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Balancing the Leeboards

June 7th, 2011 by

leeboard balance

Having a balanced life is a key to happiness. Having a balanced rig is a key to happy sailing.

Sailing a properly balanced rig is a wonderful experience. Holding a course becomes easy, steering is predictable, controlled and requires little effort.

So, what is a balanced rig?

Balance is the relationship between the center of effort in the sail and the center of lateral resistance in the keel, centerboard, or in this case leeboards.

If you are not familiar with these terms, the center of effort is a site on the sail that represents the center of the total sail area. It is the spot that the sail pulls from when it is full of wind. The center of lateral resistance is the center of the leeboard surface area that is underwater. Since the leeboards are pivoted fore and aft, the center of lateral resistance can be moved fore and aft.

This is where balancing comes in.

Balancing the leeboards basically involves setting the angle of the leeboards so that the center of resistance lines up with the sails center of effort.

If the leeboards are too far forward, the center of effort of the sail will be behind the leeboard’s center of resistance, causing the stern of the vessel to slide down wind. The result is that the boat will want to turn into the wind.  A sailor at the helm refers to this unbalance as “weather helm”.   On the other hand, If the leeboards are too far back, the center of effort of the sail will be forward of the leeboard’s center of resistance, causing the bow of the boat to be pulled downwind.   A vessel having this downwind unbalance is said to have “lee helm”.

A properly balanced rig will allow a non heeling craft to sail in a straight line with minimal input from the helmsman.

A certain amount of steering can also be accomplished by changing the leeboard’s position.  To steer upwind, the leeboard is moved forward.   To steer down wind, the leeboard is moved aft.  This is especially useful if a craft does not have a rudder or skeg. Leeboard steering is most effective when sailing on a beam reach (90 degrees to the wind) or on any reach closer to the wind, and least effective on reaches off the wind. When running directly down wind, leeboard steering will not work at all.

On the Kayaksailor, the balanced position occurs on most hulls when the leeboards are pivoted back about 25 degrees from vertical.

So, the next time you are out on the water, play with the leeboard position and try using the boards to help you steer.

Most of all, find time to kayak-sail more often.   Remember, balance is the key!

David Drabkin

Illustration by Dan Drabkin http://www.dandrabkin.com/

3 thoughts on “Balancing the Leeboards

  1. Another point on the weather or lee helm issue. With lee helm, if one is separated from their boat, the boat ultimately will sail away. With weather helm, it will continue to go in irons, minimizing the drifting of the boat.

  2. Good Point Robert. Having slight weather helm is definitely desirable for most sailboats. With rudderless kayaks, our experience has been that with a neutral helm, steering corrections with the paddle blade can be minimized. I guess we could kick the blades back a little during a capsize recovery, but Patti and I usually just lower the sail prior to reentering.

  3. Thank you so much for this article I found by chance , as this question popped up in my mind experimenting with single and dual leeboards.
    Am a really a novice sailor and on prototype 3 twins at the moment based on reading , and an unintended broach and recovery exercuse having to much fun.
    I think I am starting to understand the group of dynamics involved in sailing much better now and love building things myself.
    All of this around an old inherited 4.2m x .9 beam Canadian canoe fitted with an old 5m2 windsurfer mast , sail and boom added – and all the little things found on fancy sailboats.
    Have a nice dam and sailing club very close by to work in and really enjoying enjoying it.

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