very old saling boats...did thwy keels

gary3029

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was watching an old film the other day with these large wooden sailing fighting boats which had masses of sails. Was wondering what kept them from going over. I assume they did'nt have keels in them day
 

Danny

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Guess it's only the ballast that counts. The other items would be drunk, shot and eaten so you couldn't rely on them.

Presumably you could run out the guns on the weather side to stiffen her up and closing the lower gun ports on the lee side would probably be a good idea as well!
 

William_H

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I imagine you have looked at the obvious pendulem like shape of a modern racing yacht with fin keel and can understand how the bulb at the bottom keeps the boat upright and wonder how an old sailing ship stayed upright. Well it is not as simple as that.........

I think that mostly they relied on a wide bilge ie flat bottom to give stiffness in a breeze with sail up.
If you connsider that a perfectly semicircular bottom as in a barrel has no tendency to stay upright wheras a wide plank will float quite flat and is not easily tipped over.
A ship that has a flat bottom or specifically is wide at the point where the bottom curves to become the sides. As it heels over the whole weight of the ship lifts up unto the bouyancy of the side of the bottom. This bouyancy tends to counteract the heeling.

The extreme example is the catamaran where all righting power comes from the bouyancy of the widely spaced hulls.

So in an old sailing ship or indeed modern steam ships they stay upright from the shape of the hull. The internal balast does add some righting power by being lower than the centre of bouyancy but has nothing like the power of a bulb on the botom of the long fin keel. The centre of bouyancy is that theoretical point around which the boat pivots as it rolls. (it does move as the ship rolls as parts of the hull go under water to add to the bouyancy) The centre of gravity needs to be below the centre of bouyancy and any weight below the centre of bouyancy will help keep it upright.

The other aspect of the keel is the job of stopping sideways movement. Along relatively shallow wooden keel was fitted. Again this was not very efficient because the aspect ratio was very low compared to a modern fin keel. This relates to the water having higher pressure on the leeward side simply flowing down under the keel to the low pressure side rather than havin
g the higher pressure keep the boat ot windward. by comparison the modern fin keel has along path from one side to the other around the tip of the keel. So only a small prortion of pressure is released this way. This flow incidentally also causes turbulence and so drag making fin keel more efficient.
waffle waffle waffle from olewill
Even if they could fit a fin keel to the victory the draft would be prety deep for ports.
 

oldharry

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Most of these old ships relied on form stability (the wide plank) and ballast to keep them the right way up. Commercial ships always sailed 'in ballast' if they had no cargo - not for comfort, but because they wouldn't stay upright without it. Capsize was not limited to Vasa and Mary Rose either, and was one of the regualr hazards of seagoing life under sail. I dont remember the name but I remember reading the account of a Frigate that capsized in a squall off the eastern Isle of Wight around 120 years ago.

More recently there was the sail Training Ship Marques capsized off the east coast of America, after being caught by a sudden squall, sadly drowning most of those aboard.

Both these ships were apparently thrown on their beam ends after being caught with far too much sail up. They then filled and sank before they could be bought under control again.

Eric Newby in his 'Last Great Grain Race' (if you havent read it, its a must) describes the grain Clipper Moshulu before the war, sailing out with hundreds of tons of ballast (and a dead dog as a present from the Belfast Stevedores to add 'flavour') to keep her upright. On the return journey in 1939 he descrives a Southern Ocean storm, and recounts another ship having been 'driven under' in just such a storm with loss of all hands. Presumably it had broached (as Moshulu nearly did on one occasion) and rolled over. I cannot somehow imagine a grain clipper just pitchpoling like the famous Beken 'Silk II' Photo.
 
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