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Thread: Aluminum Ribs

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    prasmussen's Avatar
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    Aluminum Ribs

    I'm designing a fabric covered wing with aluminum ribs. If the ribs are formed over a block, it seems like there should be a clever way to treat the bent-over edge so that it won't cut the fabric/lacing. Any ideas? I have one of those double-wheeled thing-a-ma-jigs but can't get it to bend the flange far enough back on itself.

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    Quote Originally Posted by prasmussen View Post
    I'm designing a fabric covered wing with aluminum ribs. If the ribs are formed over a block, it seems like there should be a clever way to treat the bent-over edge so that it won't cut the fabric/lacing. Any ideas? I have one of those double-wheeled thing-a-ma-jigs but can't get it to bend the flange far enough back on itself.
    Factory airplanes with fabric covered aluminum ribs brake the edge of the rib flange somewhere around 10-20 degrees. This seems to prevent any unwanted interference. I get the same results as you with a cheap handheld flanging roller tool so I made some dies for a bead roller to do this. The results were first class.
    Last edited by martymayes; 02-25-2012 at 01:34 PM.

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    Quote Originally Posted by martymayes View Post
    Factory airplanes with fabric covered aluminum ribs brake the edge of the rib flange somewhere around 10-20 degrees. This seems to prevent any unwanted interference. I get the same results as you with a cheap handheld flanging roller tool so I made some dies for a bead roller to do this. The results were first class.
    Hey Marty,

    This old Pexto is what I have. You milled dies to 20 degrees? Is there a possibility you have an image or sketch? Thanks for helping! P.Pexto.jpg

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    Quote Originally Posted by prasmussen View Post
    This old Pexto is what I have. You milled dies to 20 degrees? Is there a possibility you have an image or sketch?
    Yes, I make what I need on my lathe. To brake the flanged edge of a rib you need small dia dies, like 3/4" or smaller, the bent down edge only needs to be 1/8" or so. Dies for you Pexto will have to be "stepped" down and probably extended beyond the axle to get the dia small enough. You need something similar to but not exactly like the this:

    flanging mandrel.jpg

    Where are you located?

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    Quote Originally Posted by martymayes View Post
    Yes, I make what I need on my lathe. To brake the flanged edge of a rib you need small dia dies, like 3/4" or smaller, the bent down edge only needs to be 1/8" or so. Dies for you Pexto will have to be "stepped" down and probably extended beyond the axle to get the dia small enough. You need something similar to but not exactly like the this:

    flanging mandrel.jpg

    Where are you located?
    Wish I had a lathe. But it looks simple enough. Out of what material would you recommend I get it milled?

    Google says we are 4 hours drive or 5 hours flight in my old Champ apart. Just SW of Columbus, OH.

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    Quote Originally Posted by prasmussen View Post
    Wish I had a lathe. But it looks simple enough. Out of what material would you recommend I get it milled?

    Some cold rolled 1018 bars stock will work just fine.

    Is the Culver V also in Columbus?

    Keep me posted on your ribs.

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    Quote Originally Posted by martymayes View Post
    Some cold rolled 1018 bars stock will work just fine.

    Is the Culver V also in Columbus?

    Keep me posted on your ribs.
    Culver V belongs to a friend in Columbus. He's hard to describe but he's 84 and is still as enthusiastic about building and flying as ever. I'm sure he would be happy to talk about the Culver or one of several other projects he is working on. Nice man. Bill - 614.491.0903 or 614.937.5208. Please be aware that he, like a lot of us, doesn't hear as well as he used to.

    I'll send a picture of those ribs when they are working. Thanks for the help! P.

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    Having hand-hammered somewhere on the order of 4 sets of Sonex ribs, and given Marty's answer that production fabric-covered metal ribs angle the flange slightly past perpendicular with the plane of the rib, I believe it would be possible for you to sand the edge of your form blocks to produce an angle beyond 90 degrees. This may result in a rib that is difficult to extract from the form block, but it's worth a try. As for straightening flanges / achieving any given angle of the flange relative to the plane of the rib, I used a combination of hand seamer and fluting pliers to bring the rib flanges to perpendicular. I don't see why the same process couldn't be used to bring rib flanges to an angle beyond perpendicular as well. Bend the flanges "up more" with the hand seamer. This causes the rib to bow away from the flange. Then tighten the flutes with the fluting pliers to pull the rib back to flat. Iterate as required to get the flange angle where you want it.
    Murphy's 13th: Every solution breeds new problems...

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    The ribs on an Aeronca Champ (and the Chief too) don't have any sort of edge treatment at all other than being deburred. The flanges are essentially parallel with the fabric and are at a right angle to the web of the ribs.

    So, to answer the original poster, I'm not sure any edge treatment is necessary.

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    It's true, I've never heard of a Champ wing skin splitting over a rib or rib stitching being cut by a sharp edge. Someone suggested gluing 1/2" tape to the rib edges before covering would prevent chafing. Then any movement would be fabric to fabric. How much does the wing lower surface actually push in? Suppose it depends on what system was used to tighten the fabric too.

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