I jumped ahead and fabricated the parts for the rear seat backs to take a break from thinking about systems.
There are no punched holes in these parts so it was back to the basics of measuring, marking, and drilling holes.
I cut the angles to length first and shaped the ends as specified.
![](https://airplane.allanglen.com/wp-content/uploads/2022/04/pxl_20220423_1828169376382493856242861383.jpg)
![](https://airplane.allanglen.com/wp-content/uploads/2022/04/pxl_20220423_1907089948880990566246872357.jpg)
![](https://airplane.allanglen.com/wp-content/uploads/2022/04/pxl_20220423_1907126704910144589868282857.jpg)
![](https://airplane.allanglen.com/wp-content/uploads/2022/04/pxl_20220423_1937449016410591048615310581.jpg)
I then marked the holes in the seat backs, set them with a punch, and drilled them on the drill press.
![](https://airplane.allanglen.com/wp-content/uploads/2022/04/pxl_20220423_2002398497304956470822828597.jpg)
![](https://airplane.allanglen.com/wp-content/uploads/2022/04/pxl_20220423_2034136542667507875440384188.jpg)
When match drilling the angles I found that I had to clamp down on the corrugations to “stretch” the backs to the length of the angles.
![](https://airplane.allanglen.com/wp-content/uploads/2022/04/pxl_20220423_2114213259066935706962142636.jpg)
![](https://airplane.allanglen.com/wp-content/uploads/2022/04/pxl_20220423_2159283882249152903308455610.jpg)
![](https://airplane.allanglen.com/wp-content/uploads/2022/04/pxl_20220423_2159407745223919038318674013.jpg)
I then cut the cross braces to length. The apex of these must be rounded to be fit within the radius of the flange at the top of the seat back. I then clamped them to the seat backs and match-drilled the holes on the drill press.
![](https://airplane.allanglen.com/wp-content/uploads/2022/04/pxl_20220425_132123455240662275100114614.jpg)
![](https://airplane.allanglen.com/wp-content/uploads/2022/04/pxl_20220425_1321282714940264572330293506.jpg)
![](https://airplane.allanglen.com/wp-content/uploads/2022/04/pxl_20220425_1342049728186551512166711000.jpg)
A tab is removed from each hinge half to allow the seat backs to be removed by splitting the pin in the middle.
![](https://airplane.allanglen.com/wp-content/uploads/2022/04/pxl_20220425_1404565208105994625384125371.jpg)
I then match drilled the lower brace and hinge halves.
![](https://airplane.allanglen.com/wp-content/uploads/2022/04/pxl_20220425_1436036174323329827369994692.jpg)
Looks like seat backs. Everything fit well.
![](https://airplane.allanglen.com/wp-content/uploads/2022/04/pxl_20220425_2052332823961813367660794405.jpg)
![](https://airplane.allanglen.com/wp-content/uploads/2022/04/pxl_20220425_2053013617910588469071967886.jpg)
I then deburred the parts and dimpled and countersunk for the rivet heads that sit against the cross brace.
![](https://airplane.allanglen.com/wp-content/uploads/2022/04/pxl_20220426_0156295885907220074177806775.jpg)
The final step was cutting and bending the hinge pins.
![](https://airplane.allanglen.com/wp-content/uploads/2022/04/pxl_20220426_0221073134199779085587431949.jpg)
The seat back parts are now ready for priming.