Copyright 2017 - Woods Designs, Foss Quay, Millbrook, Torpoint, Cornwall, PL10 1EN, UK
  • home built Flica 37

  • plywood Romany 34

  • lightweight 14ft Zeta mainhull

  • Strike 15 trimaran at speed

  • 28ft Skoota in British Columbia

  • 10ft 2 sheet ply Duo dinghy

  • 24ft Strider sailing fast

  • 36ft Mirage open deck catamaran

Power catamarans offer many significant advantages over monohull power boats.

  • They are safer, due to their twin hulls, high stability and self draining cockpit.
  • They offer low wake and much improved fuel economy.
  • They are comfortable under way with no slamming or broaching in waves and have excellent handling in a seaway while being very maneuverable in harbour.
  • They do not roll when fishing or at anchor and are easy and safe to beach.
  • They have more deck and interior space for a given length, not just because of their wide beam, but also because they have an essentially rectangular living space.

Thus they do not have to be as big as a monohull to give the same interior room, performance and safety.

Most power catamarans are planing boats, with all the disadvantages that the type implies. Furthermore they tend to have a narrow, 8ft beam for trailing, so that many of the advantages of the catamaran form are wasted.

My Skootas, on the other hand, uses semi displacement, non-planing, asymmetric hulls. The hulls are finer than those used on a sailing boat, because power boats always have power available to get over the hump speed, so low speed, wetted surface friction drag is less of an issue.

Tank testing has shown that there is significant extra drag caused by wave interactions between the hulls (up to 20% at certain speeds) if the hulls are close together. Thus, the Skootas have widely spaced hulls, yet will still fit in a standard 14ft wide slip.

The hull asymmetry helps fool the water into thinking the spacing is wider than it really is. This is well demonstrated by the photo below of a Skoota 20 at 15 knots where you can clearly see the difference in wave heights between the inner and outer hull sides

Before developing my Skoota range of power cats I studied the available data on "pontoon boats" those popular American power catamarans built from two or three aluminium tubes, see photo below.

I found that a typical 20ft pontoon boat weighs about 1500lbs, so is similar to a Skoota 20, yet needs a 50hp outboard to motor at 19 mph (16.5 knots). Whereas the Skoota 20 goes 15 knots (17mph) with a 25hp. Or put it another way, the Skoota hull has nearly half the resistance of a similar sized pontoon boat. Proving that proper hull design DOES matter.

Not everyone can build complex shapes, but everyone can build in flat panels. So for mass appeal the smaller Skootas are built using conventional plywood-stringer-frame construction with all surfaces glass/epoxy sheathed. Fortunately this building method is still the cheapest and quickest. Because the boats are modular much can be built in an ordinary garage (lengthened as necessary to build the hulls).

Building in sections also has a psychological advantage, especially important for amateur builders, which is that it is quick to build each section, thus progress appears to be fast. Furthermore there is little fairing to do, just smoothing the glass joints.

The Skootas offer: stability, low wake, the ability to maintain high speeds in rough conditions, superb directional stability, a self-draining cockpit, fully buoyant hulls for safety, fuel-efficiency, lots of interior space, low speed maneuverability and the security of twin engines.

Clear winners by anyone's standards.

You can download a basic studyplan pack HERE