As I understand it the British Longbow Society requires, among other criteria, that the width to depth ratio be no more than 8/5. So if a bow is 1" wide (8/8ths) then it must be at least 5/8" deep.
Typically the classic "war bow" example features the most sparse use of material, being designed to bend ever so slightly under the hand", where it's width and depth dimension are the greatest, and without any abrupt transion along it's lenght, the so called "buchanon dips." In practice most achieve a more oval section in the most working part of the limbs, more round under the hand and on the outer limbs.
It's more or less a classic design for any wood bow, what folks sometimes call a "D" bow, where function dictates form if you want to achieve the most work from the least amount of wood.
1 1/4" and 72" long would be sufficient for most man size bows if it's decent mulberry, and probably will finish closer to 1 1/8" unless you want 70#+ of draw weight. 1 1/4" (10/8ths) would demand 1" deep to maintain the 8/5 ratio.
Google will produce lots of hits.
