SEMI-SUBMERGED SHIP STUDY

[Music] whew design changes have occurred in displacement ships for several decades despite the fact that their performance is degraded by heavy seas particularly ships of smaller tonnage --is this is a five-foot-long model of a ship that should provide vessels ranging from 200 to 10,000 tons sufficient stabilization to handle aircraft in heavy seas it is a semi submerged ship to torpedo shaped holes support a platform above water on for vertical struts a series of 500 tests have been conducted to determine the inherent stability and sea worthiness of the design comparative data was obtained using a standard ship model having approximately the same displacement in most of the tests the swells generated in the tank simulated 20-foot waves if scaled to a 5,000 ton ship here the models were allowed to move freely the semi-submerged model remains relatively stable while the conventional ship quickly reaches roll resonance when the semi-submerged model turned broadside in the waves it still remains stable demonstrating that it is well damped in all respects in this test the model was held at rest restrained in yaw but free to heave pitch and roll tests like this provided data on seaworthiness in other tests the model was fully restrained and towed by an instrumented carriage down the 300-foot tank to obtain measurements of the boats lifting force pitching moment and drag force many variables were introduced such as different sea States speeds tow directions different drafts and changes in pitch and yaw angle the objective was to determine whether automatic control surfaces would keep the ship level in heavy seas in a third series of tests the model was towed by means of wires attached to the submerged noses to simulate the frost line of the ship the model was free to heave and pitch in head seas the platform does not touch the water and remains relatively stable following seas produced more motion larger waves probably would hit the platform however a control system would prevent this from happening here the conventional model photographed in real time is simulating a speed of 15 knots in 20-foot waves this is prototype time where the motion has been slowed by a factor of seven to show how an actual 5000 tonne destroyer behaves in 20-foot waves at 15 knots and here is the semi submerged model photographed in prototype time under the same test conditions the main objectives of the 500 tests were to explore the basic stability and sea worthiness of the ship concept and to determine the control forces required to provide level flight in this demonstration where the model is manually deflected it's rapid recovery clearly shows it to be well damped in all modes still another demonstration of the ship stability is shown here where the model is being towed that a relatively fast clip to obtain more information on the ship seaworthiness and maneuverability a self-propelled radio controlled model was constructed it was equipped with two paired rudders a stabilizing fin which in the prototype ship will have control flaps two electric motors which could be independently controlled and two canard control fins positioned in a protected area near the noses of the submerged hulls these two control surfaces when moved in unison induce a pitching action and a roll action when moved in opposite directions after extensive testing in the tow tank the model was placed in the bay at San Diego where its movement would be unrestricted here the model is reacting to deflections of the canards first the pitching action is deliberately induced and now roll when canards are applied to counter the effects of rough water it is expected that near level flight will result the purpose of the runs in the bay was to study the models turning characteristics its performance at angles to waves and its general dynamic behavior the canard control fins were not used in this and following runs it was found that the model has a natural tendency to Bank in turns without canard controls it was also found that the model performed well at all angles to waves its greatest movement occurred in a following sea condition the model deck is scaled to represent a height of 20 feet thus these waves simulate waves 20 to 30 feet high because of the models strong response to control it is expected that near level flight up through sea state 7 can be provided ships of this type ranging from 200 to 10,000 tons would serve the Navy well as cruise missile carriers ASW and surveillance ship's sonar platforms air capable ships and oceanic research vessels the design is so