Explorers

TECHNICAL LIBRARY

GENERAL ITEMS

TOWING

     The time might come when the vessel needs to be towed - such as a grounding or when the engine won't start. Skippers should not rely on a prospective towing vessel to have the necessary towing lines suitable for that particular vessel. Therefore a towing rig should be ready by the time a rescue vessel comes on the scene.
     The first step is to decide on the best towing point - is it to be from an existing bollard or cleat, an installed towing point or will it need to be from suitable winches? Whatever the case the skipper must choose the position that is strong enough to do the job. If it has to be from winches a suitable bridle will usually have to be prepared so that the bridle can be attached to the tow line at or near the bow - and preferably running through fairleads.
    The next step is to have a tow line prepared - strong enough and as long as possible. In rough conditions a throwing / heaving line might also be required to reduce the risk of collision as the tow line is passed. A boat hook can be useful in passing the tow. Fenders may also be necessary - either while the tow is being organised or in the final stages when the rescued vessel is being positioned on a mooring or jetty.
    If the vessel needs to be towed a long way, and / or waves and current are likely to make the tow difficult, a sea anchor should be made ready and kept in a secured position on the aft deck for expedient deployment. If a proper sea anchor is not carried a makeshift one should be prepared. An anchor wrapped with rope (to prevent flukes digging in if it encounters the bottom) or sturdy buckets can be suitable. An old car tyre can also make a useful sea anchor - the prudent skipper will be so prepared beforehand.
     Directions will need to be passed between both vessels to provide the best level of efficiency and safety. Initially this will usually be possible by direct voice but as the tow gets underway other means will usually be necessary. At night or in bad weather conditions all the directions may need to be passed by means other than direct voice. Loud hailers, radios, mobile phones and visual signals all have their uses. If there is a mobile phone on board make sure the number is known so that it can be passed to the towing vessel. Have writing material handy to also take the necessary details from the towing vessel.
      The towing vessel may have crew inexperienced in towing, in which case instructions and suggestions should be passed. The draft of the rescued vessel becomes very important if the towing vessel has less draft. The length of the tow is critical if significant wave action is to be encountered - the vessels should be at least two waves apart.
      If the vessel has steering capability advise the towing vessel and be prepared to steer to assist the tow. Usually the best course to steer will be to follow the wake of the towing vessel. A sharp knife should be kept handy to sever the tow either on instruction from the towing vessel or if a more dangerous condition arises on the towed boat. Crew on both vessels should as much as possible avoid placing themselves in an unprotected position in line with the towing line - just in case it parts while under tension.
     Positioning a towed vessel on a mooring in a confined area - especially in windy conditions, can be very difficult. The towing vessel can raft up to the rescued vessel before entering a restricted manoeuvering area or an attempt can be made to put the rescued vessel directly on a mooring. However the second method can get out of control resulting in unnecessary damage to other vessels. If the vessel is to be towed on to a mooring the tow should be shortened to about 2 boat lengths and the towing vessel can first take the mooring and pass it on to the rescued vessel. However, in a crowded anchorage, there must be sufficient room behind the rescued boat for this to be attempted. Alternatively a guide rope can be prepared - a rope about 1 metre long with an eye in both ends and a large snap hook in each eye. It is carried on the towing vessel so that as it passes the mooring line one snap hook is put on the mooring line and the other snap hook attached around the towing line as to allow the towing line to run through its snap hook. The towing vessel continues slowly pulling the rescued vessel to the mooring. The device cannot be expected to work if there are knots in the towing line that can't pass through the snap hook.

Rafting The surest and safest method to place the rescued vessel on a jetty or a mooring is by rafting. This is best achieved by securing the vessels together so that the stern of the rescued vessel is about midships of the towing vessel. Four lines are needed - a fore and aft spring and a fore and aft breast line - all from the towing vessel. Fenders will be needed to minimise damage and a foredeck hand will be needed on the rescued vessel to pick up the mooring.

The line(s) required for securing to a jetty will depend on the circumstances (wind, current, water depth, other vessels and the amount of room available). In most circumstances the simplest technique will be to nose in so that a bow line from the rescued boat can be secured to the jetty. Other control lines can then be rigged either with or without the assistance of the towing vessel.
Common courtesy demands that the towing vessel should be compensated for at least the fuel expended during the towing operation.

WIND CHILL

Wind chill is based on the rate of heat loss from exposed skin caused by the combined effects of wind and cold. As the wind speed increases, heat is carried away from the body at an accelerated rate, driving down the body temperature. The wind chill temperature, an "apparent" temperature, gives us a better estimate of how cold it really feels outside. The measure of the rate of heat loss based on air temperatures and wind speeds is not a temperature, but it allows us to understand how quickly heat is lost to the wind.
The chart gives a guide as to how much colder it really is when the body is exposed to wind. The effects are less when the base temperature is warmer. At the temperatures shown a 20 Knot wind will drop the effective temperature by about 6 degrees C - a considerable change.

WIND SPEED (Knots)	TEMPERATURE (C)
0	+4	+2	-1	-4
4	+2	-1	-4	-7
9	+1	-3	-6	-9
13	0	-4	-7	-10
17	-1	-4	-8	-12
22	-2	-5	-9	-13
26	-2	-6	-9	-13
30	-2	-6	-10	-14
35	-3	-7	-11	-14

WIND CHILL CHART

All numbers have been rounded to the nearest whole number.
Note that the effect of wind chill is greater as the still air temperature decreases

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