This document discusses sail trim and balance. It explains the two modes of sailing - push and pull, with pull mode being when the sail is in flow. It identifies the three sources of sail power as angle of attack, draft, and twist. It describes the primary controls for the mainsail and jib/genoa and how they affect angle of attack, draft, and twist. It discusses balance and how sail trim impacts heel. Finally, it provides sail trim recommendations for light, moderate, and heavy wind conditions.

1. Sail Trim and Balance
Sail Trim and Balance
with Kristen “kb” Berry

2. Sail Trim and Balance
• The Big Question
• One Language
• Two Modes
• Three Sources of Power
• Controls
• Balance
• Putting it all together

3. What makes a boat go?

4. Let’s Develop a
Common Sail Language

5. One Language
• Most sails have
three edges
• Most sails have
three corners

6. One Language
Head
Leech
Luff
Clew Foot Tack

7. One Language
LUFF
Draft
Chord
Leech
Camber

8. What are the
Two Modes of Sailing?
Two Modes of Sailing?
•Fast and Slow?
• Cruising and Racing?
•Upwind and Downwind?

9. TWO MODES
PUSH
PULL

10. Push Mode

11. Push Mode
• Sail blocks the WIND
wind. Creating
high pressure on
windward side
• More wind =
more power H H
LL
• More area =
more power

13. Pull Mode

14. Pull Mode
• Attached air WIND
flows over both
sides from leading
to trailing edge
• Outside air flows
faster because of L H
camber H
L
• Creates heel &
forward force

15. Pull Mode - Keel Lift
Keel Lift
• Keel lift works the same
way, below the water.
L
• Water flows over the
curved surface of the
keel. Leeway
• Because of leeway, high H
pressure builds on the
LEEWARD side and keel
lift occurs.

16. Pull Mode - The
Watermelon Seed
• When Sail Lift and Keel Combined
Lift balance, the boat
moves forward Keel Lift Force
• Keels takes us upwind
and sails take us
downwind
• We must have flow and
Sail Lift
balance

18. Pull mode is really
FLOW mode.

19. So what mode are you
sailing in?

20. CLOSE HAULED

21. Beam Reaching

22. Broad Reaching

23. WIND
Close Hauled
No Go
ZONE
Beam
Reach
Broad
Reach
Run

24. What are the
three sources
sail power?
sail power?

25. Angle of Attack
The angle of a sail’s CHORD
to the apparent wind.

26. WIND WIND WIND
0
45
60
Luffing Proper AoA Stalled

27. So what do telltales
show us about AoA?

28. Attached Airflow
Luff
Luff

29. Attached Airflow
Leech
Leech

30. Let it out, until it luffs.
Often doubt...
Rarely in error.
Rarely in error.
Rarely in error.
Rarely in error.

31. Draft
The AMOUNT of camber in a
sail and the LOCATION of the
deepest point of camber.

32. Flat Deep
Shape Shape
Horizontal Profile:
A deeper sail is more powerful but will also generate more
drag. A flat sail has less drag, but generates less power in
lighter winds. Deeper sails for light air and flatter sails for
heavier air.

33. Flat Mainsail Shape

34. Deep Mainsail Shape

35. Deep sails for light air.
Flat sails for heavy air.
Flat sails for heavy air.
Flat sails for heavy air.

36. Twist
The difference in Angle of
Attack from head to foot of a
sail.
The amount of leeward falloff
of a sail’s leech.

37. UPWIND
TWIST
TWIST
Note the top batten relative to
the boom. Both are showing the
CHORD of the mainsail. The
top batten is pointing to leeward
while the boom is pointing
behind the boat.

38. DOWNWIND
TWIST
Twisting OPEN the leech allows
the wind to flow freely from
leading edge to trailing edge.
More twist equals more flow.

39. TWIST
Wind Speed

40. Sail Controls
• Primary Mainsail
Controls
• Primary
Jib/Genoa
Controls

41. Main Controls
Angle of Attack Draft Twist
Angle of Chord to Wind Amount and Location Difference in AoA
Halyard
Sheet
Traveler
Vang
Outhaul
Backstay
Cunningham

42. Jib/Genoa Control
Angle of Attack Draft Twist
Angle of Chord to Wind Amount and Location Difference in AoA
Halyard
Sheet
Lead Car Blocks
Backstay

43. Main Controls
Angle of Attack Draft Twist
Angle of Chord to Wind Amount and Location Difference in AoA
Halyard ✔
Sheet ✔ ✔
Traveler ✔
Vang ✔ ✔
Outhaul ✔
Backstay ✔ ✔
Cunningham ✔

44. Jib/Genoa Control
Angle of Attack Draft Twist
Angle of Chord to Wind Amount and Location Difference in AoA
Halyard ✔
Sheet ✔ ✔ ✔
Lead Car Blocks ✔ ✔ ✔
Backstay ✔

45. BALANCE
• How does sail
trim affect affect
balance?
• How does heel
affect balance?

46. Mainsail
Center of
Headsail
Effort
Center of
Effort
☢
✇☢
Combined
Center of
Effort Center of
✇ Lateral
Resistence

47. Boat Sails Boat Turns
Straight To Port
View from
astern
Boat is heeled
Boat is level
to starboard

48. ☢ ☢
View from
astern
✇ ✇
Boat is level Boat is heeled
And TURNING and steering straight

50. What do we want?
When do we want it?
and how do we get it?

51. Light Air Days
• GIVE ME POWER!
• MORE FLOW!
• MORE DRAFT!
• MORE TWIST!

52. Light Air Days
No Stall! Eased sheets, boom off
AoA centerline. All telltales streaming
aft. Not steering close hauled.
Ease halyard, outhaul, backstay,
Draft cunningham. Move jib lead forward.
Open twist to promote flow at top
Twist of sail. Jib and main should “match”
Leeward heel to promote sail
camber. Forward weight to reduce
Balance drag. Trim crew weight to helm
“feel.” Slight tug.

53. Moderate Air Days
• No compromises
• Max point and speed
• Minimum Twist
• Design Draft
• Design Heel - Flatter is
faster

54. Moderate Air Days
Max trim, slight stall for point.
Boom on centerline. Inside jib
AoA telltale lifting, top leech telltale
slight stall.
Draft Moderate depth, starting to flatten
Twist No twist for maximum power.
Designed heel. Less than 10
Balance degrees. Trim crew weight to helm
“feel.” Neutral tug.

55. Heavy Air
• WHOA!!!!!!
• Depower sails
• Open AoA for waves
• Keep the boat balanced

56. Heavy Air Days
Traveler down for open AoA.
AoA Jib/Genoa eased or even moved
outboard
Flat, Flat, Flat. Tight halyards and
Draft OBC’s
Twist Lots of twist to help depower.
Reduce heel by moving crew weight
Balance to windward. Balance CEs to keep
helm pressure to light tug.

57. Angle/ Jib Telltale
Gear When How Boom
Heel Telltale Tales
Straight line sailing in Main eased and twisted
1st
light air Boom below centerline.
Light air with waves All flattening controls Press on the jib so that
Whenever you need eased. Wide angle
the windward telltale
Jib lead forward
Gear
to accelerate Some leeward heel
Inhauler on so mid-leech flows straight.
After tacks/motorboat
wakes pokes to leeward
When sailing in bad air Max headstay sag
Mainsheet trimmed so
2nd Flat water in light air
Chop in moderate air
top batten is parallel to
boom
Leech telltales flows
Moderate angle
Inside telltale begins to
bounce
Gear
Nearly flat boat No luff in jib
Footing mode 100%
Boom on centerline
Designed draft
Mainsheet trimmed to
3rd
Moderate breeze max
Flat water Top batten poked to Windward telltale lifts
Point Mode windward Max point mode to 45 degrees
Gear
Heavy air with flat Leech Telltale (on Flat boat Small luff bubble along
water main) stalled 50% Jib luff
Tight backstay
Little headstay sag
Tight leech, but active
4th
sheet ease to stay in
Windward telltale lifts
Overpowered control Feathering
vertical most of the
Moderate air with Top batten flowing Flat as possible
time.
Gear
more waves than wind 100% Especially if you have
Front of jib likely
Survival Max flattening to bear off for waves
luffing
Vang hard
Boom below center

58. More Helm Less helm
Move crew forward and to Move crew aft and to
Crew position leeward windward
Rake the mast farther
Mast rake Rake the mast farther aft
forward
Trim the leech harder and Ease the sheet and induce
Mainsheet trim reduce twist twist
Angle of heel Heel more to leeward Flatten the boat
Make sails fuller; especially Flatten sails; especially the
Sail shape the main main
Move it down and or
Centerboard forward
Move it up and or aft.

59. Thank you!
• Let’s go sailing!
• Submit your question
cards.
• Stay in touch - my
pledge to you.
• Resources.

60. SAIL FAST, SAIL SAFE
AND STAY IN TOUCH
KRISTEN
BERRY
KRISTEN@JWORLDANNAPOLIS.COM
PHONE - 410-599-3542

62. Steering With Heel and Crew Weight

64. VANG
ip
tt
as
m
on
aft
lls
Pu
Mast
bends
Main
Flattens
Tension
Main
Leech More Vang Boom presses
Tension into mast
causing lower mast
section bending

65. Halyard
Tensioning Halyard
moves
Draft forward and
slightly opens twist

67. Cunningham
Less Cunningham
Tension
More Cunningham
Tension
Tensioning the cunnigham has the effect of moving the draft of the sail forwards, making for
a rounder entry

68. Move the sails draft forward
Draft Draft
Forward
Draft Draft
Aft
Draft forward generates less drag
and be more forgiving. Draft aft
generates more power, but more
drag.

69. Pull Mode
Close Hauled

70. Pull Mode WIND
Beam Reaching
45

71. WIND
Pull Mode
Broad Reaching
45

72. WIND WIND WIND WIND
0 25
45
60
Luffing Pinching/Feathering Proper AoA Stalled