Hi All: I was just reading an article on the Sailnet Website, and ran across the following quote: "With roller furling now an established part of almost every cruising sailor's inventory (and I am not going to try and talk you out of it), a lot of sailing efficiency has been lost. As soon as you reef a roller-furling headsail, the sail shape goes awry, the center of effort gets raised" The part that confuses me is regarding the center of effort. When I reef, I envision a sail where the head is lower than before the reef, and the bulk of the canvas is now rolled up and reefed leaving a smaller triangle exposed to the wind. I know that the foot also is moved up a bit, but didn't imagine it was enough to offset the other factors and ultimatly raise the center of effort. Any thoughts ............ Jeff
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Jeff,
Look at the sail. The largest portion is at the bottom. AS you reef it by rolling it up, a larger area is rolled up at the bottom than at the top. Also, the larger roll on the forestay also affects the air flow to and around the sail. r.w.landau
Look at the sail. The largest portion is at the bottom. AS you reef it by rolling it up, a larger area is rolled up at the bottom than at the top. Also, the larger roll on the forestay also affects the air flow to and around the sail. r.w.landau
CE higher, but smaller, too
As usual, RW is right on. The bulk of the roller furling sail resides on the bottom of the sail, even with a "cruising" type headsail that is cut high to begin with. So, as it is rolled up, a roller furling jib does have a higher center of effort, per square foot, than a fully deployed sail. However, since the square footage is lower, that CE is not as significant a factor. I went out on Saturday in heavy winds and reefed my 150 down to about 100. The shape stunk, but at that point, it is my humble opinion that you don't really need an efficient sail shape - you just need a triagle out there to speed airflow over the back of your (hopefully) well-reefed main. The relatively-high flying jib was not a stability concern. Hope this helps. Rob
As usual, RW is right on. The bulk of the roller furling sail resides on the bottom of the sail, even with a "cruising" type headsail that is cut high to begin with. So, as it is rolled up, a roller furling jib does have a higher center of effort, per square foot, than a fully deployed sail. However, since the square footage is lower, that CE is not as significant a factor. I went out on Saturday in heavy winds and reefed my 150 down to about 100. The shape stunk, but at that point, it is my humble opinion that you don't really need an efficient sail shape - you just need a triagle out there to speed airflow over the back of your (hopefully) well-reefed main. The relatively-high flying jib was not a stability concern. Hope this helps. Rob
Rob, the mainsail.
Jeff's boat has mainsail reefing and I think that was his question. You and RW are both correct however. I can understand Jeff's question though because the sail seems to disappear from the top down as it goes into the mast. I'd be surprised if you could notice it since, as you point out, it is higher but smaller. The answer to this dilemma? Boom reefing!
Then after sticking my foot in my mouth I just noticed the title, "Headsail Reefing". Sorry about that, but he does have a furling main.
Jeff's boat has mainsail reefing and I think that was his question. You and RW are both correct however. I can understand Jeff's question though because the sail seems to disappear from the top down as it goes into the mast. I'd be surprised if you could notice it since, as you point out, it is higher but smaller. The answer to this dilemma? Boom reefing!
Then after sticking my foot in my mouth I just noticed the title, "Headsail Reefing". Sorry about that, but he does have a furling main.- Status