Quite right David, however the purpose of the exercise was to investigate lower cost methods of producing an unstayed mast. The trade off in cost, moving from carbon to glass, is clearly governed by the section diameter. Carbon will always be the best choice where cost is no issue.

 Allowing for a FOS >5 was easily achieved in the e-glass RHS section by keeping the same wall thickness as the smaller cross section carbon cylinder. The trade off is ofcourse not just increased weight, but also increased windage. Not such an issue if using a wing section tho, as the drag of the thicker foil section is less than that of the thinner round section.

Thus a good compromise is possible using a RHS spar of increased section size, with a thin outer fairing to form a wing profile. Arguably a better choice than a round "all carbon" mast.  A thicker wing mast section is also less sensitive to correct mast trim compared to that of a thinner wing section - so its not all bad.

Another good compromise is to use carbon for the unidirectional (top to bottom fibres) and glass for all the off axis fibers. This saves a good bit of money with only a small weight penalty, and negligible loss in strength for the same section providing a slightly heavier glass schedule is used in the off axis fiber. Normally not a good idea to mix fibers, but where they can be designed to take different stresses, i dont see a problem with it.
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