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  1. #1
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    Default #2 False Spar

    On my EX3 wing, if I position the #2 false spar as shown in Figure W51 and Mitch's pictures, then the fabric rivet holes do not line up. They are actually backwards.

    If I turn around the #2 false spar and line up the rivet holes then there is not enough false spar length in the back to properly space the rivets .25" apart as shown in Figure W51.

    Is it possible the rivet holes are pre-drilled wrong? What's more important, the rivet holes or the proper extensions into the nose and rear rib?

  2. #2
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    Default Re: #2 False Spar

    Quote Originally Posted by stautz View Post
    On my EX3 wing, if I position the #2 false spar as shown in Figure W51 and Mitch's pictures, then the fabric rivet holes do not line up. They are actually backwards.

    If I turn around the #2 false spar and line up the rivet holes then there is not enough false spar length in the back to properly space the rivets .25" apart as shown in Figure W51.

    Is it possible the rivet holes are pre-drilled wrong? What's more important, the rivet holes or the proper extensions into the nose and rear rib?
    I think you are talking about #2 false “rib” and not “spar” right? Are you following this thread about building the EX3?

    http://forum.cubcrafters.com/showthr...p-Hints/page14

    On this page (14), look at post #11 and it covers this in detail.

    Hope it helps.

    Dave
    Dave Embry
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    ..but if you do it right.....
    ....once is enough."..

  3. #3
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    Default Re: #2 False Spar

    I added the 2.25 measurement from the drawing and if you want follow that measurement, but want the rivet holes to line up. You could drill new rivet holes in the false rib as long as rivet edge distance is maintained.
    The 2.25 dimension is not on the factory drawings, I have provided that as a starting point.

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    Default Re: #2 False Spar

    I followed your instructions but it only leaves 0.7" of false rib behind the rear spar. That doesn't seem like it is enough length to install the 2 rivets called for in the aft rib. It also doesn't match the drawing for the amount of false rib into the aft rib.

  5. #5
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    Default Re: #2 False Spar

    Well Fig. W51 doesn't give a distance of the amount of #2 false rib that is aft of the rear spar......in "Section AF-AF" and "Section AE-AE" only shows that you should have .25" hole distances from the rear spar and from the aft end of the rib where it goes into the tail rib (Section AF) and the same on the front part that goes into the nose rib. It only shows the edge distance to drill the holes.....nothing says how far it extends that I can see. Fig. 51 just says to align the rivet holes with the other ribs and the Sections show the drill distances.

    Just line up the rivet holes on the bottom with the other ribs and it should be good to go. You can just hold the rib up to the #3 or 4 rib and see which end lines up with those holes and then you will see which way it goes. It doesn't really matter except that it looks better to have all the fabric rivet heads line up on the bottom...not structural.

    Quote Originally Posted by stautz View Post
    I followed your instructions but it only leaves 0.7" of false rib behind the rear spar. That doesn't seem like it is enough length to install the 2 rivets called for in the aft rib. It also doesn't match the drawing for the amount of false rib into the aft rib.
    Dave Embry
    "You only live once.....
    ..but if you do it right.....
    ....once is enough."..

  6. #6
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    Default Re: #2 False Spar

    Quote Originally Posted by stautz View Post
    I followed your instructions but it only leaves 0.7" of false rib behind the rear spar. That doesn't seem like it is enough length to install the 2 rivets called for in the aft rib. It also doesn't match the drawing for the amount of false rib into the aft rib.
    I just hit this step myself this week I had same issue; if I follow the suggestion to put the end that has the most-offset rivet hole looking down through the cutouts forward toward the nose ribs and then line up the rivet holes, there is much more material overlapping the nose rib than the tail rib and, as mentioned in the original post, only about .7 inches aft of the rear spar. But if I reverse the part, putting the end with the more centered rivet hole looking down through cutouts toward the front spar and then line up the rivet holes, the material overlapping the nose rib and the rail rib are pretty balanced, like in the drawing, and the cutouts are both comfortably inside the inboard faces of the spars. And it looks like the cutouts will line up just fine with he lines that connect the main and auxiliary fuel tanks.

    I plan to double check this tomorrow. If I am missing something, I would appreciate any help.

    PTB in Huntsville, TX

  7. #7
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    Default Re: #2 False Spar

    I'm not sure what's up but your #2 ribs must be different than the last 4 I have done. I am just finishing up 2 wings on my 4th kit.....same #2 rib....same instructions as below works perfect just as I described. Most offset hole goes towards the nose and moved until bottom rivet holes align with the other ribs. This works on mine....not sure why they aren't working on yours unless they are drilling the holes differently in your false ribs?? I think the important thing is that the bottom rivet holes align. This is on the bottom of the wing and will be pretty apparent if not in line with all the rest of them on the wing.

    What’s your concern? That there is more or less of the excess false rib going forward or aft? If that’s it, I don’t see where that makes any difference. You are just connecting the center (false) rib to the nose and tail ribs like we do with the other center ribs (except they are solid and attached to the spars instead). As long as you have enough to put the rivets in the connecting joints in the nose and tail ribs, I’ve never paid any attention to the amount of “excess”.

    Note again that the figures do not show any dimensions for the false rib going into the nose and tail ribs and it doesn't matter as long as you get the .25" edge clearance for the rivets.



    Here is what the forum post says:


    "The #2 rib false rib is also pretty self explanatory. The position of the rib is with the cutouts facing UP and slide it forward or back until the fabric rivet holes on the bottom line up with the hole when using a straight edge from ribs #3 and #4.

    After you line up the holes on the bottom, just place a mark on the false rib and then install the meth, clamp it and then install the rivets as shown.

    Note that there is a difference in how the holes are drilled when looking down into the cutouts in the false spar. When you have it correct you will notice that if you are looking down from the top, into the front cutout (the one closest to the front spar) that the hole drilled in the bottom of the cut-out will be more aft of the center of the cutout and the hole in the bottom of the aft (rear spar) cut-out will be more in the very center of the cutout.

    So if you install the false spar, put the end with the hole in the center of the cutout in the aft position. If you align the fabric rivet holes on the bottom of the false spar with the other center ribs on the bottom, you will see that the most aft edge of the cutout will be 2.71" from the false spar.



    (Here you are looking down onto the false spar with the nose ribs to the right side. You can see from the digital compass that it is 2.71" from the aft edge of the front spar to the most aft edge of the cutout. In this position, all the bottom holes should line up with the rest of the ribs.)"



    Quote Originally Posted by PTB View Post
    I just hit this step myself this week I had same issue; if I follow the suggestion to put the end that has the most-offset rivet hole looking down through the cutouts forward toward the nose ribs and then line up the rivet holes, there is much more material overlapping the nose rib than the tail rib and, as mentioned in the original post, only about .7 inches aft of the rear spar. But if I reverse the part, putting the end with the more centered rivet hole looking down through cutouts toward the front spar and then line up the rivet holes, the material overlapping the nose rib and the rail rib are pretty balanced, like in the drawing, and the cutouts are both comfortably inside the inboard faces of the spars. And it looks like the cutouts will line up just fine with he lines that connect the main and auxiliary fuel tanks.

    I plan to double check this tomorrow. If I am missing something, I would appreciate any help.

    PTB in Huntsville, TX
    Last edited by Daveembry; 04-27-2019 at 04:48 AM.
    Dave Embry
    "You only live once.....
    ..but if you do it right.....
    ....once is enough."..

  8. #8
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    Default Re: #2 False Spar

    I went ahead and did some measurements and photos to show what's going on.

    The #2 false rib has pre-drilled fabric rivet holes in the bottom. According to Fig. 51 (bottom right side) it says "hole spacing to align with center ribs". So in Star Trek terms.....this is the "prime directive".

    So, go to the #4 center rib (I use #4 because it's the first rib pre-drilled by the factory since we have to drill the fabric holes in the bottom of the #3 double rib. If you have already matched the holes in the #3 double rib to the others correctly, then you can use it)......on the bottom and you can hold up the #2 false rib right along side it and you will see that only 1 end of the false rib bottom fabric rivet holes will align with the holes pre-drilled in all the center ribs already (just like they are in the #2 false rib). If you try and turn it the other way the holes will not match up at all.

    You will see here in this photo that on this #4 center rib, the first hole back from the front spar ....and the 2nd hole aft is 2.4" and the distance between that hole and the 3rd hole is 3.4", etc.


    P1060888.jpg
    (#4 CENTER RIB, NOSE LEFT IN PHOTO)


    Now if you look at the #2 false rib, one end ONLY has the pre-drilled hole with this exact same spacing and it is as I described in the post. See the photo below and you will see the spacing is the same as the rest of the center ribs on the bottom.


    P1060889.jpg
    (#2 FALSE RIB, NOSE LEFT IN PHOTO)


    So.....THE FALSE RIB HAS TO BE INSTALLED IN THIS POSITION with the end with the shortest distance of 2.4" between the first 2 holes ....towards the nose ribs. There is no other way.

    If you install it this way, you will see that looking from above, this forward end of the false spar is the one with the hole offset from the center of the front cut-out area and the hole that is centered in the cut-out area will be on the aft end.

    You slide the false rib back and forth until you have the bottom fabric holes in alignment with the other center ribs and then install the rivets connecting it to the nose and tail ribs per the "sections AF-AF and AE-AE) and that's it. No other way to do it correctly.

    Hope this clears it up. I'm going to put this in the forum post to help if there are others who don't understand.

    Quote Originally Posted by PTB View Post
    I just hit this step myself this week I had same issue; if I follow the suggestion to put the end that has the most-offset rivet hole looking down through the cutouts forward toward the nose ribs and then line up the rivet holes, there is much more material overlapping the nose rib than the tail rib and, as mentioned in the original post, only about .7 inches aft of the rear spar. But if I reverse the part, putting the end with the more centered rivet hole looking down through cutouts toward the front spar and then line up the rivet holes, the material overlapping the nose rib and the rail rib are pretty balanced, like in the drawing, and the cutouts are both comfortably inside the inboard faces of the spars. And it looks like the cutouts will line up just fine with he lines that connect the main and auxiliary fuel tanks.

    I plan to double check this tomorrow. If I am missing something, I would appreciate any help.

    PTB in Huntsville, TX
    Last edited by Daveembry; 04-28-2019 at 05:22 AM.
    Dave Embry
    "You only live once.....
    ..but if you do it right.....
    ....once is enough."..

  9. #9
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    Default Re: #2 False Spar

    Mitch sent me a new drawing and it has been updated in the online manual. It shows the proper dimensions for the overlap on the ribs. I still think there is a problem lining up the holes but I think the structure is more important.

  10. #10
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    Default Re: #2 False Spar

    Quote Originally Posted by stautz View Post
    Mitch sent me a new drawing and it has been updated in the online manual. It shows the proper dimensions for the overlap on the ribs. I still think there is a problem lining up the holes but I think the structure is more important.
    OK, I just went to that and see they put in 2.25" from the inside of the rear spar to the end of the #2 false rib. This would mis-align the hole spacing by about .63" but didn't change the main drawing W51.

    I would disagree that it's structural and their drawing was not updated (Fig 51) as it still says "hole spacing to align with center ribs" (which is important). I don't see any reason to have .63" more of unused false rib sticking into the tail rib. All the other ribs have little AD3-3 rivets squeezed holding them to the nose/tail ribs.

    I'll get with Mitch on this Monday and get them to make a determination since the drawings are in conflict.

    I will still align my rivet holes since I would look up every time I walked under a wing and would see (and cringe at) that mis-alignment.
    Last edited by Daveembry; 04-27-2019 at 06:41 AM.
    Dave Embry
    "You only live once.....
    ..but if you do it right.....
    ....once is enough."..

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