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Thread: PA-18 Lower Cowl Drawing

  1. #1
    Darrel Starr's Avatar
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    PA-18 Lower Cowl Drawing

    I have emailed the following lower cowl .dwg and.pdf files to several people. Here they are attached in case others want them. The .dwg file can be used to have pieces water jet cut. The .pdf file can be printed at a FedEx Office Store or similar print place to create a full size pattern for cutting out a part -- beware: I have not made any parts from these drawings.
    I discovered that the FedEx printer doesn't print precisely to actual size so the routine is to print one full size, measure the actual lengths on the print of the 26.75 and 25.375 dimensions and adjust the printer setting. In my case that was (26.75/26.625) x 100 = 100.5% size. That worked perfectly. If you tell the FedEx printer operator what you want to start with, they will only charge you for the perfectly scaled copies, about $7 each. The .pdf drawing is a 33 x 33 inch size. Ask them to print it full scale or actual size on 36 x 48 inch paper.
    Example of the drawings as printed at FedEx:
    Attached Thumbnails Attached Thumbnails Lower Cowl 151105.pdf  
    Attached Files Attached Files
    Thanks stknrddr thanked for this post

  2. #2
    www.SkupTech.com mike mcs repair's Avatar
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    here a mod you should do to prevent the round airbox from rubbing a hole in air scoop, that is common on most cubs

    leave front and pivot every thing in red box both edges...

    presto no more issues
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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  3. #3

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    Hi Darrel

    I'll cut one on my CNC machine just for fun and post the results.

    Don
    supercub180@gmail.com

  4. #4
    Darrel Starr's Avatar
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    Don, that would be fantastic. ' hope it doesn't crash your CNC!

  5. #5
    Steve Pierce's Avatar
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    Awesome. Thanks Darrel.
    Steve Pierce

    Everybody is ignorant, only on different subjects.
    Will Rogers

  6. #6

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    Darrel

    The results of a couple of hours playing (I mean work) this afternoon:


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  7. #7

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    Darrel (and others), a couple of points about the process.

    1) your drawing had lots of unjointed vectors. For example where a straight line ends and is radiused into the next straight line. My software (cut2d) has a utility to automatically join these individual lines within a certain distance (0.010 or 0.005 works well), but it got confused by dimension lines, reference lines, etc. after deleting these lines one at a time, I was able to join all the lines into a single shape for the outside, another for each cutout etc. the cleaner the file is the better, no text, non cutting lines etc.
    2) I then setup a toolpath, select a shape, select a tool, inside or outside cut etc. this is pretty easy, experience has shown if I choose the one outside cut first, then all the inside cuts can be done with the next toolpath.
    3) export to the machines 'toolpath' software
    4) import to the machine
    5) setup the x,y,z reference points, and the bottom of material, top of material etc.
    6) turn on the 5hp vacuum pump to hold the sheet in place
    7) press start and find something else to do for 15 minutes
    voila.
    9) I left out all the rivet holes - I use a .125 router bit, and experience has shown I should drill 0.125 holes and then drill out manually, unles the hole is 0.375 or greater. I should be able to learn how to inser a drill bit, and then go around a second time and drill pilot holes for rivets. In this case, I figured the various fittings already have holes, so those should be used for locating the holes?


    aerodon

  8. #8

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    Darrel,

    Do you want to try doing another file with the modification suggest by Mike. Keep the rivet holes, I'll try drill them on the next one I make.

    Also, I have a non-oil cooler nose bowl, I'll measure up where the holes are.

    And what is the proper material to make it from?



    Aerodon

  9. #9
    www.SkupTech.com mike mcs repair's Avatar
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    Quote Originally Posted by Aerodon View Post
    Darrel,
    Do you want to try doing another file with the modification suggest by Mike.
    Aerodon
    I'm not holding my breath till then....

  10. #10
    Darrel Starr's Avatar
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    Aerodon -- that looks amazing. I'm not surprised that some of the lines and radiuses have gaps -- I usually go around the drawing zoomed in to check for connections but haven't done that with this drawing. The drawing does have several levels which can be turned off to eliminate the stuff you don't want to see, like dimensions. I'll have to check material thickness or better yet, if you want - since you are making such an effort - I will give you the parts I have on sale, all painted orange in the classified section. Some of the pieces are useable with your new bottom cowl and you can check the thickness on the cut up bottom sheet that goes along with the other parts. Just send your shipping address to darrelstarr@aol.com Kind of busy right now but I will clean up the drawing when I can and make a "cut" version minus the extraneous stuff when I get some time. This is what I usually do before handing the drawing off to be water jet or laser cut.

  11. #11
    RaisedByWolves's Avatar
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    Quote Originally Posted by Aerodon View Post
    Darrel,

    Do you want to try doing another file with the modification suggest by Mike. Keep the rivet holes, I'll try drill them on the next one I make.

    Also, I have a non-oil cooler nose bowl, I'll measure up where the holes are.

    And what is the proper material to make it from?



    Aerodon
    Anything ever come of this?

  12. #12

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    Yes, I have Darrel's drawing and can cut another lower cowl anytime. I can also cut the MCS version too. Don
    supercub180@gmail.com
    Thanks Bearhawk Builder thanked for this post
    Likes mike mcs repair liked this post

  13. #13
    C-FIJK's Avatar
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    Hello Don did you ever get this to work ?

  14. #14

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    Yes, and I bought a dimpling tool that you can borrow. I have the full CAD drawing ready to cut, but each one might be a little different depending upon the front oil cooler (or not). Don supercub180@gmail.com

  15. #15
    C-FIJK's Avatar
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    sent you a email don

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