Tie-Down Bars

The tie down bars need to be drilled and tapped and their spacers fabricated. The spacers are cut from an aluminum bar with a one inch lightening hole cut in the middle. It is called a lightening hole because it reduces the weight of the part.

The Freshly Cut Lightening Holes
The Drill Press After Cutting the Spacers

To fit the tie-down bar to the main spar, a single hole is drilled at a specific place on the bar and the bar is then placed on the spar with a bolt through the drilled hole. I’ve used a square to get perfect alignment of the tie-down bar across the spar.

With the tie-down bar clamped in place, the remaining holes can be drilled using the holes in the spar as guides.

Once the tie-down bar and the spacers are drilled to match the spar, the bar and the spacers need to be drilled for the platenuts that will hold the aileron bellcrank brackets.

Here is what the drilled components look like when they are finished.

The interior hole in the tie-down bar needs to be tapped to create threading for the attachment of a tie-down ring. Here is what the tapped hole looks like.

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