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Old 06 October 2010, 13:22   #1
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bow steer

why does bow steering hapen more in a following sea?? Ive never worked out the science
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Old 06 October 2010, 18:21   #2
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Sounds interesting! Describe this "Bow steering" I've never encountered this. Perhaps this is what some people call a "breach"?
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Old 06 October 2010, 19:04   #3
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Sort of an explanation here http://www.ifish.net/board/archive/index.php/t-743.html

"Code Brown"

I never noticed it on the Humber.
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Old 06 October 2010, 19:51   #4
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In a following sea ,the stern lifts ,,picks up ,,on a wave and as the boat is pushed forwards ,,surfs ,,the bow then being lower starts to dig in deep which can then act like a rudder and slows ,any sideways movement caused by the wave on the stern then makes the bow sheer direction ,unless its corrected by steering or slowing down ,, the stern will then in effect piviot on the bow, swing around and broach to and with a possible beam on capsize .

depending how deep a forefoot there is on the bow ,,with fast boats they dont have them ,,but boats such as the north east fishing coble are notorious for broching to in a following sea as the bow is much deeper than the stern,

one reason why in a following sea ,some boats will tow a drouge or a long rope behind the boat to help stop it from broaching to , i used to tow a few crab pots behind my old fishing boat



pic, of a northeast coble with a deep bow or forefoot ,,fantastic sea boat but in a following sea they can be a bit tricky ,
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Old 07 October 2010, 13:32   #5
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In a following sea ,the stern lifts ,,picks up ,,on a wave and as the boat is pushed forwards ,,surfs ,,the bow then being lower starts to dig in deep which can then act like a rudder and slows ,any sideways movement caused by the wave on the stern then makes the bow sheer direction ,unless its corrected by steering or slowing down ,, the stern will then in effect piviot on the bow, swing around and broach to and with a possible beam on capsize .

depending how deep a forefoot there is on the bow ,,with fast boats they dont have them ,,but boats such as the north east fishing coble are notorious for broching to in a following sea as the bow is much deeper than the stern,

one reason why in a following sea ,some boats will tow a drouge or a long rope behind the boat to help stop it from broaching to , i used to tow a few crab pots behind my old fishing boat



pic, of a northeast coble with a deep bow or forefoot ,,fantastic sea boat but in a following sea they can be a bit tricky ,
sounds feasable, but if your fast, the wave shouldnt have much force on stern will it??
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Old 07 October 2010, 16:24   #6
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sounds feasable, but if your fast, the wave shouldnt have much force on stern will it??
I'm guessing that something named after a cow (Daisy ... ) is probably not all that fast when being chased by a big sea
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Old 07 October 2010, 16:45   #7
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sounds feasable, but if your fast, the wave shouldnt have much force on stern will it??
You'd think that, but if your bow digs in and the stern lifts, the force needed to pivot the hull might not have to be that strong.
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Old 08 October 2010, 12:14   #8
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I've been looking recently at the ground handling characteristics of tailwheel aircraft as opposed to tricycle undercarriage planes. (Don't ask) Apparently, tailwheel aircraft never want to go in a straight line and will swerve off course unless prevented by instant application of lots of rudder. Apparently this is because the centre of gravity is behind the main wheels.

I wonder if it follows that, when a fast planing boat digs it's bow in, the centre of drag (or the centre of bouyancy) moves forward of the centre of gravity of the boat, making it directionally unstable.

Thinking about it, I think most fast planing boats are not directionally stable at slow hull speed, needing constant helm input. Could this be because the centre of bouyancy/drag is forward of the C of G? When planing the C o B/drag obviously moves aft as half the boat is out of the water. With C oG ahead of C o B the boat becomes directionally stable.

Above based on limited understanding of elementary physics.
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Old 08 October 2010, 17:49   #9
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why does bow steering hapen more in a following sea?? Ive never worked out the science
How was your engine trim?
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Old 09 October 2010, 03:22   #10
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I was out in some moderate Sea's yesterday and deliberately tried to induce some Bow steer (broach/breach) by travelling in a following Sea. I experimented (unsuccessfully) with different speeds and trim angles. Perhaps the conditions weren't bad enough!
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