April 22, 2009

Fabricated F-719B Angle Clips, Worked on F-719 Stiffeners - 2.0 hrs.

Today I fabricated the little F-719B angle clips that will hold the forward ends of the F-719 stiffeners to the firewall.

I'm really pleased with how these turned out. They are drilled and deburred, ready to install.

Next, I put some time into trying to fix the F-719 stiffeners. I looked back to October 4, 2008 to remind myself how I worked with the problem back then. Once again, I resorted to the brute force method. Looking ahead, I see that there are even more of these stiffeners made like this. This is very annoying and disappointing to me. If I riveted the skin to this stiffener as is, it will distort the skin and make an ugly mess of it.

The pictures above and below are from last October, when I was building the firewall. I've repeated them here to illustrate the problem with these parts. As you can see, the factory tried to put a joggle in this part but all they succeeded in doing was putting a big dent in the bottom side of the angle. The top surface is barely changed. As you can see below, when I laid this part in place with the end lapped up on the angle where it will be installed, the problem is obvious. How can you expect to rivet a flat skin to these parts without distorting it and making an ugly mess?

This time, I'll show you how I tried to fix these parts. I was only moderately successful. Here, I have clamped the stiffener to my backriveting plate. The end is lapped up on top of a scrap piece of angle that's the same thickness as the bulkhead in the fuselage that this part will be riveted to. I used this big hammer and my biggest bucking bar to beat the crap out of this part to try and flatten out the bottom while maintaining and improving the joggle on the end. Last October, when I did this to the firewall stiffeners, I also put a flute in the vertical side of the angle to help relieve the stress from trying to bend a piece of angle in an unnatural way like this. It seemed to work fairly well so I tried it again today.

I managed to flatten it out enough that it probably won't distort the skin, but I'm not happy. I'm wishing I hadn't put in the flute. This part is visible in the cockpit and it looks real crappy from the top side. I quit here for the day, discouraged and contemplating whether or not to throw this in the scrap pile and replace it. What are the odds that a new one from Vans will be any better?

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