June io, 1899.3 
" - - ■ ' — 
Yacht Designing.— XXXL 
BY W. P. STEPHENS. 
{Continued Jrom page 411, May 2T0 
The term mechanical drawing is often understood in a 
double sense, as applying to a certain method of drawing 
by means of instruments ; and also to the representa- 
tion of machines, buildings and other structures. The 
first sense is the true one, a method of drawing an ob- 
ject in its true size or proportions as determined by 
actual measurements, and by means of various instru- 
ments. It is the reverse of freehand dratving, in which an 
object is depicted as it appears to the eye, the only in- 
struments used being the pencil, pen or brush held freely 
in the fingers. From the nature of the case it follows 
that the former method is better adapted to purely me- 
chanical structures and to the purposes of the designer 
builder.' 
Mechanical drawing is itself subdivided into two dis- 
tinct methods of working; one termed mechanical con- 
struction and the other geometrical construction. In 
the former method points are located and lines are drawn 
by means of the scales, T-square, triangles, parallel ruler 
and similar instruments. In the latter, the various points 
are located and the lines drawn according to the prin- 
ciples of geometry, the only instruments necessary being 
the straight-edge, dividers and compasses. 
In theory at least, a greater degree of accuracy can be 
attained by the geometrical construction; but it is by no 
means as expeditious as the mechanical construction. The 
draftsman must use his judgment continually as to the 
method better adapted to the special work in hand, to give 
sufficiently accurate results in the least possible time. With 
instruments of good quality and careflilly preserved, all 
necessary accuracy for most purposes of. machine and 
architectural drafting can be had by simple mechanical 
construction, and at a great saving of time; and even in 
marine drafting there is much of the work that can best 
be done in this way. 
In drawing the actual lines, however, especially if on 
a large scale, it is absolutely necessary — if a design is to be 
faired up accurately in all of its numerous intersections, 
and in a reasonable time — that all the foundation lines of 
the drawing shall be truly spaced and parallel or perpen- 
dicular as the case may be. For, this class of work it is 
best to use the geometrical construction unless one can 
be sure of absolute accuracy in the tools; for instance, in 
using the T square for drawing the level lines and base 
line of the sheer plan, a very slight error in the working 
edge of the drawing board, where the head of the T square 
is in contact, will cause these long lines to diverge or con- 
verge materially at the bow, making it very difficult to 
fair in the bow-buttock lines. In this work the geo- 
metrical m_ethod saves more time in the end than is lost in 
the beginning, though it takes longer to lay off the lines 
than b}- the T square and triangle. The following simple 
problems not only serve to illustrate the use of the in- 
struments, but they occur constantl}^ in . the course of 
ordinary drafting work. Most of them are geometrical, 
but in several cases, as in Problems L and II., they are 
mechanical. 
Problem I. — To draw a straight line through given 
points : The two points are first located and marked by a 
very fine dot with a hard pencil or by a slight prick in 
the paper from the point of the dividers. In order to 
make them easily visible, a small circle is drawn, freehand, 
around each. The straight edge is then adjusted at a 
small distance, i-32in. or even less, from the two points 
and exactly the same from each, the pencil or pen is poised 
over the left-hand point, dropped to touch the paper, and 
drawn steadily onward to the right until it stops on the 
right-hand point; unless the line is to be continued be- 
yond the point. 
Problem II. — To lay off distances along a given line : 
Select the required scale, lay it on the paper close to 
the line with the zero mark of the scale coinciding with 
the starting point. Proceed along the scale, counting the 
required distances and marking each with a hard sharp 
pencil with conical point, held nearly square to the 
paper, or with a fine steel point. The scale must be 
held so firmly that it cannot move during the operation. 
If the scale is not long enough to cover the entire length 
of the line, lay off a portion the full length of the scale, 
shift the latter ahead and renew the operation until the 
total length is accurately laid off; then begin again and 
lay off the intermediate distances. All distances should 
be measured continuously from the starting point at one 
setting of the scale; instead of setting off each from the 
last marked. By the latter plan any errors are cumulative, 
and affect the truth of the whole work instead of a sniai' 
portion. 
Problem III. — To divide a line into two equal parts: 
Open the dividers to a distance a little greater than half 
of the given linCi place one point on one end of the line, 
drop the other point on the Ijne and close slightly until 
the point appears to be midway between the two spots. 
Now swing the first point over t6 the other end of the line, 
which it will probably not quite touch. Correct the 
dividers by just one-half the extent of the error, if they 
are too long by Yzin., close them i-i6in., and try again. 
After a little practice very few trials will be needed to 
give the exact center. 
This method may be repeated to subdivide one-half 
the line, and thus in turn until it is subdivided into any 
even number of equal parts. It is but little more diffi- 
cult to divide a line into three equal parts in tlie same 
manner, as is required in finding the center of a triangle, 
such as a jib. 
Second method. Let AB, Fig. 74, be the two points, 
from each in turn, with the dividers set to a radius a 
little greater than half of the distance, describe two arcs 
above and below the line. "The intersection of each pair 
of arcs, at C and D, when joined, will give a line per- 
pendicular to AB, and dividing it in the center. 
Problem IV. — To divide a line into any given number 
of equal parts : First method (mechanical). Measure the 
length of the line accurately with a scale, divide the dis- 
tance by the required number of parts, the quotient being 
the length of one part. Take this measurement from the 
scale with the hairspring or the spring bow dividers, start 
at on^ end, and space off the parts, swiiigiii^ the dividers 
as shown lis Fig. 68, Whea ths' end of the llm h 
FOREST AND STREAM. 
4S8 
reached, the point of the dividers will probably fail to cut 
the exact point, overrunning or falling short a little. The 
reason for this is that the measurement, as taken from 
the scale, was not quite accurate; and the error, though 
very slight, has been multiplied by the total number of 
divisions. If it is required to divide the line into twelve 
parts, the original error will be multiplied twelve times, 
and though it may have been no more than the breadth of 
the black line on the scale, it will now be quite apparent 
at the end. The necessary correction will be very slight, 
in this case but 1-12 the amount of the final difference. 
The line will then be stepped over a second time, making 
the lightest possible mark in the paper, and if necessary 
another correction and trial made. The terms "accurate" 
or "exact," as used in connection with this work, im- 
ply that in dividing a waterline 2 or 3ft. long into twelve 
equal parts, the point of the dividers, as sharp as a fine 
needle, should drop into the fine hole pricked with a 
needle point in the paper when the length of the waterline 
was first laid off. Such accurate work as this is not al- 
ways necessary, but the draftsman should practice it in 
order to be proficient when the occasion arises, and also 
because the habit of doing rough and inaccurate work is a 
bad one to encourage. 
Second rnethod (geometrical). Let AB, Fig. 75, be 
the line, which it is required to divide into any given nurq- 
ber of_ parts, as for instance, six. From A, at any 
convenient angle, as 20 to 30 degrees, draw AC, of inde- 
finite length. Now set the dividers to a • suitable dis- 
tance and space off from A on AC six equal spaces, Ai. 
1-2, 2-3, 3-4, etc. Draw a line through B and the sixth 
point of division, and then draw lines parallel to B6. 
through each of the other points, 5, 4, etc.; where these 
lines intersect, AB will be the points of division. 
The same method may be applied in a slightly different 
form, as in Fig. 76. Draw the inclined line AC and 
through B draw BD parallel to AC. Lay off the 
number of spaces from A on AC, and from B on BD ; 
join B-6 and A-VI, also i-V, 2-IV, etc., and the 
intersections of these new lines with AB will give the 
required points of division. This construction is strictly 
geometrical, .with the compasses set to any convenient 
distance, an arc of a circle is described from A below 
the line and from B above it. The lines drawn from A 
and B tangent to these arcs are of necessity parallel. 
The mechanical method, by the scale, is used when a 
line several feet in length is to be divided, as for in- 
stance in laying off the stations for a new design. The 
geometrical methods are the better for the division of 
short lines, as in laying off a special scale of feet and 
inches. 
Problem V.— To draw through a given point a line 
parallel to a given line : Let AB, Fig. 77, be the line and 
C the point. Set the dividers or compasses with the point 
on C, and adjust the other point to touch the line AB 
Set the point of the compasses on the line near B and 
describe an arc EF. Through C draw a line tangent to 
the arc EF at the point D, it will be parallel to AB. 
A second method is shown in Fig. 78. Set the com- 
passes on C and adjust to cut AB at E. Transfer the 
point of the compasses to E. and with the same radius 
describe the arc CF. Measure the distance CF with the 
dividers and set it off from E on the arc D; the line 
drawn through CD will be parallel to AB. 
Problem VI. — To draw a straight line parallel to a given 
line and at a given distance from it: Let AB, Fig. 79, 
be the given line; set the dividers to the given distance, by 
the scale, and describe from A and B in succession the 
arc C, D. The line CD, tangent to the two arcs, will 
be the required line. 
Problem VII. — To draw a line through a point perpen- 
dicular to a given straight line: First method. Let AB. 
Fig. 80, be the line and C the point. Set the compasses on 
C and describe the arc DE, with any convenient radius. 
From D and E in succession with a radius somewhat 
greater than half the distance between the two points, 
describe the arcs which intersect in F. A line drawn 
from C through F will be perpendicular to AB. 
It may happen that there is no space below AB, in 
which case the intersecting arcs may be drawn above the 
line, at G. 
Second method: Let AB, Fig. 81, be the line, and 
C the given point, in this case near to the end of the line. 
Place one leg of the dividers at a convenient point, as 
D, and set to cut the point C; then describe with the 
same radius an arc below the line. Now place the 
dividers on E, set to touch C, and describe another arc 
below the line, intersecting the first arc in F. A straight 
line through C and F will be the required perpendicular 
Columbia and Defetider* 
The date of the launching of Columbia is officially an- 
nounced as Saturday, June 10, on the night tide, about 7 
P. M. The launching will be public, and the high road 
in front of the shops, as well as the waters of the bay in 
front, will be free to all spectators. The work of finishing 
is being hurried in all departments. The bottorii is being 
polished by buffing wheels, followed by the crew with 
cloths and pumice stone. The topsides are as yet uiipainted. 
The deck joinerwork is being finished, to go in place as 
soon as the last deck planks are laid.. On June 3 the 
large sheer legs at the works, after being used to lower the 
30-footer Musnie into the water, were guyed back too 
far and fell over, fortunately doing little damage. De- 
fender left Bristol on Saturday and anchored in Brentoii's 
Cove, Newport, the same evening. Columbia and De- 
fender will sail a preliminary race outside Sandy Hook on 
July I, but it is very unlikely that either will race in Long 
Island Sound at any time. 
The Queen City Y. C, sailed a cruising race from 
Toronto to Port Credit on May 27 in a strong and squally 
westerly wind. Only four yachts finished out of eleven 
starters, two having capsized and one losing her mast. 
The times were, start 2 :30 : 
Finished. Elapsed. 
Petrel ..............5 15 00 2 45 00 
Faneta ........................................ .6 03 00 3 38 00 
Widgeon ...,.......o,.o...,.....,o>... = .....,...6 15 00 3 *5 00 
Turtle ..,..,..6 67 00 4 27 OO 
