Monday, October 31, 2011

I Am Such An Engineer, Part II.

Him: "Well, the original composite bows were made of heartwood, and yew* wood."

Me: "Really? How did they get the two woods to stay together back in medieval days? Glue? Had nails been invented?"

Him: (Smiling, because he is cute.) "No, it grows that way."

Me: "..."

Me: "...Oooooooooohhhhhhhh. Because it's...a tree."

Him: "Yes!"

*Note: it has come to my attention that this post is totally, and completely, inaccurate, and it's not because of the source. It's because I misremembered it and wrote it quickly. The Yew is the kind of tree. Bows were made from heartwood and SAP wood, which is true no matter what kind of tree you make it out of. Here's what Wikipedia says:

"One of the simpler longbow designs is known as the self bow. By definition, a self bow is made from a single piece of wood. Truly traditional English longbows are self bows, made from yew wood. The bowstave is cut from the radius of the tree so that the sapwood (on the outside of the tree) becomes the back two thirds and the belly, the remaining one third, is heartwood. Yew sapwood is good only in tension, while the heartwood is good in compression."

The point of using the yew tree (hopefully, not to shoot ewes) is that the yew sapwood can take much, much, more energy in tension (when you draw the bow back) than other timbers, so more of the energy goes into the arrow, meaning you can kill someone from farther away, always a plus.

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