?

    The ordinate at 37.880 is 5.7??. What are the last two digits?

    I don't have the ordinate for Sta 50.400 or any of the stations and ordinates aft of there.

    As an aside, the station called out as 9.45 on this drawing is called out as 9.4375 on other Piper drawings.
    This is from Piper drawing 13814 from the Northland CD.
    Leading edge = 1.77
    9.450 = 0.000 / 6.920
    12.600 = 0.031 / 7.390
    25.200 = 0.176 / 7.480
    37.800 = 0.283 / 5.770
    50.400 = 0.220 / 3.290
    56.700 = 0.126 / 1.780
    59.850 = 0.076 / 0.983
    63.000 = 0.000 / 0.164
    N1PA

  17. #57

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    Thanks.

    Would you confirm the Station 37.800 please?
    The drawing I have seems to read 37.880.
    I'll post the station and ordinate of the upper surface high point tomorrow.

  18. #58
    skywagon8a's Avatar
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    Yes, It is 37.800.
    N1PA

  19. #59

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    In your list, there is a missing station and ordinate at roughly about station 44.100. Do you have that station and ordinate?

    Also at either station 31.5 or 31.3. The ordinate at that point is 6.760.

  20. #60

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    The high point on Piper drawing 13814 appears to be at sta 19.346, ordinate 7.701.
    Consider this preliminary till I double check it tomorrow.

  21. #61

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    STA 44.100: .265 & 4.640
    STA 31.500: .246 & 6.760

    So it looks like it does not rise further past the STA 18.900 upper ordinate. (except for .001") That is good to know.

    Andrew.

  22. #62
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    Quote Originally Posted by JimC View Post
    In your list, there is a missing station and ordinate at roughly about station 44.100. Do you have that station and ordinate?

    Also at either station 31.5 or 31.3. The ordinate at that point is 6.760.
    44.100 = 0.265 / 4.640
    31.500 = 0.246 / 6.760
    N1PA

  23. #63

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    Thanks, guys.

  24. #64

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    Well, I finally finished redrawing the US 35B mod based on dimensions from a legible copy of 13814 that was redrawn without change June 15, 1951, compared it to leading edge skin drawing 10630, and extracted the camber line and chord line for the 35Bmod. Noticed several interesting things.

    The upper surface of 13814 is drafted wrong in front of Station 1.580. The drafting doesn't match the listed.dimensions and is too low.

    The chord line is rotated 1.755 degrees more than the old NACA reference line. Therefore all the old NACA data referenced to the angle of attack needs to have 1.755 degrees subtracted from the angle of attack to match current reference conventions.

    The leading edge radius is 1.498 inches (1.50 inches).

    The Station labled 37.800 should perhaps be 37.880 to match other drawings and to better match the listed ordinate of 5.770 (it calculates as 5.782).

    If I were to let all the listed Piper coordinates float by up to 0.0005 inch, I could slightly improve the fit, but I don't think it is worth the effort.
    Last edited by JimC; 05-26-2013 at 01:01 PM.

  25. #65
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    Great progress Jim!
    I have been busy working on the fuselage 3d for the Wag Aero 2+2, as soon I am done with that (many little mods here and there to get it just right) I will redraw the airfoil. Do you have the updated station data to make sure I use those and get the airfoil redrawn.

    All the best.

  26. #66

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    I do.

    I'm cleaning up the Acad drawing this weekend and will email you a copy in a couple of days.

  27. #67
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    Hello Darrel,

    The link to the airfoil data (after only 6 years ) is no longer working. Any leads on other good sources ?

    thanks,

    Jonny

  28. #68
    skywagon8a's Avatar
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    Quote Originally Posted by Jonnyo View Post
    Hello Darrel,

    The link to the airfoil data (after only 6 years ) is no longer working. Any leads on other good sources ?

    thanks,

    Jonny
    Is this what you are looking for? http://www.supercubproject.com/drawi...s/A3310184.pdf

    This drawing is from Bugs66's web site: http://www.supercubproject.com/
    N1PA

  29. #69
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    I found this:

    https://m-selig.ae.illinois.edu/ads.html

    Seems to be the root directory containing links to the airfoil data that Darrel linked to. Darrel no longer frequents this site. He has moved on to restoring a Curtiss.


    Wayne
    Thanks skywagon8a thanked for this post

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