In reply to your post Neihaera, the planar bows are made with special bowstrings that give the bows special magical properties. They have to be made with special ingredients that have those magical properties.
Edit// Oh, but you are asking, how come we cant make bowstrings for non-planar bows out of other ingredients. Hehe. sorry had to re-read your post.
Edited, Wed Jul 28 00:43:39 2004