Centreboards

If the centreboard and case are angled forward the board may be driven up on impact and avoid case damage. Unfortunately this design catches all floating weed and net.

Some centreboards pivot back into the hull. If the control lines are weak enough to break on running aground then this also saves damage. The problem with this design is the long slot required and the associated turbulence and drag associated with water travelling over the open slot. Rubber covers help but do not solve this dilemma.

Centreboard cases can be built with sacrificial pads to absorb the impact. Alternatively, you can build a box section behind the case to enclose any rupture so the hull integrity is not voided.

centreboard is to increase lateral resistance and transmit this effect to the hull and rig. This force jams the board against the side of the case. To raise or lower centreboards you have to break the lateral resistance. This can be done by rounding up and losing way, by bearing away and slowing down or by ooching - swinging the rudder from side to side and making the hulls zig-zag rapidly. On the race course the time to raise and lower cerntreboards is during tacking or gybing or, best of all, after rapidly bearing away and removing the lateral load on the board. Most centreboard control lines are fed back to the cockpit. Have a winch available to assist in loading up the line so that when the tack is under way the board will pop up (or down) as the lateral resistance is taken off.

Centreboard hints

To service your centreboard it is easy to raise it out of the case by using a halyard.

Antifoul any section of the centreboard that remains in the water. Ensure that this section does not jam in the case.

Some centreboards drop low in their box to save weight. This has the unfortunate result of distributing any impact over a small area of the case - increasing the likelihood of case rupture and major damage.

Centreboard controls

Most centreboards are impossible to raise or lower when the multihull is under way. This is because the very function of the

Keels

The advantages of keels are low maintenance and no cabin obstruction. Keels also provide protection for motor propellers and are a solid base with which to beach on. The disadvantages are reduced windward performance, slower tacking, an increased pitching due to increased central buoyancy, an inability to retract the keel when sideways drift is needed (e.g. storm survival - see Cyclone chapter) and reduced beach access due to increased draft and need for a greater tidal range to 'dry out' on a beach.

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