Aim for a width of at least 2" but preferably 2½" of the back of the bow. The tips may be narrower, but the center must the this wide minimum. Ash is easy to split, as long as there are few knots/defects.
Volume 1 and 2 are in the post 
i'm scraping and i've worked out what has been going on. because it was harvested in winter the first layer of wood is the darker stuff that makes the boundaries between the rings.. assuming that the larger whiter sections of rings happen when the tree grows a lot with all the sun in summer. Im guessing that winter is not the best time to harvest wood for bows because you were saying I was after 'sap' wood and that would be the new growth ring from the summer? Am I on the right track?
Do I want the hard winter ring or the larger growth one under it? Maybe the hard winter ring makes a good back actually now thinking about it..
No, you are confusing things.
First, trees (and thus wood) grow from early spring to fall. There is no wood formed in the winter. The layer you call 'winter growth ring' is the so called
latewood. The layer that was produced in the spring is called earlywood. One annual growth ring is composed of earlywood and latewood. It's not strictly demarcated, since the spring does not abruptly stop. But in ring porous woods such as ash (or hickory or oak, for that matter) you can clearly see the boundary between the latewood from one year, and the earlywood from the next year. This boundary is the darker colored latewood in ash. But you can't find the boundary between the earlywood from one year and the latewood from the same year since that is gradual. The earlywood is spongy, porous wood, which you want to avoid in woods (holes are weak). Latewood is more dense and preferred in ring porous woods.
Sapwood consists of several annual growth rings. Depending on the species of wood, about three to twenty rings. Not all species have visible sapwood, but most woods have their sapwood clearly demarcated from the heartwood by a lighter color (such as oaks). Ash has no such thing; you can't visually see where the sapwood ends and the heartwood begins. That is not a problem, since both the sapwood and heartwood in ash are equally good.
Wood can be cut at any time of year. Winter is just as good as spring of summer. Don't let anyone tell you otherwise. Yet, it is theoretically true that ash wood harvested in May will have a thin layer of earlywood directly underneath the cambium, while ash wood harvested in December will have a layer of latewood directly underneath the cambium. But that is really unimportant and will not effect the bow, nor will it pose a problem in working with the wood. In practice, it is about impossible to get the earlywood on the back of the bow. This layer is so soft, you automatically remove it and always end up with the latewood on the back of a ring porous wood bow. As long as the back is one
growth ring, it does not matter how deep in this single ring you are.
