METHOD OF CONSTRUCTION OF CONCRETE SHIPS. 5 



and cribbing at all stages of support. The details of blocking, however, are not 

 the same in both yards. At San Diego girders athwartships are placed on the block- 

 ing and support the form joists which extend forward and aft. At Mobile, the 

 girders are placed longitudinally and form the joists athwartships. 



Blocking was used at San Diego for all stages of support. On the shipways 

 transverse sills are arranged in groups that center under each alternate trans- 

 verse hull frame to carry a system of blocking, gang wedges and girders which sup- 

 port the bottom forms during construction. Here the forms are built in sections 

 consisting of removable panels of a uniform width and extend over two frame 

 spaces where their fore and aft edges rest upon transverse girders. The girders 

 for each section are supported on successive sets of blocking and are held to their 

 proper elevation by adjusted gang wedges. At the forward and aft ends the bottom 

 forms are not built in panels but as a unit. 



Scaffolding is necessary to support the outside forms. The details of the de- 

 sign of the scaffolding differed somewhat in the several yards. The general scheme 

 employed, however, was quite similar. Essentially the scaffolding consists of two 

 lines of trestles built of light wood construction, which are anchored at the bottom 

 to the sills of the building ways, and at the top, at regular intervals, they are tied 

 and held apart across the ship by trusses of similar construction. In some cases these 

 top trusses are placed quite close together (lo to 15 feet center to center), while in 

 one yard only three trusses were used for the entire length of the ship (435 feet). 

 The wide spacing of the trusses affords less interference with overhead handling of 

 materials into the hull, and is to be preferred. Struts from the scaffolding held 

 the outside forms in place. 



The forms for ship construction must be smooth, very rigidly built and braced, 

 and more exactly constructed than concrete forms for ordinary building construc- 

 tion. The concrete sections have been made a minimum in size which will accom- 

 modate the steel and meet the strength requirements, and any deviation in the form 

 construction either results in added weight of hull, lack of space or cover for the 

 reinforcement or lack of uniformity in the concrete surfaces. 



The hull lines to which the outside forms had to be constructed were obtained 

 from the mold loft floor by one of several methods. Either templets were made of 

 the cross-section required for the midship body and every frame of the forward 

 and aft body and the forms constructed in place from these templets, or the forms 

 were prefabricated in panels, the lines being taken directly from the mold loft floor, 

 or portions of the studding were cut to shape in the mold loft, thus giving the ship 

 lines, when erected, to which the sheathing was directly applied. In most yards a 

 combination of these methods was employed. 



The thin board form of templet commonly used in steel ship construction was 

 employed in all but one case where templets were used. At Wilmington, N. C, 

 an adjustable templet was devised and successfully used. 



This templet consists of a flexible batten attached to a rigid frame in such a 

 manner that the batten can be bent to any shape desired, and rigidly supported in 



