The following text may have been generated by Optical Character Recognition, with varying degrees of accuracy. Reader beware!

24 THE MarRINE REVIEW Framing of Vessels Since first I put together a few notes for this paper, I have been constrained by some of my friends who have taken a very kindly interest in its preparation, and also by the force of circumstances, to alter my plans to some extent. I had intended to say more about the various systems of framing that have been practiced from time to time both in wood and iron ships, and in that way to trace out the history of my subject, in detail. After spending considerable thought on the matter, I came to the con- clusion that it would serve the objects of our institution best if I confined myself to such structures and systems as I have been intimately connected with in the drawing office of the ship yard. When I. first began to make a practical study of ships' framing, the transverse system was taken almost as a matter of course by all naval architects and ship builders. In the drawing office we were then familiar with the open floor system, varied where water ballast was required in the double bottom, by the McIntyre system; and in warships the bracket sys- tem was the most familiar one to me, though. found undesirable for big cargo carriers. If we are to believe writers of ship building text books, among others, Mr. Thearle, now one of the well-known surveyors at Lloyds head office, the idea of transverse framing came directly from the practice of wooden ship building, and here my subject compels me to touch on the history of ship building to some ex- tent. Important writers on the subject of ship building have entered their pro- tests against blindly following a method, which, although found admirably adapted for the construction of wooden ships, of such dimensions as were generally adopt- ed for vessels of that material, is not what one would logically expect in deal- ing with material of comparatively great tenacity and offering the utmost facility for joining either in the direction of its jength or its breadth, such as iron and steel. In the. practice of building wooden ships, the transverse framing was obvi- ously necessary. Generally, no attempt was made to join the breadths of plank- ing together along the edges. On the contrary, in the operation of making the planking watertight by wedging oakum into the seams, forces were brought to bear upon the planking tending actually to open them out. As a rule, the trans- verse framing of wooden ships was very firmly and massively constructed and "bound together by strong iron knees, the frame timbers being usually disposed _*Read at Northeast Coast Institution of En- gineers and Ship Builders, Newcastle-on-Tyne. BY E. HALL CRAGGS, VICE PRESIDENT, soom and space. It is worthy of remark that it was a common practice to allow the frames towards the extremities of the vessels to be spaced wider apart than amidships. The tendency today in steel ships is to space the frames nearer to- gether, especially at the bow. It was thought necessary in the large wooden allows us to firmly attach the breadths of plating by lapping them and through riveting them at their adjacent edges. With a suitable arrangement, therefore, the skin of the ship can be at once brought into the transverse strength, and, in fact, can be made a very important member of the transverse girder. For PHOTO SHOWING GENERAL ARRANGEMENT OF FRAMING OF AN OIL VESSEL, NOW BUILDING BY R. CRAGGS & SONS ON THEIR NEW SYSTEM OF SHIP CONSTRUCTION, ships that decks should not be spaced more than about 8 ft. apart, and the in- fuence of the practice in wooden decks is still felt at the present time; for in- stance, where vessels are built to Lloyds class. When I first commenced business, it was still a matter of serious consider- ation to leave the tier of beams out of a vessel 24 ft. in depth, and it is only really In recent years that the proper nature of compensation for leaving out another tier of beams in such a ship, thereby pro- ducing a single decker, has been thor- oughly appreciated and understood. Be- fore passing to the consideration of iron and steel vessels, it is as well to bear in mind that the thickness of planking of decks bears a very substantial ratio to the interval between the transverse sup- ports. The builder had, therefore, no need to consider the local buckling of the planking or deck owing to longitudinal strains. In other words, the wooden ves- sel was relatively an incompressible struc- ture as compared with a metal one. We come now to the consideration of iron and steel vessels. The strakes of plating take the place of planks, with this great difference; the nature of material the remainder of the transverse stiffening ship builders have found it convenient to follow the practice in wooden ship build- ing as closely as possible. Coming now to the question of longi- tudinal strength, the analogy is not so perfect. The breadth of the metal frame sections supporting the skin is necessar- ily greatly reduced, and the unsupporting length between the frames is greatly in- creased. The thickness of iron plates, as compared with the distance between the points of support, bears a fae less ratio than the thickness of the planking in the wooden. vessel: be- tween their points of support, and here- in I have tried to express as simply as possible the weak point of the ordinary transverse system of framing. So long as the length of vessels was kept within a moderate compass there was little trou- ble, but as dimensions increased, espe- cially length, ship builders found the want of better support against longitudinal stresses. Scott Russell felt so-keenly on this point that he took pains to carefully enunciate his views. In his great work on naval architecture he favored the prin- ciple of longitudinal framing. In the