Re: [Cal_Boats] Heeling and Sail Selection (Charlie)

> > Here is some counterintuitive stuff I sort of cooked up in my head: > > Easing the jib halyard tension to windward, even to the point of scalloping the jib, flattens the entry of the sail and allows higher pointing. As you tension the halyard, watch the front of the sail curl moving the entry to the wind to leeward. If it is blowing, you don't need the maximum drive anyway. > > Easing the backstay tension (yes, to windward) moves the bulk of the forestay outward. This then allows you bring the sheet in further for a higher effective angle. This is primarily for flatter sails as it also gives more shape. The counter to that is that the backstay has to come in for broad reaching and running, since the loosened forestay tends to flap back and forth on those courses. Totally backwards (but then, that is me). > Yes, this is counter intuitive and counter everything I have heard if I understand what you are saying. The conventional wisdom is to tighten the backstay tension to flatten the sail. Hold a piece of paper between your fingers and pull your fingers apart. The paper is flat. Bring your fingers together and you get shape in the paper. Same thing with a sail, right? Also counter intuitive is your discussion of halyard tension. Usually people say to tighten this in higher winds to bring the maximum draft back forward where it belongs. In light winds, you may get scallops when you bring the draft forward but in normal winds you don't. Please explain what I am missing in what you are saying. Allen

Hi Allen. To take an analogy from air plane wings which work like sails to provide lift (to windward). Old biplanes used wings with very deep camber as the wind passing over them did not exceed 150k Modern planes that have nearly flat wings fly much faster except of course at takeoff. At takeoff speeds they must reconfigure the wing for the lesser wind speed so they have flaps, droops and slats to do that. So too does the modern sailboat need adjustment. A sail that works well in 8k needs to be changed to work best in 28k. Going to weather in 20+k sails need to provide less power than in 8k and the way to depower the mainsail is to increase mast bend to flatten the mainsail in the upper 2/3 and to increase outhaul tension to flatten the lower third of the mainsail.. The jib is somewhat different. The sailmaker took into consideration jibstay sag when he decided how much draft to build into the sail.A jib skould have its halliard tension increased as the wind builds to remove the wrinkles that develop at the hanks. It will do damage to the sail to allow the sail to hang on the hanks and not be allowed to distribute the load in an even manner along the luff. The draft can be modified somewnat by jib car placementand sheet and halliard tension but not as much as can be done to the mainsail. My Best, Mike --- On Mon, 8/17/09, Allen Edwards <al… [at] PaloAltoPhoto.com> wrote: From: Allen Edwards <al… [at] PaloAltoPhoto.com> Subject: Re: [Cal_Boats] Heeling and Sail Selection (Charlie) To: Ca… [at] yahoogroups.com Date: Monday, August 17, 2009, 6:43 AM > > Here is some counterintuitive stuff I sort of cooked up in my head: > > Easing the jib halyard tension to windward, even to the point of scalloping the jib, flattens the entry of the sail and allows higher pointing. As you tension the halyard, watch the front of the sail curl moving the entry to the wind to leeward. If it is blowing, you don't need the maximum drive anyway. > > Easing the backstay tension (yes, to windward) moves the bulk of the forestay outward. This then allows you bring the sheet in further for a higher effective angle. This is primarily for flatter sails as it also gives more shape. The counter to that is that the backstay has to come in for broad reaching and running, since the loosened forestay tends to flap back and forth on those courses. Totally backwards (but then, that is me). > Yes, this is counter intuitive and counter everything I have heard if I understand what you are saying. The conventional wisdom is to tighten the backstay tension to flatten the sail. Hold a piece of paper between your fingers and pull your fingers apart. The paper is flat. Bring your fingers together and you get shape in the paper. Same thing with a sail, right? Also counter intuitive is your discussion of halyard tension. Usually people say to tighten this in higher winds to bring the maximum draft back forward where it belongs. In light winds, you may get scallops when you bring the draft forward but in normal winds you don't. Please explain what I am missing in what you are saying. Allen ------------------------------------ Yahoo! Groups Links

Sorry, I thought you were saying the opposite of this in your original post. Allen On Tue, Aug 18, 2009 at 5:35 AM, mike farrell <ve… [at] yahoo.com> wrote: > > > Hi Allen. > To take an analogy from air plane wings which work like sails > to provide lift (to windward). > Old biplanes used wings with very deep camber as the wind > passing over them did not exceed 150k > Modern planes that have nearly flat wings fly much faster > except of course at takeoff. At takeoff speeds they must reconfigure the > wing for the lesser wind speed so they have flaps, droops and slats to do > that. > So too does the modern sailboat need adjustment. A sail > that works well in 8k needs to be changed to work best in 28k. > Going to weather in 20+k sails need to provide less > power than in 8k and the way to depower the mainsail is to increase mast > bend to flatten the mainsail in the upper 2/3 and to increase outhaul > tension to flatten the lower third of the mainsail. > The jib is somewhat different. The sailmaker took into > consideration jibstay sag when he decided how much draft to build into the > sail.A jib skould have its halliard tension increased as the wind builds to > remove the wrinkles that develop at the hanks. It will do damage to the sail > to allow the sail to hang on the hanks and not be allowed to distribute the > load in an even manner along the luff. The draft can be modified somewnat by > jib car placementand sheet and halliard tension but not as much as can be > done to the mainsail. > My Best, Mike > > --- On *Mon, 8/17/09, Allen Edwards <al… [at] PaloAltoPhoto.com>*wrote: > > > From: Allen Edwards <al… [at] PaloAltoPhoto.com> > Subject: Re: [Cal_Boats] Heeling and Sail Selection (Charlie) > To: Ca… [at] yahoogroups.com > Date: Monday, August 17, 2009, 6:43 AM > > > > > Here is some counterintuitive stuff I sort of cooked up in my head: > > > > Easing the jib halyard tension to windward, even to the point of > scalloping the jib, flattens the entry of the sail and allows higher > pointing. As you tension the halyard, watch the front of the sail curl > moving the entry to the wind to leeward. If it is blowing, you don't need > the maximum drive anyway. > > > > Easing the backstay tension (yes, to windward) moves the bulk of the > forestay outward. This then allows you bring the sheet in further for a > higher effective angle. This is primarily for flatter sails as it also gives > more shape. The counter to that is that the backstay has to come in for > broad reaching and running, since the loosened forestay tends to flap back > and forth on those courses. Totally backwards (but then, that is me). > > > > Yes, this is counter intuitive and counter everything I have heard if > I understand what you are saying. The conventional wisdom is to > tighten the backstay tension to flatten the sail. Hold a piece of > paper between your fingers and pull your fingers apart. The paper is > flat. Bring your fingers together and you get shape in the paper. > Same thing with a sail, right? > > Also counter intuitive is your discussion of halyard tension. Usually > people say to tighten this in higher winds to bring the maximum draft > back forward where it belongs. In light winds, you may get scallops > when you bring the draft forward but in normal winds you don't. > > Please explain what I am missing in what you are saying. > > Allen > > > ------------------------------------ > > Yahoo! Groups Links > > > > >