Bill's Aviation Log

What to do? I presented the problem at my EAA Chapter meeting. One of the chapter members, Hans E., said he had access to the well-equipped machine shop at a nearby military base and suggested bringing my steel there and seeing what could be done. It turns out the shop had the perfect tool for the job -- the "Magna-Brake". Instead of using sheer bulk to hold the material down tight like at Massey, on the little Magna-Brake, you just lay an 1/4" thick iron rectangle 1" by 36" or so over your work, hit a switch, and an electro-magnet sucks that iron bar down tight as can be, fixing your material in place. Then you can bend it normally. It worked great! Hans is building an RV-7 like myself, so to repay him, I took him for a ride in my RV-7 a few months later. He loved it! In fact, he flew my own plane better than I do!

2018 - Triplane - Spar Brackets
What holds each wing spar to the fuselage are four "spar brackets". So they are pretty important. You make them yourself out of .090 steel sheet. The plans show how in excellent detail. That said, making the 12 spar brackets was no easy task and it took me a long time to make them. Basically, here is what you have to do: 1. Cut the pieces 2. Bend the pieces 3. Weld them together 4. Drill holes in them Cutting .090 steel sheet is not a trivial thing. I tried using a steel cutting band saw over at Massey Aerodrome but I couldn't get a straight cut. I ended up using the old faithful Dremel tool and 409 cutting wheels. Then I used my file to smooth the edges. I was amazed at how well the file did with the steel. The secret was to put the steel into the vise and then you could really lay into it with the file. Did I go through a lot of cutting wheels? Yes. Did it take a long time? Yes. Did it work? Yes. The cuts weren't as straight as you would get with a waterjet machine but the Dremel tool is what I had. Here is most of the material for the 12 spar brackets cut out plus some other miscellaneous pieces like the aileron pulley mounting hinge.

The next step was bending. I just don't have the tools to bend .090 thick steel in my basement shop. So I flew over to Massey Aerodrome and used their massive brake pictured here. It bent the steel easily.

A close-up of using the big brake.

The problem was that the 12 spar brackets required deep U-shape bends. I could do one of the bends on the big Massey brake but it is too bulky to make the second. What to do? I presented the problem at my EAA Chapter meeting. One of the chapter members, Hans E., said he had access to the well-equipped machine shop at a nearby military base and suggested bringing my steel there and seeing what could be done. It turns out the shop had the perfect tool for the job -- the "Magna-Brake". Instead of using sheer bulk to hold the material down tight like at Massey, on the little Magna-Brake, you just lay an 1/4" thick iron rectangle 1" by 36" or so over your work, hit a switch, and an electro-magnet sucks that iron bar down tight as can be, fixing your material in place. Then you can bend it normally. It worked great! Hans is building an RV-7 like myself, so to repay him, I took him for a ride in my RV-7 a few months later. He loved it! In fact, he flew my own plane better than I do! Anyways, here are the 12 bent pieces.

The welding was straightforward and went smoothly. Next was drilling the three holes in each bracket: two in the side and one in the bottom. You have to be very careful with the drilling. The two holes seen here on each spar bracket have to match perfectly with the nut-plated holes on the wing spars. I spent a lot of time preparing for this. I built a drilling jig per the plans. Each spar bracket was custom-fitted to a particular spot on the wing spar. I was able to drill the two smaller holes on my drill pressin the basement. But for the larger hole at the bottom, I had to over to Massey Aerodrome and use their industrial strength drill press.

Now, this is the tool I should have had from the start. A steel-cutting band saw. This one belongs to Jim G.

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2018 - Triplane - Spar Brackets