Sizing a towline, breaking load, length and salvage

A towline has to be able to stretch, otherwise it parts at the first snatch, or tears the cleat out of the deck. Nylon stretches, Dyneema does not. The length should be chosen so that both boats ride the waves in step: at least thirty metres, and more in a seaway.

A towline that parts is dangerous. It snaps back with enormous force, which is why nobody stands in the snap-back zone, and why a weight is hung in the middle of the line.

In insurance terms the distinction is this: salvage after an insured event is covered; a simple tow because the tank ran dry or the engine broke down is not automatically covered. Anyone giving or taking a tow should agree in advance whether it counts as assistance or as salvage attracting an award, because under a Lloyd's Open Form salvage agreement that distinction can be worth five-figure sums.