Hey Krabby,
I really like your articles in the Mainsheet each month, and I have question for you”, said a dear friend of mine during a leisurely bay sail on Sally one fine fall afternoon. “You are going to think it is a dumb question, so I don’t think you can answer it in your column.” “I will be the judge of that, besides the only dumb questions are the ones that don’t get asked.”
“All right then. What is weather helm? I have been sailing for some time now so I have the basic definition in my head, but, I am not sure I understand the whole concept.”
Great question, I’ll bet there are more than a few people out there saying to themselves, ‘glad she asked that, because I wanted to know too’.
The basic idea of weather helm is the dynamic condition when sailing that makes the boat want to turn into the wind. In other words, let go of the tiller and your boat rounds up into the wind and luffs. Let me give you the how and why without a complete lecture on naval architecture:
As you may know, a boat pivots about the axis of its keel when it turns. Since most sailboats have their mast at or just forward of the keel, the forces of the sails on the mast create balance between the keel and the mast. The more force aft of the mast, the more the boat turns into the wind; or vice versa, the boat turns away from the wind. The rudder behind the keel can compensate for the imbalance of the forces. When the tiller has to be pulled to weather to maintain a straight course then you have weather helm. If you think about the action of the rudder when you have weather helm the trailing edge of the blade is to leeward in order to keep the boat from turning into the wind. Hold that thought while we talk about this whole concept.
So now, what’s the significance of all this? First of all, some weather helm is a good thing - especially in a sailing dinghy. You would certainly want the boat to round up into the wind in order to prevent capsizing when it comes to blow. Probably a good idea in a keel boat too - but too much weather helm makes it hard to sail. Furthermore, dragging the trailing edge of the rudder up the racecourse won’t bring home any hardware. Like so many things, just the right amount is just that.
You can control weather helm in different ways. Sail trim is the easiest. If you ease the mainsheet out and sheet in on the jib, then the balance will go the other way. Once you adjust your sail trim there will be more force forward of the mast and less aft. If you now have to push the tiller to leeward to compensate for the boat turning away from the wind, you have lee helm. Another way to increase weather helm is to rake the mast aft. This moves the force further aft and causes the boat to turn upwind, hence more weather helm. There are more subtle details like this involved but for now we will stay with sail trim.
Still thinking about the rudder underwater back there? Good. A little weather helm can be helpful in creating some hydrodynamic lift because the trailing edge is slightly to leeward, but that might be too much information at this point.
“Let me finish with a little example. Remember the Hot Rum Races last fall on Sally? You were on the mainsheet trimming crew, and we were smoking along upwind under the point. It was a wet, wild ride with the wind roaring down the canyons of Point Loma. Remember, I asked to ease the main in the puffs some times and other times time to ease the genoa? This was so I could balance the helm and minimize the amount of steering to control the boat’s momentum in the direction we wanted. Keeping the boat balanced makes for faster and safer sailing, and of course minimizes spilled drinks. By the way I‘m thirsty…. Got any more dumb questions? Send them in and let me answer them.