Simply put, a block in sailing ship model kits is single or multiple pulleys used as a lever to maneuver loads of rigging usually attached to fixed and running applications on a ship. In use, one block is connected to a fixed surface. The model ship kits can be easily built with the blocks.

Due to the size of a model ship, blocks that are used are general representations of blocks -a fairly poor representation at best! However, it is quite difficult to make accurate museum quality blocks. Also, the types of blocks represented in kits are typically limited to common blocks, sister or violin blocks, heart. Other types of blocks, deadeyes, hearts and bull's eyes will be touch upon.

Following is a general description of the construction of blocks used on ships

The shell is the outside case of a block and is made of ash, elm, or iron. In ship model kits, the shell is typically made of walnut or boxwood. The shell could be made in one piece or assembled from several components -which were always made of wood until the middle of the 19th century. After this time the shell was occasionally made of metal. A block consists of a shell that is made in one piece or assembled from several components -which was always made of two until the middle of the 19th century. After this time the shell was made in one piece.

The shell contained a pulley, or sheave, over which the rope ran, and which rotated on a pin. The sheave is the wheel on which the rope travels and is made of metal, lignum-vitae that has the extraordinary combination of strength, toughness, and density), or iron.

Knowing the crown and tail

The crown and tail of a block are the ends of the shell; the latter is easily known, as it has a much deeper score than the former to receive the splice of the strop, and in most cases the standing part, of the purchase. The swallow is the open part between the sheave and shell.

The score is the groove in the outside part of the shell to take the strops either single or double scores, according to what the blocks are required for. Double-scored is always double-strapped which can be specially built with special tools for ship modeling. The size of a block is denoted by the length and its classification by the flatness or thickness of the shell, the number of sheaves, the number of scores, and the quality of the strapping.

A block is supposed to carry a rope one-third its length in circumference: that is to say, a 3mm. a block would carry a 1mm rope a 6mm block would carry a 2mm. rope etc. Blocks are designed for use with a certain size of rope. Therefore, they should never be used with the rope of a larger size. Rope bent over a small sheave will be distorted, and any great strain applied will damage it and may even result in the rope wearing on the frame.

Conclusion

 Determining the size of the block to use with wire rope is impossible because of the factors involved. However, experience has shown that the diameter of a sheave should be at least 20 times the diameter of the wire rope. An exception to this is flexible wire for which smaller sheaves can be used because of their greater flexibility. The construction of the wire rope has a great deal to do with determining the minimum diameter of sheaves to be used. The stiffer the wire rope, the larger the sheave diameter required.