Deciding On A Powercat
Jeff Schionnning describes the different sorts of hull shapes his designs offer and the performance results of each. We hope that this will help you decide which design is best suited for your intended use.
‘Hull types will be important in your decision as they offer very different end possibilities. There are two basic types: The first being a planing type which runs on the surface with high speed potential. The second being the displacement type which in our designs, have been refined to a semi-displacement hull as is seen in the Prowler and Alaskan. We have developed a hybrid design offering more than the best of both shapes in our registered, Vapour Trail (VT950 and VTR1100).
The speed you require from a boat is one of the main determinants in choosing your design. If you are aiming at less than 30knts, then the Semi Displacement hulls provide for comfort and fuel economy unmatched by others. They run in the water and therefore are not surface sensitive permitting a very soft ride in all conditions.
Planing hulls are capable of higher speed, but are surface dependent which in reality makes them ideal in flat seas, but as sea conditions deteriorate so does their comfort levels. Once speed is reduced efficiency drops dramatically. Unfortunately sea conditions are ideal only 10 – 20% of the time. To achieve the high speed, we need more power which burns 2 – 4 times the fuel required by the semi displacement hulls.
With all efficient high speed cats the hulls have to be very narrow to offer the advantages they can deliver. The compromise for this is that living space below is reduced and is tunnel like, and the carrying capacity low. Modern materials such as the ATL composites we use and smart engineering can now halve the shell weight which offsets the issue of weight.
The VT designs are unique in that they offer fuel efficiency at a level between that of the 2 hull shapes, and offer high speed, and a very smooth ride in all conditions. The width of each hull is much greater than most cats.
The semi displacement type hull falls into 2 types that are governed by speed and carrying capacity: The Prowler is slim and fast with a 28knt top speed when powered by the 212hp motors. The Alaskan is a little slower and fatter, achieving speeds of up to 24knts.’
I hope this helps you in choosing,
Jeff Schionning
