TO SHIP CONSTRUCTION. 235 



Tests on the resistance to vibration made both in England and, in this country, at the Bu- 

 reau of Standards indicate that the arc-welded joint, properly made, is entirely able to stand 

 repeated stress to almost the same extent as the unwelded plate, provided the working stress 

 in the weld is limited to about 60 per cent of the fiber stress developed in the unwelded plate. 

 Vibrations of over 5,000,000 have been obtained by repeated stress on UiJton-Lewis machines. 



As to ductility, a valuable point in ship design, that is being investigated by the Welding 

 Committee in this country, and the report of Lloyd's in this country, and the British Ad- 

 miralty in England, both throw considerable light on this factor. Considerable difficulty is ex- 

 perienced in assuring ductility. 



The question of corrosion has been made the subject of study both in England and in the 

 United States, both natural corrosion in sea water and accelerated corrosion in dilute acids. 

 At Norfolk tests were made on various electrodes with different currents and current densi- 

 ties, and the information we ha,ve acquired to' date, including examination of specimens at- 

 tached to the bottom of ships in service, is entirely favorable to the welded joint. There 

 seems to be no reason to doubt the ability of the welded joint to withstand corrosion in an 

 entirely satisfactory manner. 



Most people accept the principal claims for arc welding — low cost, time saving, reduc- 

 tion in weight, strength and inherent water and oil tightness — and it is only the two or three 

 questions to which I have just referred that cause the comment. 



There are, however, certain disadvantages inherent to arc welding. I have noted four 

 here. The first is the difficulty of supervision and inspection ; that presents one of the most 

 serious difficulties and is being investigated on all sides. The break in the towing targets at 

 Norfolk just referred to was entirely due to poor supervision, because we knew it was the 

 wrong way to weld a strapped butt, and yet that particular job was welded in this manner. 

 We are getting samples from other butts, welded in the same incorrect order, and will subject 

 them to tensile tests. 



The second objection to arc welding is interference to other workers. The arc is very 

 harmful to the eyes, so that it is necessary to afford protection to others in the vicinity. That 

 is well taken care of by screens when working on horizontal surfaces, but presents more diffi- 

 culties when the men are working up and down the sides of ships. We are working on de- 

 signs of screens for that purpose, but, having relatively little of this welding to do, the inves- 

 tigation has not proceeded very far. 



A third objection to arc welding is the distortion due to heat developed by the arc, a 

 serious difficulty, and we have already had trouble in the battle-towing target due to that 

 cause. That was first encountered in bolting up some of the earlier work, and we thought 

 we knew how to handle it, but it has continued to give trouble. Experience will soon indi- 

 cate means for O'bviating this difficulty. 



The fourth objection to arc welding is the difficulty of opening up for repairs a welded 

 ship or other welded structure. No doubt that will be difficult. I find that the electrical en- 

 gineers who design motors and generators, which we in the navy yards have later to repair, 

 do not think much about the way to get their machines apart. They are solidly put to- 

 gether, and the poor devil who has to take them apart to get at an inner winding has his 

 troubles. We will, of course, have troubles in the case of the welded ship, except that the 

 oxy-acetylene cutting torch will enable us to cut a hole so neat that the plate removed can 

 be welded in again. 



The immediate development of the art would seem to require us to push vigorously the 



