Regardless of whichever point of sail your boat is on, if you center your rudder and yet still notice that your boat is turning upwind then you are experiencing weather helm. On a real boat you adjust the sail trim of your mainsail and headsail separately and so this phenomenon arises when there is an imbalance in the sideways forces generated by the mainsail (located aft of the center board or keel) and the headsail (located forward of the center board).
Even when using manual sail trim in the game, the trim is always affecting both main and head sail together so this imbalance will not show up so readily ... that is unless you are flying your kite (sailing with your spinnaker up) and making a course that is dangerously approaching a broad reach or with some asymmetrical spinnakers a beam reach. A small change in wind direction toward the bow of the boat or a small increase in wind strength can bring on this weather helm effect.
You can smoothly recover from weather helm by manually easing the trim on your sails. By far the easiest/quickest recovery is to release sail trim altogether as you adjust your course to be more downwind than it was and then re-engage the sail trim. This maneuver takes only a fraction of a second whereas if you try to adjust your course without releasing the sail trim the helm will be slow to respond and you will very likely find that your boat accelerates the turn to windward until you are sufficiently broadside to the wind that the forces on your spinnaker and main sail flatten the mast to the water and, of course at that point, your boat will have lost all of it's forward motion. This dramatic event is called a broach (rounding up) and also happens in a fraction of a second if you fail to notice the signs described earlier or if you notice but fail to respond to them.
It is best that you develop a memory for the highest safe point of sail for any given wind strength and then monitor TWA and TWS to respond early with small rudder adjustments long before the onset of round up.
Having said that, do practice steering the boat under spinnaker while the sail trim has been released altogether. Your reward from this exercise will be the ability to fly your kite all the way to a gybe mark by periodically making course corrections that place your boat above the layline while keeping the apparent wind sufficiently aft so as to avoid rounding up. The secret is to realize early on in the leg that several adjustments along the leg will be needed to gain that extra little bit of ground upwind and then taking care not to bear away too much when you resume sail trim to gather boat speed before repeating the maneuver.
- Always gather boat speed before trying a maneuver with a de-powered sail.
- Lee helm
- Imbalance leading to a gradual turn downwind is the opposite effect to that described above however the author cannot recall a boat model where this effect is noticeable. If you can recall then please be sure that the corresponding wiki article for that boat model make mention of it.