Bomber-style seats have been used in street rods since the '40s, and "back in the day" most of these came from military surplus yards. Lately these seats have become enormously popular, and now we are seeing a lot of newly constructed bomber seats in cars (such as the ones from Frank Wallic, a regular contributor to STREET RODDER). They've always been considered kool, and for good reason; they're practical, lightweight, and they give a car a purpose-built look with an aircraft flavor.
I've loved the look of bomber seats for years, and recently decided to build a pair for my aluminum-bodied roadster. I looked closely at the various designs I've seen, and I identified several features I wanted to incorporate in my own seats. While a lot of true aircraft seats have a flat back, I much prefer the look of a rounded back. Most true aircraft seats are riveted together, but some seats, which have a lot of curved components, are welded. I wanted a lot of curves, so I designed a bottom to be welded into place, but I like the look of rivets very much, so I decided to use rivets to attach the reinforcing edge of the seat. Last and perhaps most importantly, I liked the look of the seats with lots of holes. Of course, in the aircraft world where these seats were developed, holes were used to shave valuable weight from each part. The weight issue is not so important for a street-driven car, but man, do I like the look of holes. So early on, my plan was to design a seat that would have just as many holes as possible.
I recently got a set of the Mittler Brothers Punch and Flare tools. These are made in seven sizes, from 1 inch to 3 inches in diameter, and they are cleverly designed to both punch the hole and flare the edge in one operation. I wanted to use every size for my seat, and my design is based on how these progressive hole sizes could be used in a pleasing pattern.
I hate to invest a lot of time in a project without knowing for sure if I will like the look of the finished product, so I took the time to do a quick, full-size mockup of one half of the seat, based on my initial design. When I saw this mockup I realized that I wanted to make many small adjustments in the hole sizes and placement, and I saw an opportunity to use even more holes. I made a second mockup incorporating these changes, and this one looked great, so I used it to make the chip board master pattern for the seat. I align this pattern on the centerline of the metal blank for the seat back, so I can flip it over to mark each side. This simplifies the pattern, and ensures the seat back will be symmetrical.
Next, I cut a rectangle of 0.063-inch thickness 3003 H-14 aluminum sheet to size. I put a centerline on the panel, and using my chipboard pattern, I laid out the edges of the seat, and the center for each hole. Next, I drilled 1/8-inch holes in the center of each hole location.
While the seat back could have been bent freehand, since I plan to make at least two of these seats, I decided to make a simple bending fixture to ensure that the bends on each side are identical, and will be identical for all future seats I make. The fixture was made from 3/4-inch MFD, and since sheetmetal has a lot of "spring back," I had to experiment a little to find the proper shape for the form that would allow the aluminum to be bent tightly against it and then spring back to be the shape I wanted. I also had to plan ahead with the shape of the fixture so the first bend won't collide, hampering the second bend.
1. I designed this seat from scratch, incorporating design features I liked on several other seats I've seen. One of the first steps is doing a rough layout of the allover shape and hole placement on some aluminum sheet.
2. Next, I made a full-sized mockup of one half of the seat. After seeing this mockup, I decided that more holes would be better, so I made a second mockup (seen on the left).
3. Once I was satisfied with the design, I made an accurate half-pattern from chip board, and laid out both sides of the seat from the centerline. This will ensure that the seat is symmetrical.
4. I could have bent the seat back freehand, but I made a simple MDF bending fixture so I could make any number of seats and know they would all be exactly the same shape.
5. The fixture is designed to over-bend the metal, so it springs back to the exact shape I want. This took a little trial and error, but now I can make repeated bends with accuracy.
6. The second bend is made in the same way. My fixture is configured so that the first bend would not interfere with the second. Again, this took a little trial and error.
7. The sequence of operations is very important. First, the bending is done. Second, the beads are made. Third, the holes are punched and flared. Last, the edges are trimmed.
8. I used a 3/4-inch beading die on the seat back. Note the layout lines that I used to guide the dies so the beads would be positioned correctly and end at the right place.
9. Here you can see the crisp beads made by the Lazze beading machine.
10. This is the Mittler Brothers Punch and Flare Tool. This clever device punches the hole and flares the edge in one operation. These come in seven sizes, from 1 to 3 inches, and I used them all.