Classic Boat — November 2017

CLASSIC BOAT NOVEMBER 2017 63

HOW TO READ LINES PLANS

3-D RENDERINGS OF 2-D

LINES PLANS

10 9 8 7 6 5 4 3 2 1 0m -1 -2

12 11 AP 9 8 7 6 5 4 3 2 1 FP -0.5

dwl

-1

-2

-3

-4

2

1

DWL

Diag.^1

Diag.^2

Diag. 1

Diag. 2

CL

Thisdrawingistheproperty of G.L. Watson & Co. Ltd. It may not beusedin any other contract or project.It must bereturnedtoG.L.Watson& Co.Ltd.immediatelyuponrequest andany electronicversionsdeleted. Thereceipt andacceptanceof thisdrawingimpliesthat theseconditionsasstatedareaccepted.Thisdrawing, itscontentsandany information receivedwith it may not becopiednor disclosedtoany3rdpartywithout expresswrittenpermissionofG.L.Watson& Co.Ltd.

Martins Building Water Street Liverpool L23SXUKT: +44 (151) 6018080 F: +44 (151) 6018070www.glwatson.com

G. W. N L ATSO

IssueDateStatus Notes

270 Britannia

ApprovedByDrawn ByDrawing# ScaleRequestedByDate ApprovedClient ApprovalDate

DrawingTitle

Design# Project

Area

0 21-01-09Preliminary

JRG 1:75 21-01-09

LinesPlan

Exterior

SECTIONS

The CAD opposite shows what would happen if a half model were sawn across

just as it might have been in real life 100 years ago. The body plan of the yacht

indicates relatively full sections forward with plenty of reserve buoyancy in the

overhang, promising a sea-kindly ease of motion that resists pitching, and a dry

foredeck. The midships section shows a powerful turn of the bilge which, at this

scale of yacht, will confer huge sail-carrying ability to augment the deep ballast

keel, while the ‘hollow’ (concave) sections of the run actually begin forward of

amidships, encouraging the cleanest of wakes from this mighty yacht described

by U­a Fox as: “Handsome is as handsome does.”

WATERLINES

The waterlines are the easiest part of a lines plan to understand and can o­er

the ‘key of the door’ to a neophyte yacht connoisseur. As one would expect from

the board of a designer of GL Watson’s calibre, Britannia’s waterlines, seen here

at the lower part of the illustration, run fair from stem to stern, with no

suggestion of a distortion anywhere. As is often the case, the entry appears far

finer in this view than it does to the non-specialist eye looking at the body plan.

Notice the way the lower waterlines, the ones which begin well aft, lie virtually

on top of one another for much of their length, denoting the dead-drop of the

keel. In way of the quarter, the upper waterlines seem to suggest that the beam

in the aft part will not balance the entry. This is deceptive, with reassurance

readily to hand by reference to the underwater sections and the buttocks, as

they sweep sweetly into the perfect counter stern.

BUTTOCKS

The buttock nearest the centreline of a yacht often reveals some strange

influences, particularly in the area of deepest draught. It does so here. This is no

cause for alarm, however, as it reflects the almost vertical sides of the lower part

of the keel. Further up towards the load waterline, the truth is revealed. The

vertical lines on the profile drawing which represent the sections tie the buttocks

in to them. Following each buttock line from bow to stern shows, in Britannia’s

case, a balanced hull with the easiest of runs o­ aft where the critical wake is

generated. A less refined design often su­ers from sharp turns in the buttocks

aft, promising uneven water flow and a slow boat. In Britannia’s case, the water

will run away to the stern so easily that it will be positively anxious to leave.

Waterlines

Buttocks

and in profile (from the side). By noting the points at

which each succeeding section cuts a predetermined line

horizontal to the load waterline on the design ‘grid’, it is

possible to plot a line scribed around the half hull which

is equivalent to a slice cut horizontally through the

model. A number of these so-called ‘waterlines’ are

constructed, and while the architect’s main concern is

that they should fall into a series of sweet curves

without bumps or hollows to disturb water flow, the

observant sailor can usually draw further conclusions

from their shape.

The ‘buttock lines’ complete the picture of the vessel.

They represent vertical slices parallel to the centreline,

providing a further check on fairness in the body plan.

Their form can be as revealing as the waterlines.

While producing a similar dissertation many years

ago for the Yachtsman magazine, I reasoned that a set

of visual aids would be a great help, and asked the Boat

Building School at Falmouth College to make a run of

half models for us to cut up. Such material extravagance

is anathema to post-financial-crisis thinking, but,

happily, something similar can be achieved today using

CAD. Master of CAD is naval architect Paul Spooner,

who came riding into the breach with a series of

creations around a generic classic yacht shape. These

can be related to the lines plan of the GL Watson Royal

Yacht Britannia, designed in 1893 and reproduced here

by kind permission of GL Watson and Co Ltd.

A lines plan works for any shape of boat, from a

smack built on the beach with a half model to a yacht of

Britannia’s sophistication from the board of an

acknowledged master. Reading lines is an unceasing

pleasure because they are greater than the sum of the

data they represent. Like the boats they describe, they

have aesthetic qualities and the more one looks at them,

the more enlightened one becomes. In time, picking up

the essence of a fine yacht from a sheet of paper is no

longer a matter of analysis. It develops into the thrill of

discovering a creation of three-dimensional art.

Sections

10 9 8 7 6 5 4 3 2 1 0m -1 -2

12 11 AP 9 8 7 6 5 4 3 2 1 FP -0.5

dwl

-1

-2

-3

-4

2

1

DWL

Diag.^1

Diag.^2

Diag. 1

Diag. 2

CL

Thisdrawingistheproperty of G.L. Watson & Co. Ltd. It may not beusedin any other contract or project.It must bereturnedtoG.L.Watson& Co.Ltd.immediatelyuponrequest andany electronicversionsdeleted. Thereceipt andacceptanceof thisdrawingimpliesthat theseconditionsasstatedareaccepted.Thisdrawing, itscontentsandany information receivedwith it may not becopiednor disclosedtoany3rdpartywithout expresswrittenpermissionofG.L.Watson& Co.Ltd.

Martins Building Water Street Liverpool L23SXUKG. W.T: +44 (151) 6018080 F: +44 (151) 6018070www.glwatson.com N L ATSO

IssueDateStatus Notes

270 Britannia

ApprovedByDrawn ByDrawing# ScaleRequestedByDate ApprovedClient ApprovalDate

DrawingTitle

Design# Project

Area

0 21-01-09Preliminary

JRG 1:75 21-01-09

LinesPlan

Exterior

CB353 How to read lines.indd 63 26/09/2017 16:17