PRESENT STATUS OF THE CONCRETE SHIP. 195 



to 29, 1918, thus becomes a notable event in the annals of naval architecture; notable, 

 not alone as the first voyage of the first large concrete vessel, but as the occasion 

 when definite and reliable stress records were first obtained on a ship at sea. 



A section of one of the autographic records is shown on Plate iii. 



Some of the typical features of several of the concrete floating craft which have 

 been designed by the Emergency Fleet are shown in the accompanying illustrations. 

 (Plates 112 to 129.) 



The present status of the concrete ship is as follows : — 



1. All analytical investigations so far made demonstrate that the concrete ship 

 can be designed so as to carry all the strains which come upon a ship just as safely 

 as a steel ship. 



2. The tare weight of a concrete hull has been reduced to such an extent by the 

 development of a light weight aggregate that it has a proportionate carrying effi- 

 ciency greater than wooden ships and only slightly less than steel ships. 



3. All available experience with concrete ships to the present time does not dem- 

 onstrate any structural weakness which might indicate unsoundness in the theory of 

 design of concrete ships or probable limited life. 



4. While ships of small size are being built in many places throughout the world, 

 the large ship (over 3,000 tons) is being developed in the United States. 



5. There is no perceptible difference in the frictional resistance offered by a 

 concrete ship as compared with a steel ship. 



6. Our general knowledge of reinforced concrete as compared with steel struc- 

 tures makes the success of its further adoption for ship construction appear a cer- 

 tainty, but actual experience is lacking and therefore its future cannot be predicted 

 with absolute certainty. 



DISCUSSION. 



The President : — This paper. No. 12, entitled, "Present Status of the Concrete Ship," 

 is now before you for discussion. 



Mr. E. H. Rigg, Member: — Mr. President and gentlemen, I have a few remarks which 

 I have committed to paper — they are not extensive, and will not take up much time to read. 

 However, before I read what I have written, I think it can be safely stated that the concrete 

 ship has definitely arrived within a certain range. The concrete barge and the small self-pro- 

 pelled coasting vessel of reinforced concrete are unquestionably successes. They have been 

 developed in countries that are not rich in iron, and that form of construction has proven 

 satisfactory. They also have a distinct war value in releasing steel and iron for other pur- 

 poses. When you come to ocean-going ships of relatively large dimensions, that is something 

 else ; I do not propose to detain you with a discussion on that point because there has been a 

 great deal published of late on the subject. The transactions of the Institution of Naval 



