21st February – Good week this week, a new type of work. It has been interesting learning how to deal with 4130 and I feel like I now know how best to cut, shape, file and fabricate the required shapes. Since I first made the spar attach plates, I had been waiting on access to a press to bend the 6.5 sweepback for the top wings. When I cut my first pieces of metal, had tried to bend them myself at home with what I had. Tried a hammer, a vice, a brake and nothing would move it. A friend has a nice 11 tonne press – perfect for the job. This week went and spent a couple of hours to set up and bend the plates. Took some time on some scrap to get the set up right. Originally I planned to use three 1/2 inch bolts to do the work. Two underneath and one on top. We found we couldn’t get the metal to fold tightly enough around the bend line. So slightly modified our approach and used the black steel plates underneath. In the photos below you can see the initial approach with the lines marked for the bolt centres.
Then the final approach we used the top bolt and just the flat on the black plates underneath. Once we got our method…we got going and knocked over them all in about 40 minutes.
The picture on the right is the measurement of the bend…. almost there. Very fiddly to get it right on the 6.5 degrees.
And now for the finished product. Still on a jig, welding is yet to come.