Fishing Craft Technology (1+1)

Unit 4 - Boat building materials and construction of boat

4.11.Deck fittings and equipments

(i) Mast and derricks:
Mast is a vertical spar primarily meant to carry sails but it is also used to carry radar, satellite aerials and navigational lights. The masts are of different types. They are made either wood or steel. Derrick is a large spar fixed to mast by goose neck and is used like a crane for hoisting heavy weights. The length of derricks should be adequate to bring the cod end aboard. It is fixed in such a way that the derrick swings through a wide area. These are commonly found in all types of fishing vessel. These are probably the oldest and most basis installation on boats. Mast or masts like structures are vital if all the necessary lifting operation is to be performed. Wooden masts are still perfectly acceptable or if available, steel pipe may be used.

(ii) Block and pulleys:
These are common in all types of fishing vessels and these are used for a variety of purpose like leading the ropes to convenient position for handling or as towing points for the warps in trawling. A block is a wooden or metal case in which one or more sheaves are fitted. Blocks and pulleys are attached to strong points on the mast and derricks. Good quality blocks are expensive but the investment is worthwhile. Cheap blocks will break or seize up or create unnecessary friction, good blocks will last for a long time. They should be made of best hard woods, nylon or steel and should have proper bearings or bushes that are self lubricated or can be lubricated. For boats with small winches or limited power –3 fall and 4 – fall blocks can enable the crew to lift heavy loads on board provided the mast and rigging have the appropriate strength.

(iii) Power take-off and winch drives:
Power take-off is the units to take the power from the main engine for the winch drive. From the power take-off point, belt drive is preferable to chain drive as it has more flexibility. Hydraulic drive may prove cheaper than mechanical drive in the long run, provided that expertise and spare parts are locally available. On small fishing boats, the most usual power take off is for winch or Hydraulic oil pump for line hauler or power blocks in purse seiners.

(iv) Gallows and davits:
Gallows are used in trawlers and purse seiners. Trawl gallows are used in hitching up of heavy otter boards as well as for passing of towing warps. Though inverted “U” shape is the most common one for trawl gallows, other types like bipod, tripod etc., also exist. The positioning of gallows is important as they must be forward of the rudder axis to allow the vessel adequate manoeuverability but not so forward that the warps foul the stern when turned sharply. Purse seine gallows are used to lead the purse line and tow line to the winch in larger vessels. The gallows is of strong construction with three blocks. In smaller vessels, this function is carried out by davits. Davits are used in purse seiners, gill netters and pots. In smaller purse seiners, single portable davit with blocks is fitted on to mountings at the bulwark for passing of purse liners. It also supports a snatch block for tow line handling. American gill netters haul the nets by power blocks mounted on the davits.

(v) Winches:
Different types of winches are used for different fishing methods. They may be placed in the fore and after direction or athwart ship depending on the requirement. They are used commonly in trawlers, purse seiners and Danish seiners to haul the net and the catch on to the board. Trawl winches can be single drum (split type) two – drum on one shaft or two or more drums on parallel shafts. The last type is most suitable for double rig trawling and purse seining.
A winch may or may not have warping heads. When, present warping heads are used for auxiliary hauling requirements such as hauling sweep lines, wings etc., Split winches are common in large trawlers as they enable straight lead from winch drum to gallows/gantry. Winches can be driven either mechanically from the main engine or electrically or hydraulically or direct drive by a separate engine. Mechanical drive is preferred in small vessels as it is simple, reliable easy to maintain and repair and less expensive. Electric drive is confined to large vessels due to the necessity of a large capacity generating plant and auxiliary diesel. However, electric winch offers good flexibility of operation and control. Hydraulic drive is popular due to its many advantages but is used only in large vessels. Direct diesel drive has not become popular due to problems like requirements of more space fuel supply and exhaust arrangements.