Uf 



SHIP. 



SHIP. 



SIR 



graatest tranrrerso Motion is made. Each trapezold, in an orthogonal 

 projection uf the fora and after pert of the (hip made on a plane 

 parallel to the greatest transverse lection, U then divid. ,1 into two 

 triangle* by a diagonal line, and the area of each projected triangle 

 (found by admeasurement of iU aide* on the Kale of the drawing) i- 

 inultiplied intu the reenlTed force of the water upon it ; that resolved 

 force being expressed by the abeohite force multiplied into the square 

 of the tine of the inclination of the triangle on the ship's surface to 

 the direction of the motion. The sum of the products is taken for 

 the whole resistance of the water against the ship. In comparing the 

 rrxuUnce against one ship with the resistance against another, it is 

 evident that the absolute force of the water on each may be represented 

 by unity. 



Experiments sufficiently prove that the remittance experienced by a 

 body in moving through a fluid is lees when the greatest breadth of 

 the body u at some distance before the middle of its length, than when 

 it is precisely at that place, but the most advantageous situation of 

 what is called the mi<Mip tertion (the greatest vertical section taken 

 perpendicularly to the length of the ship) Is far from having been as 

 yet determined. In order to find its dependence upon the direct 

 resistance of the water, M. Chapman proceeds in the following manner : 

 Re considers the ship to be represented by a solid in the form of 

 two isosceles wedges joined together at their heads and to move in 

 the water with the planes which are perpendicular to their edges 

 parallel to its surface. Now it is evident that when the solid is at 

 rest in still water, the opposite pressures of the water against the 

 faces in front, and against those which ore behind the plane of junc- 

 tion. or of the greatest transverse section, will be equal to one another 

 in directions parallel to the length of the solid. Also that, when in 

 in- ti. 'ii, the front faces will experience directly that resiatance of 

 the water which is due to the velocity of the solid, and that the 

 after faces, by receding from the water in consequence of the advance 

 of the body, will lose a portion of the pressure which they would 

 have experienced had the body been at rest, and which would thus 

 have indirectly contributed to force the body forward. It must 

 moreover be observed that the water in driven forward in front of 

 the vessel with a velocity which may be represented by r' ; and that 

 as the water in front becomes higher than that which ia behind 

 the greatest transverse section, it will flow towards the stern with a 

 velocity which may be represented by r". Hence if A be the sum of 

 the areas of the two oblique surfaces in front of that greatest section, 

 and B that of the surfaces abaft of the same section ; also if 8 and 

 IK- the inclinations of those surfaces respectively to the line of motion, 

 and r be the velocity of the body, we shall have, supposing the resist- 

 ance to vary with the square of the velocity and the cube of the sine 

 of the inclination, 



A (r - 1/) 1 sin.' 8 + B (v + t")* B 



for the value of the whole resistance ; or, for A sin. fl and B sin. ff 

 putting their equal c {Jhe area of the transverse section) the C.NI 

 for the resistance becomes 



This formula indicates that such a body will always meet with less 

 resistance when c is in front, than when it is abaft of the middle point 

 in the Itngth ; that in, when 9 is greater than V : it indicates also that 

 tl.i- pl.ve of the greatest breadth when the resistance ia a minimum 

 ds on tho values of r u' and of r+r", and that the greater r' 

 and r" are with respect to r. tin- farther should the greatest 1 

 ! in front of tin- middle point. 



Imagining a horizontal section through a ship at the surface of the 

 water to present the form of four portions of parabolas, the two in 

 front of the greatest transverse section being similar and equal on 

 opposite sides of the longitudinal axis ; and likewise tho two portions 

 abaft of that section being similar and equal to one another, but different 

 from the two former portions, Chapman finds, as approximations to the 

 place of that greatest section, that its distance in front of the middle 

 of the ship's length may be four, six, or eight times the horizontal 

 distance of the centre of gravity of the whole .-hip from that middle 

 point And his observation U that the first distance might serve for 

 sharp vessels, as frigates, and the last for merchant ships, which are 

 much broader than the others in proportion to their lengths. ' 

 Beaufoy's experiments with solids of various forms indicate that, ii: 

 general, the distance of the midship section in front of tho middle 

 point in the length should be one-tenth of the length. 



:t U- mi<lerntood that the assumptions on which the formula) 

 'Xprcwing the relations between the principal dimensions. of ships, ami 

 between the dimensions and velocity, have been inv. -tigated, are far 

 from being conformable to the circumstances of a ship when moving 

 through the water, and the same may be said of the above process for 

 finding the place of the greatest transverse section ; consequently, the 

 formuUc afli.rd but remote approximations to the rules which should 

 guide the naval architect in the formation of a' design. A far more 

 perfect knowledge than we have at present of the action of the win. I .1 

 the nails, of the resistance of tho water, and of tho conditions ol 

 stability in a ship, will be necessary before the results of analysis wili 

 be capable of being applied directly to the details of construction. 



Having thus noticed the general mathematics involved in the 

 quettion of producing the best form of floating body for propulsion 

 along tho surface of a fluid, and aa adapted to the conveyan. > t 

 of heavy weights from place to place ; the forms under which such - 

 wdies are usually constructed, either for purposes of war or eoiumeree, 

 demand our notice. The consideration of the mode of construction 

 forms no port of the requisites of this article; we refer, th. . 

 to the general question of naval architecture, as illustrated uinl. 

 words Smriiru DINO and STEAM-VESSEL. 



The most essential conditions in the construction of a ship are, that 

 :t be capable of carrying its stores and its artillery or lading ; that it be 

 moved by wind or steam with great velocity, and that it reodiK 

 the motion of the rudder ; that it have the necessary stability, so as 

 not to be overturned when acted upon by the wind or waves; and, 

 finally, that its rolling or pitching be attended with as little sti. 

 [Hjssible on the timbers. These conditions are in some respects con- 

 trary to each other; and the degree of attainment tor i-.-ioh will 

 lep.-nd in part on the purpose, whether of war o. 

 which the ship is built. The skill of the architect lies therefore in 

 adopting such a construction as shall allow the quality most re. i 

 to be obtained in the highest degree, without being attended by too 

 great a sacrifice of the others. The form indicated !.- 

 experience been found to afford the means of uniting the ditl/ieut 

 conditions, as far as they are consistent with each other ; 1 .1 

 form is capable of being varied within very distant limits. Th 

 subject of the resistance of fluids against bodies immersed in th. 

 also so imperfectly known, that the most proper proportions which 

 the several dimensions should have to each other, hi order thai 

 resistance may be as little as possible, ore yet to be deU-rmine. i 

 in the present state of science, those proportions can only 1>< ol 

 from the dimensions of ships of different clauses whieh have been 

 observed to possess the best sailing properties. 



In merchant ships an ample rapacity is frequently of more impoi I - 

 ice than a great velocity in sailing; and in this case the. rvl 

 between the length, breadth, and depth depend less upon hydrodyna- 

 inical principles than the corresponding relations in ships of war. 

 With respect to the latter, it is observed by Mr. Morgan, in his papers 

 on naval architecture, that the number and weight of the guns con- 

 stitute the basis of the design ; for from these the weight of the 

 whole ship, or the volume of the water which it will displace, may be 

 estimated. The distance between the guns on the decks must bo such 

 as by experience has been found sufficient for working them ; and 

 hence tho number of decks being given, the least length whi. 

 ship should have becomes known. The breadth also must in part t.o 

 determined by the artillery ; for on, each side of the ship, between tin- 

 hatches or ladder- ways and the rear of the gun-carriages after the 

 recoil, there must be room for a free passage ; but this element, must 

 also be great enough to afford the necessary stability, that the 

 tendency of a lateral wind to turn the ship about a longitudinal axis 

 uiay be resisted. The draught of water (the depth to whieh the ship 

 is immersed) may depend on the depth of water in the harbom 

 roadsteads ; but it should also be determined from experience, so that 

 the ship may be prevented as much as possible from making ]<, 

 and the height of the ship above water must be such that, while the 

 upper tiers of guns ore kept as low as possible, the height of the 

 lowest tier above the water, when the ship floats upright, may be not 

 less than six feet, in order that the lower guns may be worked wlu-n 

 ili . r-liip has considerable inclination. Finally, the form of the l.o.ly 

 must be that which is most favourable for velocity, by causing the 

 least possible resistance of the water at the bows ami along the 

 whieh allows the greatest lateral resistance ; and which will permit the 

 rudder to act with most effect in causing the ship to be turned 

 a vertical axis. And if, when in the design for a ship all the- 

 ditious are fulfilled, the displacement (weight of the volume of 

 which would rill the space occupied by the ship below the r 

 .surface of the watei in which she floats) is equal to the whole 

 weight of the ship, the several dimensions may be considered as nearly 

 correct. 



With regard to ships of war, a reference to our word NAVY will 

 show that so great are the changes resulting from the adoption of tho 

 screw as a means of auxiliary propulsion, that, together with a total 

 revolution commenced in the system of armament, the 

 herein of embryo theories would be incompatible with our plan, 

 t'ud.r the words OuN-BOAT, Cui'PKR, Ac., the subject ha.- 

 alreody touched upon, but a few general remarks will be added under 

 the heading StKAM-VugsiL. 



Ships intended for the merchant service may be divided into three 

 classes, as either " passenger carrying," " cargo vessels." ... 



sels." Among the first may bo found perhaps some of 

 t ! n n i..,st beautiful models of steamers which the art of man, at this 

 period, can produce. It is necessary, however, to concede that notions 

 of beauty in a ship vary as our notions of their adaptation to certain 

 purposes; for if we take speed alone as our standard of n f. 

 slimness of form and lightness of rig appeal to tho judgment, while 

 the nautical connoisseur will, like the jockey among horses, . 

 at once among shipping the distinctive qualifications which stamp tho 

 racer, the charger, or, so to speak, the home of burden. 



Unfortunately, however, this apparent facility of rough appreciation 



