The dies are very efficient at setting a curve into the clamped section of longeron. In fact, I was easily able to "over-bend" the longerons with only a couple of squeezes with the vice. It was definitely a learning process that I am still uncertain I have mastered.
Once clamped, the longeron could be pulled or pushed to pre-load and set a significant bend.
After setting several bends, it was time to compare the curve in the longeron to the canopy deck or "template" as it is referred to.
Another issue for me with the longeron bending process was my uncanny ability to induce a twist into the cross section - very frustrating! How can that possibly happen with use of dies?! Most everything I had read on the subject of this project reflected the author's opinion of from "very easy" to "almost impossible". Invariably, I approached this project with my natural optimism, but was quickly humbled by the daunting task. I would have to say that I am currently in the latter camp....not impossible, but you can see it from here.
Pictured below is the most curved section of the longeron, exhibiting the battle scars of the dies. Once I was mostly satisfied with the shape of the longerons, I proceeded to buff out as much of the surface abrasions as possible. They actually came out looking pretty good after scuffing, priming and top coat.
Now as I approach the process of match drilling the holes in the canopy deck to the longeron, I am questioning the accuracy of the .025" overhang (lack of uniformity) along the curved edge of the assembly. The overhang of the canopy deck is to serve as a butt joint for the upper edge of the fuselage side skins. I have probably .035 - .045" inch variation at the worst points along the length of the assembly. The issue then becomes will the inconsistent overhang affect the assembly. Obviously, I can rivet the longeron to the canopy deck as is and then file away any excess overhang of the canopy deck. My greatest concern is that I induce a wrinkle in the fuselage side skins because my longeron curvature does not exactly match the original shape of the canopy deck. As I compared the longeron curve to that of the arm rest member, which is parallel and located several inches below the canopy deck, it appeared that the differences in curvature were minimal and the risk of skin wrinkle or warp improbable...but that is definitely a guess!
Several days later: Okay, after finally positioning the canopy decks on to the longerons, it quickly became clear that my concerns over the variation in the overhang was a non-issue. Once the match hole drilling/cleco-ing process began along the length of the longeron, slight thumb/index finger pressure applied to the longeron brought the overhang into a very consistent margin as prescribed by the manual. Problem was way over-analyzed!
Though not possible to tell from these views, they do show the longeron cleco'ed into place with the canopy deck. First picture shows the longeron/canopy deck temporarily cleco'd into position.
Final picture in this blog shows the longeron/canopy deck resting in place after the side skin holes were match drilled. More to continue in the Mid-Fuselage Assembly Part 3 posts.
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