Setting PERFORMANCE out of your headsails

In order to understand more about the performance and trim of your headsails, you must first understand the basic controls of these sails. The controls that shape the jib or genoa are the halyard tension, the sheet tension and sheet lead position.

Halyard tension is very important for sails made of Dacron or any such woven cloth. In a nutshell, when you increase halyard tension, you stretch the luff of the sail, thus moving the draft forward and in turn reducing the depth or camber. Easing the halyard tension, naturally does the opposite, increasing the camber, or depth, making the sail fuller, and moving the position of the draft aft. If you have draft stripes this can be seen quite easily. However if you don't have draft stripes, use a seam line about half or three quarters up the sail. Have someone adjust the halyard tension for you while you observe the changing position and depth of the draft.

For light air you want a moderately full shape giving a smooth foil shape, whereas in heavy air you want a flatter shape. If the wind builds a little then flatten the sail some more. It should be noted that you don't over tension the luff. This can be seen by vertical wrinkles form or flat "hard" spots develop, and when this begins to occur slack the halyard until they disappear.

With laminates, i.e., Mylar, Kevlar etc. tensioning is done just to point of taking the wrinkles out of the luff tape. Care must be taken not to over tension this type of sail.

Sheet lead position is the fore and aft positioning of the fairleads or "cars" on the jib or genoa track. It is extremely important in achieving proper sail set. To begin determining the proper sheet lead position, you need an approximate starting position. This can be determined by striking an imaginary line from the 50% point of the luff length through the clew to the track. That is a very good beginning point to set the sheet block cars We now fine-tune our sheeting position by moving the car forward is the top telltale flutters. However, if the bottom telltale is fluttering then move the car a little aft or back. Keep moving the car or lead until all the telltales are streaming aft evenly. When you tack, all the telltales should break at the same time. The sheeting position that you have just determined is good for the wind and sea conditions that you are presently sailing in, if the wind increases or decreases the lead must changed once again. If your sheeting is slightly off, it is better to error on the position being slightly aft, since this adds more twist in the sail and is more forgiving.

Sheet tension, is what determines how flat or full the headsail will become, thus controlling the shape. Therefore, when you are beating, "close hauled" the harder the wind is blowing the more tension on the sheet, and the flatter the sail. In this case you do not want to let the sheet out since this would make you fall a little off and you would gain more power, increasing the heel. Also, when the sail is sheeted tightly in, the genoa should be ab9out 4 to 6 inches of the spreaders, not hitting them.

Lastly, I would like to mention the use of the leechline. The main purpose of the leechline is to stop the leech from fluttering when the designed windspeed is exceeded or the sail is showing its age. You can also control the flutter by changing your halyard tension and/or lead position. This line is not a shape control.

For the sail that is older, or has seen some tough times, the leech has stretched making it looser. If tightening the leech line has no affect, then a sailmaker can take up on the leech slightly, which should cure the problem somewhat. If the leech line is over tensioned, the leech may become severely hooked, which will affect boat speed in a negative way. The line should be tensioned a little at a time, just to the point where the leech ceases to flutter. If the wind picks up then a little more tension will be necessary.

Mariner Sails
705 Cook Street
Ketchikan, Alaska 99901
Ph/Fax: 907-225-2983
lbsail@marinersails.com


 

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