MSS Towline assemblies consist of a main towline, a pennant and may also include a stretcher.
The main towline is installed on the tug’s winch with the pennant connected to the free end of the towline. This is passed to the tanker to be towed. If fitted, the stretcher is placed between the main towline and the pennant.
Main towlines are deployed from the tug’s winch on the bow or main deck, depending on the tug’s design.
Towing pennants are short lengths of UHMWPE line used to prevent damage to the main towline.
A stretcher is a heavy-duty hawser. It is also referred to as a shock line or towing spring. A stretcher may comprise of a single leg or grommet (doubled length), of synthetic line with high strength and elasticity. The purpose of a stretcher is to reduce the dynamic loading caused by wind waves and swell, protecting the assembly from high shock loads and fatigue.
These main line, pennant and stretcher can be linked by cow hitch or soft shackles.
| Dia (mm) | Circ (ins) | Linear Density (Ktex) | MBL (KN) Unspliced Rope | MBL (KN) Eye-Spliced Termination |
|---|---|---|---|---|
| 24 | 3 | 331 | 520 | 470 |
| 26 | 3-1/4 | 386 | 600 | 540 |
| 28 | 3-1/2 | 445 | 685 | 615 |
| 30 | 3-3/4 | 508 | 775 | 700 |
| 32 | 4 | 575 | 865 | 780 |
| 34 | 4-1/4 | 646 | 965 | 870 |
| 36 | 4-1/2 | 722 | 1070 | 965 |
| 38 | 4-3/4 | 801 | 1175 | 1060 |
| 40 | 5 | 884 | 1285 | 1155 |
| 48 | 6 | 1255 | 1775 | 1600 |
| Dia (mm) | Circ (ins) | Linear Density (Ktex) | MBL (KN) Unspliced Rope | MBL (KN) Eye-Spliced Termination |
|---|---|---|---|---|
| 52 | 6-1/2 | 1464 | 2045 | 1840 |
| 56 | 7 | 1688 | 2330 | 2095 |
| 60 | 7-1/2 | 1928 | 2635 | 2370 |
| 64 | 8 | 2183 | 2950 | 2655 |
| 68 | 8-1/2 | 2453 | 3285 | 2955 |
| 72 | 9 | 2738 | 3635 | 3270 |
| 76 | 9-1/2 | 3038 | 4000 | 3600 |
| 80 | 10 | 3353 | 4375 | 3940 |
| 88 | 11 | 4028 | 5180 | 4660 |
| 96 | 12 | 4762 | 6040 | 5435 |
