Originally Posted by
fixedweasel
The whole idea behind a double butted is to try as much as possible to have equal length straight gauge between the thinner butted center portion. Because of this, there is an equal tension placed on the straight gauge portion which directly leads to the thinner portion/middle of the spoke to flex as close at/to the center as possible. Can you cut the end of a double butted spoke to fit? Of course you can. Will it work? Yes, of course. Wheels overall are an absolutely wonderful design/work of art. They are built to be terribly strong and are a Physics dream to rotation under torque. But as soon as you start pulling away to much distance from the end of the spoke, you begin to lose your center of relieving stress from the center of the butt. Yes, it will still work, but if you have to cut too much, just save the integrity of the design and get the proper length spoke.
I think you're imagining a lot more going on than really is. If it were important at all to have exactly equal lengths of thicker sections on each side of the thinner center, I'd think more of the spokes I'd purchased over the years would have had them.
The main reason to have the elbow and threaded sections thicker than the center is because they are slightly weakened by the forming and the threading. (Looking at it the other way, a straight-gauge spoke is stronger in the center than it needs to be, compared to the ends.) The thick section between the elbow and center section is probably just due to manufacturing, and any remaining thicker section between the center and the threaded end is so that you don't have to swage every spoke length a different amount.
