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Permalink Reply by Henri Luyckx on July 8, 2009 at 4:27pm

Hi Dwayne,
The problem is that the bending brake opens up in the middle. You wil see that most bending brakes have an arrangement too put pressure on the middle of the break (see the picture).

See also http://www.ch601.org/tools/brake_plans.htm
Here is another link to make a simple, cheap but good working brake: http://www.ch601.org/tools/bendbrake/brakeplans.pdf
I made a bending brake like that but I replaced the steel angle wit aluminum ones because the steel ones at the local shop were not straight enough.

The bolts you see all along the upper angle keep it firmly to the base. There must be enough distance between the bolts and the edge to allow room for the flanges of the spar.
Remove some bolts if you want to bend larger pieces.

When I wanted to bend 0,032 sheets I had to replace the piano hinge with an array of stronger hinges.

The bending of the 0.040 angles for the fuselage was done by a friend of mine at a metal workshop.
I found bending the biggest problem to overcome for plans builders. The good thing about plans building a Zenair plane is that you have always the otion of buying those parts individually from them.
Hope this will be of some help.

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Permalink Reply by Dwayne Roos on July 8, 2009 at 8:53pm

Hi Henri
I agree with what your saying,I thought that on my first one the brake form may have moved.I used four c-clamps in the middle and four woodworking clamps towards the edge and I sucked them down as tight as possible.On my later bends I flipped the blank over to counter the roll as it was shipped to me rolled and the last three spars where nice and straight.Thats the only difference between the first and consecutive spars.I think the first one slipped in the middle,causing the bow.
By the way,nice brake.I have the prints for the one from Mark T. but I would have to get some one to weld it and haven't looked into what that would cost me.I ran into the same problem with steel angle as well,couldn't find a straight enough piece,never thought about aluminum angle.
Thanks for your thoughts on this matter
Dwayne

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