1. Sail Trim for Cruisers
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2. Introduction
Many sailors most cruising sailors are self taught and have limited knowledge of the fine points of sail trim
Knowing how to optimize your boat can:
Make you safer
Shorten your transit times
Add to your enjoyment

3. Sail Trim for Cruisers Agenda The Basics Shaping the sail
Draft
Twist
Trimming for different wind speeds
Related topics
Boat balance
Reefing and it’s impact on sail shape

4. The Basics
Wing Mode
Kite Mode

5. The Basics
Two “modes”
If wind is forward of the beam…..the sails act as like a wing

6. The Basics
Two “modes”
2. If wind is aft …..the sails act as like a kite

7. The Basics
Up Wind
In this mode a low pressure area is created on the back of the sail and the boat is “pulled up wind”
The forward portion (first foot or two) of the sail (luff) should be pointed into the wind… or parallel to the Windex arrow
You want to achieve equal flow over both sides of the sail…make both telltales fly!

8. The Basics Up Wind…”How to”
If back telltale is stalled point the boat further up wind or ease the sheet
If inside telltale is stalled point the boat down wind or trim the sail in toward the center of the boat

9. The Basics
Telltales
On the head sail in three places about 18” back from the luff
Typically only on the leach of the main due to turbulence from headsail

10. The Basics
Down wind
Position the sails at roughly 90 degrees to the wind
Sometimes increasing draft can add more power
In this mode the boat is literally pushed by the wind and of course can not go any faster that the wind speed.

11. Basics The sails react to apparent wind
As wind true wind speed increases (or boat speed decreases) apparent wind moves aft
As boat speed increases (or true wind decreases) apparent wind moves forward

12. Shaping the Sail Draft Effects power and pointing ability
Moving the draft forward improves pointing
Deeper draft for more power in light conditions
Flatten sail to depower in heavy conditions

13. Shaping the Sail Draft …how to… To create more draft easy the outhaul
To move draft forward add halyard tension
To further flatten the sail add backstay tension

14. Shaping the Sail Backstay tension
Increasing backstay tension causes the middle of the mast to more forward…effectively flattening the sail

15. Shaping the Sail Twist Why does the sail need twist?
Wind aloft can be higher than ground wind due to friction with the surface of the water
The difference is commonly known as “Shear”
Apparent wind angle is dependent on true wind speed
Since the wind speed is higher at the top of the sail the wind angle is also higher (moves back)

16. Shaping the Sail Twist Boat Speed Top of the sail True Wind Speed
Bottom of the sail
True Wind Speed

17. Shaping the Sail Twist ….“How to” reduce twist
Increasing tension on the leach of a sail decreases twist (“closes the top of the sail”)
For the head sail…move the genoa car forward
For the main…add Vang tension or put the traveler directly under the boom (“traveler down”)

18. Shaping the Sail Twist ….“How to” increase twist
Decreasing tension on the leach of a sail causes increased twist (“opens” the top of the sail)
For the head sail…move the genoa car aft
For the main…remove Vang tension and/or put the traveler to windward to allow the boom to lift

19. Shaping the Sail To twist or.. not to twist…
To power up the sail… adjust twist to make the all telltales fly
To depower sail… twist the sail to stall the top portion

20. Boat Balance A properly balanced boat is fast and easy to handle
A improperly balance boat is slow and can be dangerous

21. Boat Balance
Too much mainsail and/or too little headsail will cause weather helm
If weather helm is excessive the boat will be slow (drag caused by the rudder) and difficult to steer
If the boat is grossly out of balance the rudder will not be able to correct and the boat may roundup
Weather Helm
Drag

22. Boat Balance
Too little mainsail and too much headsail will cause excessive lee helm
The boat will be slow (drag caused by the rudder) and difficult to steer
If the boat is grossly out of balance the rudder will not be able to correct and the boat may experience an uncontrolled Jibe
Lee Helm
Drag

23. Boat Balance
Most modern boats are designed with a small amount of weather helm
This gives a better “feel” to the rudder and provides a margin of safety if the helm is left unattended (boat will go up into the wind and stall)

24. Reefing The first time you think about reefing do it!!
Reefing usually changes the balance of the boat so it is important to check the balance by letting go of the helm and see what the boat does
On older boats with big overlapping genoas it is best to reef the head sail first
On newer boats with fractional rigs, reef in the main first

25. Reefing Remember that reefing usually changes the shape of a sail
Reefing a large genoa can dramatically reduce your ability to get the boat up wind
Modern rigs (fractional with loose footed mains) are better at maintaining sail shape when reefed.