6 TOWING


We’ve talked about the need for a strong towrope but even the strongest will be useless if the cleats are too flimsy. The stoutest cleat or bollard is typically the one used to secure the anchor rode but, of course, it’s up in the bow and therefore of little help when towing. A useful compromise is to rig a bridle from the stern cleats, backed up with a pair of lines from forward (Fig 6:3).


Keep your speed down Fig 6:3


If the tug is larger and potentially faster then the tow, a serious problem can arise. Back in Chapter 1 (page 11) we saw that the maximum speed of a displacement type boat is called ‘hull speed’ and that this is limited by waterline length. To put this point in context, a boat with a 20ft (6.1m) waterline will be capable of only about 6 knots while one having a 40ft waterline will do nearly 8.5 knots. Now imagine the larger boat towing the smaller one flat out (Fig 6:4). The tow will be travelling 2.5 knots faster than its hull speed and its stern will have sunk into the trough behind its bow wave. In extreme cases the water could slosh over its transom


and the boat would be swamped. Planing type boats may be less susceptible but even they can experience more than the usual degree of excitement.


It’s therefore essential that the tug matches its speed to one that’s comfortable for the tow. In practice, this will be well below the smaller boat’s hull speed – say, no more than 5 knots for our example. Not only will this greatly reduce the resistance – and thereby the load on the towrope – but it will ensure a kindly-meant rescue doesn’t turn into a tragedy of its own making.


In brief:


■ Take up the strain gradually then keep your speed down. If you see water boiling up behind the tow’s transom, you are going too fast. Remember that a large, powerful boat can pull a smaller one under vert quickly.


Fig 6:4


44


RYA Seamanship for Sea Anglers


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