Monocat: a new kind of hull for high speed watercraft.

Tipology:	International patent	Nr.	[omissis]
Data of approvation:	[omissis]	Brief descr.	Monocat

Project's synopsis

The present invention has the scope to supply a type of bottom, called Monocat, that allows to have high performances with contained power cobining the advantages of the single hulls with those of the catamarans. The best speed performances are obtained with catamarans (see fig. 1). But these hulls lose their advantages in rough sea situations, since the wave-motion causes, in the tunnel between the two hulls, periodical increases and lessenings of pressure of the water mass, with increase of the resistance and structural sollicitations. The energy of the wave-motion manifest itself on the liquid surface, while under it the movements they are more regular and the pressure homogenous, so the solution is to model the immersed part and the emerged one in different ways. The part over the floatation is conformed in a classic way, while that dipped one as a catamaran shape, with a cross section as in Figure 1. In order to avoid that the wave-motion threads between the two semihulls it is necessary that the wave forehead is divided as in the normal boats and that it slides along the external flanks. In order to obtain this scope it is designed so that the external flanks of the catamaran converge from each other to the prow joining it with an angle not dissimilar from that one of the greater part of boats. This can be caught up, without losing the advantages of these hull, with the limitation of the distance between the two semihulls (indicated with "A" in fig.2), preserving in this manner the hydrofoil advantages and creating the constructive conditions that allow the construction of a classic prow. Since the hull described is a planing one, it will have a determined angle of pitch. In relation to this dynamic trim, with the prow in higher position than the stern, it must be defined, in the point of beginning of the tunnel under the prow, the distance between the roof of this and the water surface, in dynamic, but calm, water conditions. This part, that we will call the roof of the tunnel, continues until the stern and it ends at an height above the water that allows the escape of the air in the greater part of the operating conditions, but that in stopped condition can also be under the waterline. At the end of the tunnel, near to the stern, can be applied some devices for regulating the air pressure in dynamic phase so that an air cushion can be created to damp the vertical accelerations at high speed.
The roof of the tunnel has a longitudinal course that increases his height towards the stern, with an inclination that can correspond to or that can be grater than, the trim of the boat. It can be designed also by steps, but it does not have to generate aerodynamic carrying capacity, which would provoke only a resistance increase, because the planing of the boat is obtained with a much more efficient system, described as follows.
One flap of opportune profile is applied Under the hull, in cross-sectional position regarding the axis stern-prow, and under the longitudinal position of the barycentre, with a variable tolerance of centimeters. The distance from the hull of this surface must be in such way not to disturb to the water flow, so obtaining the maximum carrying capacity with a direction contrary to the weight force of the boat. The effect of this profile will lighten the boat, which, in motion thanks to this carrying capacity, will move a smaller water amount. The smaller water amount moved, corresponds exactly to the weight quota supported by the carrying capacity and will provoke a great reduction of the resistance. The vertical accelerations towards the waterline that are the responsibles of the blows that the boat produces on the water are damped by the presence of the carrying surface.