Comments on catamaran hull beam: As Dennis OConnor says,  Well, hull beam is an interesting subject but there are so many more variables involved. So many in fact that, at the end of the day [or at the end of the design spiral] the fineness ratio of the hulls may be more likely determined by the values of the other variables, rather than any predetermination on the part of the designer except possibly in a very general way. He points out that there are numerous decisions that the designer has to make, all of which will likely impact on the performance. Not the least of these is what the boat is to be used for:- day cruising, live-aboard,ocean going, charter etc. For example: a ferry boat is usually much lighter than a long range ocean cruiser as people are relatively light and the fuel load is usually very small. So our experience is, that our ferries are more efficient than our similar sized long range cruisers ie: they use less fuel. Probably of much more importance [if you must have a single parameter] is the displacement/length ratio or the length/speed ratio [Froude Number]. Also of major importance is the actual hull form that is being used especially on as gross a level as planning .v. displacement. However John Winter also has a point when he says that extreme fineness ratios on displacement hulls are not necessary and have some associated problems. Certainly if the fineness ratio is too high you start paying a viscous drag penalty. Particularly at higher speeds. Pacific Harmony had a very high fineness ratio. However it should be realized that it was not actually designed with this high a ratio. During construction it was lengthened to 86 ft from the original as designed 72 feet with the concomitant increase in the fineness ratio. The displacement also increased which meant an increase in the size of the engines from 600 to 800hp. This also did not help with the amount of available space around the engines! Fineness, or perhaps we should call them fullness, ratios at the other [low] end of the range can also cause problems. The hull waterline beams and performance figures quoted for Sunreef power catamarans indicate that they will require just over twice the horsepower to achieve the same top speed as one of our CS hulls of the same length and displacement. Published fuel consumption figures for a Scott Jutson design, again compared with a similar CS hull, shows the Jutson hull using 62% more fuel at 6 knots and 20% more fuel at what is a probable long range cruising speed of 10 knots.At the top speed of 22knots the "CS" hull used 78% of the fuel of the wider hull. This probably does not matter if we are only talking about short distances but becomes significant as the distances, and the cost of fuel, increase. John Winters new proposed vessel has a hull fineness ratio of somewhere between 8.5 and 9 [depending on the exact figures for length and hull beam]. This is certainly a lower ratio than Scott is usually using. This does, as Paul Christman says, give superior space in the hulls compared with finer hulls. But is there too high a price to be paid in the probable increase in fuel consumption? It will be interesting to see. And of course whether or not the price is acceptable all depends on what your main priorities are anyway. The New Yorker 57 is a series production boat with ocean crossing capabilities. We are just not publicizing it as such until the prototype is trialed. Pat, we have designed "your" perfect boat and it is being built. It is called the Domino 20. But as you say there is no boat that can be all things to all people. Malcolm Tennant. ARINA MA Malcolm Tennant Multihull Design Ltd PO Box 60513 Titirangi, Waitakere 0624 NEW ZEALAND ph +64 9 817 1988 fax +64 9 817 6080 e-mail malcolm@tennantdesign.co.nz www.tennantdesign.co.nz www.catdesigners.com