APPENDIX 3 



Mechanical Properties of Water, Air, 

 and Other Media 



X3.1 General 915 



X3.2 Reference Data for Weights, Volumes, and 

 Mass Densities of "Standard" Fresh and 

 Saltwater 915 



X3.3 Mass-Density Values of Fresh and Salt 

 Water, in English and Metric Engineering 

 Units 918 



X3.4 Kinematic-Viscosity Values of Fresh and 

 Salt Water, in English and Metric Engi- 

 neering Units 920 



X3.5 Other Mechanical Properties of Fresh and 

 Salt Water at Atmospheric Pressure; Dy- 

 namic Viscosity and Surface Tension . . 920 



X3.6 Data on Change of State of Fresh and Salt 



Water 921 



X3.7 Elastic Characteristics of Water and Other 



Common Liquids 922 



X3.8 Mechanical Properties of Air and Exhaust 

 Gases at Atmospheric Pressure and at 

 Sea Level 922 



X3.9 Mechanical Properties of Other Liquids and 



Gases 924 



X3.10 Chemical Constituents of Sea Water . . . 924 



X3.ll List of Pertinent References 925 



X3.1 General. There are many published 

 sources of information concerning the mechanical 

 properties of water, air, and other common 

 fluids. The tabulated values in these sources, 

 while often differing within the range of significant 

 figures shown, are all sufficiently precise for the 

 usual problems in engineering design. 



Nevertheless it is disconcerting, to a student or 

 especially to an engineer, when shifting from one 

 field to another, say in a time of national emer- 

 gency when everyone is harassed, to encounter a 

 group of different values for what is apparently 

 a standard state of some medium. Furthermore, 

 certain ratios in everyday use in naval architec- 

 ture are by no means consistent when derived in 

 several different ways. To clarify this situation 

 for the marine architect a set of so-called "stand- 

 ard" values has been evolved, for both fresh 

 and salt water. They are described and tabulated 

 in the sections which follow. A set of standard 

 values for air already exists. 



While the five significant figures embodied in 

 these "standard" water values are by no means 

 necessary in making first and second approxima- 

 tions or in the early stages of a ship design, they 

 lend themselves to the desk-machine calculation 

 now almost universal in the later stages of a 

 ship design, or in the preparation of technical 

 reports. 



X3.2 Reference Data for Weights, Volumes, 

 and Mass Densities of "Standard" Fresh and 



Salt Water. The so-called standard unit weights, 

 mass densities, temperatures, and specific grav- 

 ities in use for many years by naval architects 

 and by model basins, at least in America, were 

 selected for the most part because they were 

 round numbers, easy to remember, and easy to 

 use. Indeed, if they approximated 1.0, they were 

 often thrown away. That they were anything 

 but consistent among themselves was not too 

 important, because the deviations involved were 

 generally of smaller magnitude than the overall 

 precision of measurement of the various opera- 

 tions. 



They began with the use of the round numbers 

 35 ft^ per ton for sea water and 36 ft^ per ton for 

 fresh water. These gave values of 64.000 lb per 

 ft' for salt water and 62.222 lb per ft' for fresh 

 water, based on long tons of 2,240 lb. Incidentally, 

 because some seas in the world contain fresh 

 water in their upper levels, the term "salt water" 

 is used in this book; it also stands in better 

 contrast to "fresh water." 



When round numbers were used, the specific 

 gravity of salt water on a basis of fresh water 

 came out as 36/35, or 1.0286. Since this was 

 larger than the ratio existing in most parts of the 

 oceans, the U. S. Experimental Model Basin, 

 half a century ago, adopted a smaller value of 

 1.024. The origin of this figure is not known but 

 it was embodied in all the calculations of the 1910 

 edition of D. W. Taylor's "The Speed and Power 



915 



