EMERGENCIES 12 Search pattern


If you fail to find the MOB you must search for him – and do so methodically. The best method is to conduct what’s known as an ‘expanding box search’. Here’s how to go about it.


■ Drop a floating marker nearest to the point where you think the MOB might be. This will be your ‘datum point’, the start of your search pattern.


■ To keep matters as simple as possible, motor in a northerly direction until you can still just see the datum point, the distance you have motored we shall call ‘D’, meaning ‘detection range’. If the boat has no means of measuring distance, it might be helpful to note the time it took and use this as your reference.


■ Then turn right and motor the same distance (or time) in an easterly direction.


■ Then turn south. You will see from the diagram that the length of the leg increases by one D every two legs – thereby expanding the box. Continue until you locate the MOB.


3d d 3d d 2d 2d


Fig 12:3 Effects of stream and wind


Because both the MOB and your search pattern will be drifting with the stream, you should make no allowance for it. However, boats with high superstructures may need to allow for the effects of the wind, which will affect them much more than the MOB.


Most GPS sets have an MOB button which records the position and gives the course and distance back. You must remember that this is the position over the ground and that the MOB will be carried downstream and could be some distance away by the time you return.


RYA Seamanship for Sea Anglers 87


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