What is wing trammelling and how does it affect wing stability and performance?
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asked Aug 4, 2018 at 11:58
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It's just making sure the rectangle formed by the spars, compression tubes and cross bracing is square. It's done using a trammel bar, which is just a stick (which the guy in the picture is holding) with a metal point at each end that is used to make sure diagonal reference points along the spar beams are the same distance apart when set across one leg of the X formed by the cross bracing, then the other leg. The effect on stability and performance is indirect insofar as you don't want a rectangular wing to be trapezoidal (swept - unless the sweep is part of the design like the upper wings of some biplanes, in which case you trammel to that requirement), as well as the fact that parts won't fit if things aren't square.
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$\begingroup$ Pls pardon my ignorance,........so the purpose of wing trammeling is to make sure that the internal braces form squares in a rectangular wing,correct? @Jonh K $\endgroup$ Commented Aug 4, 2018 at 18:04
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$\begingroup$ Yes, in a perfect 90deg rectangle the distance between to opposite corners is the same. A trammel bar usually has a point that can be slide to a specific distance, such as the center of two wing spars at given rib stations. The opposite rib positions should be the same distance - if not then you have a parallelogram, not a rectangle. see en.wikipedia.org/wiki/Parallelogram $\endgroup$ Commented Aug 5, 2018 at 18:11