Sailing with your sails or CE/CLR

Before I start with the main topic of this article I need to insert a small disclaimer.

DISCLAIMER:
I am not an MIT trained physicist (nor do I play one on TV) and, despite what my mother thinks, my math skills border on 9th grade level. Well, maybe not that bad, but I don’t anticipate being awarded any genius math prizes in the near future.

Since the business part of this post is complete we can get to the nitty-gritty fun stuff.

It’s no small secret that I love to race sailboats and if you’re reading this you probably do too. I consider myself an intuitive boathandler. I’m constantly tuning into the feel of the boat as it moves through the water, is it sluggish or is it rising up beneath me? I’m feeling the sheet in my hand and the pressure on the tiller. Every sailor has a different perspective on boat handling and approaches to tuning, tactics and strategy are equally varied. Most racers enjoy trying out different stuff and sharing it with fellow sailors. That’s a big part of what makes this sport so satisfying. I call it the “Sailing Continuum” (NOTE: initial caps means muy importante). It’s a perpetual cycle of learning and mentorship that is a natural part of the sport we love. I mention this because I have been a beneficiary—learning from great sailors—and lately a contributor through my coaching of youth sailors. 

But I digress; on to our main topic: CE/CLR. No, it’s not some crazy physics thing (actually it sort of is) but it is real. Here’s the definition according to Dave Acree* (smart dude from the web). “The Center of Effort (CE) is the geometric center where the wind pressure on the sails exerts its total heeling effect. The Center of Lateral Resistance (CLR) is the geometrical center of the yacht while in the water.” All I can say is, “WHUUH!”, muy importante stuff.

So what does this all mean is layman’s terms? Basically, there are forces acting on a boat above the water; the wind flows on either side of the sail, causing lift. The lift force is countered by lateral resistance created by the keel. The balanced combination of the two forces causes a sailboat to move forward in a relatively straight line. If the sail is trimmed properly, for example: trimmed in over the centerline of the boat on a close-hauled course, the boat will feel balanced, exhibiting neutral helm.

Let’s say you are sailing along in one of our Courageous Rhodes 19s, on a close-hauled course, at a 45 degree angle to the wind (Remember, we’re talking a Rhodes 19 here). You see a puff of breeze coming. The water is pretty dark and rippled so it’s probably a good size puff. All of a sudden it hits and WHUMPF! Your weather helm increases dramatically, the boat heels A LOT, and you round up into the wind.  What just happened?  For one thing when the puff hit the CE shifted from a balanced position—closer to the mast, in the center of maximum draft—to an unbalanced position—towards the leech of the mainsail moving the draft “abaft the beam” (love those nautical terms) as if the Incredible Hulk’s fist just pushed really hard on the back of your sail. Why did this happen? When the puff hit, the apparent wind increased. Therefore, the angle of the breeze shifted backwards. You just experienced a super sized lift. The boat rounded up because you didn’t ease your sail (or drop the traveler) when the puff hit.

FUN RHODES FACT #67: In the puffs: EASE-HIKE-TRIM
Some boats you can “feather-up” in a puff (steer towards the puff and gain height). The Soling is a good example of a boat that feathers well. The Rhodes 19 isn’t. The moment you get her up past a minimal heel she’ll start to slide sideways (tubby keel, rounded bottom). At that point you’ve negated CLR. So what’s a sailor to do?

The key to sailing efficiently upwind is:

• EASE in a puff to keep CE in it’s proper location
• HIKE your butt off to get the keel as straight down in the water as possible
• TRIM and harden-up once the boat flattens to gain speed and height

Now that you hopefully understand the mechanics of CE/CLR how can you take advantage of them on the race course? Most importantly, you'll stay in control of your vessel, which is essential in a crowd of boats. A boat that is in danger of rounding-up can cause havoc and damage to surrounding vessels. Learning how to shift CE forward or backward will improve boathandling skills. For example: use it to maneuver into and maintain position on the starting line. A trimmed main and luffing jib moves CE backwards and drives the bow up into the wind. An eased main and backed jib moves CE forward, driving the bow down. Another great use is when rounding marks. Ever try steering around a windward mark on a breezy day with just the rudder? You quickly learn that the boat resists your efforts, especially the Rhodes 19. The windier it gets the less effective the rudder is, but if you quickly ease your main and follow it with the jib the boat will turn on a dime. CE has moved forward and the boat turns downwind. Conversely you should start to trim your main before you’re about to round the leeward mark. CE will move back, the boat will round up, and you’ll have a tighter rounding. BTW-rather than cranking the jib in tight trim it through each point of sail ‘til you are on your close-hauled course. Trimming in too soon causes a bow down effect.

PRACTICE:
Go out on a puffy day (we get a lot of those in Boston harbor this time of year) and play. Sail on a close-hauled course, when a puff hits, do the ease-hike-trim thing.  Don’t be afraid to experiment with timing, angle of heel, and sail trim. If you’re heeling substantially take note of the boat’s slide to leeward. As you EHT note how the weather-helm (pressure on the rudder) releases, the boat resets to a straight-line course and you are able to drive up into the puff. Look up at the mainsail and try to pick out the effects of the puff. Can you see the draft moving backwards?

Put out a couple of marks and practice rounding them (mooring balls work too). Try to round a windward mark without easing and look back at your wake. Then do it again while easing the mainsail. Do the same thing with a leeward mark: round without trimming in and check your wake. Then do it again. When you are about a boat length from the mark start trimming (about 1/2 way). As you round trim in completely and look back at your wake. I guarantee you'll "sea" a difference. Keep in mind that while the principals are the same your boat will behave differently in different wind and sea conditions.

Most of all – try new stuff, have fun, don’t hit anything, don’t break anything. Be safe.

I welcome you comments and suggestions for topics!
Look for new postings to Center of Effort every couple of weeks. Topics include aspects of racing tactics and strategy, boathandling, and interviews with some of our best Boston area racers. As always I enjoy hearing your comments and topic ideas.