I have been trying to find some real numbers on how strong a single solid piece of aircraft graded spruce wood timber is, but haven't had much luck and the numbers that I have found so far were either not for aircraft graded spruce or the sources weren't credible enough or simply the numbers were conflicting with what else I had found previously.
My question therefore is: How much of an evenly distributed weight a piece of aircraft graded spruce can take e.g. as a wing spar or struts before structural failure?
The length and thickness of the timber doesn't matter as long as the spar and/or strut went under the load test alone. The reason that I'm saying this is that I can find numbers for aeroplanes that have spruce spars for example, and based on the maximum G, weight of the aeroplane, etc. I can have a rough guess for how much load the entire wing is certified for, but an entire wing is made of other components that will have an effect on the results of those tests, which means those maximum numbers may not necessarily be the limits of the spruce spar itself e.g. the wing ribs or wing surface might have a lower tolerance, therefore reducing the performance numbers in the certificate.