Ash was used for sinewbacked, setback-handled shortbows, with a drawlength of about 20-25" and a total length of 44-56" in the plains area. pacific cost natives mainlymade wide, flat short(40"-56") sinewbacked(paddle) bows, with a slightly narrower, but bending handle and up to 3" wide midlimbs.
I'd suggest a handle bending bow, being 1 1/2" wide at the handle, and 3/8" at the tips. start the taper from about midlimb.
I would make it 76"ntn, and like 90#@ 32", but for a 'normal' drawlength of 28", and a more 'normal' drawweight of 60#, you can go down to 64"ntn without problems.
If your first bow, you better make it 4" longer
Nick