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Thread: Corben Jr ace build.

  1. #11

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    Nov 2017
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    How I build a rib:
    Nose block, and preformed upper and lower capstrips are placed in the jig. Both capstrips are left long at the trailing edge, the lower sits atop the upper for now. Intercostals are added, forcing the capstrips into final shape. The upper capstrip is marked where it abuts the lower. It's then removed from the jig, trimmed with a razor saw and sanded to final fit. Then all the joints are hit with a sanding bar to bring the pieces down to the same thicknesses, there is some slight variation between them. A vacuum with a brush attachment pulls up all the sanding dust before gluing begins.
    Here are all the parts in the jig post sanding.
    Cardstock spacers are used either side of the spar blocks to allow easier installation of the finished rib on the spars.

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    Next, the nose gusset is laid in place with an aircraft nail partly driven into the upper and lower capstrips to act as a locator pin and to remind me which side gets epoxy. (I've already finished smearing epoxy on two nose gussets only to realize I did wrong side)
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    I then trace out my nose block template onto the gusset to help me see where to nail.
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    I then lay out all the remaining gussets around the rib in the appropriate pattern for the rib I am making. Some ribs have large gussets at the trailing edge, and the ribs that will get compression struts don't have two of the upper gussets. Laying them out now gives me a chance to catch a mistake before everything is covered in glue.
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    Back side of the nose gusset smeared with epoxy. I started off using acid brushes to spread the epoxy, but felt like more glue was being used to fill the bristles than was actually getting on the parts, so now I just spread it around with the popsicle stick I mixed the epoxy with.
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    Here I've switched from the nose gusset to one of the smaller gussets because it's easier to fit in frame. The steps are the same for all of them.
    I smear a little epoxy down into the joint I'm working. Then set the gusset, epoxy-slathered side down, on top of it.
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    I drive a few nails to hold it while I glue and set the rest of the gussets. These suckers are tiny, so they need to be held with tiny pliers or a hemostat when starting them.
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    Then I come back in and finish nailing the gussets down, as per the nailing pattern from the plans.
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    The nose gusset and trailing edge gusset get nails all the way around their perimeters, again, as per the plans.
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    The rib is then removed from the jig so the process can be repeated on the other side.
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  2. #12

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    looks good - are those brass nails?

  3. #13

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    Fantastic! Thank you so much!

    Everything looks very neat and tidy. I was expecting "EPOXY THIS SIDE" scrawled in pencil on the parts, though; I guess you're a lot brighter than I am.

    I was a bit surprised to see that the diagonal ribs pieces are square on the ends and the triangle formed filled with epoxy. I'd of thought they'd be pointed to fit into the joint. I suppose it really doesn't matter, as they're gusseted, and epoxy is strong stuff.

    One of the many reasons I'm excited to see your build. All I know is aluminum tubing, gussets, and pop rivets.
    The opinions and statements of this poster are largely based on facts and portray a possible version of the actual events.

  4. #14

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    Nov 2011
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    Quote Originally Posted by Frank Giger View Post
    I was a bit surprised to see that the diagonal ribs pieces are square on the ends and the triangle formed filled with epoxy. I'd of thought they'd be pointed to fit into the joint. I suppose it really doesn't matter, as they're gusseted, and epoxy is strong stuff.
    Ya, me too. Caveat: I know nothing. So can someone with aeronautical structural engineering weigh in here regarding this methods ability to carry the same load as one with diagonal angled joints without failing.

  5. #15

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    This is heartily debated around the internet; cutting the capstrip with square ends vs mitered ends. The overwhelming consensus is that the gusset plate carries the load so there is no difference in strength between the two methods. There have been numerous test both scientific and backyard to confirm that hypothesis.

  6. #16

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    That's kind of what I was thinking - that and the fact that the epoxy is pretty strong stuff, forming a solid plug at the joint.

    Besides, if the stresses on the aircraft are so strong that the joints on the ribs are breaking it is probably the least of the concerns at that point.

    And now we've given Tench something to worry about that he doesn't need to! Well done, my EAA brothers, well done.
    The opinions and statements of this poster are largely based on facts and portray a possible version of the actual events.

  7. #17

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    The Tony Bingelis method is clean the excess epoxy from the joint. Adds weight and no strength. Otherwise, Tench745's ribs follow standard practice and in no time he'll have a complete set.

  8. #18

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    Quote Originally Posted by martymayes View Post
    The Tony Bingelis method is clean the excess epoxy from the joint. Adds weight and no strength. Otherwise, Tench745's ribs follow standard practice and in no time he'll have a complete set.
    Yep, I read a bunch of Tony's stuff before starting on this. I'm coating the joints with epoxy, but not entirely filling them. It makes me feel like I'm adding strength even if I'm not. The backs of the gussets are left epoxy coated so I don't have to get in there with a brush later to varnish it.

    Frank, I would like to point out that I don't actually know anything about building an airplane either. I am a theatrical carpenter so I know something about wood, and something about welding, but I'm teaching myself and learning as I go from manuals, books, videos, and all the great materials from the EAA. I read everything I could get my hands on for about six months before admitting to myself I had to build an airplane.
    Soon I'll join the local chapter, 486, and start learning everything I can there too. This past summer they were rebuilding an unairworthy Sonex from scratch and the building bug bit me hard.

    Also, only the leading and trailing edge gussets are orientation specific; all the others are (thankfully) reversible.

  9. #19
    Jeff Point's Avatar
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    Looks good so far.

    One thing to remember- the plywood gussets have a light coat of varnish on them, so they should be lightly sanded on the epoxy side to achieve a stronger glue joint. This is a debated topic for sure, but you could make a few test pieces and pull them apart to see for yourself if it is worth it.

    pro tip- easier to sand the large sheet before cutting into gussets.
    Jeff Point
    RV-6 and RLU-1 built & flying
    Tech Counselor, Flight Advisor & President, EAA Chapter 18
    Milwaukee, WI
    "It All Started Here!"

  10. #20

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    Quote Originally Posted by Jeff Point View Post
    Looks good so far.

    One thing to remember- the plywood gussets have a light coat of varnish on them, so they should be lightly sanded on the epoxy side to achieve a stronger glue joint. This is a debated topic for sure, but you could make a few test pieces and pull them apart to see for yourself if it is worth it.

    pro tip- easier to sand the large sheet before cutting into gussets.
    Known and done. All plywood gussets were sanded on both sides, some of them even before they were cut. There are 602 of the 1.25"x.75" gussets. I sanded them before cutting. Almost all of the rest I had to do after.

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