20 



Towing Speed, 0.5 Knot 



Towing Speed, 2.0 Knots 



Towing Speed, 4.. 5 Knots Towing Speed, 5.5 Knots 



Figure 17 - Photographs (jf TMB 4l-Inch Planing Float Being Towed 



These tests were made under loads imposed by the 75-pound weight towed from the after towpoint. 



on the curves of Figure 10, the result would be a closed contour starting 

 beyond the humps and ending near the boundary of the porpoising region and 

 lying above the curves for loading by the 50-pound faired weights. Since it 

 was not possible to determine whether these oscillations were due to some 

 instability in the faired weight, which was reflected in the motion of the 

 float, or whether they were due to the float itself, they have been mentioned 

 here without further attempt at analysis. 



Furthermore, for all loads except the 75-pound weight towed from 

 the after towpoint, fully developed porpoising failed to materialize. Under 

 the load imposed by the 75-pound weight towed from the after towpoint, how- 

 ever, violent porpoising developed almost immediately in the region beyond 

 the limiting curve of "incipient porpoising." 



