What's so Good About Water Ballast?

The reaction of many boating people to the words "water ballast" is to think of performance oriented ocean racers, who use tanks on port and starb'd, alternately filled with water to increase the righting effect. A pump between the tanks transfers the water, and this system seems to work well, though you better hope the pump doesn't fail. This system is only suitable for ballasted keel yachts as the prospects of failure, or an accidental gybe would result in instant capsize. We were initially a little sceptical about the use of water as a centrally placed ballasting agent. Would it only start to "work" for you when lifted out of the water? Surely lead is more efficient? How would we empty and fill it? The truth is it has been a real revelation for Swallowboats. Our lightweight craft are just the sort to derive most benefit from taking on water in a concealed tank below the floor. The water acts plain and simply as a mass. On SeaRaider that means 300kg of water, which is the equivalent of 4 adults lying in the very bottom of the boat. And more importantly, they stay there if you capsize, helping the boat to return to upright unaided. Yes, lead is more efficient, as it's centre of gravity can be placed lower in the boat for a given weight, but lead is not supplied free and you don't want to throw it overboard when conditions change. To our way of thinking, water ballast has so many advantages over fixed lead ballast. For a start, the boat is much lighter on the trailer, which means she is easy to push around your garden, or up your drive. Our SeaRaider design weighs 325kg and takes on a further 300kg of water. If that were fixed lead it would push her very close to the limit for an unbraked trailer in the UK. Trailers that have to have brakes are more expensive and more prone to going wrong. You could get away with less than 300kg of lead to create the same righting moment, if you put the lead lower down, in the centreboard say. But then you have the problem of raising and lowering a very heavy board. It also needs to be locked in the down position so that in an inversion, or any knockdown greater than 90 degrees, the board does not come back up into the boat. Sailing with the board locked down negates many of the benefits of a centreboard - you might as well use a daggerboard. A Heavy board like this would also create larger stresses on the boat when on the trailer, meaning a heavier and more expensive construction. When launching her, you decide whether or not to fill the tanks depending on the conditions. If you play safe, and you find the wind drops, you can always sail the tanks empty through the self bailers, which dramatically increases your speed potential. If you find yourself caught out in heavier weather than you anticipated, fill the tanks on the fly and she suddenly feels and behaves like a ballasted boat. With SeaRaider, we clocked over 10 knots with tanks empty during tests; during the same session we filled the tanks and never got more than 7. The feel of the boat from tanks empty to tanks full could not have been more marked. Initially she felt like a big dingy, a handful to manage but exhilarating and fun to sail. With the tanks full she became much more docile, despite the conditions, with a real feeling of steadiness. It is this dual personality that makes Water Ballasting so attractive. If you have a nervous sailing partner or children on board, fill the tanks and you won't come close to any "hairy moments". But take some experienced sailors along, or sail in light conditions, then empty the tanks and suddenly your sail area/displacement ratio goes through the roof and you leave other boats standing.