Some thoughts on boat handling and safety that I posted in another thread (about handling boats in waves). A bit war and peace but hopefully it will be useful for some:
A couple of thoughts; there has been some great advice here and (no disrespect) some not so good. I don't want to appear a know all but it is really important people understand these issues, and you could say I have a fair bit of background in these matters.
1. Always, always, always wear a life jacket. Always. Preferably an auto-inflate job in case you get knocked uncoscious as you go in the water (more common than you think). Oh yes I nearly forgot, always wear a life jacket.
2. Immersion suits are highly recommended when the water is below 18C, and should be obligatory below 16C. This is standard practice in many organisations at sea. You'd be surprised how quickly hypothermia sets in.
3. There are, in fishing boat terms, roughly 2 types of hull: displacement and planing. Displacement hulls (typical wooden fishing boat-type) displace the water ie move through it. These are more stable but not as fast as planing hulls, which are designed to plane on top of the surface above a certain speed (such as rigid inflatable boats or RIBs), and usually have more powerful engines to enable that.
4. Strictly sea terminology rather than lakes, but be aware of sea and swell. Sea is the waves made directly as a result of wind that is blowing at a given time. They will vary with the wind strength and direction. The variation with strength is obvious, but direction matters too: the waves will be a lot smaller if the wind is blowing off the shore of a lake and you are 100yds from the shore from which the wind is blowing than if you are 1 mile away from the shore. The wind will have had a mile to increase the sea state (the size of the waves), and they will be much bigger. Hence the reason for seeking the 'lee' of the land ie get in the shelter of it so that it is between the wind and you. The distance the wind has to blow over uninterrupted across the surface of water is known as 'fetch'. So, being in a boat close inshore when the wind is blowing offshore is limiting the wind's fetch. The same wind speed acting across a small body of water cannot build the sea to the same extent as the wind acting on a large expanse of water therefore the sea state on the smaller water is said to be 'fetch limited'. This has obvious benefits. Swell is the waves that result from wind acting on the water's surface either at distance from your location or some time ago. These waves are the large, rolling ones that make good surf on ocean coast beaches. Remember, sea can be superimposed onto swell, creating a bigger problem than may be anticipated from the weather forecast alone. You may also have sea and swell from opposing directions, which can make boat handling difficult to say the least. Swell is more of an issue at sea than on UK lakes, but it pays to be aware.
5. Be aware of drift. Even a strech of water with little fetch will have little effect on reducing your boat's drift, and drift can be dangerously imperceptible. It can put you aground, as the wind acts the same on your boat regardless of the sea state. Try this: with your boat stationary pick two objects on the shore that are exactly in line in your line of vision. Keep still but keep looking at them and when they start to spread apart, you are drifting. You will know your direction from the way they spread. If you can't see a spread, try picking two objects at 90degs from the ones you were initially looking at; you could very possbily be drifting directly away from or towards the place you initially picked. The second 2 objects displaced by 90degs will tel you this, as they will move apart. If neither set of objects move, then happpy days. Oh, and drift can be due to wind, current or tidal stream (where applicable), orany combination of the 3. Boats with higher freeboard (distance from waterline to top of hull, or gunwhale) with a correspondingly shallow draught (depth of hull under the water) will drift more than a vessel with lower freeboard and/or deeper draught, but only when drift is caused by wind. If the drift is mainly tide and/or current, the effect will be the same regardless of type or size of boat.
6. Handling the boat in waves. A planing hull will usually have most of the weight at the back, and will, proportionally, be lighter forward than the displacement hull. It therefore follows that this boat is more susceptible to being flipped up. In fact any boat is when the weight is displaced toward the stern of the vessel. Try to distribute weight evenly both along and across the boat for maximum stability. The issue of flipping the boat up bows first and going over backwards is usually due to the wave pitching the bow up and the wind getting under it, and affects RIBs and the like particularly, especially small, flat bottomed ones such as Geminis. To avoid it, slow down. It may be that you make very little headway and simply keep your station (known as 'heaving to') while riding the storm out. Not usually an option in small boats, but keeping head roughly to sea is a valid way of staying safe. If you are taking water over the bow, then reduce speed and distribute weight a little to the rear, to make the bow sit a little higher. Running across the waves will cause you to roll, the disadvantages of which are fairly obvious, but this may be better than flipping over backwars, or coming on to what was mentioned by Grouse; the wave coming over the stern. Remember, a boat only floats because the amount of air in it has a greater effect than its weight. It's known as the reserve of bouyancy. If you top up a wooden hulled boat with kit and then add some water, the cumulative effect is to remove the reserve of buoyancy. Once gone, the boat sinks. Anyway, waves from astern. The wave breaking over the stern is known as 'pooping' a vessel, and is undersirable, not least due to the name... The other risk is of broaching, and is more of a risk to a displacement hull with a conventional rudder rather than an outboard. Running down sea (waves coming from behind you), slower than the wave speed, with the waves overtaking you, poses the greatest risk, especially if you are at abouit 60% and greater of the wave speed ie a similar speed to that of the waves. The risk is increased if the wavelength is the same as the length of the boat. The risk is that the boat surfs on the wave and the boat is going slightly faster than the wave, it falls down the face of the wave and increases speed. The bows pitch in when the boat reaches the bottom of the wave (the trough) and as the rudder needs water passing over it as speed for it to work (if you move the rudder in a stationary boat the boat will not turn but it turns more easily for a given rudder angle the greater the speed), it loses effect, as the relative speed of the rudder through the water is reduced to about 30% or less of the speed at which the boat is moving. This will leave you unable to correct any shear that results from the bows digging in, and the boat can then swing suddenly across the waves (or 'beam on'). Waves coming from the side can then break over the boat and/or capsize it. This is known as broaching and is exceptionally dangerous. So, try to head into the waves at slow speed, or travel down sea at less than 2/3 wave speed. Please note that doing this can increase the risk of waves breaking over the stern (pooping), so it can be a no-win situation, in which case it really is better to be sure of the conditions and not go out. Or, if the waves are small enough, go across them. If not, and your course to get to safety is across the waves, go up into the waves, at a slight angle towards where you are going, then wait for a lull and turn quickly down sea, and repeat until you zig zag your way to safety. This should only be attempted if you are caught out there and there is no alternative. The point is here that there simply is not always a way out of trouble, other than avoiding it in the first place.
7. Wave length is important. The bigger the wavelength, generally the better as you have more time to react between waves.
8. Always, always know what the weather is going to do and if in doubt, don't go out.
Some of this sounds a bit melodramatic, but don't take any chances. Similarly, some of it may appear long-winded and technical. For that I make no apologies; if it simply serves to make people think "I don't know much about this - I'd better get some tuition and swot up" then I will have done my job. Thanks for reading and be careful in boats. Any questions, feel free.
Oh yes, wear a life jacket.
Last edited by Bumps; 17-01-2010 at 10:03 PM.
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how stupid...,,, Royvs the same as myself obvious only after you read it. That,s what prompted this thread.
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