International Moth


Upwind technique

  • More vang improves VMG upwind.  With a 16:1 you should needmoderate tension once up and foiling and very tight tension upwind oncefully powered up.
  • Less vang is better for speed, i.e. when trying to get to one side of the course or for getting through another boat.
  • Once fully powered up, i.e. TWS greater than 14-15kts max vang.
  • Downhaulshould be fairly loose in marginal conditions, as the TWS increases thedownhaul should be pulled until you can sail with a full sail.  If yourweather tell tales are luffing then you need more downhaul, if yourleeward tell tales are luffing ease the downhaul.
  • Once fully overpowered upwind max downhaul and vang as hard as you can pull.
  • Outhaul about 150mm off boom in light winds and 100mm in breeze, never tighter than 100mm.
  • Shroud tension tighter for power, looser if overpowered, typically leeward shroud just loose.
  • Flatto slight heel to weather in light wind to power rig up as much aspossible.  More heel to weather as the windspeed increases.  Heel toweather more for high mode and flatter for fast mode.  Keep in mind thatmore heel reduces the apparent wind angle and the effective sail area.
  • Ride height as high as possible without rudder ventilating.

Downwind technique

  • Outhaul eased LOTS.  Probably foot of the sail 200-250mm fromboom, 8mm bungee wrapped around leech helps the outhaul ease, as doesUltra High Molecular Weight Plastic Tape under your boom and large clewtie lines or a Velcro strap.
  • Vang cracked, but not too much.  Just enough to make gybing easier seems about right.
  • C-Ham eased till there are just wrinkles on luff in light wind, a little less in breeze.
  • When heating up for speed add a little more downhaul especially if fully powered up.
  • Hikewhen enough pressure to hike against and still feel good apparent windpressure, but don't make it a priority to hike unless you can hike hardto increase speed and carry the building apparent windspeed down to asimilar angle as a non-hiking angle.
  • Heel is flat in most wind conditions, but slight to weather once hiking hard
  • Ride height as high as one dares depending on the windspeed

Taking a page from big boat racing, a good set of targets can be helpful.  I am using this as my starting point.  Obviously a good guess is required on the approximate windspeed.  Downwind Speeds are a little more approximate, maybe the top guys are a few knots quicker downwind as the breeze increases:

 Upwind Targets  Downwind Targets
 Windspeed Boatspeed  Windspeed Boatspeed
 8 10.5      8 12.00
 10 13.00  10 14.5
 12 14.3  12 17.00
 14 15.1  14 19.00
 16 15.5  16 20.5
 20 15.8  20 22.00
 24 16.00  24 24.00

Please visit Chris William’s Blog for the latest developments in the North Moth range.

Good Luck on the Water!

Contact the International Moth Experts:

Ruairidh Scott

+44 (0) 1329 443 430 Work


ruairidh@od.northsails.com