18 



Towing Speed, 0.5 Knot 



Towing Speed, 2.0 Knots 



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TMB 11836 



Towing Speed, ^.0 Knots Towing Speed, 5.5 Knots 



Figure 15 - Photographs of TMB 4l -Inch Planing Float Being Towed 



These tests were made under loads imposed by the 50-pound weight tewed from the after towpoint. 



lOO-pound faired weights at speeds as low as 7-5 knots, and for the loading 

 conditions imposed by the 50-pound weight at speeds near 10 knots, the float 

 showed a tendency to begin porpoising. As deduced from observations made 

 during the actual tests, the speeds at which signs of porpoising appeared are 

 indicated by the small arrows on the curves of Figure 10. The resulting 

 smooth curve, shown on Figure 10 as the boundary of the region of incipient 

 porpoising, is, however, somewhat misleading. Sometimes, especially for the 

 highest loading condition, small oscillations in yaw were observed at speeds 

 below this boundary. For the 75-pound weight, these oscillations appeared 

 to become completely damped out before reaching the porpoising boundary. For 

 the 100-pound weight, on the other hand, the oscillations became converted 

 into a pitching motion and subsequent porpoising. If the end points at which 

 the oscillations in yaw began and at which they were damped out were plotted 



