The Stobbe Vane: Tacking Upwind with the Self-Steering Vane By Mike Stobbe In the previous article, I described how the vanes built by Jeff Stobbe should be prepared for use. Sailing with the self-tacking vane is relatively straightforward. Much of it comes down to careful preparation beforehand. Many thanks to Drew Marshall for his review and helpful comments contributing to this article. It is assumed that the boat has already been dynamically balanced with respect to the mast position and jib pivot position. If the boat is well balanced to windward, it will pretty much sail itself, and the vane will have a very light duty to perform. A "problem" with vane-controlled boats is that even a mediocre vane setting will enable a boat to beat so relatively well, that many skippers are content to leave it at that and not bother to seek the most out of it. You are now ready to go sailing. This article is not about rigging or the setting of the sails, however, it's worth mentioning to the reader that for good upwind performance, the rigging should be set to ensure that the jibstay is really taut. Set the vane onto the vane post, and engage the operating pin with the tiller slot. Clip on the safety line. Tacking upwind (beating) with a self-steering vane is quite simple. With the vane locked, rotate the vane body until it is pointed exactly straight ahead, with the feather right aft. The correct way to do this, is to rotate the vane until the operating pin is hard up against the end of the tiller slot, and then to continue rotating, against the friction grip of the clamp-screw, until the vane body aligns with the straight-ahead mark obtained from the degree-board. The incorrect way to do this, is to grasp the rudder blade, and rotate the vane while holding tiller in the straight-ahead position. The latter method will torque the tiller's clamping block on the rudder post. It may slip, unnoticed until you release the boat…too late! The correct method puts no stress on the rudder post or the construction joint between the rudder post and rudder blade. The vane must be locked to make this straight-ahead setting. After the vane is set to the straight-ahead position, use the beaded chain to set the rudder-centering elastic to a very weak tension, just enough to keep the beaded chain from dragging on the deck. If the boat is equipped with a slotted comb, set the beaded chain on- center. No rudder offset is used when beating. Note that the centering elastic not only returns the tiller to center, it also offers resistance to the vane rotation. When beating, we want the former, but not the latter. Thus, we want as little tension on the centering elastic as will still do the job. Now unlock the vane. Ensure that the gying spring is hooked on the side of the feather bracket that is nearest to the shore that you will be walking on. At Spreckels Lake, the prevailing wind and shape of the lake dictate beating westward, walking along the north shore. Thus the gying spring will always be attached to the starboard side. If you wanted to sail a windward board walking along the south shore, you would clip the spring to the port side of the feather. 1 With the sheets set in their beating positions, place the boat into the water, pointing into the wind. Holding it by the stern, allow it to pay off until the sails just fill and stop luffing. As the boat begins to heel over to the wind, let it go, and closely observe its progress. Potential adjustments will be to the gying spring tension and the tacking angle. The tension in the gying spring should be fine-tuned each day that the boat is used. Take note of how the quickly the boat tacks upon release or turn-out with the pole. If it consistently tries to tack immediately, within one or two boat-lengths from shore, then the gying spring is too tight. If it goes all the way across the lake without tacking at all (apart from induced tacks caused by large wind shifts), then the gying spring is too loose. The difference between too loose and too tight is very slight, however. This is a very sensitive adjustment. Make gying spring adjustments of only about ¼" or less, by sliding the transverse adjusting hook on the feather bracket. Observe the boat to gauge its effect before adjusting again. The initial setting should prove to be very close. However, in general, windier days require a bit more tension, and lighter days a bit less tension. Also, be aware that for the vane to flop over, the boat must come upright at least momentarily, due to a lull in the wind or being headed by a wind shift. On Spreckels Lake one can always count on this, but if sailing elsewhere under strong and steady wind, the boat may stay heeled over on its initial tack for a long time; the vane unable to flip over due to the steady wind pressure on the vane feather. In such conditions, the gying spring will need significantly more tension. For the same reason, the boat should be turned out far enough for the sails to fully fill. The boat needs to be heeling a bit as it leaves the shore to ensure that the feather droops to leeward. If it leaves the shore with the feather still flipped to windward (i.e. in the same position it was in when it approached the shore on the other tack), then the boat will immediately try to tack, and will probably fail because it will not have gained enough momentum (known as "way") to complete the tack. Failure to tack is more fully discussed at the end of this article. As mentioned at the beginning of this article, a really well-balanced boat will sail itself, going to windward. A clear advantage of vane control, however, is a faster response to being headed. With or without a vane, a well-balanced yacht will naturally rise to a lift. A headed yacht without a vane, however, will begin luffing, slow down, gradually pay off until the sails fill again, and then gather speed on the new course. A well set-up vane-controlled boat, by contrast, should quickly steer to the new course when headed, with only a brief moment of luffing, provided that the skipper has the correct relationship between the slack gying spring tension and the tiller-centering elastic tension. Upon consideration, one will realize that this relationship also plays a role in a vane-controlled boat's ability to complete a tack, as tacking is essentially a continuation of the response to being headed. After a little practice, you will soon become familiar with the effects of the gying spring tension. Once you're experienced enough to be confident of the effects of adjustments to the gying spring, you may even try using it as a racing tactic. Two scenarios are likely possibilities during a race. In the first case, shown on Figure 14, one is nearing the last tack of a windward board on a lake where the wind direction is far from perpendicular to the finish line. Under such conditions, one end of the line will be favored over the other, and a shorter sailing distance will be required to reach the favored end. Note, as depicted on Figure 14, that if two boats leave Point "B" the skipper who increases his gying spring tension to 2 force a short tack, may reach the finish line at Point "C". The skipper who continues with a gying spring having a low tension, makes a long tack, and is shown reaching the finish line at Point "D". The second skipper will only have reached Point "D' " when the first skipper finishes. Figure 14. Short Tack vs. Long Tack to the Finish Line 3 Figure 15. Short Tack vs. Long Tack for the Best Wind The second scenario involves using the gying spring tension to induce a long tack or a short tack to avoid known wind shadows caused by trees, or to stay as much as possible in areas of the lake known to have the best winds. An example is shown on Figure 15. A word of caution, however. On a lake with very shifty and unsteady wind such as Spreckels Lake, the distance a boat will travel before self-tacking is very uncertain. One must weigh the risk of wasting the time for a change of trim for the purpose of taking advantage of what may be a very fleeting wind condition, against a benefit that may or may not be realized. 4 The vane tacking angle must also be fine-tuned, but once set, will not need to be adjusted very often. Once you are satisfied with the tacking angle, you can leave this adjustment alone much of the time. The final tacking angle is dependent upon many factors; some are under the skipper's control, and some are built in to the hull design and cut of the sails. Notice I don't refer to the "correct" tacking angle. There is no "correct" tacking angle. There is only the tacking angle best suited to your boat and the way you like to sail it. Good windward work depends entirely upon sail trim. The angle at which a boat sails into the wind will vary with the trim of the sails.