Mark;
You are probably close in your surmise that the rail meat is very close to being directly over the center of mass of the boat when it reaches 63 degrees of heel. However, there is still a righting moment, though the moment arm is getting short. As it heels, the boat rotates around the center of buoyancy, not the center of mass. The center of buoyancy is above the center of mass (the closer they are when the mast is vertical, the more tender the boat. If the center of mass were above the center of buoyancy, the boat would turn turtle at the slightest provocation.) and the center of buoyancy moves to leeward as the boat heels because of the form stability of the hull. In more modern hulls than ours, with relatively flat bottoms and wide turn of the bilge carried from max beam to well aft, generate a lot of form stability. Hence the center of buoyancy moves quite a bit to leeward as the boat heels, while the center of mass moves some amount to windward. It is the lateral offset between centers of mass and buoyancy that provide resistance to heeling. Paul; I agree with your calculations, except that the length of the moment arms for the rail meat and the weight aloft need to be adjusted slightly to account for the leeward movement of the center of buoyancy. Add a few inches to the righting arm of the rail meat, and subtract the same number of inches from righting arm of the weight aloft. So at 20 degrees of heel, the 10 pounds aloft might have the same effect as 38 or 39 pounds on the rail. Now Ive not looked into purchasing any high tech halyards for my 38. What I have (7/16 Cajun XLE) is large enough in diameter to have a good hand and to not creep in the rope clutch. I have a Barient 27 halyard winch to preload luff of the main to 500 pounds or so and take up the stretch in the line when the wind is strong, and I really dont want to put much more load than that on the 3/16ths or ¼ inch Dacron cord that reinforces the luff of the main. If I trim the vang and the traveler right the load on the main from a gust of wind isnt going to change by all that much to generate more than an inch or two of additional, transitory stretch in the halyard. But I have recently purchased floating, high tech spin sheets. They needed to be about the same diameter as the old sheets in order to have acceptable hand and work on the winch drums. My floating lines are way stronger than they need to be, and consequently have no stretch (which, unfortunately, you kind of want in spin sheets). What I found is that the high tech, floating line was more than twice as strong as the old sheets, but only about 4 pounds lighter for 100 feet of line. So the saving for my main halyard would be around 2 pounds. If I went from 7/16ths XLE double braid to 3/8ths Spectra core the strength doubles, the stretch goes from 12 (@ 1300 pounds of load) to about 3, the halyard costs about $60 more, and the weight savings is about 3 pounds. The way I sail, I dont see that much value. In my experience the racers who salivate over decreasing weight aloft tend to be the same guys who have toothbrushes with the handle cut short, and who leave the seat cushions, locker covers, power cord, and all the beer and ice at the dock in order to save weight. Not that I think they are wrong, its just that we have a different perspective than I do. Maybe I should think about keeping a cooler full of ice and beer on deck, so it can be moved to the high side of the boat to offset the extra weight of halyards aloft. Now theres an idea that should make the crew happy. Rick Brass From: CnC-List [mailto:cnc-list-boun...@cnc-list.com] On Behalf Of Dr. Mark Bodnar Sent: Tuesday, December 03, 2013 10:45 AM To: cnc-list@cnc-list.com Subject: Re: Stus-List halyards again( 10 aloft = 1 on the rail ) Add to that the fact that as the boat heels the weight on the rail is also getting closer to the center of mass for the boat I'd guess that at 63 deg heel the rail is likely dead overtop of the center of mass - and thereby providing zero counterbalance. Mark --------------------- Dr. Mark Bodnar B.Sc., D.C., FCCOPR(C) Bedford Chiropractic www.bedfordchiro.ca --------------------- There is no cure for birth and death save to enjoy the interval. - George Santayana On 02/12/2013 9:42 PM, dre...@gmail.com wrote: I guess don't follow the adage of 10 aloft equals a man on the rail. While the mast to rail distance is a factor of 10, there is a sin(heel) factor for the aloft weight whereas it is a cos(heel) for the rail. That is, at zero heel any weight aloft is equal to zero on the rail. At 20 degrees heel, 10 lbs aloft is approximately 36 lbs on the rail. The heel would need to be 63 degrees before the 10 lbs aloft is equivalent to 200 lbs on the rail. Also, since all of the weight aloft is not at the head of the mast, it would seem that it is even less of an effect. Am I missing something? -- Paul Eugenio 1979 C&C 29 mk1 S/V Johanna Rose Carrabelle, FL --------------------- Subject: Re: Stus-List halyards again Message-ID: <CAD+F8b+evHRag9d=l2my2lfsvo_whsqwbvsja-wuvbszubb...@mail.gmail.com> Content-Type: text/plain; charset="windows-1252" Hi David, ... The weight aloft does make a difference....I don't remember the numbers but 10 lbs aloft equals one man on the rail.....or something like that !! Now, bear in mind that I am a recovering racer and have carbon main and headsails. Makes a difference and, after all, isn't your boat as special to you as any AC vessel. Niall Buckley. 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