On Water Setup and Tuning

WHEN DO I NEED TO CHANGE SAIL SHAPE

Key Takeaways

  • Boats like a 5O5 need to be sailed flat. When you are unable to do this it is generally a sign that you need to change gears.
  • As wind increases and a boat becomes overpowered sails must be flattened to reduce their power.
  • In light air, crew moving on and off the trapeze has a considerable impact on mast bend and generally requires a significant gear change.
  • Until you become overpowered the boom should always be in the center of the boat.
  •  Communication between helm and crew is important to make sure you never (sailing upwind) have the boom off the centre line if helm or your crew are not fully hiking.
  • As you de-power with increasing wind, the boom can and will need to be off the centre line but it should never consistently be further out than the inside edge of the side tank when going up wind.
  • When you depower the mainsail you generally need to also make changes to the jib sheeting.
  • Mainsail power is generally controlled by mast bend. Jib power is generally controlled by jib sheet tension.

The various Tuning Grids will help but here are some specific things you can observe that are good signals that will help you know when to change gear (adjust a control line to change sail shape).

Typically the easiest conditions most of us are comfortable in is when the crew is on the trapeze and we can keep the boom in the centre of the boat without crew and helm having to lean too hard.

Boats fully powered, boom should be on centre line, jib barber haulers in board. Crew does the work to keep the boat flat.


Imagine we are sailing in these conditions, the mast is bending perfectly (no Cunningham) and we have just the right amount of leach twist so the sails are setting up perfectly just as the sail maker designed them .  The boom is