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196 THE MARINE REVIEW /TIDOLE LINE FIG. 2—DETAIL OF KEEL CONSTRUCTION OF ENGLISH SHIP and on account of its superior strength, southern pine is prized for ship building, although it does not grow as large as western fir. Also, in spite of 300 years of exploitation, the forests of New Eng- land still contain vast quantities of ship timber of unusually satisfactory character. In fact, New England is one of the two sections of the country in which wooden ship building main- tained a continuous existence through the lean years, 1880 to 1916. The north Pacific coast is the only other region where the art of building wooden vessels failed of complete extinction during the period just mentioned. It is from the traditions of both of these important sections, separated by 3,000 miles of continent, that the revived art and the new literature of wooden ship building must be drawn. Power for Wooden Ships Wooden hulls are best adapted to sail power, but for obvious reasons such a method of propulsion cannot be depended upon in modern times, except for certain special trades. In the war zones, sailing ships are under a severe handicap because of their high visibility. Some form of chanical propulsion, therefore, is de- sirable for practically all of the wood- en vessels now under construction or to be built during the next 24 months. Virtually only three types of power present themselves, oil engines of the pure or semi-diesel type, reciprocat- ing steam engines and steam turbines. The advantages of the oil engine in fuel economy, increased cargo space, low ‘visibility, etc., are well known, and for these reasons a large number of the wooden vessels now on the stocks will be fitted with internal com- bustion motors, usually working twin screws. Undoubtedly, this arrange- ‘ment is one of the most satisfactory that could be devised for large wood- Tes: en merchant ships. But if the wooden ship building capacity of the. country is to be greatly expanded in the next 15 months to meet war demands, there is doubt if there are enough skilled oil engine builders in the country to supply the demand. In the normal course of events, therefore, oil en- gines will be used as far as possible, after which recourse will be. had to steam. For a full powered ship, the concensus of. opinion seems to be that about 1,500 horsepower is neces- sary for propelling a 3,000-ton vessel. WATERWAY 4" THick June, 1917 In spite of the advantages of the oil engine, steam is not without its advocates, especially among those who point out the space saving possibilities of the turbine. Effective arguments also are brought forward showing that skilled steam engineers are much more easily obtainable than gas engine ex- perts, and that there are hundreds of steam engine builders in the country who could readily turn their efforts to the marine field. _ Types of Hull Construction Compared with steel vessels, wood- en ships are weak in both _ longi- tudinal and transverse directions, al- though their greatest structural fail- ings appear to be in longitudinal planes. Large wooden hulls are sus- ceptible to both hogging and sagging. In the former case, the deck bends con- vexly, the ends becoming lower than the midship section; in the case of sagging, the deck bends concavely and the sheer is exaggerated. Also, in a seaway, some wooden hulls are sprung up from the bottom, causing the decks to bulge. These weaknesses are largely due to the rectangular construction of wooden ships, in which the fastenings are depended up- on almost exclusively for stiffness. In the nature of things, it is impos-. sible to fasten the members of a wooden vessel together as stiffly as LY LL =) DEEP /2" Top TIMBER SIDED 64" Port da? ; frouno 5" S1DEDI0" MOLDED 9", | - MC. POUND 2 /DED 8! FOLDED 6” ar] SHELF OROAD 3, HH 8 iu SIDED 63" To 73 MoLveED 63" 44 SiIRMARH Sai SDED 7"to 7$" Repd aids /MoLbEo 67" ery EEP 6" S/DED 8" to 9 MolDdED 7$ Fspyd { Sibee 9" toy" /ToLpED BF" 130 5* Loor 1144 StI0ED 9" To 11" FIG. 3—MIDSHIP SECTION OF A TYPICAL NINETEENTH oLpED 6f" CENTURY ENGLISH SHIP