Building the Explorer.

The drawing office and lofting.

The evolution of a ship begins in the drawing office where naval architects and draftsmen carry out the process of design,  putting down on paper, scale drawings of the ship.  These include a shell expansion drawing (example above not Explorer) and a plan and profile view showing the various curves of the hull.  The loftman’s job was to take these drawings and amplify them into full size patterns which could be used by the steelworkers to fashion the plates, frames, stringers and strakes of the ship for assembly on the slipway. 

Drawings and terminology

The drawings on this page, DRAWING N°4 MIDSHIP SECTION and DRAWING N°3 PROFILE & DECK.
They contain most of the information required to build the ship. The shell expansion drawing would be included here but it is not in our possession.  Some of the terms will be unfamiliar to those not of a marine background so in no particular order:

Strakes are the steel plates which form the hull. Drawing no.4 shows the A strake connected to the keel and the H strake up by the bulwark. Explorer’s drawings shows the strakes to be between 0.4″ and 0.5″ thickness.

BP= between perpendiculars. The length BP is essentially the length along the waterline of the ship from the stem to the sternpost.

MLD=moulded  The breadth moulded is the breadth of the hull less the plate thickness. The moulded dimension allows the naval architect to place structural members and internal tanks etc where the shell thickness is irrelevant.

Scantlings is the term given to the dimensions of parts of the ship’s structure.  

The keel is the lowest longitudinal structural part of a ship.


The Explorer is of riveted construction. It’s probably worth explaining the principle of riveting.  A rivet is a mushroom shaped piece of steel which is heated till it is red hot. It is then inserted into a hole in the components to be joined.  The riveter would then either hammer or hydraulically squeeze the end of the rivet flat. As the rivet cools it contracts drawing the components tightly together.  

The size of rivets are specified in the drawing below


Midship section drawing

Laying of the keel is considered the start of construction.   The Explorer’s keel is an 8″x 2″ flat bar. Once the keel is laid other components can be attached to it.  Obviously a piece of steel 183’6″ long would be difficult to transport from the steel mill so shorter sections would be joined probably with double riveted butt joints.

Frames are transverse steel girders conforming to the profile of the hull. The frames are drilled to accept rivets spaced to conform to the holes on the strakes.  The spacing of the frames varies from 21″ down to 17.5 at the bow for ice strengthening. 

Strakes are steel plates suitably shaped and drilled.  They are then riveted  to the frames and to the adjacent strakes to form the hull. these are 0.44″ to 0.4″ thick increasing at the bow to a thickness specified in the shell expansion plan which is drawing the society doesn’t possess. Drawing No. 4 above shows the strakes indexed from A to H.  The strakes attached to the keel are known as the garboard strakes and the uppermost strakes are known as the sheer strake

Longitudinal girders called stringers are riveted between the frames to increase the stiffness of the hull as specified in drawing no.4.

Ship No747 -FRS Explorer drawing No3 Profile and deck

Fitting out.

When the hull plating is complete, the fitting out stage of construction can progress. Some fitting out will be done on the slipway such as installing the propeller, shaft and rudder and of course all seacocks to ensure the hull is watertight for launching. Other pieces of machinery such as the main engine and boiler may be fitted on the slipway particularly if they are required to ensure stability on launch. 

No such thing as a free launch

The launch is a significant occasion in the life of a ship. Not only is it the first time the ship enters her natural environment, it is also the moment she changes from being ship no. 747 to becoming FRS Explorer


I’m not a real shipbuilder, so if your completed vessel sinks due any omissions on the page, it ain’t my fault. If any corrections, faults, or entire nonsense is detected, contact and we shall make any corrections necessary. 

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