In primitive boatbuilding, the builder often used width of hand, length of forearm, and length between knuckles as units of measurement. Notched sticks also were used for measuring. More advanced building methods, using molds, required that the keel, the stem, and the sternpost be set up on stakes or blocks and that an arbitrary midship frame be erected in place. The curved members required for this frame were made from molds, used by shifting the butts to produce boats of varying size but similar form. After the midsection frame was put in place, two or more battens on each side were secured, one to form the sheer line, one along the turn of the bilge, and often one along the ends of the floor timbers, or short frame members, that crossed the keel. Sometimes other battens were fitted between the bilge and sheer battens and between the bilge and floorhead battens. Individual frame members were then shaped to fit inside the battens at selected intervals; when all the frames were made, the battens were removed and the hull was planked. All frames were hewn from crooked timber.
I. The Half-Model
The next development in boatbuilding was the use of drawings and the builders' half-model. Using drawings to delineate the shape of the hull apparently evolved slowly, but records are obscure. Similarly, little is known of the evolution of the half-model, but it appears to have developed along with the use of drawings. It is known that the use of such plans was common in 16th-century England, during the reign of Queen Elizabeth I, and Mediterranean builders probably employed crude drawings at least as early as the beginning of the 15th century. According to some authorities, the ancient Greeks and Romans also used drawings in shipbuilding and boatbuilding.
By the middle of the 17th century the art of designing boats by drawing plans was known throughout Europe. The sections were formed by compound curves made with the compass; the longitudinal curves were arbitrarily made according to the same principles that had governed the use of battens. The designers employed shifting molds based on the midsection form, so that one set of frame molds could be used by shifting butts to form all the frames; this system became known as whole molding. The boat design was drawn to reduced scale, and then, in a process known as lofting, a full-size drawing of the ship or boat was made. By 1800 drawing up the plans for ships and boats was fully developed, as was the lofting process.
The use of the half-model in lieu of the reduced-scale drawing appears to have originated in Europe at an early date; by the early 18th century carving a model from a solid block of wood was a popular method of design in commercial boatyards and shipyards. The shape of the model was determined by the judgment and art of its maker. The sections needed to form the mold frames controlling the hull shape of the boat were obtained by sawing the model at the desired transverse mold stations and scaling off these sections by drawing ordinates.
II. Lift Models and Lofting
By the middle of the 18th century, builders had developed another type of model, consisting of a blackboard cut to the shape of the hull profile, with the sections formed of thin plank secured at the desired mold stations. The sections were made fair, or capable of being planked smoothly, by battens at suitable locations. Finally, about 1795, the so-called lift model was developed, made of boards of equal thickness pegged together and shaped to the desired hull form. The shape of the mold frames was obtained by taking the model apart and tracing the shape of the lifts, or planks, in their proper relation to one another. By drawing lines across these shapes at frame stations, the transverse widths at the ordinates formed by the lift thicknesses could be determined. The lift model is still in use in many boatyards and remains practical for small craft.
Lofting consists of drawing the full-size shape of the hull on a suitable platform or floor. The required drawing shows the mold sections, or transverse forms, usually five to seven in number. These sections usually are tested by drawing in some longitudinal curves, such as the sheer, and a few waterlines or level lines duplicating the so-called lift lines of a half-model. In addition, buttock and bow lines, longitudinal vertical sections parallel to the centerline of the hull, may be used. Diagonals, representing the batten curves over the molds, may be drawn in. In making the longitudinal drawing, the profile of the hull usually is drawn full size. Lofting is an important operation in boatbuilding, for it is the only way a design may be reproduced accurately or repeatedly. In the more advanced boatshops the structural details also are drawn full size, the lofting being done in minute detail.
I. The Half-Model
The next development in boatbuilding was the use of drawings and the builders' half-model. Using drawings to delineate the shape of the hull apparently evolved slowly, but records are obscure. Similarly, little is known of the evolution of the half-model, but it appears to have developed along with the use of drawings. It is known that the use of such plans was common in 16th-century England, during the reign of Queen Elizabeth I, and Mediterranean builders probably employed crude drawings at least as early as the beginning of the 15th century. According to some authorities, the ancient Greeks and Romans also used drawings in shipbuilding and boatbuilding.
By the middle of the 17th century the art of designing boats by drawing plans was known throughout Europe. The sections were formed by compound curves made with the compass; the longitudinal curves were arbitrarily made according to the same principles that had governed the use of battens. The designers employed shifting molds based on the midsection form, so that one set of frame molds could be used by shifting butts to form all the frames; this system became known as whole molding. The boat design was drawn to reduced scale, and then, in a process known as lofting, a full-size drawing of the ship or boat was made. By 1800 drawing up the plans for ships and boats was fully developed, as was the lofting process.
The use of the half-model in lieu of the reduced-scale drawing appears to have originated in Europe at an early date; by the early 18th century carving a model from a solid block of wood was a popular method of design in commercial boatyards and shipyards. The shape of the model was determined by the judgment and art of its maker. The sections needed to form the mold frames controlling the hull shape of the boat were obtained by sawing the model at the desired transverse mold stations and scaling off these sections by drawing ordinates.
II. Lift Models and Lofting
By the middle of the 18th century, builders had developed another type of model, consisting of a blackboard cut to the shape of the hull profile, with the sections formed of thin plank secured at the desired mold stations. The sections were made fair, or capable of being planked smoothly, by battens at suitable locations. Finally, about 1795, the so-called lift model was developed, made of boards of equal thickness pegged together and shaped to the desired hull form. The shape of the mold frames was obtained by taking the model apart and tracing the shape of the lifts, or planks, in their proper relation to one another. By drawing lines across these shapes at frame stations, the transverse widths at the ordinates formed by the lift thicknesses could be determined. The lift model is still in use in many boatyards and remains practical for small craft.
Lofting consists of drawing the full-size shape of the hull on a suitable platform or floor. The required drawing shows the mold sections, or transverse forms, usually five to seven in number. These sections usually are tested by drawing in some longitudinal curves, such as the sheer, and a few waterlines or level lines duplicating the so-called lift lines of a half-model. In addition, buttock and bow lines, longitudinal vertical sections parallel to the centerline of the hull, may be used. Diagonals, representing the batten curves over the molds, may be drawn in. In making the longitudinal drawing, the profile of the hull usually is drawn full size. Lofting is an important operation in boatbuilding, for it is the only way a design may be reproduced accurately or repeatedly. In the more advanced boatshops the structural details also are drawn full size, the lofting being done in minute detail.
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