My stepfather had a Morgan +4, and I think that had a wood frame, too. But it might have been oak.
Norman ash is a favored bow wood here, too. Doesn't quite have the kudos hickory gets as a board bow, but close. Red oak is in the same league. Top woods for self bows here are Osage orange, Pacific Yew, black locust, and elm.
I'm sure the folding kayaks had the best wood for the purpose in ash -- it's very tough, relatively light for its strength and flexible. It's also used as sail battens for sails -- inserted into pockets in the roach. Baseball bats are also traditionally made of ash because of its flexibility and light weight.
It isn't subject to rot in those other uses, since it's usually not sitting in the damp or fresh water -- nobody keeps a folding kayak (decked canoe actually) on a mooring or at a dock. They are folded and stored indoors -- or should be!
But i can also confirm what Andrew says about its susceptibility to rot. I cut a lot of wood around here for heat, and will often use fallen or standing deadwood trees if they are sound, for preference. But nothing rots as fast as ash, I've found. If it falls, you have to get it that same year, or it's mush. The birches are a little better. Red maple can go a few years with only the outer sapwood breaking down. Red oak can go three years and be mostly sound. Cherry seems the longest lasting of all on the ground. I've cut seemingly rotten cherry logs five years old -- just to move them, and found a hard center an inch under the softer wood.
Russell, thanks so much! Glad it's turned out to be interesting -- I was kinda wondering if it would be on a machinist site.
I think maybe I like bows because they're active. Woodworking isn't so interesting to me because I really like engines and airplanes, and stuff like that-- things that move and have performance. That's always got my interest. While something like a bowl or furniture is static. Yet I have all this wood, and always wish I could do something interesting with it.
So finally hitting on bows is really capturing my imagination. Because they are kind of like engines themselves. They store energy, they move, and they have performance, which is easy to see. And they have a long and varied history. So there's a lot to think about.