vertical bow motion - SailNet Community

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Go Back   SailNet Community > Skills and Seamanship > Learning to Sail
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Old 01-19-2012
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vertical bow motion

Am I correct in stating that putting the bow down (by luffing?)slows the boat?
Does the bow being lower aid in slowing or is that merely a way of describing the act of slowing?
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Old 01-20-2012
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Do mean turning the boat into the wind while sailimg hard on the wind (upwind) ?
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Old 01-20-2012
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Quote:
Originally Posted by Sailinsolo View Post
Am I correct in stating that putting the bow down (by luffing?)slows the boat?
Does the bow being lower aid in slowing or is that merely a way of describing the act of slowing?

Generally 'putting the bow down' means bearing off from close hauled, quite the opposite of 'luffing', which is pinching/pointing the bow up towards the wind.

Luffing does reduce heel and slow the boat; however you need to be careful not to unintentionally tack if you're not prepared for it.
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Old 01-20-2012
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Boat trim counts in addition to sail trim...a low dragging aft creates...well...drag in the water...a dragging bow creates a submarine. Racers move crew/live ballast fore and aft as well as port and starboard.

...but I don't think this is what you're talking about in the OP.
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Old 01-20-2012
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Often times allowing the boat to luff up a bit will make it seem as if the bow is going down, as the reduced heel of the boat changes ones perspective. This reduced heel often causes a bit more drag since the wetted surface area of the boat will increase a bit. However, the main reason the boat slows is both the reduction in motive force and the increased drag produced by the sails as they luff and become inefficient.
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Old 01-20-2012
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A yacht driving to windward at or near hull speed generates a wave form with crests at the bow and stern and a hollow amidships between the two. In essence, the yacht's displacement creates the wave and the driving force powers her up the wave. When the power is suddenly taken off--by luffing, the bow initially pitches up as the boat is no longer has the power to ride up and onto over the residual bow wave and then suddenly drops while the wave hollow amidships, which still carries the energy of the formerly faster speed, fills and proceeds to raise aft as the yacht's inertia "carries her way", forcing the yacht into a "bow down" position. The yacht's inertia may then lead to "hobby-horsing" for a few minutes before she reaches a new equilibrium. The "bow down" effect is a consequence and not cause in a luffing situation.

FWIW...
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Old 01-20-2012
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You might be mixing terms.
If you put the tiller down (to leward) the bow will point up into the wind causing the jib and/or main to luff which will reduce heeling pressure. "Down" can refer to a horizontal as well as verticle direction. Horizontally it almost always means to leward or down wind.
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Old 01-20-2012
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Quote:
Originally Posted by Sailinsolo View Post
Am I correct in stating that putting the bow down (by luffing?)slows the boat?
Does the bow being lower aid in slowing or is that merely a way of describing the act of slowing?
With reference to course or point of sail I prefer the terms "head down / bear away" or "head up" - which are unambiguous.

eg

To the helmsman : "The jib is luffing, head down slightly"
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