Sail trim and balance 2013 draft
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Sail Trim and Balance with Kristen “kb” Berry
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Transcript of Sail trim and balance 2013 draft
Sail Trim and
Balance
with Kristen “kb” Berry
Sail Trim and Balance• The Big Question
•One Language
• Two Modes
• Three Sources of Power
• Controls
• Balance
• Putting it all together
What makes a boat go?
Let’s Develop a Common Sail
Language
One Language
•Most sails have three edges
•Most sails have three corners
One Language
Head
TackClew
Luff
Leech
Foot
One Language
Chord
Camber
Draft
LUFF
Leech
What are the Two Modes of
Sailing?
•Fast and Slow?
•Cruising and Racing?
•Upwind and Downwind?
TWO MODES
PUSHPULL
Push Mode
Push Mode•Sail blocks the
wind. Creating high pressure on windward side
•More wind = more power
•More area = more power
WIND
H HL L
Pull Mode
Pull Mode•Attached air
flows over both sides from leading to trailing edge
•Outside air flows faster because of camber
•Creates heel & forward force
WIND
HH
L
L
Pull Mode - Keel Lift
• Keel lift works the same way, below the water.
•Water flows over the curved surface of the keel.
• Because of leeway, high pressure builds on the LEEWARD side and keel lift occurs.
Keel Lift
Leeway
L
H
Pull Mode - The Watermelon Seed
•When Sail Lift and Keel Lift balance, the boat moves forward
• Keels takes us upwind and sails take us downwind
•We must have flow and balance
Keel Lift
Sail Lift
Combined Force
Pull mode is really FLOW mode.
So what mode are you sailing in?
CLOSE HAULED
Beam Reaching
Broad Reaching
WIN
D
Close Hauled
No Go ZONE
Beam Reach
Broad Reach
Run
What are the three sources
sail power?
Angle of Attack
The angle of a sail’s CHORD to the apparent wind.
WIND
45
WIND WIND
60
WIND
Luffing Proper AoA Stalled
0
So what do telltales show us
about AoA?
Attached Airflow Luff
Attached Airflow Leech
When in doubt... Let it out, until it
luffs.
Often doubt...Rarely in error.
Draft
The AMOUNT of camber in a sail and the LOCATION of the deepest point of
camber.
Flat Shape
Deep 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.
Flat Mainsail Shape
Deep Mainsail Shape
Deep sails for light air.
Flat sails for heavy air.
Twist
The difference in Angle of Attack from head to
foot of a sail.
The amount of leeward falloff of a sail’s leech.
UPWINDTWIST
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.
DOWNWIND TWIST
Twisting OPEN the leech allows the wind to flow
freely from leading edge to trailing edge.
More twist equals more flow.
TW
IST
Wind Speed
Sail Controls
•Primary Mainsail Controls
•Primary Jib/Genoa Controls
Angle of Attack Draft Twist
Angle of Chord to Wind Amount and Location Difference in AoA
Halyard
Sheet
Traveler
Vang
Outhaul
Backstay
Cunningham
Main Controls
Angle of Attack Draft Twist
Angle of Chord to Wind Amount and Location Difference in AoA
Halyard
Sheet
Lead Car Blocks
Backstay
Jib/Genoa Control
Angle of Attack Draft Twist
Angle of Chord to Wind Amount and Location Difference in AoA
Halyard ✔
Sheet ✔ ✔
Traveler ✔
Vang ✔ ✔
Outhaul ✔
Backstay ✔ ✔
Cunningham ✔
Main Controls
Angle of Attack Draft Twist
Angle of Chord to Wind Amount and Location Difference in AoA
Halyard ✔
Sheet ✔ ✔ ✔
Lead Car Blocks ✔ ✔ ✔
Backstay ✔
Jib/Genoa Control
BALANCE
•How does sail trim affect affect balance?
•How does heel affect balance?
☢
☢✇
✇
Mainsail Center of
Effort Headsail Center of
Effort
Combined Center of
Effort Center of Lateral
Resistence
View from astern
Boat is levelBoat is heeledto starboard
Boat Sails Straight
Boat TurnsTo Port
View from astern
Boat is levelAnd TURNING
Boat is heeledand steering straight
☢ ☢
✇ ✇
What do we want?When do we want it? and how do we
get it?
Light Air Days
•GIVE ME POWER!
•MORE FLOW!
•MORE DRAFT!
•MORE TWIST!
Light Air Days
AoANo Stall! Eased sheets, boom off centerline. All
telltales streaming aft. Not steering close hauled.
DraftEase halyard, outhaul,
backstay, cunningham. Move jib lead forward.
TwistOpen twist to promote flow at top of sail. Jib and main
should “match”
Balance
Leeward heel to promote sail camber. Forward weight to
reduce drag. Trim crew weight to helm “feel.” Slight
tug.
Moderate Air Days•No compromises
•Max point and speed
•Minimum Twist
•Design Draft
•Design Heel - Flatter is faster
Moderate Air Days
AoAMax trim, slight stall for
point. Boom on centerline. Inside jib telltale lifting, top leech telltale slight stall.
Draft Moderate depth, starting to flatten
Twist No twist for maximum power.
BalanceDesigned heel. Less than 10 degrees. Trim crew weight to helm “feel.” Neutral tug.
Heavy Air
•WHOA!!!!!!
•Depower sails
•Open AoA for waves
• Keep the boat balanced
Heavy Air Days
AoATraveler down for open AoA.
Jib/Genoa eased or even moved outboard
Draft Flat, Flat, Flat. Tight halyards and OBC’s
Twist Lots of twist to help depower.
BalanceReduce heel by moving crew
weight to windward. Balance CEs to keep helm
pressure to light tug.
Gear When HowAngle/Heel
Jib Telltal
e
Telltale
TalesBoom
1st Gear
Straight line sailing in light airLight air with wavesWhenever you need to accelerateAfter tacks/motorboat wakesWhen sailing in bad air
Main eased and twistedBoom below centerline.All flattening controls eased.Jib lead forwardInhauler on so mid-leech pokes to leewardMax headstay sag
Wide angleSome leeward
heel
Press on the jib so that the windward
telltale flows straight.
2nd Gear
Flat water in light air
Chop in moderate air
Footing mode
Mainsheet trimmed so top
batten is parallel to boom
Leech telltales flows 100%
Boom on centerline
Designed draft
Moderate angle Nearly flat boat
Inside telltale begins to bounce
No luff in jib
3rd Gear
Moderate breezeFlat waterPoint Mode
Heavy air with flat water
Mainsheet trimmed to max
Top batten poked to windward
Leech Telltale (on main) stalled 50%
Tight backstayLittle headstay
sag
Max point modeFlat boat
Windward telltale lifts to 45 degreesSmall luff bubble
along Jib luff
4th Gear
OverpoweredModerate air with more waves than
windSurvival
Tight leech, but active sheet ease to stay in control
Top batten flowing 100%
Max flatteningVang hard
Boom below center
FeatheringFlat as possibleEspecially if you have to bear off
for waves
Windward telltale lifts vertical most
of the time.Front of jib likely
luffing
More Helm Less helm
Crew position Move crew forward and to leeward
Move crew aft and to windward
Mast rake Rake the mast farther aft
Rake the mast farther forward
Mainsheet trim
Trim the leech harder and reduce twist
Ease the sheet and induce twist
Angle of heel Heel more to leeward Flatten the boat
Sail shape Make sails fuller; especially the main
Flatten sails; especially the main
Centerboard Move it down and or forward
Move it up and or aft.
Thank you!
• Let’s go sailing!
• Submit your question cards.
• Stay in touch - my pledge to you.
•Resources.
Steering With Heel and Crew Weight
Pulls
aft
on m
ast t
ip
Tension Main Leech More Vang
Tension
Mast bends
MainFlattens
Boom pressesinto mast
causing lower mast section bending
VANG
Halyard
Tensioning Halyard moves
Draft forward and slightly opens
twist
Less CunninghamTension
More CunninghamTension
Tensioning the cunnigham has the effect of moving the draft of the sail forwards, making for a rounder entry
Cunningham
Draft forward generates less drag and be more forgiving.
Draft aft generates more power, but more drag.
Move the sails draft forward
DraftDraft Forward
DraftAft
Draft
Pull ModeClose Hauled
WIND
45
WINDPull ModeBeam Reaching
WIND
45
WINDPull ModeBroad Reaching
WIND
45
WINDWIND
25
WIND
60
WIND
LuffingPinching/FeatheringProper AoA Stalled
0
