I found the paragraqph about catamarans in Frank Bethwaites book :
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<br>Advatages :
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<br>- ratios power to weight can be very high
<br>- slender hull shape escapes the force mode drag which is very important at medium speeds say around 10 knots
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<br>concludes : moderate wind performance should be superiour when properly designed.
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<br>Disadvantages :
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<br>- Total wetted surface of the twin hulls is always more than a single monohull
<br>- They can not heel to use gravity to twist of their sails in light air with he experimentally shows to be VERY important.
<br>- Their slender hulls can not plane and therefor they can not go really fast as the 18 ft skiffs.
<br>- Very litted volume in the bow so you can drive them as hard on a crosswinder or broach reaching.
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<br>concludes : Light air performance is disappointing and heavy air performance is okay but not great.
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<br>Assume Frank is right. How do we attack all these points ?
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<br>First we thank him for the advantages !
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<br>Than we conclude that the wildthing manourvre must be considered to be the first thing to be mastered on a cat in light air in combination with light weight and a big twist in the mainsail c.q. squaretops mains. This will be the reason why all F16HP's will have boards and squaretops, otherwise wilthinging will become very dificult.
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<br>So the first two points will more or less succesfully attack the first two named drawbacks.
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<br>The third point : this is a tough one ! I don't think we will ever overcome this without inclining daggerboard so that they act as foils or to incorporate lifting spis. He calculates huge speed increases for planing boats but I feel that increase should be less due to trying to run over hilly country without shock breakers. The smoother ride of the cat could go some way in closing the cap. And the greater stabiliy of the cats should help in outrunning all but the true professional skiffers
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<br>Forth point : diving. Well, I have a video of the 18's at home and I don't see any of them with their bow section touching the water at all. So if they stay up by putting weight aft and lifting their bows out than why should a cat be limited in speed by their small bow volumes ???
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<br>Must be a small oversight by Frank.
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<br>This is to all would be designers and homebuilders. Bear these points in mind and go get those 49-ers on elapsed time.
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<br>Wouter<br><br>