As a sailmaker, I sometimes feel like a doctor talking to an ill patient calling me with a list of symptoms, asking me—without a proper examination, mind you—to diagnose the ailment and offer a cure. Most of the calls from my “patients” come Monday morning, right afer a racing weekend. The calls go something like this, “We had great speed forward, but could not point with the rest of fleet,” or “I had tons of helm and could not keep the boat flat. I think my new sails are too full.”

Once I’m done listening for telltale clues I ask questions to come up with a diagnosis. “How tight was the jib halyard,” “Where was your jib lead?” “What model main were you using?” I will then ask if the customer has set up his boat according to the tuning guide that comes with each sail. Human nature being what it is, everyone answers: “Of course, I have!” From there, I mine into the details of the tuning guide and how it applies to their specific boat.

The difference I’ve found over the years between sailors in the middle of the fleet and those at the top is that the top sailors have learned, for their particular class, why the information in the tuning guide is there. Why, for example, you set up a J/24 always with a maximum length headstay, and why, in the Etchells class, two seemingly identical boats have mast rakes that vary by an inch or more, and yet both boats are fast. The best sailors are like chefs
who have gone through Le Cordon Bleu, learned to follow all the standard recipes, but are now creating their own variations because they understand how the basic ingredients go together.

In this first installment of a two-part series we’ll focus on getting beyond the tuning guide and developing the tools to really understand how your particular boat performs best. Think of it as putting aside the “cookbook” and getting into science of the recipe.

Let’s start by looking at the basics of most tuning guides—setting up the rig in the boat—and then proceed to the parts of the guides that include sail trim and how to get to the next level and make sail-trim decisions on the fly.

Getting a balanced package
The most basic requirement for having consistent boatspeed is a balanced helm. In its simplest form, a boat is balanced when the center of effort (CE) of the sails (geometric center of the sailplan) is over the center of lateral resistance (CLR) of the underbody of the boat (geometric center of the underbody). Anyone who has sailed a windsurfer knows there’s a spot where the mast is held in just the right position, fore and aft, which results in the
board sailing straight. Your keelboat or dinghy experiences the same thing.

When sailing your boat, it helps to remember that the CE and CLR are actually displaced significantly forward from their geometric centers. The CE shifts forward when sailing upwind due to the camber in the sails (assuming a standard sloop rig). A similar thing happens with the CLR, due to the camber in the underwater foils most boats have. It’s also helpful to consider that the CE moves aft as the apparent wind moves aft and we start heading downwind. This is why boats, when close reaching, tend to get loaded up on the helm until turning downwind, at which point the CE shifts forward to the geometric center. It is also why, in most boats, raking the mast forward downwind and reaching is fast. It helps to give more of a neutral helm, especially on a reach.

Almost all tuning guides I’ve read or written start with the absolute basics on to how to set up the boat, mainly positioning the mast. Usually, a few key numbers are there: mast rake, baseline shroud tension and pre-bend (static bend at the dock), mast-butt position, mast position at the deck, and spreader deflection, if the boat has swept spreaders.