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  1. Replies
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    Re: Nautitech 441/442 Onwers?

    Almost every fiberglass boat in every yacht harbor has balsa core decks. I've never had any problems with balsa core decks, in 46 years of sailing.
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    Re: Extremely Disappointed in Maggi Chain

    I have read that chains stronger than G4 are not marine grade.
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    Re: Unsinkable? How, why?

    sorry, but water does not weigh in gallons, (yes 1gallon is 10lb) and volume is not in square feet.

    Yes, cats will be down by the stern, the engines are there.

    Mike[/QUOTE] Just getting dotty...
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    Re: Hull Release Party for Alpha 42

    Based on subsequent experience, it should have been a wake.
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    Re: 50' Hybrid Diesel Electric Steel Catamaran

    Caesar, steel, 50', catamaran, and low power are not a good combination. A traditional shallow monohull river boat with a low RPM diesel is best for your use, if it must be steel. If you look for...
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    Re: Water Tight bulkheads?

    It's easy enough to design a catamaran with all major compartments being watertight. I think the problem is that safety at sea is usually much less of a priority than making a catamaran feel...
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    Re: Unsinkable? How, why?

    Water weighs about 64 gallons per square foot, so if your cored hull and furniture have less volume than this, add foam floatation. Sorry for the ancient units of measurement, but I'm a) American,...
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    Re: Wavepiercing Bows on Catamarans

    If the boat to be altered does not have a very fine bow, I have another idea for a forward extension - add a T structure of solid glass, the top of the T against the bows, the base of it extending...
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    Re: Wavepiercing Bows on Catamarans

    I'm pretty sure they were for incapacitating and even drowning the enemy by bashing the enemy's hulls near or below the waterline. So, they might very well have an application in racing. It's hard...
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    Re: Wavepiercing Bows on Catamarans

    Well, I suppose you could cut the boat down the middle on the center line and spread it wider. If you want more buoyancy when pitching, I suppose you could give it a raking bow above the waterline,...
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    Re: Wavepiercing Bows on Catamarans

    It looks like the added bow section has put hollow (aka reverse,) in the waterline. It's been a long time 40 or 50 years maybe, since anyone has advocated that. :confused:
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    Re: Gunboat Rainmaker Abandoned

    Hi, Peter

    I think it was a reef in the Caroline Islands, west of Kosrae, but I don't recall the name.
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    Re: Gunboat Rainmaker Abandoned

    Hi, BrianH - There was no land in sight at sundown, but you could see an atoll the next morning when we over the coral heads. You do remind me of another amazing but sad story - I was in Kosrae in...
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    Re: Gunboat Rainmaker Abandoned

    I had read that the boat had all plain sail up, but early reports are often wrong.
  15. Thread: Bi-Rig Cats

    by BigCat
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    Re: Bi-Rig Cats

    Hi, Solarbri - I'm not sure what you mean about the leech following the luff. I have made two versions, one with a straight luff and one with a curved luff. In both, the leech is curved.

    A...
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    Re: Gunboat Rainmaker Abandoned

    Hi, Brian - Perhaps I have an exaggerated idea of how dangerous it is to be in the Gulf Stream in winter, since all of my sailing has been in the Pacific. I suppose the sea stories that travel this...
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    Re: Gunboat Rainmaker Abandoned

    http://en.wikipedia.org/wiki/The_Gulf_Stream_%28painting%29#mediaviewer/File:Winslow_Homer_004.jpg
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    Re: Gunboat Rainmaker Abandoned

    http://www.sailnet.com/forums/vessels-lost-missing-danger/185113-gunboat-55-dismasted-abandoned-off-hatteras.html

    Fools go where angels fear to tread. Cape Hatteras is where the Labrador Current...
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    Re: Liferaft. Yea or ney?

    Hi, Brad - I wasn't arguing with the placement of a few D-rings where they would be useful when capsized, either. I have come across a couple of photos of tenders with people in them tied between...
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    Re: Liferaft. Yea or ney?

    My point isn't that one should have a liferaft, but that some provision should be made for dealing with the fact that the boat will trim differently when upside down. If the Chris White design is...
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    Re: Liferaft. Yea or ney?

    I think you should take a look at the capsized Chris White Atlantic 57 off of Tonga on Youtube, before you decide that an inverted bridgedeck is a great place to be. ...
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    Re: Formulas, rules, and Benchmarks

    "My thoughts on rudder shafts are that the fattest, thickest tube that will fit easily into a 13% section, with the top bearing about at the same distance from rudder top as from the center of...
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    Re: Formulas, rules, and Benchmarks

    Early on, Hatfield recognized that speed and energy efficiency of hulls were highly dependent on hull length-to-beam ratios. For his early trimarans, he employed ratios of 9:1 or greater. But,...
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    Re: Formulas, rules, and Benchmarks

    I established this thread to post yacht design rules of thumb, so I suppose I am replying to myself.
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    Re: Formulas, rules, and Benchmarks

    Bruce Number (BN = SA^0.5/Displ^0.333 Where:SA = Sail Area in square feet
    Displ = displacement in pounds,) has a few significant drawbacks that prevent it from being more
    comprehensive than you may...
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    Re: Formulas, rules, and Benchmarks

    It turns out, after some 150 years or so of analysis, that performance is closely related
    to Cp. That is, there is an optimum range of Cp for various speeds of the boat traveling
    through the water....
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    Re: Formulas, rules, and Benchmarks

    "The biggest factors affecting performance are the built in washing machine and the granite countertops.....

    After that its the length, weight (which implies a certain slenderness ratio)and...
  28. Re: Thin hulls have less wave drag than fat ones. Are you sure?

    dennisail, you're just too arrogant to teach. Go post on http://boatdesign.net/ for a while, post your absurdities, and take your lumps.
  29. Re: Thin hulls have less wave drag than fat ones. Are you sure?

    "If all else is equal," is what I prefaced that remark with. The source is Skene's Elements of Yacht Design, but it isn't some controversial proposal. It is yacht design 101. You keep making...
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    Re: Formulas, rules, and Benchmarks

    "Previous tank testing had shown that the factors worth paying particular attention to are, length to beam ratio, wetted surface area, block coefficient, hull draft, length to draft ratio, and...
  31. Re: Thin hulls have less wave drag than fat ones. Are you sure?

    dmmbruce, Prismatic coefficient is a measure of how much boat there is underwater towards the ends, as opposed to how much there is at the point of greatest underwater area, which is usually a bit...
  32. Thread: Bi-Rig Cats

    by BigCat
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    Re: Bi-Rig Cats

    Derek's design, Cool Change, has been sailing in New Zealand for a number of years, now. http://www.sailcoolchange.co.nz/boat-charter-catamaran/

    Attached is a drawing my my latest design, one...
  33. Thread: Bi-Rig Cats

    by BigCat
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    Re: Bi-Rig Cats

    The front half is just an airfoil, like the section of a rudder or dagger board. The after half is just a straight rigid batten which pivots at the end of the foil section. At cruising boat speeds,...
  34. Re: Prismatic Coefficient and getting wrapped around a wheel

    Actually, I have not made any assertions at all. I am the one who started this thread, and I started it in order to draw together the rules of thumb concerning yacht design that I have come across. ...
  35. Re: Prismatic Coefficient and getting wrapped around a wheel

    The comment was entirely a quote from Malcolm Tenant. I think he might possibly have known something about the subject.

    "Over the 45 years of Malcolm’s career, a steady stream of designs have...
  36. Re: Prismatic Coefficient and getting wrapped around a wheel

    With our particular displacement hull form, provided it is allowed for at the design stage, a bit extra weight usually makes very little difference to its performance. This is because most of the...
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    Re: Shaft drive catamarans (35-42') and questions

    With the engine placed well aft as it usually is with a sail drive, your alternative is to turn the engine around, aft end forward, and install a v-drive. The shaft ends up under the engine, and it...
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    Re: ATTENTION, Check your Rudder Shaft Sizing

    Doane stated originally that the boat was stopped by a wave, or perhaps pushed SLIGHTLY backwards. Also, he edited his post about the bent rudder LONG after his post - no wonder he is answering...
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    Poll: Re: Poll - would you buy an Alpha 42?

    The forward and aft bulkheads are part of the box beam. I am well aware that many catamarans use a single, integral bulkhead that go down into the hulls, in which the forward and aft bulkheads of the...
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    Poll: Re: Poll - would you buy an Alpha 42?

    The deck house is the usual way of holding the forward part of the hulls together, commonly with a beam aft. The wider the two parts of an I-beam are, within limits, the stronger the beam is. A...
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