Hardwoods don't have the elasticity, spring back, whatever it might be called, that softwoods have. I never had a problem straightening them, ash included, and they generally stay straight after they're sealed, unless one does something to bend them. For example, I have a habit of carrying my bow with attached bow quiver under my arm. This puts pressure on the arrow shafts right in the middle and will bend them over a day or so of carrying. No problem to restraighten them. Just needed to remember to do so. That will happen with cedar, too, but the effect won't be as great and it takes longer to occur.