^4 
FOREST AND STREAM. 
[Jan. 16, 1891 
• 
YACHT bESIGNING— XII. 
BY W, P. STEPHENS. 
[Continued from page 35.] 
The model shown in Fig. 31 is of unknown origin, an old- 
time fishing schooner with the cod's head and mackerel's tail. 
It will be noticed that the topsides amidships have a slight 
tim^Meliome, the breadth at the upper side of the third lift 
being greater than the breadtb on deck. The model is of 
white pine, Sl-Jin, long, the scale being |in. to the foot, so 
that the vessel herself would be about 60ft. "on the keel," as 
these craft were measured. The model is a typical one in 
that it represents only the form of the inner surface of the 
planking, and not the complete exterior surface of the ves- 
sel. The stem, keel, sternpost, rudder, centerboard and 
masts are left entirely to the imagination. The model was 
cut by the builder, every third frame station was marked on 
it at intervals of 3iu., equal to 6ft. in the vessel; it was taken 
apart, the lifts being fastened by the two dowels sliown, and 
the half breadths at each station were measured with a car- 
penter's rule and marked in pencil on the lifts. From these 
rough offsets the lines were laid down on the mould loft floor 
and the moulds for the frames were made. The exact shape 
of stem, keel, rudder, etc, and the location of the center- 
board and masts, were all determined by the builder as the 
work progressed, and no record of them was made on the 
model. In all probability, no drawing was ever made. 
The method of drawing without the actual model, of per- 
forming all the operations of cutting and drawing the sec- 
tions by means of the imaginary planes described in the 
previous chapter instead of the material saw, is not only 
easier when once understood, but more rapid, thorough and 
conclusive. In order to explain this method in a very short 
time and with few words, the models shown in Figs. 20, 22 
and 23 were made by the writer for use in the lecture men- 
tioned in a previous chapter. Fig. 20 is merely the usual 
half model of a yacht — in this case an attempt to copy by 
eye the then new wonder, G-loriana, Fig. 22 represents the 
same model in skeleton, the section at each station being cut 
out of cardboard and mounted on a wire in its true position 
relative to its fellows. The outlines of the model were formed 
by wires lashed to the proper points on the cardboard sec- 
tions, and other wires v?ere run to represent the "load water- 
line" and the "middle bow-buttock line." The large wires sup- 
porting the sections were fastened in the bottom of a box, 
the front and top being absent, the wires being parallel to 
the back of the box. The dropping of the stern shown in 
the figure is due merely to a collision in the process of pho- 
tographing, and is not the serious and irremediable defect 
that is too often seen in even prominent yachts. 
The immediate purpose of these two models was to pre- 
sent directly to the eye the solid model, with its curved 
surface free" from all lines, as in Fig. 20, and the same sur- 
face as indicated by the mere skeleton of lines formed by the 
edges of the sections and the wires. From these two it is 
hoped that the reader, even though unfamiliar with the 
imaginative processes of marine drafting, will grasp the 
idea of the cutting of lines from the surface of a solid by 
imaginary planes 
The various intersecting or auxiliary/ planes in this case 
are indicated on the different sides of the box surrounding 
the skeleton model.- There are first the vertical planes 
across the model, indicated by the cardboard sections, by 
vertical lines on the back of he box; and corresponding lines 
across the bottom, as in Fig 23. Then there are the hori- 
zontal planes, indicated by the lines on the back and ends 
of the box, the upper one also by the wire representing the 
load toaterline. Then there is the vertical plane parallel to 
the back of the box, indicated by a vertical line on each 
end and a horizontal line on the bottom, as well as by the 
wire representing the middle how-butt-ock line. 
The Inies being thus cut from the surface, the next step is 
their projection on the sides of the box, the coordinate planes. 
From the wire representing the l.w.l, a silk thread is run 
vertically at each station to the bottom of the box, indicat- 
ting the projection of the l.w.l. on the bottom, as better 
shown in Fig". 23. The projection of the bow-buttock line on 
the back of the box is plainly visible in both figures. The 
projections of the outlines of the different cardboard sections 
on the ends of the box were originally indicated by silk 
threads drawn from points along each section to its corre- 
sponding projection. In order to make this part perfectly 
clear, the seciions from the middle forward are projected 
on the end next the bow, and those from the middle aft on 
the end next the stern. 
The relation of the solid model to the skeleton, and of the 
lines composing the skeleton to their corresponding pro- 
jections on the various sides of the box, being now clearly 
understood, we may go a step further by folding back the 
sides and the bottom of the box (Fig. 23), which are hinged 
to the back, until they are all In one plane, coincident with 
the surface of the drafting table, showing, if our work has 
been sufficiently clear, the final relation between the sides of 
the box on which the lines of our model have been pre jected 
and the flat drawing of the designer. 
In the skeleton model comparatively few lines are shown, 
for the sake of clearness, hut in Plate I. the same design — 
Fig. 23 — is shown on a larger scale and with all the neces- 
sary lines of a complete drawing. From this time on the 
original conception of the solid model may be relegated to 
a secondary place, and we wiU deal directly with the 
flat drawing on paper and its numerous straight and curved 
lines; through these alone, by practice, being enabled to see 
in imagination the solid form of the vessel. 
In examining the different lines we will take up first those 
which form the basis or foundation of the drawing rather 
than the shape of the model, bpginning with the base line. 
This is a horizontal line parallel to the lower edge of the 
paper, and forming the bottom of each of the three plans, 
though in Fig. 24 it is represented at the top of the half- 
brPAidth plan. This is the first line drawn in beginning a de- 
sign. Parallel to the base fine in the sheer plan and body 
plan are numerous straight lines known as level lines, or 
sometimes as waterlines, the former term being the more 
exact. One of these lines, the load icaierlir.e, commonly de- 
noted by the letters l.w.1., is of special importance as the 
initial point of every modern design. The term waterline is 
manifestly correct when applied to the level lines below the 
l.w.l., but is less directly applicable to those above; for this 
reason it is preferable to use the term level line to cover all of 
these lines, whether above or below water. The level lines 
are designated in various ways, there being no one recog- 
nized method; sometimes they are numbered continuously 
from the top or from the bottom, sometimes the l.w.l, is 
called No. 1, the numbers running downward from it and 
those above being lettered. We have found it convenient to 
designate the load wateHine as l.w.l. and to number down- 
ward, the first below it being called Wl, the next ^2, etc. 
The first above the I w 1. is called A, the second B, etc. 
The level lines are invariably straight in the sheer and 
body plans, and they may be drawn in at the will of the de- 
signer, being spaced at equal intervals, usually some even 
figure, as 6in , 1ft., 2ft., etc , according to the size of the 
drawing. In the half-breadth plan the level lines are a] ways 
curved, unless the vessel be a scow, and they are drawn in 
as other portions of the work are advanced. 
Next in importance come the stations, or square stations, 
the former term being sufficiently definite and thus prefer- 
able. These lines are straight and vertical in both the sheer 
plan and the half-breadtfu plan, and, like the level lines, they 
may be located at will and drawn inwithjthe very beginning 
of the design. In the body pMn, however, they are curved, 
and can ouly be drawn in later. 
In the location and designation of the stwti-ons there is no 
uniformity, as already explained; in the old models they 
were located where the frames were to come in the vessel, 
and this practice is still followed by many 
The starting point for laying off the stations on the old 
models was the midship section., or dead flat. In nearly all 
the old vessels there was what was termed a straight of 
breadth, or dead flat, the mirtdle portion of the vessel being 
of one uniform size and seqtion for an appreciable distance 
iiiethod, and locate the stations in conformity with thu 
frames, but there are good reasons against doing this. Fo ? 
purposes of calculation it is necessary that the under wate 
portion of the, hull shall be divided into some number o 
equal spaces or intermls, and also that there shall be' an ever 
number ot spaces. Taking then the two ends of the l.w.l. 
we can divide the distance hptween them into 8, 10, 12 or l(i 
equal parts. A, division of 10 is most commonly used, as i 
gives quite enough stations; in fact, 8 is usually enough, bu\' 
of all divisions we prefer 12 Itwdl be found convenient it.i 
first getting the "design into form to use a small number o:) 
stations, but when it comes to the final fairing a larger num ' 
ber is necessary. If 12 in.tervals be used, all of the prelimi 
nary work can be done by omitting each alternate station 
leaving 6 to work rn, then in fairing the onaitted station; 
will be run in. If 10 be used the half will be 5, an unever 
number that cannot be used for the calculations If 8 inter 
vals be used, the half, 4, makes too few stations; and if 8 b( ' 
used for the prelimmary work, twice this number, 16 
makes additional work in the final fairiiig, taking off off 
sets, etc., and is no more accurate than 12. We will thei 
divide our I w.l. into 12 equal parts, continuing the same, 
division along the prolongation of the I. w.l. at each end, si) 
as to include the overhangs. 
It is j robable that this spacing will not bring the stationf 
Fig- 32. 
before beginning to tap^r toward how and stem. The sec- 
lion at this portion, necessarily the greatest cross section of 
the vessel, was termed the midship section, or dead flat, and 
the mould for this section served for several frames at least. 
The terms straight of breadth and dead flat are now obsolete 
so far as yachts are concerned, and largely so in other vessels, 
but the term midship sectio?i is still retained, and always will 
be. Unfortunately the term itself is incorrect and rather 
misleading; the midship section is not the section amidships, 
at the middle of the vessel; it is very seldom indeed that it is 
located there; formerly it was forward of the middle, now 
it is invariably aft. It is in reality the section of greatest 
hreadth, and might much more properly be termed the beam 
section than the midsldp section. 
It if seldom, however, that the greatest breadths on the 
different level lines occur at the same station. In order to 
coincident with the mo.et desirable spacing of the frame 
when we come to bnil'1, but this is Sr%€ry, small matter. A 
present we are concerned simply with the drafting of th> 
outside of the hull and not the construction. This portioi 
of the work properly done ^nd the lines complete on thi 
board, or laid down on the mould loft floor, it is merely a mat 
ter of a few hours' drawing to run in the extra lines of tht 
frames or moulds at the required points. 
As in other similar matters, there is no uniformity ohserved 
in designating the various stations, but the numbering begini 
at the fore side of the stem at deck, at the fore end of thi 
l.w.l., or even at the after end of the design The best sy- 
tem is that shown in Plate I,, the station at the fore end c 
the l.wll. being numbered 0 and that at the after end 12 
These two and their intermediate stations are the ones usee 
in the calculations, and the numbering is thus in uniformitj 
Fig. 23. 
obtain an easy entrance, the designer carries the point of 
greatest breadth on his l.w.l. well aft of the middle, and to 
obtain at the same time an easy run he begins to cut away 
forward of the middle down toward the keel. This is shown 
in Plate I., the greatest breadth on deck being at Station 7, 
while the greatest breadth on the different level lines as we 
go downward approaches nearer to Station 6. The dotted 
line, m s, between Stations 7 and 6 in the half -breadth plctn, 
shows the position of the largest transverse section of the 
yacht. This section is calletl a raking midship section, as the 
breadths on each successive level line are not in the same 
vertical, but in an inclined line. The true midship section,, 
as will be shown later when we come to the subject of the 
proper distribution of the bulk through a curve of areas, is 
at the widest part of this curve, or in the present case just 
forward of Station 7. 
In the old models and drawings the midship section, this 
clearly defined point of location of the largest frame, was, 
the initial point for the laying off of the stations, and they 
were spaced forward and aft from it at intervals of one, two 
or three frame spaces. The midship section was indicated by 
this mark El or a similar one; the frames forward of it 
were denoted by letters, a, b, c, etc. , and those abaft it by 
numbers, 1, 2, 3, etc ; thus a lettered frame was always in 
tbe fore body and a numbered one in the after body. In Fig. 
21 the stations are marked in this manner: the midship sec 
tion thus Si , the next station forward being c, the two 
frames a and b being omitted, and similarly aft, 3, 6, etc. 
In most of the work of the old shipyards the l. w.l. was 
never considered ; it was not used in any way for measure- 
ment or tonuage, the hngth on keel or on deck being of far 
more importance, and the base line of the model or drawing 
was often the bottom of keel or the rabbet line, the level lines 
being thus out of parallel with the l.w.l. and the stations out 
of square to it. 
In modern vessels, and -especially in the sailing yacht, the 
l.w.l. is of the first importance; even in cruising craft the 
proper displacement can only be decided on by first assum- 
ing some waterline at which the yacht shall float, and in 
racing craft, in addition to the necessity for some exact 
amount of di.^placement, the 1 w.l. is the most important 
factor of measurement. Instead, then, of beginning at the 
midship section, wc will take the load waterline and estab- 
lish our first station at its fore end, where it intersects the 
line of the stem or keel, from this point laying off all of our 
stations. 
At first sight it might seem desirable to follow the old 
with the method followed in the calculations: that of Hi 
multipliers used in calculating the position of the 0 B, C . 
K, etc. Abaft the l.w.l. the numbering is continued for tl 
stations of the counter; forward we have found it convenien 
to use the alphabet reversed, Z for the first station fcarward c 
the l.w.l., Y for the second, etc., as shown; there are se I doc' 
more than three such stbtions. It would be mere natural t 
use A, B, C, etc. , for the fore end of the yacht, but this 
confusing, the same letters being already used for the uppe 
level lines. 
This method of division and marking makes it an eas 
matter, to compare different drawings. No 0 is always th 
fore end of the! w.l.,.No 12 the after end, and No. 6 thI 
middle. If the last station is No. 15, it shows that the aft* 
overhang covers at least three intervals, or is of one quarte; 
the length of the l.w.l. ; Z is the station just forward of th 
l.w.l.. No. 4 is at a certain place in the fore body, and No 
in. the after body. To appreciate the advantage of followiuji 
some ouQ system, it is only necessary to attempt to compar 
three dra'Wings: one with the stations marked in this waj 
one with all numbers beginning at the extreme point of th 
bow, and one with the, fore end of the l.w.l. numbered 1 
The base line, level lines and stations are arb.trary line 
that may be located by the designer at will; we will no\ 
take up another set of lines, those which indicate the bounc 
ing surfaces of the half model. 
The first of these is the keel line in the sJieer plan, or, for 
broader term, the keel contour. This line shows the outsid 
of the stem, keel, sternpost, rudder and counter, as projecte 
on the sheer plan. The projection of the same parts in th; 
half breadth and body plans is called the side line. It usualli 
happens in modern yachts that the lower part of the kee 
does not present a flat bottom and two straight sides, S' 
shown in the figure; but that the angle is boldly rounded off 
the section of the, bottom of the keel being sometimes a semi 
circle. It is most convenient, however, to draw the kee 
with a flat bottom and a positive angle, as in the figure, i" 
order to get a side line for the ending of the stations, Afte^ 
other parts are completed, the rounding-off of the corners c 
the keel to any desired extent may be. drawn ini as in th 
present plans. . 
The side line shows the Tialf breadth of the stem, keel, etc 
at the outer and lower surf aces.' . 
The highest line of the sheer plan We will call the slm 
lim, rgpresenting4he upper :edge of rail, bulwa,rk or dect. 
as the case may-be. There are at this part of the vessel 
number of luaes that are usually shown: the upper and lowe 
"i 
