All true. At Vd and limit g loads, you have worst case for wing spars in shear and bending moment. Va is a close second, but the wing is generally sturdier against bending here. Va is the place where loads forward from lift are maximum and is the big stressor on drag and anti-drag bracing of a fabric covered wing. Put the air moving horizontally, the wing pitched up 18 degrees, and lift is vertical, lift has a significant component towards the front of the wing, which is trying to wrack the wing tips forward. This is why we have some form of diagonal bracing between the spars of fabric covered wings, usually drag and anti-drag wires to hold the wing square. When you go to structural skins, they carry these loads. Anyway, we have long established empirical guidance on sizing of these braces.So it seems that I must concern myself not only with distributed loads on the fwd and aft spars at high AOA, but also all the way down to the AOA that produces Max G at Vd ... So the question this logic would create is how to determine what AOA is going to create Max G at Vd. I suspect this is a complicated answer that involves things like Coefficient of lift and can be better found after TOWS is read and understood. If there is a "rule of thumb"

The Design References sticky includes ANC-18 for wooden structure design. Someone has posted links for it. Not my area, so not at my fingertips.This design already has a V-strut and I don’t see any reason to complicate things by changing that to a parallel strut so, to calculate the cabanes needed I need to be able to work with the V-strut arrangement ... I’m not sure the tension and compression capacity of these members is equal to the simple sum of their parts, and if tables exist for the tension and compression capacity of rather thin plywood.

One the topic of strut loads, this is all truss theory. There are a number of good videos online about this and can get you started on how to resolve vertical loads, and then how the loads further increase when the strut is angled.

True, but it does allow an easy calculation of an upper bound on wing bending moment curve. Useful for those just starting to calculate such things. Reality is different.Please refer to the attached diagram which is supposed to represent a high wing strut braced aircraft ... If this is the case then the I would assume that “rectangular lift distribution” would be like that shown in “A” and does not really exist because there is always (except in a few oddball designs like flying donuts and such) less lift at the tips due to spanwise flow, that being which results in wingtip vortices. This being the case “rectangular lift distribution” is not what is found on a “Hershey bar” wing and really is only a theoretical idea that does not exist on any wing design or planform.

I am accustomed to linear reflecting the plan form of the wing. It too shows too much lift in the outer portion of the span, and demands not enough of the inner portion. Not real, drives excess structure and may underestimate stall speed.Then you have “linear lift distribution” which is shown in D which also probably does not happen in the real world.

All ellipses are similar. The line is vertical at the tip and horizontal at the centerline. When you hold span constant (you are flying an airplane with wings not changeable in flight) and you unload the plane, the lift distribution curve scales down , pull back and load up the plane, the lift distribution scales up. All still elliptical.Now ellipses are not all the same (as I recall it has to do with the spacing of the foci, among other factors) so you can have more than one lift distribution that would still be called elliptical – say by comparing B to C.

As to our typically using the upper half of an ellipse instead of a whole ellipse, this is just convenience. If you use the whole ellipse, you still get the same shape, just scaled differently. And the quarter- or half-ellipse is more intuitive to calculate and synthesize from.

Billski