A #30 bow, at 28" draw, and 70+ inches long can be made with just about any type of wood.
Cut the tree down the center, flatten the cut, and make the rounded part the belly. Theoretically, you could make two bows. I'll be willing to bet you don't even need to back them. The hardest part would be drying the stave(s) without cracking them. IMO.
I for one would like to see the results.