NO. 2 liYDROMECHANIC EXPERIMEXTS RICHARDSON 3 



and 1 59 1 -3 was thus derived. The result was that the spray was held 

 down, the planing- effect increased and the resistance reduced, an all 

 round improvement. 



Model 1 592- 1 was made from the lines of the Navy Flying Boat 

 C-i. 



Model 1 593-1 was made from the lines of the Xavy Flying Boat 

 D-i. 



Model number 1602-1 was derived from 1 591-3, but the beam was 

 increased from 30" to 34", otherwise the bottom was the same, at 

 the same time an attempt was made to improve the form by changing 

 the form of the front hood, and by sloping the upper deck abaft the 

 position of the planes. The results of these changes are apparent in 

 the submerged runs. 



Model 1592-5 was derived from 1 592-1 by adding a shallow V 

 bottom just forward of the step of 1 592-1. 



Model 1617-1 was designed on the general lines of the E-i, combi- 

 nation type (Owl, type). The object of this experiment was prin- 

 cipally to determine whether the shorter form was disadvantageous 

 from an air resistance point of view. 



An inspection of the performance of 1591-3, shows that from 

 a resistance point of view it excels all but 1592-5, and an inspection 

 of the change of level curves will show this to be intimately asso- 

 ciated with the valuable " planing " qualities of 159 1-3. 



1 592- 1 behaves very similarly but the resistance is higher, while 

 1592-5 behaves very similarly but the resistance is lower than either 

 of the two preceding and the change of level curves clearly demon- 

 strate that the improvement is due principally to the improved " plan- 

 ing " effect, and it is also due to the better flow induced by parting 

 rather than pushing the Avater aside, due to the V-shape at the step. 

 1602- 1 behaves much the same, but the broader beam appears to 

 increase the resistance slightly except where the planing effect 

 reaches its maximum : 



1 593- 1 behaves well at low speeds, but the resistance grows to a 

 maximum at a much higher speed than any of the other models and 

 falls off steadily but much less sharply than any of the others. The 

 hump for the resistance curves occurs at about 27 m. p. h. for this 

 model; at about 21 m. p. h. for 1591-3, 1592-1 and 1602-1, and at 

 19.5 m. p. h. for 1592-5. The sustained hard running of this model 

 is clearly due to its failure to " plane " as is evidenced by the change 

 of level curve. 



1617-2 has high resistance at speeds corresponding to 24 m. p. h., 

 but in general behaves similarly to the other central step models. 



