If looking at the cross section of a Yew stave it sometimes has very tiny riples or waves between the bark and sapwood. Instead of violating the sapwood's outer ring I leave some of the brown stuff on,makes a nice decoration. If some of it wants to come off it will do so when you start to bend the bow. If the sapwood have an acceptable thickness I start bending the stave without taking off the bark, it usually pops off or can be gently pried off and leaves a perfect surface without any scraping. It sounds kind of scary because the bark cracks like the stave is breaking. Even though Yew can have very thin year rings I find it easy to get the bark off without violating a ring, if you have to scrape it. Patience and good lighting is the thing. Bue--.