So just what is scratch building?
Scratch building is fairly rare both in full size and model aircraft, which I think is unfortunate, but it just seems to be a sign of the times. I personally enjoy building, whether it be my latest idea for carrying tools around on my work trailers or building an aircraft, the personal satisfaction I get from it gives me a kick every time. Every component that you see on these pages was made with simple hand tools and a few jigs and tools that I made out of various bits of steel, off cuts and left overs from my work. My wife and I are self employed which means that we have a variable income and erratic working hours . We don't have a large disposable income but we do get time when the weather or just bad luck means that we get a couple of unplanned days at home. Now I think that it is wonderful, for others it would stress the hell out of them but it is a life style that I enjoy.
The very beginning...
After 4 months of procrastination, I started with the wing ribs. Sonex's theory is that once you can make one of these, then you can make everything else. Funnily enough it is actually correct.
These pictures show the tools you need to make one. The crimping pliers I made from a set of cheap pliers that I bought from my local Bunnings. I simply drilled a 1/4" hole down the end of the pliers while I held them closed in a drill press. The wooden formers were simply cut out with a band saw from the left over ply from what I used to make my work bench. The 'V's that you can see show the locations for the crimps that need to be done to the flange to enable the flange to be folded over. The blue flanging dies I bought from Sonex in the USA but you could make them out of timber or aluminium and spinning them up on a lathe. You need these to form the 45 degree angle around the lightening holes in each rib. The few grams that are saved from each rib are negligible but the simple flange around the hole makes an enormous difference to the stiffness of the rib once it's done. The photo shows how the aluminium blank is sandwiched between the two forming blocks. By a combination of hammering with a soft hammer and crimping the flange with your nifty pliers allows the flange to be bent almost to a 90 degree angle. Once you remove the blank from the formers, it is relatively easy to hammer the flanges to a 90 degree angle. The banana bend is taken out by either increasing the depth of the crimps or straightening them out.
Folding sheet aluminim...
This caused my a degree of worry plus a little bit of stuffing around to get the knack of it. I'd looked at bending brakes sold commercially, but the ones that I could afford could only fit a piece 1200mm wide where the longest fold needed is a bit over 3 metres long. The ones that can do that which you buy from shop cost many thousands of dollars and you need a crane to move it around. I stumbled onto this idea while googling for inspiration. Mine is made from 2 lengths of 5 mm thick 50 x 50 mm angle steel that are hinged together with piano hinge bought from my local hardware store. I mounted it to the side of my work bench, mostly to save money by not having to build a stand for it, but it turned out better this way in practice as it enabled the aluminium to held more securely.
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