This describes the first phase of an effort to develop a robot crane for shipbuilding applications. The focus of this phase is on the study of the stiffness characteristics of this robot as a function of its geometry payload and height. A brief description of the design of the main part of the robot crane consisting of a six-wire parallel link manipulator is given. The stiffness of the manipulator to side loads and moments was studied. The nonlinear and linearized mathematical model of the manipulator stiffness matrix is derived. Stiffness measurement tests were conducted using a small size laboratory model. The results of these tests for various external loads, heights, and payloads are given. Computer simulation and theoretical results are also discussed.