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Hey everyone,
I've been working on wing ribs off and on for a while, and while they started out great as flat pieces fresh out of the routing jigs, I wasn't at all happy with the way they started looking when being bent over forms and holes flanged. Just short of scrapping them and starting over, I thought I'd see if there was a better way to get them straight. Using a combination of a few techniques I researched in several other builders' logs (even those outside of the Bearhawk world), I came up with a technique that totally straightened out those little turds, and dangit if they don't look wonderful. I'm seriously relieved!
I started in the usual fashion of routing the ribs, clamping them into the form sandwich, hammering over the edges, and the flanging the holes. No matter what I did, they were coming out a twisted mess. I'm sure it had everything to do with pressures applied here and there and everywhere, but it just wasn't washing out which ones needed to be tweaked. So I gave it a little bit of help.
Starting with the oak bending form, I'm sure we've all drawn the lines on the edge of the board so we knew where the rivets were to go, and then we transferred those to the ribs, and then made sure we made our flutes between those marks. I helped mine out a little bit by chucking up a 1/4" straight-cutting bit into my router, and cut a channel right in the center of the lines. Then I took some sandpaper and a block and relieved the edges as to not damage and tear the metal (ask me how I know this needs to be done). Lastly, I marked it with a Sharpie so I could see the notch more clearly.
Second, since I already had these ribs flanged, I had to cut a circular relief about 1/4" deep on the inside surface so that the lightening hole flanges had somewhere to go. The form is two-sided (flip the backer board for left or right), so one relief circle on one side, one on the other, as you can see in the pictures.
After sandwiching the rib in the form, I went over the rib flange with a TMT flow-forming head in my rivet gun at the suggestion of N3UW and his building project, although I found later I really didn't need it. I then used a 1/4" diameter screwdriver and rubber mallet, and I lightly pounded the flutes into the notches on an angle to stretch the metal across the flats of the form. It's amazing how much more effective this was than the fluting pliers approach for me. And the flats of the form really helped to shape the ribs and keep everything straight. It only took a few minutes per rib if I was taking my time.
Lastly, I removed the rib from the form, and took it to the flange straightener, also at N3UW 's suggestion, and it's absolutely amazing how straight those ribs came out! There's hope for me yet!
You know, there are hundreds of ways to build an airplane, and it's so cool to see how others do things. Combine a few of those techniques together, and magic happens.
Hopefully someone can use this technique to their advantage as well. It certainly saved me hours and hours and hours of rework!
Best regards,
Chris
I've been working on wing ribs off and on for a while, and while they started out great as flat pieces fresh out of the routing jigs, I wasn't at all happy with the way they started looking when being bent over forms and holes flanged. Just short of scrapping them and starting over, I thought I'd see if there was a better way to get them straight. Using a combination of a few techniques I researched in several other builders' logs (even those outside of the Bearhawk world), I came up with a technique that totally straightened out those little turds, and dangit if they don't look wonderful. I'm seriously relieved!
I started in the usual fashion of routing the ribs, clamping them into the form sandwich, hammering over the edges, and the flanging the holes. No matter what I did, they were coming out a twisted mess. I'm sure it had everything to do with pressures applied here and there and everywhere, but it just wasn't washing out which ones needed to be tweaked. So I gave it a little bit of help.
Starting with the oak bending form, I'm sure we've all drawn the lines on the edge of the board so we knew where the rivets were to go, and then we transferred those to the ribs, and then made sure we made our flutes between those marks. I helped mine out a little bit by chucking up a 1/4" straight-cutting bit into my router, and cut a channel right in the center of the lines. Then I took some sandpaper and a block and relieved the edges as to not damage and tear the metal (ask me how I know this needs to be done). Lastly, I marked it with a Sharpie so I could see the notch more clearly.
Second, since I already had these ribs flanged, I had to cut a circular relief about 1/4" deep on the inside surface so that the lightening hole flanges had somewhere to go. The form is two-sided (flip the backer board for left or right), so one relief circle on one side, one on the other, as you can see in the pictures.
After sandwiching the rib in the form, I went over the rib flange with a TMT flow-forming head in my rivet gun at the suggestion of N3UW and his building project, although I found later I really didn't need it. I then used a 1/4" diameter screwdriver and rubber mallet, and I lightly pounded the flutes into the notches on an angle to stretch the metal across the flats of the form. It's amazing how much more effective this was than the fluting pliers approach for me. And the flats of the form really helped to shape the ribs and keep everything straight. It only took a few minutes per rib if I was taking my time.
Lastly, I removed the rib from the form, and took it to the flange straightener, also at N3UW 's suggestion, and it's absolutely amazing how straight those ribs came out! There's hope for me yet!
You know, there are hundreds of ways to build an airplane, and it's so cool to see how others do things. Combine a few of those techniques together, and magic happens.
Hopefully someone can use this technique to their advantage as well. It certainly saved me hours and hours and hours of rework!
Best regards,
Chris
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