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Can someone help me understand the differences between these three terms? Even the mighty Wikipedia has left me scratching my head a little. Thank you!!
 

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Knockdown - Storm comes up and you didn't reef, drop sails quick enough. Strong wind gust, your boat is knocked on its side i.e. 90 degrees. Usually come right back up but can lead to .....

Capsize - Boat rolls over mast points down keel points up. The boat may or may not right itself depending on design.

Broach - Might not have this one right but, my understanding is the stern swings to one side leaving the boat pointing in a direction 90 degrees or so from what it's heading was. Best example would be running with the wind, wave catches stern, stalls the rudder, stern is moving faster than the bow, stern swings to one side and now you're parallel to the waves. This can also happen with weather or lee helm and sudden strong gusts of wind.
 

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Learning the HARD way...
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Broach - boat is pushed to an extreme angle of heel (40º+) - usually by wind

Kockdown - boat is pushed to an very extreme angle of heel (50º+) - usually wind or wave. Boat may right itself. (boat was knocked down, but popped right back up)

Capsize - boat is turned upside down (90º+)

Others will weigh in, and tell you something different ;):)
 

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Freedom isn't free
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Knockdown - boat goes over, might splash the occupants, usually comes with a burst of air/gust... sometimes water over the railing, into the cockpit (no biggy).

Broach - you, like an idiot (sorry chastising my self on this one) decided that steering UP with the spinnaker up and oscillating, was smarter than steering down, usually directly preceding is a massive gybe, then an overcorrection by an over-zealous helmsman (pronounced massive NEWB) spin rolls hard to leeward, pulling you down with the gybe, then HOLDING your boat down, generally filled with water like a HUGE sea anchor. Broaches are FUN, because unlike a knockdown where you bounce right back up again, the broach will hold you down until you FIX your stupid mistake (hint RELEASE THE HALYARD YOU NITWIT, again sorry that was for me).

Capsize - generally reserved to board boats (centerboard), as keel boats generally remain upright and tend to get that way without a broach... boat is over mast in water, sometimes upside down (turtle), usually for a capsize. Again a keel boat doesnt' like to be that way, the keel makes sure of it. Now if you are unlucky enough to have your keel fall off (all due respects to the recent tragedy with the Beneteau 40 Cheeky Rafiki) then capsize is nearly unavoidable. its not unusual to capsize a laser, a sunfish, a 505, or even a decent number of smaller day sailors... all centerboarders. It's POSSIBLE to capsize a keelboat, but it requires the cabin to fill with water, or lazarettes or both. Look up J/24 capsize, and you'll see what I mean. My Capri 25 also has a similar design flaw, where the lazarettes open to below, and can flop open on a knockdown, fill with water, scuttle the boat, or capsize it, or worse yet, sink it.

Hope that's clear.

Knockdown (looks like they were attempting to do this intentionally):
https://www.youtube.com/watch?v=w00suzaDh_A

Broach (in glorious fashion, note he too steered to high with the spin up)
https://www.youtube.com/watch?v=fJy7HVDz2OI

Capsize, note they gybed, but were still to low, a scramble to high side would have kept them dry! Boat looks similar to my Capri 14.2. Start watching around 1 minute. If you watch it through, you'll note the crew waited until they got to shallow water to get back aboard (cheating, its a real PITA to get aboard once its totally righted, easier to ride your way up while it's righting).
https://www.youtube.com/watch?v=Xl9hFqCN840
 

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Agree with above.

Capsize means the hull has lost stability and ain't coming back up.

Broach to me means you got sideways to forces of wind, or sea, or both that you shouldn't have, and are being rolled, or held down. this can be either from a knockdown (heeled way to leeward and headed up too high off that run) or from a bear-off-too far with kite up, deep roll to windward which quickly becomes leeward in a crash jibe, and a broach as you head "up" on your new involuntary tack to where you're beam-on to the seas and new leeward rail deep in the water (also affectionately known as the "death roll" or the "burnout").


Wait, are we sure we want to get into all this gory stuff in the "Learning to Sail" forum??? ;-)
 

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Crealock 37
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You don't need sails or a spinnaker to broach. Ever had one of those real sporty landings taking the dink to the beach through the surf?
 

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Here's a definition: "broaching" - The unplanned turning of a vessel to expose its side to the oncoming waves. In heavy seas this could cause the boat to be knocked down.

So, this is something that can happen when sailing on a broad reach or run. The action of the wind and or waves pushes the stern down and you end up broadside on to the following wind and waves. This can then lead to a "knock down" where the mast goes horizontal (in the water) and maybe a capsize if the boat turns upside down.
 

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Broach: "That was some sh*t."

Knockdown: "That was some bad sh*t!"

Capsize: "OH, S H I T !!!!!!!!!!!!"
 

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"Broach - boat is pushed to an extreme angle of heel (40º+)"

Wait... 40 degrees is extreme angle of heel? I tend to start thinking that maybe it's about time to start adjusting my sail trim at about 45 degrees. But I'm new at this. Should I try to keep heeling to a lesser amount?
 

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Bristol 45.5 - AiniA
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Knockdown - not just wind, a large wave at the wrong time can have a lot to do with this (ask me how I know)
 

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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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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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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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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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bell ringer
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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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Farr 11.6 (Farr 38)
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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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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.
 

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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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