276 



FOREST AND STREAM. 



Diagram "No £3. 



DIAGRAMS FOR YACHT MODELS. 



fasting md Routing. 



HIGH WATER FOR THE WEEK. 



Date. 



Boston. 



New York. 



Char lesten 



Nov. 9 



H. M. 



2 06 



2 54 



3 42 



4 85 



5 29 



6 23 

 T 15 

 2 06 



H. M. 



11 09 



Mid. 



30 



1 18 



2 08 



2 57 



3 51 

 11 09 



H. M. 

 10 20 



Nov. 10 



Nov.11 



Nov 12.; 



11 09 

 11 58 

 24 





1 14 



Nov. 14 



2 04 



Nov. 15 



Nov. 16 



2 54 

 10 20 



BOATS AND YACHT BUILD- 

 ING. 



By Natjtictjs. 

 drawing, model-making, etc. 

 There are other ways of "fairing" the lines 

 and proving the correctness of our drawing, tut, 

 if four- or more buttock lines are used, we may 

 consider our work "fair," and dispense with any 

 further proof. In our drawing we have made 

 the rabbet of keel the base for the body and 

 sheer plans ; but where there is much difference 

 in the draught of water forward and aft, it is 

 customary to make the load water line the base. 

 The water lines in our drawing are parallel 

 with the load line and with one another ; if 

 there is much "drag'' or difference in the draught 

 of water forward and aft, the intermediate water 

 lines are drawn at equal distances between the 

 load water line and the rabbet of keel. As these 

 papers are designedly elementary, we will con- 

 fine our remarks to the method explained in 

 the previous papers. Those who wiBh to pursue 

 I the fascinating study of designing are referred 

 to the elaborate work of J. S. Russell— The 

 Modern System of Naval Architecture, price for- 

 ty dollars ; Rankine's Ship-building, price forty 

 dollars ; Fincham's Outline of Sbip-building, 

 price fifteen dollars ; Marrett's Yachts and 

 Yacht-building, price live dollars ; Bretts' Notes 

 on Yaohts, price three dollars. Also Kemp's 

 new work on Yacht designing, price twenty-three 

 dollars . 



The last mentioned work I have not seen, but 

 from the reputation of the author, have no hes- 

 itation in recommending it. After the drawing is 

 completed, the designer may wish to make a 

 model, and, as model making iB a source of con- 

 siderable amusement and pleasure, I will explain 

 the method of making one from the drawing. 

 Models are usually made to represent one-half 

 of the proposed vessel, and may be made of pine 

 or of alternate pieces of pine and mahogany. 



Cut pieces of board the length of the sheer 

 plan, and as thick as the distance from cne water 

 fine to another, a piece is provided for each 

 water line or other longitudinal division of the 

 sheer plan. The widths to cut the pieces of 

 boards are found* from the half 1 breadth plan— 

 the width of each water line at midships, giving 

 the width to cut the pieces of board. Each 

 piece of board has a water line of the half breadth 

 plan marked on it. Cut the several pieces to the 

 outlines marked on them, pile them up on one 

 another in their proper positions, work down 

 the ridges with spoke-shave, gouges and rasp, 

 and finish with sandpaper. If a fine finish is 

 wanted, rub down with oil and pumice stone, 

 varnish and polish. If the displacement of the 

 model is required, the pieces of boards from the 

 proposed load line down should be of the same 

 width and length before cutting, thus forming, 

 when piled together, a block. Weigh the block 

 before cutting, and measure its length, width 

 and depth — from which data the cubical contents 

 can be calculated. After the model is finished.re- 

 weigh the part from the load water hue down, and 

 the difference between the two weighings gives 



the data to compute the displacement to the load 

 water line. If the wood used is of uniform den- 

 sity, and the calculations made with care, the 

 results are quite accurate. The following ex- 

 ample which I have worked out will explain the 

 method : Block to proposed load line measured, 

 before cutting, 21.625 inches long, 2.9375 inches 

 wide and 1.6875 inches deep. It weighed twenty- 

 four ounces ; cutting reduced its weight to seven 

 ounces, or seven-twenty-fourths of its previous 

 weight. The dimensions of the block, as given 

 above, multiplied by twenty-four to give the di- 

 mensions the full size of the proposed boat, 

 would be 43.25 feet long, 5.875 feet wide, and 

 3.375 feet deep ; this reduced to cubic feet 

 equals 875.5 cubic feet ; as cutting reduced the 

 weight to seven-twenty-fourths of the whole 

 block, we take seven-twenty-fourths of S75.5 

 cubic feet, which leaves two hundred and fifty 

 cubic feet as the displacement of one-half the 

 proposed boat. Multiplying by two for dis- 

 placement of whole boat, we have five hundred 

 cubic feet total displacement. Water weighs 62.5 

 pounds to the cubic foot ; reducing our figures 

 to tons, we have 15.6 tons displacement. The 

 displacement— calculated by Chapman's rules, 

 which are probably the most accurate known— 

 is 14.9 tons. The above method is simple, easi- 

 ly done and sufficiently accurate for small ves- 

 sels. The position of the "centre of gravity of 

 the displacement" longitudinally, can be found 

 by balancing all that part of 'the model below 

 the load water line, on a pencil or similar object. 

 Thus far we have considered "half models" such 



s for : 



el yachts, the pieces of wood used are tmce the 

 width of the half breadth plan, and have the 

 water lines drawn on both sides of a central lon- 

 gitudinal line. After the outside of the model is 

 finished, the pieces are taken apart and the in- 

 terior is cut out, leaving the pides any thickness 

 the builder may fancy. Afterward put on a stem, 

 stern post, keel and deck, gluing all together; 

 polish and varnish. The "centre of effort" of 

 the fails should be at the " point velique, '< 

 which is found as follows : Step an upright mast 

 at the centre of gravity of displacement, ballast 

 the little vessel until the load line comes down 

 to the level of the water, tie a cord to the mast, 

 and pull the model smartly through the water 

 without jerking ; if the bow is depressed in the 

 water, slip the cord lower down on the 

 mast ; if the stem is depressed in the 

 water, slip the cord higher up on the mast. Ex- 

 periment until a point on the mast is found 

 from which the model can be pulled smartly 

 through the water without depressing either bow 

 or stern. This point is the "point velique." If 

 the mast is at the "centre of lateral resistance," 

 the model can also be pulled sideways through 

 the water without any tendency to turn around; 

 if when pulled sideways either end of the boat 

 turns around toward the experimenter— either 

 more keel must be added to that end, or some 

 cut off the other, until the resistance is equal on 

 each side of the point from which the cord pulls. 

 The centre of lateral resistance can be found by 

 cutting a piece of sheet lead into the exact size and 

 shape of the outline of the model below the load 

 water fine, and balancing it on a pencil. The 

 balancing point is that on which the vessel turns 

 when acted on by the sails and rudder; for conven- 

 ience, we call this point the "centre of lateral 

 resistance." Properly speaking, it is the "cen- 

 tre of the vertical longitudinal section immers- 

 ed." The mode given for finding the centre in 

 question is simple and sufficiently accurate for 

 our purpose. The centre of effort of the sails is 

 the point where, if an imaginary line were 

 drawn either horizontally or perpendiculary 

 through it, the pressure of the wind on one side 

 of the line would balance the pressure on the 



other. If the centre of effort of the sails is in 

 the same vertical plane with the centre of later- 

 al resistance of the hull— the vessel in sailing to 

 windward will keep her course without any ten - 

 dency to turn either way. A vessel is said to 

 have a "lee" or " weather" helm as the position 

 of the centre of effort is before or abaft the cen- 

 tre of lateral resistance. A small amount of 

 weather helm is desirable, therefore arrange the 

 sails so that the centre of effort will be a little 

 abaft the centre of lateral resistance ; there is 

 no exact rule for the proper amount. Marrett 

 gives it aB .0C6 to .01 of the length of the lqad 

 water line for Bchooners, and for cutters .02 to 

 .05. The area of a triangular sail ia found as 

 follows : The triangle ABC, Diagram number 

 twenty-one, represents the jib of a sloop ; draw 

 a line perpendicular to the eide A C to the point 



B, multiplying the distance from D to B by the 

 distance from A to C, and divide the amount by 

 two; this gives the required area. The cen- 

 tre of gravity is found by bisecting the side A 



C, draw a line from B to the bisected 

 point at E, then two-thirds of the distance B E, 

 set off from B toward E will be the centre of 

 gravity of the triangle ABC. The area of the 

 main sail of a vessel is found by dividing the 

 trapezium^. B C D—diagramnumber twenty-two, 

 into two triangles, by a diagonal line from A to 

 C, or from B to D ; find the area of each triangle 

 separately and add them together. The centre 

 of gravity of the trapezium A B C D is found by 

 first finding the centre of gravity of each of the 

 four triangles A B C, A C D, A B D and B C D ; 

 the four centres are marked on the diagram at E 

 P G H. Join the opposite centres bylines drawn 

 from one to another as shown on the diagram, 

 and the intersection of the lineB is the centre of 

 gravity of the trapezium A B C D. If a vessel 

 carries but one sail, the centre of effort is at 

 once known, as it will be at the centre of gravity 

 of the sail. If two or more sails are used, the 

 height of the centre of effort of the combined 

 sails iB found by the following rule : mul tiply the 

 area of each sail by the perpendicular distance 

 of its centre of gravity from the water line, then 

 dividing the sum*of these products or "moments" 

 by the sum of the areas, the quotient is the re- 

 quired distance. As an example, diagram num- 

 ber twenty-three is worked out thus : 



Areas. Height of C. G. 



above L.W.L. Momenta. 

 8 feet. 984 



11 " 3124 



— New Orleans has a new rowing organization* 

 the Mississippi Rowing Club. 



New York, Nov. 2, 1877. 

 Editor Porkst and Stream : 



We want a good little sloop-yacht, about 25x10 

 feot and with some depth, say about Zy z feet, at 

 least, and flat bottomed, so that we can go out- 

 side in them. We don't want any more of these 

 skimming diBhee, with lots of ballast in th m and 

 five or six men to manage them, but staunch 

 little boats with a cabin, so that if we get caught 

 in the rain away from home we can •' bunk" ?nd 

 not get dieDehed. Such a boat I intend having 

 built as soon as I can get a model to suit me. I 

 want to make a cruise next summer up the llud- 

 sorTand Lake Cbamplain, I wish to have a boat 

 I can handle myself and not get upset every time 

 it breezes. Can't you give me a model in your 

 paper of such a boat in the course of your 

 papers ? Yours, etc., Bitoeia. 



[We intend to devote a certain amount of 

 space to this exact build of boat.— Ed. J 



Sq- ft. 



Jib 123 



Mainsail.... 284 



407 



4108 



4108 divided by 407 equals 10 09 feet— the 

 height of (he centre of effort above the load 

 water line. The position of the centre of effort 

 of the sails, relative to a perpendicular from the 

 water fine at the centre of lateral resistance, is 

 found by dividing the difference of the moment 

 of sail before and abaft the perpendicular by the 

 sum of the areas of sails. The moments of 

 sails before perpendicular, are marked minim; 

 moments of sails abaft the perpendicular, plus : 

 the centre of effort will be before or abaft the per- 

 pendicular, according to the preponderence of 

 plus or minus momenta. Example : 

 Dist. of the C Q 

 Areas, from perpd'lr 

 Sq.ft. attheCofLR. Momenta. 

 Staysail or jib. 123 8.5 feet minus 1045 



Mainsail. 284 5.26 " plus 1491 



407 

 then (1491—1045) divided by 407 equals 1. 09 feet- 

 distance the centre of effort is abaft the perpen- 

 dicular at the centre of lateral resistance. It is re- 

 quisite that the designer give the greatest care and 

 attention to the adjustment of the various centres 

 to one another, to insure a well-balanced and 

 safe vessel. It iB true, the vessel can be sd bal- 

 lasted as to bring the centre of lateral resistance 

 farther forward or aft, but in such a case the 

 skill expended in modeling the vessel is lost, as 

 the water line will not be the one designed. The 

 rnast may be moved farther forward or aft; or 

 one of the. sails may be reduced in size and an- 

 other enlarged, but all such alterations are cost- 

 ly, and after being done are only a, " botch," 



Yachting in Bute Wasebs.— Yachting is unde- 

 niably looked upon by the mass of the community 

 in the light not only of a slothful and luxurious 

 pastime, but as an actual waste of time ; yet it 

 is none the less true that the larger number of 

 those who cruise upon blue water are men of 

 positive character, who, becoming impatient of 

 the humdrum conventionalities of society, prefer 

 to assert their manhood in contention with the 

 elements. And these men, who may have pre- 

 viously been skiruiiehers on the outposts of 

 science, are not infrequently, by the very nature 

 of their new pursuit, drawn within its charmed 

 circle, and by their observations and experiments 

 become important contributors to it. 



The enthusiastic yaehtBtnan can not sail his 

 vessel for ever so short a time without discover- 

 ing certain peculiarities in her build which he 

 flatters himself he could improve upon, and his 

 active mind at once institutes intelligent inquir- 

 ies into the laws of force and resistance, exam- 

 ining critically the various theories, principles 

 and formulas held to by the shipbuilder, inform 

 ing himself as to the varieties of ship timbeiv- 

 their tenacity, density, etc., until he almost uv, 

 consciously finds himself drawn within the laby- 

 rinth of marine architectural disputation, and 

 what at first was a diversion, soon becomes an 

 absorbing passion. Having ample leisure and 

 means usually at his command, he dives con 

 amore into the most difficult paths of applied 

 mechanics, creates, destroys and recreates, un 

 til he finally effects radical and startling im- 

 provements in the art. Indeed, it is to this rest- 

 less spirit that wo owe the success of the yacht 

 America, which, after thirty years of vicissitude 

 uncommon to even the sea-going vessel, is proba- 

 bly to-day as staunch and fast as any vessel 

 afloat, fort her owner, Mr. Stevens, built three 

 large yachts, the Wave, the Onkahye and the 

 Maria, 'before he was satisfied tnat he had dis- 

 covered the lines which would insure speed and 

 seaworthiness. 



No yachtsman who has the energy and pluck to 

 cruise on blue water would be willing to remain 

 an hour longer than necessary a supernumerary 

 aboard of his own yacht, or to give up control of 

 her to his sailing-master. That would be all 

 very well for the smooth-water yachtsman, who 

 finds sufficient excitement in the click of a cham- 

 pagne cork or the admiration of his lady guests; 

 but once on blue water, a man would feel like a 

 prisoner in charge of a jailor if he were not in 

 supreme command. Hence he feels that he must 

 at once tackle what has always seemed to him 

 the intricate science of navigation ; but he soon 

 discovers that, so far aB its ordinary practice 

 goes aboard ship, it has been reduced to a simply 

 mechanical operation, by which men with the 

 merest rudimentary education may with ease 

 solve itB problems. ' This only incites him. ^ He 

 is not satisfied to work " by rule of thumb." It 

 is all very well for his sailing-master to take his 

 sextant and measure an altitude of sun, moon, 

 or star, or a lunar distance, and define bis posi- 

 tion by means of tables computed for him, but 

 he must know why such angles and such distances 

 give such results," and is thus led to investigate 

 the foundation of the theorems, and familiarize 

 himself with the movements of the heavenly 

 bodies, and calling to his aid his half-forgotten 

 mathematical training, finds himself engaged in 

 an intensely interesting pursuit 



Meteorologv, which is essentially a science 

 kindred to that of navigation, ranks among 

 its students the practical philosophers of our 

 times, and they rely, to a very large extent,^ 

 upon the notes entered on the "logbook',' 

 for data for the confirmation of their 

 theories. The flight of a bird, the floating 

 mass of sea. weed, the hamacle-coTered log, the 



