A New Hull Form For Catamarans

Peter Richwell suggested that I should register the idea of using my hull design for catamarans, hoping that such attributes as are derived from testing it as a mono-hull will shine when two are joined across.

The profound rise in the use of catamaran construction for commercial and military vessels is a reflection of the design's general ability to improve or solve some the limiting aspects of mono-hulls by way of speed, stability, space, and draft. Costs compared to mono-hull construction, however are greater - after all there are two hulls. However it must be said that such hulls for sailing catamarans do not need the keel, keel section and bottom strength as would a sailing mono-hull and here at least there would be some savings. Indeed the method I have used to build the hull from effectively a single sheet, even denying in a way the actual existence of a keel might mean a great a considerable saving in time and material. Contentious of course are the hull configurations in relation to symmetry and spacing. Allowing for such contention and that the 'mono' hull I have built is for ergonomic benefit, it might be construed that two such symmetrical hulls will offer the same benefits when made into a catamaran. This has been shown not to be always the case and the degree of spacing between them also can markedly effect performance. However in defence of my expectations one might reflect on that the intense crowding, almost 'sardines in a tin' like confinement, of fish being hustled by prey would suggest that there may even be some survival (speed)advantages of being close.( web ref.S.P.E.E.D. Hull design). It seems that proximity of birds flying in certain formnations, especially over long distances like ducks and geese, works to conserve energy. The essential shape of all birds in flight is, teardrop - blunt end forward - the same applies to fish.

 Depending on speed the bottom of the bow should effect some planing, and with the relatively shallow and thin trailing underwater section, the resistance should be low. I expect the boat I have built, calculating from knowing her weight and from the observed displacement of the model to be a light displacement boat. Overall at 18 feet her expectant waterline length is 15 feet. However if she behaves in the manner of a displacement hull 5.2 knots max is all that one might expect, and allowing she is being powered by a modest 9.8 hp outboard, and that her trials will not necessarily be in ideal water and weather conditions, this figure could be knocked down further. Also how much of an encumbrance the stabilising pod will have is yet another thing of concern; it is designed tear drop shaped in the vertical plane to reduce forward resistance but is flat when viewed laterally to increase side-ways resistance and therefore stability against rocking
 Therefore much rests on her trial and a speed of 6 knots or more will be quiet a revelation.