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A sail used in 'light' winds usually needs to be FLAT ... so you dont develop what known as a 'separation stall' on the backside of the sail ... a stall that that will not be 'noticable' to the naked eyeball in 'light air'.
Most 'off the shelf' mainsails are cut/constructed for service 15 kts. and will be 'too full' for 'extremely light' winds. To flatten such a sail: 1. BOW the mast forward (if you can), 2. just 'raise' the sail and than add 'little' to 'zero' extra halyard tension (will tend to 'flatten' the luff section). 3. Tight outhaul. 4. bring the leech of the genoa *closer* to mainsail (if you can). 5. move the mainsheet traveller to WINDWARD and then tension the mainsheet so that the aft section of 'second batten from the top' of the mainsail is parallel to the centerline of the boat (while 'beating').
6. (most important) get some tell-tales on ALL the leeches and near the luffs ... then 'shape' and 'set' the sails so that ALL the telltales on the leeward side are 'streaming straight back' ... especially the leech tell-tales on the mainsail. Once the winds strength gets to ~8-10 then you can return to your 'normal' settings.
FLAT sails are needed in very light winds so that you dont develop a 'separation stall'. With wind with little energy such as in very light winds the airstreams will not 'follow' the shape of the sailcloth on the leeward side and will 'separate' from the sail leaving you with NO 'drive'. Tell-tales are the KEY in light wind sailing so you get the 'correct' amount of draft needed.
Last edited by RichH; 07-28-2007 at 02:05 PM.