How our unbalanced sailplan messed up our rudder
In a previous post I described what happened to us when we were sailing in northern Sardinia, and how the extreme helm pressure required to head up into the wind caused the rudder linkages to slip on the rudder shaft. The rudder slipping was a symptom of a sailplan balance issue. In this post I will explain what happened and what we can do to fix it.
Our current sailplan is unbalanced in strong conditions
A balanced sailplan is important. In basic terms, we need to have the force that’s trying to turn the boat into the wind, balanced by the force that’s trying to turn the boat away from the wind. The mainsail is behind the center of the boat, so when the wind blows from the side, it will push on the mainsail and rotate the bow upwind (this effect is called weather helm). The headsail (jib) is forward of the center, so the wind blowing on the headsail will push the bow downwind (lee helm). If these forces are not balanced, the rudder must be used to counter the unbalanced force and keep the boat moving in a straight line. Rudder pressure acts as a brake and slows the boat down, so unbalanced sailplans are not efficient, and create more work for the helm and autopilot.
Here’s a good article that explains weather helm and lee helm and the importance of a balanced sailplan.
Most boats are well designed, and their sails are balanced in most conditions. Wildling is like this, she is a very balanced boat, requiring virtually no rudder pressure to keep her sailing straight. Our last boat was not well balanced and had too much pressure from the mainsail, so she kept trying to steer up into the wind.
The problem becomes how to keep these forces balanced as the sailplan changes. On Wildling this is a problem when we reef the mainsail without changing the headsail. As the mainsail is reefed, it gets smaller, so the force pushing the bow to the wind gets less. Since the headsail hasn’t changed, it’s force starts to overcome the mainsail and we have the bow constantly turning away from the wind. If the wind gets strong enough, the amount of rudder pressure required to point up into the wind becomes considerable. If we reef the jib, the problem gets even worse, because we move the force on the bow forward, so it has a greater lever effect. This is what happened to us in Sardinia.
The solution is simple, and is what Outremer recommends: When the mainsail is reefed, you switch to a smaller headsail positioned further back towards the mast. In this configuration it’s possible to keep a balanced sailplan upwind in winds up to 45 knots.
Wildling was built to have the staysail and storm jib added, but I haven’t ordered them yet, because I wasn’t sure how I wanted to incorporate them into the sailplan along with our self tacking jib (which I LOVE by the way).
On the other 5X boats I have seen that have staysails, they have the inner sail setup on the auto-tacker, and a genoa that tacks manually around the staysail. Like this:
But on Wildling, we don’t want the staysails to interfere with the self-tacking jib, so we need a way to rig them when necessary that isn’t too onerous in strong conditions, and I would really like to be able to disconnect the sheets from the jib and connect them to the staysails, so we can autotack on all of the headsails. I’m not exactly sure how we will do all of this, so I’m going to work with the Outremer factory to see if we can find a good solution.
So although the rudder slipping problem was a hassle at the time, it was very easy to fix, and it helped me see clearly how important it is that we add a staysail and storm jib to our sailplan!