Weather Helm

Chatting with Barry last night at the East Coast Dinner, we got onto the subject of weather helm. Since Random went gaff last season she is heavy to steer and tends to end up on her ear. Of course Barry put a huge mainsail on a tall mast. So what he would like to do is stiffen her up and improve the weather helm. He thought of putting some ballast under the keel, but has decided its too difficult. So he is going to add some internal ballast, which will help. Neither of us were sure how the fore and aft position of the ballast would affect weather helm.

I remembered something in Emiliano Marino's wonderful 'Sailmaker's Apprentice' and went to look it up. He says there are two main things that affect weather helm. One is the 'lead' - how far ahead of the centre of mass the centre of effort is. He says you can reduce weather helm by increasing the lead by moving the mast forwards, raking the mast forwards, making the mainsail smaller, making the bowsprit longer or flatten the mainsail. The other issue is that as the boat heels, the centre of effort is off the centre line,creating a twisting force. Obviously keeping the boat upright is the answer to this. So adding the ballast will help, and if it goes in aft then it will increase the lead slightly by bringing the centre of mass aft.

A little googling brought me to 'Sailing' by E F Knight. In Chapter III he discusses this very issue: "Sometimes a vessel's sails are not properly balanced because the ballast has not been stowed in the right place. It is obvious, for instance, that if ballast be shifted aft the weather helm will be diminished, for the stern of the boat will draw more water and so offer more lateral resistance, whereas the stem of the boat will draw less water, and will therefore be more easily blown round."


So it looks like Barry should try his new ballast towards the back.