Twist and Telltales
What a great weekend in Newport! From the feedback, it sounds like everyone had a blast and from the volunteer side of things, I would have to agree. A big thanks to those who traveled to Newport this weekend for the First Chance Clinic and Regatta. Even though the wind didn’t bless us on Saturday, everyone had a chance to get out and dust off the keel bolts. In fact, I think I saw some leaves come out of a bow launcher on the first set!
Sitting on the side lines is tough. But being an active RO sure is fun and it really gives you the perspective of trying to support the sailors. With the help of Rosemary Jones and Kelly Jordan, we sure had a blast on the RC boat (courtesy of Tom Lemaire). We got off 9 great races and could have gotten off a lot more if Saturday’s winds would have cooperated.
From the observation deck of the 22′ Mako there were two small items that could make a big difference in light air; Mainsail Twist and Telltales. Now each of these are important independently from each other but together they are your speedometer in light air.
First let’s talk about twist. Twist relates to the horizontal chord profile of the draft of your main. Essentially if you look vertically up your boom, envision lines drawn from the luff to the leech of your sail. The alignment of these imaginary lines helps determine the twist of your sail. (Google Mainsail Twist)
So when we talk about adding twist in light air, also referred to opening up the leech, we are talking about not needing leech tension to allow the sail to be shaped properly for maximum power/flow (more on this in a minute). The two biggest controls for controlling leech tension are your main sheet and vang. Less tension on the leech opens up the top of your sail and allows for your main to work efficiently and not lose flow. How do you know? Telltales.
Going back to the addition of twist, separating your boom from the traveler decreases downward force and allows the leech to open when there is minimal pressure. The only thing pulling down on the leech is the weight of the boom. The tighter you trim your mainsheet the more leech tension you add.
There were a lot of times this weekend, where I was looking at a boom and it was trimmed in very close to the traveler car (bad sign in light air). This means you are sheeted in, so the logical progression is to look up the leech and see 2 of 3 or all three telltales stalled or hiding to the lee of the sail. Not fast. But an easy fix. Ease the mainsheet, bring the traveler up and make sure vang is off.
So to summarize, in very light air (0-5kts) skippers should peek up at their mainsail every 30 secs and check to make sure the telltales are flying. If they are then you have enough twist in your sail. If not, check to make sure you have no vang tension and pull the traveler up while easing your mainsheet. Looking at your main is like keeping your foot on the accelerator. If you don’t look up you are probably taking your foot off the gas pedal.
Another tip is the top batten. Have your crew sight up the side of the boom and see if the top mainsail batten is parallel or twisted. This is a great gauge for showing a crew what twist is all about. You can argue with the crew later on whether twisting screw tops or pop tops are better in the cooler.
-Dave Johnson Jr.