Sailing boats between 10 and 12 m with flat bottoms, 2 or 3 chines and a centreboard, are particularly popular in France, (we may like to remember the OVNIS, made in light alloy), where they are appreciated by those who love long and demanding navigations. In Italy they have not gained the same popularity due to aesthetic rather than functional reasons; in fact, not even the Anglo-Saxon market is particularly keen on these boats, perhaps because traditionally, according to an English conception, the “blue water yacht” has opposite characteristics (for some aspects) to this type of boat: it is narrow, heavy with very low centre of gravity, deep hull and reduced stern volumes. In fact, each of these characteristics has its own justification and personally, I would not readily define the SPHERA as a real blue water boat. Should I have to face a storm around Cape Horn, I would prefer to do so on an English type of boat of similar dimension than on the SPHERA. However, under typical normal conditions - that an average yachtsman has to face - it is perfectly safe and able to meet quite easily, even cruises with a certain amount of difficulty, with the advantage (compared to the traditional heavy displacement English boats) to allow greater performance with less sail - which at times, allows you to escape from bad weather, instead of having to face it. The SPHERA has an average-low displacement (182 of displacement/length ratio) and quite a generous sail surface, even if not excessive (the sail area/displacement ratio is 18.8, rather high for a cruise boat), a feature which guarantees good speed performance. The high beam, (the length/ beam ratio is 2,78 on deck and 3,15 at waterline), affords good initial stability and allows full use of the sail plan, even with quite strong winds. These characteristics, however, besides the hull shapes, make it more suitable for reaching downwind, rather than beating upwind, which for cruising does not represent a great hindrance. Draught is greatly reduced thanks to the low aspect ratio with centreboard and to the double rudder, a classical solution which has been well experimented for boats of this type. Among the advantages there is also improved direction stability, which is an appreciated feature during long passages. The fixed keel in which the centreboard casing is housed, avoids taking up valuable internal space and allows the lead ballast to be placed in the lowest possible position. The centreboard may be made of cast iron (heavier) or in steel and wood (more simple to build for an amateur constructor). With the SPHERA, we have aimed at maximum simplicity from the construction point of view and construction is without particular difficulty: all the surfaces of the hull, deckhouse and cockpit are made and built in plywood. The internal flat bottom offers the advantage of exploiting all the available internal height (between 180 and 190 cm) and a rational distribution of spaces. The lay-out is typical of modern boats of this dimension, but it is also possible to choose other lay-outs. Construction is quite easy in relation to the dimension even if, increasing the size of the boat, the advantages of marine plywood construction tend to diminish in comparison with cold moulded or strip planking construction.