194 PRESENT STATUS OP THE CONCRETE SHIP. 



A priming coat of magnesium fluosilicate (MgSiFlo) is applied to the entire 

 hull. The solution shall contain not less than 15 per cent by weight of salt and not 

 more than one per cent of any other substance in solution, nor more than 0.2 per 

 cent of total chlorine. The paint which will give the best service has not been de- 

 termined upon. Two types are being tried. One is a high grade spar varnish which 

 is applied in two coats, and the other a bituminous paint consisting of asphalt base 

 thinned with petroleum distillate. One or two coats of this latter is applied fol- 

 lowed by a coat of the same paint thickened with about 15 per cent of finely pow- 

 dered silicious matter and 15 per cent short fibred mineral asbestos. An antifoul- 

 ing paint is applied on under-water parts and a boot topping paint on upper portion. 

 The interior of the tank ships is coated with two coats of spar varnish. 



Not less important than the design and material problems are the construction 

 problems. While a concrete ship is composed of steel bars and concrete, never 

 before have we attempted to build structures with such proportionately large quanti- 

 ties of reinforcement, with steel to be bent very exactly in irregular curves, concrete 

 to be placed around this great mass of steel in very thin walls, with few or no joints, 

 and forms to be built to exact and irregular curves. 



It is a task of great magnitude and deserving of much study. In this connection 

 we have had specialists working upon the form construction, steel fabrication and 

 concrete placing problems, and have made many tests and investigations. 



Another important field of the work of the Emergency Fleet which will espe- 

 cially interest you is the investigation of the stresses in the hull of a ship at sea. 

 This work is under the direction of F. R. McMillan. 



In its solution attempt is being made for the first time in the history of naval 

 architecture, except for a single test reported by Biles^ to establish experimentally a 

 basis for scientific analysis of hull stresses. This work involves not only the plan- 

 ning and carrying out of tests on a scale not heretofore attempted in any structural 

 investigation, but also the development of special recording instruments for the 

 measurement of strains in any part of a hull under conditions encountered in a storm 

 at sea. 



Progress to date has been satisfactory. The Strainagraph, a recording strain 

 gauge, as shown in Plate no, has been developed, which has proven thoroughly suc- 

 cessful. A recording pressure instrument specially adapted for measurement of 

 wave pressures on the hull of a ship has also been perfected. Twenty-five of the 

 former instruments and thirteen of the latter are being provided for the test of the 

 "Liberty"' ship now under construction at Brunswick, Georgia. Other arrangements 

 for this test, which is planned to be very extensive, are well under way. 



As a preliminary to the important tests to follow, advantage was taken of the 

 opportunity offered by the maiden voyage of the Faith to try out the instruments and 

 to further develop the methods of test. For this test nine strainagraphs were avail- 

 able. The records taken by these instruments simultaneously at nine different points 

 in the ship were synchronized so that the exact stress at any instant at each of these 

 points is known. The voyage of the Faith from San Francisco to Seattle, May 22 



