One of the first questions everyone asks me is how safe it is to sail on a boat without a keel.
Having sailed twice across the Drake Passage to Antarctica and back, both times on a centreboard boat, and having experienced on two occasions winds between 50 and 60 knots, this was a perfect opportunity to test the boat’s stability under such conditions. On both occasions the boats performed perfectly well and took the high cross-swell in their stride. Both Aventura III and IV have an integral centreboard, which means that when the board is raised, it is fully retracted into the hull. The ballast is also internal. The ballast to displacement ratio of both was 32, which is similar to that of most modern cruising yachts.
One of the main reasons for choosing a centreboarder is to increase my cruising options, and having a boat whose draft can be reduced instantly is an important advantage.
But shallow draft is not only ideal for exploring places that other boats cannot reach, but also a safety factor, because it allows you to access a protected shallow spot if needing shelter in an emergency.
Also, as most integral centreboard boats have a flat bottom, it means that with the board fully up, the boat can dry out on any beach, tidal bay or estuary. When the tide runs out, the boat settles down comfortably. We dried out Aventura III on many occasions, whether to put on a quick coat of antifouling between tides while cruising in Southern Chile, or to access a shallow bay in Alaska so we could watch grizzly bears fishing for salmon.
One other advantage of a centreboard is that it can be used as a sounding board when entering an unfamiliar shallow anchorage. It is a technique I learned from Erick Bouteleux and taught me a new meaning for the term ‘sounding board’.
To my shame, I did not put that unique feature to good use when we entered an anchorage in the Northwest Passage and hit an uncharted rock in an area that showed a minimum depth of four metres. Although we hit the rock quite hard, the centreboard did its job and swung up, it scraped along the top of the rock, then dropped back into its lowered position. The only damage was to my ego, but any other boat would have been in serious trouble.
Shallow draft is a major attraction of centreboard yachts, but there are also some considerable performance advantages. The main role of the board is to provide lift when sailing closehauled, and to reduce leeway when reaching. With the board fully down Aventura III drew 2.4 metres and, when sailed properly, it could point as high, or almost as high, as most keeled cruising boats.
Sailed properly means that when sailing on the wind sail trim is critical and the sails must be perfectly set to achieve the desired performance. It also means that a good speed must be kept up, and heeling too much must be avoided, or you end up making too much leeway. With a draft of 2.8 metres with the board down, Aventura IV performs even better than her predecessor.
There is a certain technique in sailing a centreboarder efficiently, not just on the wind but off the wind as well. This is when the centreboard becomes a true asset as it allows you to reduce the wetted surface.
Also, the ability to lift the board gradually as the apparent wind goes past 135°, and then continue lifting it up to the point where the board is fully retracted, is a great advantage as the risk of broaching is virtually eliminated. The absence of a keel to act as a pivot in a potential broaching situation means that the boat does not tend to round up when, in a similar situation, a keeled boat would do just that. It is a feature that I have blessed on many occasions, and that has allowed me to continue keeping the spinnaker up longer than I would have done otherwise.
The board is normally retracted when motoring in calm waters and the reduction in wetted surface provides an extra 0.3 to 0.5 knots of speed.