How We Build The Perfect Hull.
The process of designing a catamaran hull is equal parts physics, experience and technology, and as it is a significant investment in time and resources, it needs to be done extremely well. Here, Greg McLogan, VP of Product Development, describes what goes into World Cat’s ‘secret ingredient’ – the hull:
- Before any design work is initiated, a full exploration of the boat’s intended use and desired performance characteristics is charted out. Will it be primarily used for fishing or for cruising? What speed, fuel economy and handling are desired? What type of ride is optimal (like cars, performance vs. ride is a balancing act)? What key features are critical? How can this boat be priced to maximize appeal? All factors need to be simultaneously solved.
- For example, a boat designed for fishing will have more livewell capacity, fish boxes and rod holders, and accessibility around the deck. A cruising boat will put a bigger priority on seating space, relaxing/refreshment areas and other creature comforts.
- Then, a general layout of weight and balance factors begins – what are the biggest weight contributors on deck, and how can these be optimally balanced around a center of gravity? How does this shift as people are added or as fuel is depleted? What engines are appropriate and how does their weight and power impact performance? How can stability be ensured if, for example, several fishermen are fishing from the same side of the boat?
- Once these basic priorities are identified, the hull design begins:
- Consistency/predictability across conditions.
- Amount of planing at certain speeds.
- Speed to plane.
- Angle at which hull reenters water after a wave (smooth reentry rather than pounding).
Catamarans generally have significantly greater planing characteristics than comparably sized monohulls.
- Factors in design:
- Distribution of deadrise (angle at which hull departs from centerline on hull): shifts from 35° in bow to 12° amidships, with the planing surface at transom.
- Shape of chines (deflects water in front; lifting surface aft).
- Required lift – defined by four core coefficients of form, boats have to have enough dynamic lift upward to overcome the weight of the boat and ultimately result in planing. This is accomplished by the number, location and shape of lifting chines and strakes.
- Planing surface (“delta pad”) – the flat surface that the boat rides on while planing. Catamaran planing surfaces are much more efficient than those on a monohull, which relies on lifting strakes to lift the boat. Instead, catamarans’ planing pads act like a lifting strake, which allows planing at lower speeds. The key to a great planing surface is the perfect balance of size, proportions, distribution, and how far forward on the hull it extends from the transom.
- Key balancing act: a high tunnel accommodates more water but forces higher gunwale heights.
- Tunnel shape is designed to eliminate vibration and avoid ‘tunnel slap’ created by water movement.
- Critical to incorporate elements to aerate incoming water to reduce water friction. The Vector Pod, situated in the tunnel directly between the forward bows, is a key factor here.
- Also important to minimize ‘sneeze’ (the occasional forward puffing of water due to too much incoming water) – this is mitigated by downward deflection at the top of the tunnel in the bow.
- Importantly, need to design so that it can be built with sufficient durability to provide years of trouble-free enjoyment.
- All design work includes the incorporation of essential features like anchors, through-hulls, doors, and motors.
- Functional factors, such as hull stiffness in critical areas and water deflection at the bow, are explored.
- Aesthetics are always a top priority, including everything from rubrail location to the way hull lines accommodate different colors.
At World Cat, we believe we have the industry’s best-performing hulls. But as we design new hulls, we continue to strive to seek out new shapes and materials to further improve the catamaran experience.