That is exactly what he was saying as I read it. -----Original Message----- From: CnC-List [mailto:cnc-list-boun...@cnc-list.com]On Behalf Of dwight Sent: Thursday, December 05, 2013 7:44 PM To: cnc-list@cnc-list.com Subject: Re: Stus-List Now Stability - was List halyards again( 10 aloft = 1on the rail )
Forgive me for this Chuck, but some things seem obvious to me.however, sometimes I get confused.but if buoyancy is ever less than displacement would that not be a submarine or sunken vessel and if COB is below COG would she not be inclined to topple over??? -------------------------------------------------------------------------------- From: CnC-List [mailto:cnc-list-boun...@cnc-list.com] On Behalf Of Chuck S Sent: December 5, 2013 8:38 PM To: cnc-list@cnc-list.com Subject: Re: Stus-List Now Stability - was List halyards again( 10 aloft = 1 on the rail ) Neil, Sorry, I'm heavily biased by life experience, logic, hundreds of books on boats. Read Skene's Elements of Sailboat Design. Center of buoyancy on a keelboat is always above center of gravity. On my boat the CB is a foot above the WL while the CG is 4 feet below. The Drawings prove it. Buoyancy must exceed displacement also. Sailboats face different requirements than cruise ships so should never be compared. Another source: http://www.engineeringtoolbox.com/centre-gravity-buoyancy-d_1286.html Chuck Resolute 1990 C&C 34R Atlantic City, NJ -------------------------------------------------------------------------------- From: "Neil Gallagher" <njgallag...@optonline.net> To: cnc-list@cnc-list.com Sent: Thursday, December 5, 2013 4:49:53 PM Subject: Re: Stus-List Now Stability - was List halyards again( 10 aloft = 1 on the rail ) Marek: Picture a large cruise ship: its draft might be 10 m, so its vertical center of buoyancy is a little more than 1/2 way from the keel to the waterline, say 6m above the keel. The center of gravity is not only above the center of buoyancy, it's well above the waterline, sometimes 20 m above the keel, yet unless it happens to buzz too close to an Italian island, it will stay upright. Or picture a small sailing dinghy without anyone on it, the CB again is below the waterline, while the CG is well above, but they don't capsize until the sheets are pulled in. A yacht's form stability is the same as a ship's; for sure, adding a keel to a yacht improves the stability by lowering CG, but it does not necessarily put the CG below the CB, in fact it usually doesn't. (There is a point called the metacenter, which is an imaginary point on centerline through which the buoyancy force always acts, that is the point which must stay above the CG for positive stability...but now we're getting deep into naval architecture.) Check out the illustration below: http://www.troldand.dk/en/?The_Yacht:Stability#.UqDzkvIo5Ik Neil Gallagher Weatherly, 35-1 Glen Cove, NY -------------------------------------------------------------------------------- No virus found in this message. Checked by AVG - www.avg.com Version: 2012.0.2247 / Virus Database: 3658/6393 - Release Date: 12/05/13
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