25 



Figure 21a - Photographs of the Two Types of Flow at 5.94. Knots 



In the photograph on the left, the float was accelerated to 5 •94. knots; in the photograph on the 

 right, the floa^t was decelerated fl^m a speed beyond the hysteresis region. 



Figure 21b - Photographs of the Two Types of Flow at 6.20 Knots 



In the photograph on the left, the float was accelerated to 6.20 knots; the photograph on the 

 right shows the float just after it had suddenly yawed to its port side with a resultant 

 breakdown of flow to the more stable type in which water is thrown forward and to the sides. 



Figure 21 - Photographs of the Flow about the TMB Planing Float 

 in the Hysteresis Region 



These tests were made under loads imposed by the 100-pound weight towed from the forward towpoint. 



this region, showing the hysteresis loop, is plotted in Figure 22. The photo- 

 graphs in Figure 21a, which were both taken at a speed of 5-9^ knots, exhibit 

 clearly the two possible types of flow in the hysteresis region. Near the 

 entrance of the hysteresis loop, shown in Figure 22, conditions are least 

 stable, and the flow tends to change from one type to the other. The flow in 

 which water is thrown forward of the float, occurring on the upper branch of 



