Building the rudder is definitely sharpening my skills. There's a bit more hand work here in the form of skin stiffeners and shims, and the thin skins are much easier to damage. There were a few minor mishaps on the way, but overall I'm happy with my progress. See below- ;0)
For the first bit of fab work, these pieces of angle are cut in 1/2, to yield 2 skin stiffeners each. The stiffeners will be riveted to the skins, and will add rigidity to the finished structure.
The plans have a diagram to follow. I used my handy metal shears to make the rough cuts, and finished with the scoth brite wheel. This is a bad photo; there are really only 3 lines marked to cut, but the shiny metal reflected a 4th one for the camera!
The scotchbrite wheel comes in handy for this kind of work.
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I mishandled a stiffener, and it developed a small crack. Instead of trashing it and starting from scratch, I drilled and radiused the crack and ended up with this. No real sacrifice in strength because of size and location of the dressed area, and now there will be no crack to spread over time and break the part. I've seen A&P's use this trick with metal and plastic.
And here we have all the stiffeners duburred, radiused ready to go.
The next step is match-drilling.
I used a piece of 3/4 MDF as a backing material for drilling the stiffeners to the skins.
...and here's where we ran into a problem. You can see from this image that I got a little sloppy when drilling this hole. Thankfully a moment of inattention didn't ruin my whole day! I happened to have just the cure for that ugly hole.
Here we have a selection of NASD1097 rivets, better known as Oops Rivets. From trolling thru forums and reading other builders' sites, I'd come across the opinion that having a few of these around was a good thing -so I ordered small quantities of each size from Van's. From what I'd read, these little guys can come in pretty handy. Little did I know it would be so soon!
The premise behind these specially-sized rivets is this: you can drill out a hole if you need to but still keep the smaller-sized flush head. Click on the pic for a full view, and you'll see what I mean. Pretty slick, eh?
OK, back to assembly. The method that gives best results in this case is back-riveting. This means that the factory head of the rivet rests on a steel plate (which acts as the bucking bar, in essence), and the shank of the rivet is attacked with the pneumatic gun and an attachment called a back-rivet set. It's basically a steel shaft with a spring-loaded collar, the collar serving to hold the pieces to be riveted together as the hammer is applied.
Here I am taping the rivets into place with some Scotch removable tape...
...and now the rivet gun. Obviously, everything has already been deburred, dimpled and primed at this point.
Everything turned out ok! Back-riveting is the easiest task I've had yet. Here are the stiffeners...
...and you can see how nice the factory heads look on the rudder skin. Stay tuned, lots more rudder work to be had! :)
