knockdown vs. capsize vs. broach - Page 2 - SailNet Community
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post #11 of 21 Old 08-07-2014
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Re: knockdown vs. capsize vs. broach

Knockdown - not just wind, a large wave at the wrong time can have a lot to do with this (ask me how I know)

Back home on Lake Ontario after something over 36,000 nm circumnavigator. Not surprisingly there is a lot of stuff I want to get done on Ainia both cosmetically and functionally. Getting an early start so it will be ready to go for next summer (Lake Superior?).
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post #12 of 21 Old 08-07-2014
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Re: knockdown vs. capsize vs. broach

I think for a broach to occur the rudder has to stall if not the boat will simply round up. Burying the rail is not a broach. I have raced on boats where burying the rail does happen quite often. On these boats the stanchions and lifelines are removed, mostly for sheeting but a tertiary benefit is there is less drag when the rail is buried.
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post #13 of 21 Old 08-07-2014
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Re: knockdown vs. capsize vs. broach

One definition for the word broach is to break through the surface from below. I always thought when you broach while sailing you lose control of the boat because your rudder has lost its ability to steer. So maybe it is when you heel enough the rudder breaks the surface (hence the name "broach") and you lose control of the boat. I am not offering this as an answer, more of a question.
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post #14 of 21 Old 08-07-2014
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Re: knockdown vs. capsize vs. broach

A broach is the thing Johnny makes out of the weather report in Airplane!


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post #15 of 21 Old 08-07-2014
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Re: knockdown vs. capsize vs. broach

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I always thought when you broach while sailing you lose control of the boat because your rudder has lost its ability to steer.
The rudder stalling is the result of the broach caused by a spirited gust or if sailing DDW the boat can start to rock from side to side and the rocking can get more extreme to the point of losing stability where the boat rounds up and then becomes pinned. This can result in a gybed broach. Though I have experienced numerous broaches from these two causes, I have never had a gybed broach.
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post #16 of 21 Old 08-07-2014
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Re: knockdown vs. capsize vs. broach

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Though I have experienced numerous broaches from these two causes, I have never had a gybed broach.
Correction - I forgot doing it twice in a ten minute span at night during an offshore race.
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post #17 of 21 Old 08-08-2014
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Re: knockdown vs. capsize vs. broach

knockdown - cry like a little girl

broach - scream like a little girl

capsize - water fills your mouth when you try to scream
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post #18 of 21 Old 08-08-2014
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Re: knockdown vs. capsize vs. broach

I was not going to weigh in on this but it does not seem like anyone has nailed this one in terms of the way that these terms are used in yacht design. This is not all that complex.

A knockdown refers to the rapid change in heel angle from a acceptable, normal heel angle to something beyind that point.

A broach refers to a rapid change in direction (yaw) that will usually lead to increased heel or perhaps a knockdown, but nothing in the definition of a broach requires either to occur.

A capsize is heeling to the point where stability switches from positive stability (trying to turn upright) to negative stability(the point at which the boat no longer tries to right itself.)


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post #19 of 21 Old 08-08-2014
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Re: knockdown vs. capsize vs. broach

Done all three, but only in small dinghies, thank God.
Knockdown - strong gust of wind puts the mast and sail almost flat on the water. That happens a lot when you sail hard, but it is relatively easy to correct.
Capsize - the sail and mast are in the water and are staying there. You have to do all kinds of gymnastics on your dagger board to right the boat. Often you need help to get out of that pickle.
Broach - the wind and wave conditions create situation where the boat is uncontrollable and very fast on it's way to capsize. Very scary and unpredictable. Have a nice short prayer composed for just that kind of occasion.

Be kind, for everyone you meet is fighting a hard battle.
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post #20 of 21 Old 08-08-2014
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Re: knockdown vs. capsize vs. broach

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Originally Posted by ScottUK View Post
I think for a broach to occur the rudder has to stall if not the boat will simply round up. Burying the rail is not a broach. I have raced on boats where burying the rail does happen quite often. On these boats the stanchions and lifelines are removed, mostly for sheeting but a tertiary benefit is there is less drag when the rail is buried.
Agree, broach is caused by loss of rudder control, usually by stalling (equivalent of airplane wing stall) the rudder. I think this can also happen on some boats when they are on the ear so far that there isn't much rudder left in the water.

So your carrying your spinnaker in too much wind, you head up a hair, the boat leans over a bit, you try to correct back down wind but the rudder is just dragging thru the water, it doesn't work, so the boat keeps heading up until the rail is in the water or worse, and you cannot fix it with the rudder. You gotta get rid of some sail or it just sits there on it's side...rudder is stalled, ineffective.

Or, your surfing down a wave, you get going real fast, you head up a little, the rudder stalls, and you lay over on your side or worse roll the boat over...like surfing in over a bar. Again a rudder stall, the rudder becomes ineffective.

At least that's what I thought.
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