In securing the towline, you must keep in mind of letting go in an emergency. In letting go, it is desirable to have a break in the line near the stern. It would be advisable to have a shackle connecting two parts of the line at or near this point, together with some arrangement like a pelican hook for slipping. The possible whip of towlines and bridles when these are released at any point may be overcome by the use of preventers.
If the towing ship is comparatively large and has a chock at the stern, the line should be brought in through it. It is a good plan to use a short length of chain for the lead through the stern chock, shackling it outside to an eye in the end of the towing hawser and inside to a towing bridle. The chain through the stern chock takes the chafe but by its flexibility does away with the dangerous nip that might be thrown into the wire if the tow was to take sheer on the quarter.
Where the chain is not used for taking the chafe in the stern chock, the towline must be fully protected by chafing gear in the form of a pudding. The stiffness of this pudding reduces the sharpness of the nip; without the pudding, the nip would be thrown upon the towline from time to time by the sheering of the ships. Manila should be wormed, parceled, and served. Canvas, hides, burlap, and old rope should be used on wire towlines.
If the strain is not too heavy, one pair of bitts may be used to secure the towing line.
When one pair of bitts is not strong enough, the line can be taken to as many as three sets of bitts. To divide the strain, it is advisable to take one turn around the first set, two around the second, and three around the third.
If pelican hooks are used for letting go, the strain is taken on the hook, relieving the shackle so that it can be disconnected and the towing hawser slipped. This arrangement, with the pelican hook taking the steady strain of towing, offers the quickest emergency release.
If pelican hooks are not used, a strap may be attached to the wire or chain outside the shackle and a heavy purchase hooked to the strap and taken to a winch. In letting go, the strain is taken by the winch long enough to disconnect at the shackle, and then the strap is cut. A preventer must be used to prevent a dangerous whip upon letting go.
There are some conditions under which it is convenient to use a span on the towing ship. Its two parts are brought in through the quarter chocks. This makes it easier for the towing ship to steer, and this advantage may become important in cases where a small ship is dealing with a heavy tow. If the line leads from a chock directly over the rudder, it binds the stern in such a way that it can swing. A large ship can take care of this situation by the power of her steering gear, assisted if necessary by the propellers, but a small ship with a heavy tow and the line leading through the stern chock will steer very sluggishly if she steers at all. Tugs fitted for towing have their bitts well forward of the rudder to allow the stern to swing; the fittings abaft the bitts allow the line to sweep freely across from one quarter to the other.
Spans may be made up of chain, wire, or line. Plans must be made for letting them go quickly in emergencies.
A convenient plan is to bring the tow line in through a quarter chock and bend a hawser from the other quarter to it at such a point outside that the two parts shall form a span of good length. This plan has the advantage that by letting go the second line we get rid of the span at once and have to deal only with the tow line itself.
