In general, there are a few types of hull geometry:
- Flat-bottom hulls: These are characteristically very stable, great for fishing and other uses on calm, small bodies of water, but are the roughest riding in choppy waters.
- Round-bottom hulls: These are characteristically “displacement-style” hulls designed to move smoothly through the water with little effort (ex: canoe, kayak). Round-bottomed hulls are less stable and can capsize more easily.
- V-shaped hulls: These are characteristically “planing hulls” and are most commonly used for powerboats and PWC. V-shaped hulls are designed to plane on top of the water at higher speeds and provide a smoother ride through choppy water. V-hulls have a greater surface area (ie. resistance) thereby requiring more power to move.
When it comes to Jetskis, they often combine multiple hull shapes for the desired balance.
Flat-bottomed hulls are prone to “slap” or pound itself over waves – particularly at speed – and due to the minimal surface area, are typically “looser” or harder to control; requiring constant steering correction by the rider. GTI’s are marketed as being “loose” and “playful,” allowing the rider to freely “spin-out” on demand and generally goof-off far more than the Ultra.
The solution to maintaining the balance of a flat-bottomed hull while retaining the tracking and handling of a V-shaped hull has been found by reducing the deadrise and adding strakes to provide compensating lift. While chines can generate some lift, they are primarily used to manipulate how the hull will behave in a turn.