F27 Hydrodyamics
The F27 is all about hydrodynamics which is about how moving vessels interact with the varying and diverse environment of the sea. While foils simplify this by elevating the hull out of the water altogether, a vessel without them must interact with the sea and its shape is very important. Depending on what you want to do you must optimise this interaction for its intended purposes.
The purposes identified here are;
- To eliminate impact between the hull and the sea.
- To enable the hull to achieve planing speed.
- To eliminate turbulence and drag.
- To harness displacement and achieve lift at the stern.
Bow section.
The forefoot is five feet in height, from keel to deck line. It has a fine entry both horizontally and vertically. It looks like an axe head. The draft at this point goes deeper than the hull at the keel. This keeps the bow in almost constant contact with the surface and provides directional stability while avoiding slamming or pounding which is not good for the boat or its occupants.
Stern section.
The hull has a hard chine making the bottom relatively flat. Aft of the keel this becomes inverted and emerges at the transom as an arch. On either side of this there is a diminishing hydroplane which increases in draft as it narrows and becomes a fin at either side, extending past the transom by 2 feet.
The rudder is mounted on the transom between these fins which, in conjunction with the deep forefoot, contribute to directional stability and reduced leeway. The hydroplanes induce lift as they force displaced water under the stern across the rudder, controlling the release of energy from the displacement and thereby avoiding turbulence and resulting drag.
The beam carries well forward at the deck line giving abundant buoyancy when entering a wave, either on or off the wind.