In order to apply fracture mechanics to hull designs, a new design method using unique models is proposed. This method has following characteristics. 1) Ordinary hull designers, who have no special knowledge in fracture mechanics, can estimate, 2) both crack initiation life N, and crack propagation life N _p, 3) using only the stress distribution in the condition without cracks, 4) without troublesome analysis of K Value, 5) without a computer, 6) with enough accuracy. This paper represents the theoretical background of the new method, verification of the accuracy of K Values estimated by the method and application examples.