Chesbay.net - advanced tag

Improving as a Racer, Part 2.5, More on the Sails

Wed, 24 Feb 2010 18:09:00 GMT

A big question is how "good" do the sails need to be for a developing sailor. And how do we know? I want to be able to say something like "ignore high-tech fabrics" or "Go to a used-sail loft" or something. But I'm realizing it isn't that simple; the question is unanswerable as a general case.

Basically, we have to have equipment that is as good as the top rung of the ladder we want to climb. The ladder is our ruler, we measure performance against the fleet. So first question is, "can my team manage the boat around the race course and perform the standard maneuvers"? At that point we need sails that keep us in competition with the fleet. When everything is settled and we're hanging with our part of the pecking order in the fleet and our power and boat speed are equal. But, the sails have to work so that we can change gears as needed. Usually that's not a cheap sail. Depending in our fleet and it's competetiveness and culture, that may well mean new sails every year.

But, can I really SEE the difference between good and great sails (as determined by the fleet culture). If I can, I should go for them because it's my passion; why would I short change myself. And I can copy the way the top of the fleet set up.
But with that advice comes this: don't think that we'll necessarily win or get the most out of those sails. Time on the water is the coin that matters. Time on the water means that we'll be able to pull the strings to get the sail shaped correct for the conditions. If we have a lesser sail, it's much harder to see the effect of getting it set properly.

As an example, one of our competitors on Wednesday nights in the past few years wins with his personal recut sails from Bacons. He probably starts racing with sails as good as the top of the Wed night fleet or a bit worse. He knows how to set them right. His sails are good enough so that other aspects of racing determine his place but always in the top. But, he does not race CBYRA weekend races where the sailors would be as good as him, but playing with newer sails.

So bottom line: sails are an issue when we have boat speed issues that are not explained by some other factor like crew weight, bottom not clean, rig out of tune, etc. In the same breeze, current, etc. and with clear air and the other boat is just faster, then we might see and identify the problems in our sails.

Improving as a Racer, Part 2, the Sails

Tue, 23 Feb 2010 19:13:00 GMT

I'm always a bit amazed at the poor condition of sails on many sailboats. As a sailor, these are the engines of the boat. Otherwise, we're powerboaters! But for the improving racer, how important are the sails? This is really a question about sail shape.

The problem with sails and sail shape for the developing racer is fundamentally one of perception - our ability to see color, depth, shape, dynamic effects and most importantly to remember these features. Visualizing the three dimensional shape of a sail is a talent; no amount of theoretical knowledge can replace our intrinsic ability to see the subtle perceptual details of sail shape and identify what's right and what's not. Sailing is such a dynamic process with so many factors in play that it is impossible to isolate one factor and exclude the effects of all of the others.

The problem is compounded when trying to compare two sails on the water in the same time frame - our visual memory can hold the images for just so long .   We may not be able to ID and then remember the critical differences.

Coaching or sailing with more experienced sailors is the usual way a sailor develops an intrinsic talent for seeing sail shape. The match between the coach's ability to identify key features in the sail shape, vocalize or describe these observations to the sailor and have the insight sink in and become usable by the sailor is the essential factor. The simplest example of this process concerns the use of telltales. Most sailors get this when they are trained on understanding and using telltales and then adjusting the jib car to get the tell tales to break evenly. Actually seeing the shape change in the sail is where the perceptual talent comes into play. Being able to see the sail shape and the effects of sheet tension, rig tension and car position on the sail shape will be the difference between mid pack and top of the fleet.

For example, Beach catamaran sails are fully battened and this allows us to set two boats up on dry land and study the shapes of two sails side by side in very light breeze. Of course a bit more sheet tension or cunningham or mast rotation *by design* changes the sail shape. We've spent hours trying to make sure we see what is happening dynamically, alternating between looking at the sail and rig from astern and then looking at that shape from the helm position and trying to remember the sail shape. Once out on the water it's all different but we have developed a solid basis for making adjustments and our ability to match the wind and water to the rig and sail shape as well as change gears = speed.

So, the question about good and best sails is complicated. Are we talking about cloth, construction, design shape, stage of the sail's life cycle or marketing and reputation? Let's assume, for the sake of argument, that "Good Sails" are half way through their racing life cycle while "Great Sails" start at new and work backwards.

I believe we can't learn or be able to practice gear changes and optimize sail shape unless we have good sails on the boat.   The sail has to be good enough so that when we make the gear change adjustment we will see the shape change and measure or feel the boat respond. It is so hard to match perceptual cues to the dynamics of the wind and waves anyway that without good sails we won't be able to feel the boat or keep pace with the fleet. Most importantly, we won't be able to improve our sailing performance if the equipment can't keep up.

The most difficult thing to do is have the opportunity to SEE THE CONTRAST between two sails, i.e., the perfect one and the sail that has been used for some time.    This contrast is important in knowing what gears you loose as the sail gets older and the shape distorts. When we pull strings on both sails the great sail should adjust full range; as it gets older it looses some of that range. For most of us, we use experience to cue into the critical features and then pull the strings to match the conditions on the water. As mere mortals, we never quite know that we've have nailed the solution. Speeding this process up requires at least good sails and the coaching/talent in seeing both shapes of good and great sails. Of course, we have to pull the strings properly!

If we don't pay attention to the subtle details, i.e., we set the jib cars and the break is OK but we haven't studied the sail shape and noticed how it changed and how the shape is changing with pressure and age, then spending lots of money to keep great new sails on the boat won't translate into wins. We might do better but this is a case where a boat speed/tuning coach can be money better spent then for new sails.

If you are purchasing sails, what's critical is the rig. We can't easily change the rig properties. On Tornado's and A cats each mast is different and we need to get the sail to match the mast as well as have the fast sail shape built in. In most monohulls the sailmakers are less interested in measuring each mast, but each boat typically has a rig tuning guide. Assuming the materials are constant, design shape is probably a bit over stated - after all, its a well known problem.   So matching the mast, tune-ability, construction execution, and service become the key factors.

The affects of current on apparent wind

Mon, 15 Feb 2010 18:32:00 GMT

There are many mis-perceptions about currents and how to work in them. Especially in distance races such as the overnight Governor's Cup and Solomon's Island races, skippers often work towards deep water what the current is in a strong ebb, and towards shallow water in a strong flood. This makes some sense because distance races on the bay tend to be southbound races, winds in the summer tend to be out of the south (the famous Bermuda High). And the bay being somewhat east-west narrow limits the distance races to either north or southbound directions. But what's really happening here?

The wind is almost never the same at a point in time across or up and down the bay. Taking a look at Sailflow for the Chesapeake area (http://www.sailflow.com/windandwhere.iws?regionID=108&regionProductID=30&timeoffset=0), we can see that in different parts of the bay the wind is different. And as the wind changes, it changes differently in different places too. Same with the tidal currents. So part of the navigational problem for a distance race is the balance between the varying wind speed and direction and the positive or adverse affect of current across the bay and the race course.

But, so make that more complicated, we should also consider the effect of the current on the wind. How does that work? For me, it is easiest to think of sailing in a current as like sailing on a magic carpet - the carpet is moving (in the direction and with the speed) with the current. All the boats around me are affected in pretty much the same way - sailing along, but also being carried along by the carpet. But the carpet is also creating wind. The easiest way to think of this is, if there was no wind at all and my boat is sitting still on the water, and if the magic current-carpet is moving at 1 knot, then I would feel a 1-knot wind coming from the direction in which the current is heading. So, to complete the picture, the affect of current is somewhat similar to the way apparent wind comes about with the motion of the boat changing the direction and speed of the wind. This can be calculated using a good calculator and a lot of patience. And certainly the instrument packages available on some of the high-end yachts include these calculations. But, for the average racing sailboat, those instruments are out of reach. And part of the suite of automation tools Chesbay.net will offer includes this kind of calculation over the race course.

It's important to understand the impact when making the navigation decisions. Currents on the bay are generally light - not much more than 2 knots during peak ebb or flood. But in increase or lessening of the apparent wind by 2 knots may be very significant. Especially in light winds. Let's take the following example problem.

We're sailing south in our J35 "Uncle Joe". Suppose that the wind is from the southwest at 6 kts. Let's say 210 degrees. In the western channel, the current is ebbing at 1.75 knots - let's say at 180 degrees. The effect of this is that the wind we feel will shift forward (coming from about 204) and increase in speed to about 7.5 knots. On the eastern side, in the shallows, the current is running at about .75 knots. The apparent wind speed would be less (about 6.6 knots) and the wind angle would be closer to 207. Now, which side to go to depends on tacking angles of the boat and the rumb line - having the come forward to 204 may well mean we have to tack more often to beat down the bay. This may well more than make up for the slight decrease in wind. On the other hand, our forward speed is going to be faster in the deep water, and faster also because of the increased wind speed. So the decision becomes greater speed with more tacks or less speed with less tacking.

Tough decisions, but now based on knowledge.