the way i can tell maple apart is what i refer to as ray flecks they are small(minuscule) compared to oak. on the face grain one of the adjacent faces will have a little showing of the ray flecks. they are straight and run with the grain. as a hobby i woodwork and only have access to oak maple walnut pine and poplar for that hobby. I haven't ran into any that would use maple for spar material, not saying there isn't just none that I have seen. for the planes I have built i was fine with spruce or basswood for a spar. carbon fiber is nice but too expensive for the airplanes i would build since i build mostly sport airplanes.