Yes started making the jig for bending the top tube of the rib yesterday, and this is what I ended up with.
Its not to hard really, just takes some time. You just use a tape measure and try to measure the radius of the curve, by moving the “center” until the measurement is constant for a little distance.
A bit too hard to explain, so I did draw an example on a bit of paper with 3 bits of a circle with different radius’s. So basically you try to find all these bits of circles, and map the whole curve, in this case of the wing rib.
Then for creating the jig, you go the opposite, but also you need to reduce the radius of each circle segment.
I did that by starting with the first circle segment at a radius of 0.7 of the original one. Cut it out of the sheet of ply and bend the first segment with the tube, and then check out what it looks like. If its too big still, you reduce it a bit more, so use 0.6 of the original radius. When its right then you continue with the next circle segment etc etc. Have a good look at the photo below were you see 5 different circle segments 🙂
And then to finish it I had to make one more change as for one of the segments I made the radius to small. See the result below. And yes I can easily now bend the top tubes in seconds. They are all almost identical. Some need just a little tweak here and there, but yes happy with it.
Once I have the bottom tube done I will copy the jig on a piece of paper and mail it to Robert for future builders 🙂