GLOSSARY ENTRY (DERIVED FROM QUESTION BELOW) | ||||||
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08:07 Sep 18, 2008 |
French to English translations [PRO] Tech/Engineering - Ships, Sailing, Maritime | |||||||
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| Selected response from: ormiston Local time: 00:02 | ||||||
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Summary of answers provided | ||||
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5 +1 | keel bulb |
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4 | torpedo shaped weight |
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4 | ogive |
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3 | ballast / counterweight |
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ballast / counterweight Explanation: The keel on a "normal" sailing yacht consists of a large steel aerofoil hanging vertically below the boat, tipped with a large torpedo shaped lump of lead. This keel serves two purposes - first the fin provides horizontal "lift" which discourages the boat from being blown sideways by the wind, and second the large lump of lead ballast provides a righting moment that discourages the boat from heeling over. The keel designer thus has to design it to do two different jobs - and as is always the case when something is designed to do two jobs, it does neither well. When the boat is upright, the lead ballast provides no righting moment and is just dead weight, slowing down the boat. And as the boat heels over, the fin also inclines, so reducing its efficiency at reducing sideslip. from http://fenderkicker.typepad.com/fenderkicker/tech/ there's a good picture too. for info: my search was google.co.uk -- image / keel lead you have to go to .co.uk from France to avoid google deciding that you wand your results in French... |
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torpedo shaped weight Explanation: As I see it, the term posted is a definition of the 'bulb' - I've found this equivalent: "Ever been to a regatta, and when you have looked at all of the model yachts, have you ever noticed the different keel bulb shapes? I have seen long bulbs, short bulbs, fat bulbs, and skinny bulbs. Why are there so many different shapes? Which bulb shape is best? If you remember, when an object is moving in water, drag is created, and slows the boat down. For model yachts to keep upright while sailing, they require a weight at the bottom of the keel. All weights are made of lead, and are in the shape of a torpedo. The question is what is the best torpedo shape that gives the best performance with the least drag. Torpedo keel bulbs don't provide any lift to the keel, they are just there for the ride to keep the boat upright. The goal of designing a bulb is to minimize drag. According to the U.S. National Advisory Committee for Aeronautics (NACA), if the bulb's volume of weight is constant, the size and length does make a difference. A long bulb with a small diameter produces a large wetted surface and frictional drag, but is low in form drag. A bulb that is short and fat produces a low wetted surface and frictional drag, but is large in form drag. Both of these two extremes will not give the performance that the model yachter wants. There must be a happy medium between the two. |
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keel bulb Explanation: 28 Jun 2006 ... Radio-controlled sailing model | Ballast and Keel Bulbs. Ballast: Many modelers are shocked to find how difficult and costly it can be to ... sailingmodels.blogspot.com/2006/06/radio-controlled-sailing-model-ballast.html - 16k -------------------------------------------------- Note added at 48 mins (2008-09-18 08:56:05 GMT) -------------------------------------------------- then I would use ogive shaped lead ballast. |
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Notes to answerer
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ogive Explanation: it's an architectural word and I've never heard it in a sailing context but why not? OGIVE 1. Architecture. The diagonal groin or rib of a vault, two of which cross each other at the vault's centre. LME. 3. a. Architecture. A pointed or Gothic arch. M19. b. A thing, esp. the head of a projectile, having the profile of an ogive; such a profile. E20. * ogived: adjective consisting of an ogive or ogives; having the form of an ogive or ogee: E17. OED -------------------------------------------------- Note added at 22 hrs (2008-09-19 07:00:46 GMT) -------------------------------------------------- The term “Ogive” is commonly used to describe that specific point where the curving part of the bullet nose begins–i.e. where the bearing surface ends and the curved part begins. http://accurateshooter.wordpress.com/2007/07/10/283/ |
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