That is Black walnut.I have made a lot of bows with black Walnut saplings. It has a thick outer growth ring that is very strong .I debark them green ,and ax,and rasp to 80 percent so I can get it shaped on a form with 4 inch back set. Take the twists out of it, and line the tips up with the riser heating ,and clamping.Let it dry in my basement. Give it a good belly heat treat before you take it off the form.Then tiller ,and heat treat one or two more times. It can take a lot of set ,so heat treating is important.Makes a light smooth drawing bow. Make it wide pyramid style. Will make a good self bow. Over looked as a good self bow wood, but built right works fine. Wood will ding easy. It is a soft hard wood.I have made them short, but my best bows were 62 inches long, 2 inches wide coming off the fades to 5 eight,s at the tips.Good luck.