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Benefits of daggerboards By far the vast majority of the production cruising catamarans have low aspect ratio keels. The well known French boat manufacturers market 95% of their boats for the charter industry and make a great product. These boats have very spacious interiors, high spec finishes, and are perfectly adaptable for live aboard families or the charter trade. This charter industry, driven by the French government tax incentives to invest in a yacht in the French Caribbean, has an obvious influence on the requirements and design of their charter fleet, which further has a trickle down effect to other builders who also market their cats for private ownership. Design parameters for these charter cats are often centered around 2 week multiple family vacations in the steady trade winds and day sails between closely spaced islands of the Caribbean. The features of these keel catamarans obviously put less demand on pure sailing performance or upwind sailing characteristics, but rather try to please by offering great live aboard comfort and affordable construction. However daggerboard catamarans have several advantages over their keel counterparts, some of which are well known and others that are more subtle and sometimes only recognized by people who have used them. Upwind ability: depending on the sea conditions, a daggerboard catamaran will point up to 5 degrees higher, and experience 2 to 5 degrees less leeway. This does not seem much, but for the same speed, a catamaran tacking at 54º will add 20% more time for its journey than a catamaran tacking at 45º, increasing its exposure to bad weather. Surfing and running deep: when running deep in large seas, even a heavy keeled catamaran can reach incredible speeds above 20 knots when surfing. In fresh conditions, the volume and resistance of the keel will act as a brake, and in combination with the forward pressure of the sails, force the bows down, with the risk of suddenly stopping the boat, and to the extreme, pitch-poling. This won't happen with daggerboard catamarans. Furthermore, by lifting the daggerboards and pointing up, one can induce leeway and increase apparent wind, crabbing faster to destination. Tacking and Helm Feedback: Cruising catamarans are often thought to tack slowly and behave sluggishly to movements of the helm. This is certainly true for some heavy keel catamarans and much less so for ones equipped with boards. In complex seas, some of the heavier keel cat’s only option for a safe tack is back winding the jib. Monohulls with only one fin will always tack quicker than multihulls, just as foil equipped catamarans will be more responsive than keel multihulls. Maneuverability under one engine: If you use only one engine and retract the board on the hull which has no engine power, but leave the powered hull’s foil down, the boat will go straight and turn easier. Because of the retracted foil on the un-powered side there will be much less drag induced turning moment, the boat will be more balanced and the other sides deployed board will provide sufficient bite for “survival” steerage in case you loose one engine. Daggerboard cats also can motor a bit faster, since by retracting the foils they have less resistance. Breaking waves: Major capes, including in Mediterranean (famous Cap Creus or Cap Beart), are notorious for rough conditions and breaking seas where the ability to navigate safely becomes imperative. In extreme weather, it is of paramount importance to enable a catamaran to side-slip rather than to encourage the possibility to flip. A catamaran behavior in side waves is decisive, and the possibility to lift underwater appendages is essential. Collision: The single biggest psychological deterrent of daggerboard cats is the vulnerability of the boards and trunk in case of a collision. Obviously the most critical area in daggerboard design is the construction of the daggerboard trunk, which has to be the most solidly built part of the structure. In case of a violent impact, the foil must be designed to snap and leave the daggerboard trunk unscathed. The risk is actually increased with shallow keels, as they can resist minor collisions but could leave the hull open in case of major collision. This is why Fountaine-Pajot uses the same sacrificial principle on its keels, but this essential safety item is not used by many builders :
As compared to a sacrificial keel, due to its thin shape the daggerboard will be more easily damaged in case of light collision, but it has the undisputed advantage to offer the possibility to be interchanged between hulls, or be shortened or repaired on the spot without having to take the catamaran out of the water. Handling: Keels offer a distinct advantage, in that they do not need to be handled at all. Most people think that the operation of daggerboards is complicated. Daggerboards might seem heavy, but they generally have positive buoyancy, making the operation very easy: in standard conditions, it takes three second for a couple to fully raise a daggerboard, and no more than ten seconds for a single-handled. Cost: Indeed the analysis would not be complete without mentioning the financial factor. The foils, their surrounding trunk, structure reinforcement, and the associated deckware makes them more expensive to build, so most builders will prefer to stay away from them given the choice, to simplify construction and be able to offer a more appealing price. From Gregor Tarjan, Aeroyacht Ltd |
