IMPORTANT EVENTS IN OCEAN ENGINEERING HISTORY

THE CONSTRUCTION OF WOODEN SHIPS

INTRODUCTION

We can imagine the first people to travel on water using a tree log as a float and propelling it by kicking out with the feet. Other floats, which are still used up to the present day, included blown up animal skins or bundles of reeds. Alexander the Great ferried troops across rivers on several occasions using the skins which covered his men's tents, stuffed with grass, and sewn tightly at the edges. The next step would be to sit astride the log or, for more stability, tie two or more logs to make a raft. Bundles of reeds can also be used to make rafts and these rafts, as in ancient Egypt, can not only be used on rivers but also be made large enough to be sea-going.

From a very early period in human development dugout canoes were made by hollowing out the trunks of trees. If the wood is soft this can be accomplished quite easily using fire and primitive tools made of stone or shell. With the coming of the Iron Age tools became available which could easily cut and shape wood into planks and new methods of construction became possible. The dugout trunk was reduced to a keel, in effect a backbone, from which ribs spread upwards and outwards and the hull of the vessel was built up using planks fastened to the ribs. Wood placed in steam for a period becomes flexible and this allows ribs and planks to be bent into shape without breaking.

METHODS OF CONSTRUCITON

Wooden vessels can be either CARVEL BUILT or CLINKER BUILT. The latter method is sometimes known as LAPSTRAKE.

In carvel built craft the ribs are set up in the right position on the keel and the planks are bent round them and fastened edge to edge so they lie flush with one another. Each single width of planking running the length of the vessel is known as a STRAKE. The strake nearest the keel is the GARBOARD STRAKE and the top one is the SHEER STRAKE. The sheer strake is usually strengthend by a GUNWALE, pronounced and sometimes written as gunnel (a WALE is any extra timber added as band outside the hull). The ends of each strake are fastened to a STEM POST to form the pointed bow and at the other end they can either be fastened to a STERN POST in the same way, making bow and stern similar (a DOUBLE-ENDER), or, more usually, they can be fastened to TRANSOMS, which are timbers running from side to side across the stern and fixed to the stern post. This gives a TRANSOM or SQUARE STERN. Other timbers going across the width in the bottom of the hull are known as FLOORS.

In clinker built craft the keel and the stem and stern posts are set up and the planks are fitted without an internal framework. Starting with the garboard strake each plank overlaps the one below and the two are fastened through the overlap. When the planking is complete the ribs are fitted inside the hull and fastened to the planking. Thus it is the complete converse of the carvel process. Generally speaking the early carvel built ships were used in the Mediterranean countries while northern Europe, where the saw was not yet known, built clinker ships which required less precision in cutting timber but were limited in size. Later all big ships were carvel built.

SHIPBUILDING

In a large ship the ribs are too big to be single pieces of wood steamed and bent and they have to be made from pieces of timber known as FUTTOCKS (originally foothooks) which are sawn to shape and several of them together form the curved rib or frame.

In a shipyard the MOLD LOFT is a large building where the plans of a ship can be drawn out full size on the floor by the master shipwright. This known as LOFTING the lines and is the important first step. From these drawings molds, or patterns, are made from thin wood which are used in cutting out the futtocks and other parts of the framework.

A ship is built on STOCKS on a slipway leading down to the water. Stocks are large blocks of wood spaced some 4 or five feet apart on which the keel is laid. and the various pieces of timber forming the stem post and the stern fixed in position. The names of these pieces are shown in the diagrams. The floors are fitted in position and the KEELSON, another longitudinal timber, is fitted over the keel inside the hull. The FIRST FUTTOCKS, the lowest, are placed between the ends of the floors and the frames continued up to the top of the hull, the final pieces being the TOP TIMBERS. Wherever possible timber in which the grain follows a natural curve is used.

Wales are usually fitted around the outside of the ribs before the planking is started and beams, supported on knees, are fixed across the hull to support the various decks. Vertical partitions between the decks are known as BULKHEADS and any planking forming a skin inside the frames as a CEILING.

On small craft the planking is fastened to the frames by using copper nails which are clenched over or riveted on the inside of the hull, drawing the two parts tightly together. On large ships with thick timbers, parts are joined using TREENAILS, pronounced trennels, which are round or octagonal pieces of oak driven into undersize holes in the planking, frames and other timbers.

After launching the masts are fitted. These go through the decks and rest (STEPPED is the correct term) on the keelson. On a large ship the masts will be in several sections - the lower mast, the topmast, topgallant mast etc.

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