Canting Keels and Daggerboards

The keel on a "normal" sailing yacht consists of a large steel aerofoil hanging vertically below the boat, tipped with a large torpedo shaped lump of lead. This keel serves two purposes - first the fin provides horizontal "lift" which discourages the boat from being blown sideways by the wind, and second the large lump of lead ballast provides a righting moment that discourages the boat from heeling over. The keel designer thus has to design it to do two different jobs - and as is always the case when something is designed to do two jobs, it does neither well. When the boat is upright, the lead ballast provides no righting moment and is just dead weight, slowing down the boat. And as the boat heels over, the fin also inclines, so reducing its efficiency at reducing sideslip.


The evident solution is to design two separate appendages to do the two different jobs of a traditional fin keel - the canting keel and the daggerboard. The lump of lead ballast is attached to the end of a slim foil, which can be "canted" towards the windward side of the yacht - thus even if the yacht is fairly upright, the ballast provides a strong righting moment, allowing the yacht to carry more sail. The leeward daggerboard - a lightweight carbon fibre hydrofoil - is then lowered through its slot to prevent sideslip. The slot is angled so that when the boat is heeled over, the daggerboard is vertical, so maximising its effect. The windward daggerboard is raised completely out of the water in order to nullify its drag. The further benefit of this separation is that the overall weight of the ballast can be lower than on a fixed fin yacht, as it is more efficiently used. Thus we have a lighter boat that can carry more sail - and that makes for a big increase in speed.

So far canting keels have mostly found favour on exotic racing machines such as the Volvo 70s. But they are now starting to find their way into more cruising orientated yachts, such as Rusalka, a Baltic 78 which BCR Yachts has just welcomed as our latest charter central agency.

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