Determining the lines of a boat otherwise known as determining the sheer


The lines of a type of boat are determined by the sheer of the strakes and the shape-defining elements such as the wale and the splash boards.

Tools and equipment used by the boat builder to determine the lines of a boat.

When determining the lines of a boat the master boat builder only uses a few tools.

Long, flexible laths are the most important tool. These can be of a flexible type of wood, however, plastic pipes can also be handy. In addition, gluing clamps and/or small nails are used.


The ultimate lines of a new-build boat are the exclusive responsibility of the master boat builder.

When building the skin of the boat he, or she, will determine the sheer of the boat at regular intervals. Determining the lines, otherwise known as determining the sheer, is a continuous process that starts after fitting the first strake, often referred to as the garboard strake, up to and including the fitting of the wale and splash boards.

When doing this he/she is assisted by a helper who positions the flexible lath at the required height. The lath is secured to the frames using small nails or gluing clamps.

The boat builder can then evaluate the line, or the sheer as it’s also known, from various distances and from various positions. On the basis of his/her instructions the helper raises or lowers the lath on the next frames, until a line is created to the satisfaction of the master boat builder. The next strake can be fitted when the boat builder gives his/her approval for the line.

Each type of boat has clearly recognisable lines. However, differences in boats of the same type are found. These differences can be due to:

1)     Yard of boat-builder preferences.

2)     Preferences or requirements of the person ordering the boat.

3)     Modifications for the boats future use.

4)     Evolutions in technical possibilities.

These, most minor, differences within the same type of boat mean that a trained eye at the yard can determine the area of navigation of the boat or the period in which the boat was built.

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Tools Required

  • Gluing clamps
  • Small nails

Materials Required

  • Flexible laths
  • Plastic pipes