Section 1 General

1.1.1 This Chapter applies to self-propelled tugs, pusher tugs and launches, defined as follows:

1. A tug is a ship designed primarily for the towage of other ships, which does not exclude occasional pushing duties, if arranged for this purpose.

2. A pusher tug is a ship designed for the pushing of other ships.

3. A launch is a ship designed primarily for the transport of personnel and small quantities of cargo.

1.1.2 The structural requirements of this Chapter are intended to cover ships having a length not exceeding 50 m, a ratio of length to depth not exceeding 18 and a ratio of breadth to depth not exceeding five.

1.1.3 Launches having a speed exceeding 20 km/h may be constructed according to the requirements for fast small craft, incorporated in the Rules and Regulations for the Classification of Special Service Craft.

1.1.4 The scantlings of the ship’s structure are to be not less than required in Pt 3, Ch 5 Fore End and Aft End Structure and Pt 3, Ch 6 Machinery Spaces so far as applicable or as specified otherwise in this Chapter.

1.1.5 The remaining requirements ofPt 3 Ship Structures (General) are also to be complied with as appropriate to the intended arrangements.

1.2.1 This Chapter provides for a basic structural configuration of a, generally, single decked hull with a single bottom, single skin side construction and a transverse or longitudinal framing system.

1.2.2 For pusher tugs and tugs with relatively high engine power having twin or multiple screws, it is recommended that a double skin side construction be adopted and/or to fit continuous longitudinal bulkheads extending as far forward and aft as practicable.

1.3.1 Pusher tugs and tugs with their relatively high engine power are liable to experience a high level of vibration and noise. Attention is drawn to the fact that certain National Authorities specify a maximum level of noise. It is therefore recommended that special attention be given to acoustic insulation and to flexible mounting of the deckhouse, etc.

1.4.1 Ships complying with the requirements of this Chapter will be eligible to be classed ‘A1 I.W.W. tug’, ‘A1 I.W.W. pusher tug’ or ‘A1 I.W.W. launch’.

1.4.2 The Regulations for classification and assignment of class notations are given inPt 1, Ch 2 Classification Regulations to which reference should be made on the survey request form.

1.4.3 Where a ship has been specially designed, modified and/or arranged in accordance with the additional requirements for Zones 2 or 1, for service extension or for navigation in ice, the appropriate class notation will be assigned.

1.5.1 For the information required, see Pt 3, Ch 1, 5 Information required. In addition the following are to be supplied:

1. The maximum pressure head in service on tanks, also details of any tanks interconnected with side tanks.

2. The pull, which can be exerted on the towline or the push at the push stem.

3. Arrangements for the stowage of cargo and details of the deck loads.

4. Details of cranes or masts for the handling of the cargo, if fitted, and their supporting arrangement.

5. Support structure and foundations of towing equipment.

6. Skegs, propeller guards and other structures which support the weight of the vessel during dry-docking.

1.5.2 The following supporting documents are to be submitted for information:

1. Towing arrangements, including lines of action, magnitudes and corresponding points of application of towline pulls on towing equipment.

2. Details of the breaking strength of the components of the towline system, together with maximum pull and brake holding load, or equivalent, of towing winches where applicable.

1.6.1 The following symbols and definitions are applicable to this Chapter unless otherwise stated: