By Sean Semmens, Dart Sails
Strip all unneeded weight out of the boat. Excess weight is only of use in a steam-roller!
If Impalas have an Achiles heel it would be light airs, especially against a light weight boat or IOR style boats. The Impala is not blessed with masses of sail area, and is quite heavy for the wetted surface area; which answers why the IRC rating is quite generous All you can do about sail area is have new sails to the maximum sizes allowed in the rules, some boats advocate a slightly oversize spinnaker for handicap racing. It is worth noting that sails shrink with age especially laminate fabrics, so new sails are especially important in light airs. Sails need twist in light airs. The halyards on both Main and Genoa should be slack, wrinkles out of the luff are fast. The Genoa car should be well aft in very light airs, often as far back as the track will allow. The mainsheet traveller should be fully up to windward with no vang on and the sheet eased so the boom is on the centre line. The top of the Mainsail may be too full. In the very lightest of winds try a little backstay – this will flatten the top of the sail and help twist off the leech.
The dilemma for the no.1 genoa is that they are usually designed with more breeze in mind to maximise pointing as that is what Impalas are typically good at but this creates a distinct lack of power in light winds. If you only have one Genoa to cover 0-20 knots then the chances are the sail will be too flat in light winds. This can be helped by dramatically easing the cap shroud tensions to induce some forestay sag (see separate rig tensions guide) but the most successful solution to the problem is to have a dedicated light No.1 Genoa which is designed far fuller to maximise power in light wind
Spinnaker trim is at its most difficult in light winds. The pole must be constantly adjusted as well as the sheet. Do not over square the pole as the sail will set better out in front of the boat.
The pole must be lowered in the lulls and raised in the puffs. Do not run too deep, as you will loose speed. Reaching to about 150 degrees apparent is a good guide to best VMG. Crew weight must be kept forward. Crew weight in the cockpit will dig the stern in and increase drag. Try weight well forward, to leeward, upwind and as low as possible. Sending crew down below decks is very fast when there is a slight chop around from motor boats. Communication between the trimmer and the helmsman is crucial in light winds, be careful to heat up the angles as soon as pressure and speed drop and soak back down when the speed is back up.