I was reading that loosening the halyard on the main will put more belly forward, while loosening the outhaul will add belly aft in the sail. I am assuming this will help in light winds. I am not sure, however, whether this sail trim maneuver is more complex than that, and what conditions dictate having the belly forward or aft.
Sail Trim
- Thread starter wufibugs
- Start date
Tension on the luff (halyard) pulls the belly forward, so right on that one. Tension on the outhaul flattens the sail in general, but I don't think is considered to move the belly around.
So breezy, high tension on halyard and outhaul, lighter winds less tension. I have heard it said that in really light conditions you want the sail relatively flat, I dunno how true that is.
So breezy, high tension on halyard and outhaul, lighter winds less tension. I have heard it said that in really light conditions you want the sail relatively flat, I dunno how true that is.
Well, all sail controls are inter-related. But you are asking about draft position.
Generally it should be at about 50% aft of the luff. If its not you need to have a reason. As more breeze comes on, mast bend and sail stretch will move it aft. Halyard or cummingham will move it back were it belongs.
Moving it forward say 5-10% gives more power but less speed potential for choppy water (lower gear)
Moving it backward a bit does the opposite. Flat water trick only.
Generally it should be at about 50% aft of the luff. If its not you need to have a reason. As more breeze comes on, mast bend and sail stretch will move it aft. Halyard or cummingham will move it back were it belongs.
Moving it forward say 5-10% gives more power but less speed potential for choppy water (lower gear)
Moving it backward a bit does the opposite. Flat water trick only.
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Hey,
It's not a trick, and it does work. When the wind is light, say 5 kts, I like to see 'speed wrinkles' along the mast. The halyard should be loose enough so that you actually see wrinkles along the mast track. I also like to see a lot of draft by easing the outhall. The sail should have a very noticable curve from the luff to the leach.
As the wind picks up the boat will heel more. No you start to add more tension to the outhall and halyard to keep the boat 'on her feet'.
Experiment with this by noting the speed (a knotmeter is very handy for this as it will react very quickly). Play with the tension and see how the boat reacts. I have found that the 'uglier' the main looks (wrinkles, big belly), the faster the boat goes.
Good luck,
Barry
It's not a trick, and it does work. When the wind is light, say 5 kts, I like to see 'speed wrinkles' along the mast. The halyard should be loose enough so that you actually see wrinkles along the mast track. I also like to see a lot of draft by easing the outhall. The sail should have a very noticable curve from the luff to the leach.
As the wind picks up the boat will heel more. No you start to add more tension to the outhall and halyard to keep the boat 'on her feet'.
Experiment with this by noting the speed (a knotmeter is very handy for this as it will react very quickly). Play with the tension and see how the boat reacts. I have found that the 'uglier' the main looks (wrinkles, big belly), the faster the boat goes.
Good luck,
Barry
Richard, have you read Don Guilette's excellent Sail Trim book? THE best one I have ever read, and I've read them all. It's available right here on sbo.
Stu, I have that book and reading it is what prompted the question. That book also generated another question. Don says that the mainsail chord is the distance between tack and clew. Wouldn't this mean the the chord length is roughly the same as the boom less any adjustment of the outhaul [except, I guess for mains that can be furled inmast]? Further on in discussing angle of attack he defines it as the angle between the chord line and the apparent wind. The drawing that accompanies that discussion measures that angle from some point on the belly of the sail. I was unable to work out why the angle is measured from that point on the sail.
That definition is not technically correct. The (or a) chord is the line between a point on the luff, and a point on the leach perpendicular to the first point. One chord is the one Don describes, but there is essentially an infinite number of them.
It depends. don't you love it when someone answers like that? As mentioned above, when going up wind, in general, the more wind the more you should tighten the halyard and outhaul. If you aren't sailing close hauled you want to ease both off a bit. Once you get to a broad reach you will want more belly so loosen the outhaul and halyard.
Basically, if you want more power, give the sail more belly. Flatten to reduce power. Except when the wind gets really light (under 5 knots) where the theory is that you want to reduce the amount of curvature of the sail to keep the airflow attached. This takes some finesse since you want to keep some depth to keep the sail powered up. In really light air keep the halyard loose but take up a bit on the outhaul.
You can pull the maximum draft forward a bit by tightening the halyard but it is mostly dictated by the cut of the sail.
Backstay tension can change the shape of the main quite a bit but you may not have that option on a Hunter. More backstay flattens the main by bending the mast which pulls the middle of the sail forward.
Basically, if you want more power, give the sail more belly. Flatten to reduce power. Except when the wind gets really light (under 5 knots) where the theory is that you want to reduce the amount of curvature of the sail to keep the airflow attached. This takes some finesse since you want to keep some depth to keep the sail powered up. In really light air keep the halyard loose but take up a bit on the outhaul.
You can pull the maximum draft forward a bit by tightening the halyard but it is mostly dictated by the cut of the sail.
Backstay tension can change the shape of the main quite a bit but you may not have that option on a Hunter. More backstay flattens the main by bending the mast which pulls the middle of the sail forward.