817 



SHIP. 



SHIPBUILDING. 



618 



forms one of the drawbacks to which naval architecture is liable. It 

 is nevertheless capable of demonstration, that as in the horse an 

 expectation of speed or otherwise is inferred by closer inspection, say 

 of the length and freedom of the femur, so may the nautical eye 

 scrutinise profitably various of the undermentioned qualifications of 

 the ship. That a ship whose hull has been constructed according to 

 the best rules of art does not always fulfil the conditions required, may 

 depend on several causes. If the burden is placed too low, the rolling 

 will be heavy, and the masts may be endangered ; on the other hand, 

 if the burden is too high, there may not be sufficient stability. With 

 all the researches which have so lately been renewed, there seem to 

 remain a few well recognised and established laws as to form which 

 cannot be dispensed with in the construction of a perfect ship. It is 

 by means of these that the unscientific builders of the country some- 

 times produce wonderfully good models. The following are the prin- 

 cipal, namely : 

 The bow should be sufficiently sharp to cleave the water with the least 



possible resistance : 

 Of sufficient fulness above load-water line to prevent too great 



plunging in bad weather : 

 Sufficiently free from unnecessary top-weight also to ease a ship in 



a sea way : 



A bow in which the fluor extends as far as possible into the forefoot, 

 but blends easily into the general lines of the hull ; serving as 

 another check on inconvenient vertical motion. 



The hull should have bearings or powers of floatation, so distributed 

 as to sustain the internal weight without strain upon any particular 

 part of the general frame of the vessel : 



Should be so capacious as to admit of ample stowage, while its dis- 

 placement at any depth presents a water-line free from too great 

 curvature. 



The II... i- should have such an arrangement of draft lines as to admit 

 of both speed and stability, according to the work to be dune by 

 the vessel ; for speed is well known to be influenced greatly by tin- 

 fulness or otherwise of the midship section at Ike bilge, inasmuch 

 ax the shape of this part contributes largely towards the delivery 

 <>r retardation of displaced water as it passes into the run. of the 

 ship past the stern-post : great proportionate length in a ship 

 ]>enmta a fuller bilge line. 



era should have the submerged part (called the run) as nearly 



wedge-shaped as possible in its water-lines, as viewed from above : 



the smaller the angle of the wedge the cleaner the run is said to be : 



The lines of the run to spring from or blend with the lines of the 



hull without sudden change in the curve : 



While so clean as to cause no dead water, yet to have the bearings 

 above the light-water line so judiciously adjusted in the vertical 

 sections as, from the capacity and gradual displacement of water 

 at such times, to furnish an easy check to the violent motion of 

 rolling or pitching : 



So well arranged in its upperworks as to prevent unnecessary top- 

 1 , while giving sufficient internal space for cabins and the 

 requisite deck operations : 

 A proportion of length and breadth to nicely determined as not to 



give speed at the expense of stability, and ri vend : 

 A forefoot so deep as to give what are called weatherly qualities, or 

 to prevent the vessel, when close hauled, from being driven off the 

 wind by every wave which meets the weather bow while not so 

 deep as to impede ready working in stays : 



A heel so deep as to give sufficient power to the helm in its ample 

 hold of the water, without increasing unnecessarily the draught of 

 water. 



It may well be imagined that the above requirements, so antagonistic 

 in themselves, generate a vast variety of forms of vessels ; but not even 

 the absolute shape of the fabric itself can insure an accurate perform- 

 ance when iimler sail ; for other important considerations arise even in 

 the fitting and masting of the ship, as for instance : 



The masts should be so distributed in her length as to incline a 

 little towards the stern (or should rate, as the phrase is) ; this has a 

 double advantage : 1st, it tends to steadiness of the hull in a sea way 

 when moving upon her midship axis, in the action of pitching, inas 

 i , as the weight of the spars, sails, and rigging upon a raking nia.il 

 has to be rained by the motion of the ship before the mast can be 

 perpendicular; while in a perpendicular mast, such pitching motion is 

 facilitated by any vertical disturbance of the water-line, inasmuch as 

 in this case the weight of the .whole mast tends towards a lower point 

 2nd, In a heavy gale the wind has less power on a raking mast when 

 the ship is lying-to. And further : it has long been the practice tc 

 place the foremast of a line-of-battle ship very far forward, eo fai 

 indeed as in some to plnrnb the forefoot. Thi.s has been supposed tc 

 be necessary from the general form of the hull, as a counteraction of toe 

 great an amount of weather helm when the ship heels, but it i 

 scar* :i;ible whether the new form of bow will not show tin 



former disadvantage of placing the foremast, in some ships weighini 

 I is thirty tons (including spars, sails, and gear), so far from th 

 centre of gyration of the whole mass. It is no uncommon thing t< 

 see these old liners, when riding for instance at anchor in the Downs 

 pitching bow." under, to the manifest danger of masts and everything 

 Another great defect of rig is mostly apparent in foreign vessels 



herein the lower masts are so long as to throw the centre of effort of 

 lieir top-sails and top-gallant sails higher than necessary above the 

 ecks, and by thus increasing the leverage of the force of the wind, 

 browing the hull out of the perpendicular and distorting the water- 

 ine, as in the following diagram. 



Water-line. 



Water-line. 



When such is the case, the vessel has a constant tendency to fly up to 

 imhvard, and requires the helm to be so placed as to counteract this 

 #ndency, but it forms a complete drag upon her motion. (See a in 

 .he above figure.) 



Enough has been said on the general consideration of a ship as 

 i mere sailing body, as adapted to the propulsion of such bodies by 

 iteam. The subject will admit of further remark under the word 

 STEAM-VESSEL. A few outline diagrams are here added in illustration 

 .f terms usually applied to the different descriptions of sailing vessels. 



Ship. 



Barque. 



Brig. 



Schooner. 



Calliot. 



Ketch. 



Yawl. 



Lnfger, 



Cutter. 



Sloop. 



SHIPBUILDING, as a science, has, under the term Naval Archi- 

 tecture, become so extensive a subject as to render it difficult to 

 condense within the limits of a concise statement, sufficient to illus- 

 trate even its main principles, without undue intrusion upon the 

 ' rnt limits of a Cyclopaedia. 



The precise form of a ship need not here be a main consideration ; 

 under the word STKAM-VESSEL will be given such information here- 

 upon as illustrates the question of speed ; which, although belonging 

 also to certain classes of sailing-vessels, is more immediately and more 

 generally connected with steamers whose powers are dependent on a 

 ! amount of their primary means of propulsion, namely, coal. 

 We here only consider, under this word, the hull or body of a ship as a 

 hollow shell, intended to accomplish a required displacement of water 

 under different specific amounts of immersion. Were it merely the 

 object to build such a fabric as is capable of floatation in a fluid at rest, 

 the elucidation of principles already given would suffice ; but we ha\v 

 to illustrate certain considerations which are conducive to ttrm;/'^ 

 and a difficulty arises of fairly estimating the amount of strength 

 demanded, not at any particular part in the frame of a ship, but 

 throughout the whole mass; for it becomes a most intricate question 

 to estimate in a ship even an approximate amount of relative strain, 

 and its importance in the economical distribution of material may be 

 said to comprise the most exacting demands on the skill of the accom- 

 plished mechanic and mathematician. 



The subject here would evidently divide into two distinct branches ; 

 for while there exists in vessels of the mercantile marine a series of 

 qualifications adapted to the general requirements of commerce, such 

 as the carrying of heavy burdens, or of passengers, another class of 



