Lee Helm versus Weather Helm


Eliminate Lee Helm and Reduce Adrenaline Rushes

I didn't sail as much as I would have liked in the summer of 2013, but those times I did get out were real eye openers. Among other lessons, Mother Nature (the Head Mistress) and Lake Erie (teacher extraordinaire) joined forces to alert me to the perils of having a boat with lee helm. They let me know of the downside associated with lee helm, but they weren't so forthcoming about how to balance the helm to address the problem.

Before getting into lee helm versus weather helm, let's take a look at what lee helm is and the problems it presents to sailors. Anyone out there who is a nautical engineer or experienced sailor, feel free to chime in – this is my take on the situation.

Sailing a boat is a little like riding a puck in a giant game of air hockey. Unlike the puck, the captain and crew of a sailboat have control surfaces such as the sails, keel (and centerboard), and rudder to control the direction and speed of the sailboat. Magic Moments has a large genoa and mainsail, a short stubby keel and centerboard, and a rudder to make course changes (as well as an outboard Wink)

The sails are controlled by lines running back to the cockpit – lots and lots of lines. OK, truthfully there aren't that many lines – but they seem to be everywhere after tacking, either rolling underfoot in an evil attempt to toss me overboard or trapped underfoot at the moment when I'd really like to let them run free. Sorry, I didn't mean to get into my personal problems – back to controlling lee helm.

Lee helmThe air hockey puck under your command can change speed and direction based on the forces acting on the control surfaces mentioned above. Somewhere, there exists a Center of Effort (CE) which sums up all the forces on the sails, whether caused by wind, set of the sails, or other driving force on the sailboat. Similarly, there exists a Center of Lateral Resistance (CLR) which sums up all the forces resisting the forces at the CE. The CLR summarizes the resistance from the keel / centerboard, the rudder, and the hull itself.

If our air hockey puck was long and narrow, the CE would be somewhere between the bow and the stern, as would the CLR. If the CE is forward of the CLR, the bow will move forward and in the direction of the wind (lee helm), but if the CE is aft of the CLR, the stern will move forward and in the direction of the wind (weather helm). Windsurfers are able to turn their boards without any rudder at all by moving their sail forward or aft.

Why is a lee helm undesirable? When a sudden puff of wind hits your sails, a lee helm causes your sailboat to fall off, exposing more sail area to the wind, and driving your boat still further off the wind. As you fall off, the additional wind load causes your boat to heel further, ultimately causing a knockdown. Worse, if your boat has lee helm and you fall overboard while singlehanding, your boat may sail on without you. Conversely, if your boat has weather helm, it will turn into the wind and stop – much better behavior in a man-overboard situation.

Without further ado, here are six ways to reduce lee helm and reduce the amount of adrenaline caused by your boat zigging when you'd like it to zag:

  1. Trim the main (without stalling it!) or ease the genoa to reduce lee helm.
  2. Use a smaller  jib or genoa, or shake a reef out of the main. If you have a roller furling genoa or main, furl the genoa a bit, or expose more of the main. Either will move the CE back and reduce lee helm.
  3. Slide the genoa car aft on its track or tighten the halyard on the main, either of which will help reduce lee helm. Magic Moments doesn't have a halyard for the roller furling main; instead, slide the boom car forward.
  4. Keep weight forward to keep the bow down (whether crew weight or weight in the V berth). Doing so will move the CLR forward and reduce lee helm.
  5. Drop the centerboard to move the CLR forward, which will also reduce lee helm.
  6. Rake the mast aft to move the CE back and reduce lee helm.

I'll delve a little more into each of the above in future posts. Stay tuned.

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