Keep firmly in mind that this is the correct design of the bow; for your pattern lines will disappear under your plane as you proceed with the rounding of the belly. The depth of your bow must taper from 1/18 inches at the handle to 5/8 of an inch at each end without taking any wood away from the wide crest of the original flat surface which you chose for the back.
If you have not already learned it, from the diagrams or otherwise, let me say here that the back of a finished bow of the kind we are discussing (the English long bow) is the side held farthest from the archer in shooting. The belly is the side held toward him. And the sides of the bow parallel the arrow.
In shaping the belly, much importance attends cutting the dips, which begin at the grasp. These dips have a depth reaching 1/4 of an inch below a straight line from the 1 1/8-inch belly surface of the grasp to the 5/8 inch point at the tip of the bow's limb. Their length, to the 1/4-in.ch point, or the center of the dip, is 5 to 6 inches, depending on the weight, or drawing strength, of the bow. (See diagram.)
The dips should begin right at the handle, and rather quickly, their sweep being less abrupt as they return to the straight line of the taper from handle to limb tips. This line to be the ridge of the belly for most of its length, but an imaginary one above the dips.
The round of the belly may be any desired, but it may be remarked that the bow will cast better for not being made too flat. Your jack plane will be the best for taking off the bye-wood. If you have a model bow to work from, make frequent use of a gauge in order to prevent taking off too much.