212 THE SUBMARINE OP TO-DAY AND TO-MORROW. 



German boats around the British Islands and also to the Dardanelles, are all very 

 convincing as to sea-keeping qualities. In these last cases, the average surface 

 displacement involved is about 700 tons. 



In the special case under consideration, the limit of permissible cost would fix 

 the upper limit at say 550 tons. If we allow for the prevailing United States stand- 

 ards with respect to armament and the features affecting habitability, safety and 

 access, as well as durability and reliability of machinery, a surface displacement of 

 at least 500 tons is indicated. 



Assuming that the military conditions can be met by an effective cruising radius 

 of 2,500 miles at 1 1 knots with normal fuel supply, it will be interesting to set down 

 some possible solutions where the submerged speed and radius and the surface 

 speed are the only variables. In all these solutions, armament, safety, habitability 

 and roominess are the same and the same character of machinery is contemplated, 

 except where noted. The percentage of buoyancy is varied as it should be to meet 

 the actual conditions as to surface speed and as to speed-length ratio. 



Table VII. 



Design Design Design 



No. I No. 2 No. 3 



Displacement, surface, tons 500 500 500 



Buoyancy, per cent of above 20 24 28 



Displacement, submerged, net tons 600 615 640 



Surface radius at 11 knots, miles 2,500 2,500 2,500 



{\ tubes 4 tubes 4 tubes 



Armament (all tubes internal) < 8 torpedoes 8 torpedoes 8 torpedoes 



L 1—3" gun 1—3" gun 1—3" gun 



Surface speed, knots 13 14 15 



Submerged speed, knots 11 11 10^ 



* Submerged radius at 5 knots with 



Battery A 115 100 80 



Battery B 132 115 92 



Battery C I45 126 loi 



All things considered, the author believes that Design No. i presents the most 

 valuable combination of qualities, but as this would involve a change in prevailing 

 practice, it is perhaps more probable that the characteristics of U. S. coast defense 

 boats of the near future will more closely approach Design No. 2. Whatever may be 

 the decision of our naval authorities as to the surface speed necessary, the author is 

 firmly convinced of the relatively greater importance of the submerged qualities for 

 this type of boat, and consequently believes that battery capacity and submerged ra- 

 dius and speed should not be unduly sacrificed either in the interests of durability 

 or first cost. 



♦Type A is a heavy durable battery with positive plates of the Plante type. Type B involves the use of 

 thinner plates of the pasted type with a probable sacrifice in durability of about SO to 60 per cent. Type C is of 

 special construction equal to Type A in life, but more expensive, so that its use would increase the first cost 

 of the boat by from 4 to 5 per cent. 



