BOAT HANDLING Chapter 4 BOAT HANDLING OF WIND AND WATER
Before we cast off and go fishing, it might help to think about the nature of the environment we’re entering and see how dissimilar it is to the landlubberly world we’re familiar with. Compare driving a car to manoeuvring a boat. Ashore, the road is stationary beneath the car’s wheels. There may be some buffeting from strong winds but the driver can expect his vehicle to remain steadily on track, following the path he has chosen for it.
The boat on the other hand is carried on a moving platform of water that can flow in any direction, depending on currents, tides and other factors. We’ll call them all ‘streams’ unless the type of stream makes a difference. Then there’s the effect of the wind. A boat’s grip on the water is much less than that of tyres on tarmac, so even a modest breeze can blow it off course. This may all sound like bad news – and it has to be admitted that it can cause problems – but, once you understand the principles, you can put them to good use. Indeed, you can make boats perform manoeuvres that cars are incapable of. For instance, boats can move directly sideways, perhaps to slot into a gap only inches longer than themselves. This trick is known as ‘ferry gliding’ – a technique employed by small ferries and other craft since the earliest days of power. Let’s see how it’s done.
Ferry gliding
Stand on a busy quayside and watch the tripper boats enter and leave. One boat might be waiting a few metres off, apparently motionless, while another is busy alongside pulling up its gangplank and casting off its mooring lines. Soon the second boat leaves and, without fuss, the waiting one slides into the now vacant berth to take its place. Now, you might think that the waiting boat was just adrift with its engine in neutral, but that could not be so. A strong tidal stream runs along the quay and would have swept it away. What it was actually doing was pointing its bow exactly into the stream and maintaining just enough forward power to overcome it – ‘stemming the tide’ as it’s called. If, say, the stream was running at two knots, the boat would have to maintain two knots through the water to remain stationary. And neither was the helmsman sitting back having a cuppa with his feet up because that phrase ‘exactly into the tide’ is extremely important in keeping that boat in position. If the boat were allowed to skew a little, say, to port, the boat would crab sideways in that direction, and vice-versa. Done deliberately, that
4
Fig 4:1 The combined forces of the stream and the boat’s course and speed through the water result in a sideways movement
crabbing action is the secret of ferry gliding and lies at the base of so many useful manoeuvres. In such circumstances the tide is our friend not our enemy.
RYA Seamanship for Sea Anglers 23
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84 |
Page 85 |
Page 86 |
Page 87 |
Page 88 |
Page 89 |
Page 90 |
Page 91 |
Page 92 |
Page 93 |
Page 94 |
Page 95 |
Page 96 |
Page 97 |
Page 98 |
Page 99 |
Page 100 |
Page 101 |
Page 102 |
Page 103 |
Page 104 |
Page 105 |
Page 106 |
Page 107 |
Page 108 |
Page 109 |
Page 110 |
Page 111 |
Page 112 |
Page 113 |
Page 114 |
Page 115 |
Page 116 |
Page 117 |
Page 118 |
Page 119 |
Page 120
