sail technology and trim
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SAIL TECHNOLOGY AND TRIM
Nick TurneyNorth Sails
Nick Turney Sail Maker for 10 years Professional Sailor
TP 52 Farr 40 RP 65 Cookson 50
Professional Coach Farr 40 TP 52 One Design
Sail TechnologyRig Profile
Using measurements from your boat
Sail Sizing
We use the rig profile to design sails that best fit the rig
SpiralEdge Curves
Horizontal and vertical curvatures
Broadseaming
3D LayoutPuts a yarn or panel layout on a design surface
Flow
Pressure map for the sail plan
Membrain Applies pressure from Flow to rig and sails. Coupled with specified material properties and sail control settings, sails and rig are deformed to match sailing conditions for the specified wind speed
Membrain
Sail TrimRIG TUNE SAIL CONTROLS
Vertical shrouds (Uppers/ Cap) Rake, headstay sag, prebend
Diagonal shrouds (lowers) Side to side bend Flatness of main sail
Back Stay Headstay sag, mainsail shape
Runners/ Checkstays Headstay sag, mainsail shape
Big Lines Sheets
Small Lines Outhaul Cunningham Vang
Rig Tuning
1. With your boat on land and your mast up, plumb bob the keel to make sure it is straight up and down
2. Set mast parallel to keel
3. Note that sheerline and chainplates are often inconsistent.
RAKEThe fore and aft relation of center of effort to center of resistance creates helm, weather or lee
More rake increases weather helm, less rake decreases it.
PreBendStatic amount of bend in mast. Affected by:•Shroud tension
• Upper• Lower
•Spreader angle•Mast butt placement•Placement at deck
Shroud Tension
Increased Tension on uppers, gives•Increased compression on mast---more prebend•Increased forestay tension, to a limit.
Rig Tuning
Sail TrimBasic Rule
Oversheeting the mainsheet will close the leech, increasing weather helm and making the bow want to point up
Easing the mainsheet opens the leech and decrease weather helm, making the boat easier to sail straight
Mainsail Trim
• The traveler changes power in the mainsail by changing the angle to the wind
• The traveler will also affect pointing ability
Traveler
Boom on center line
Adjust to keep helm Neutral
Up in light airDown in heavy air
Draft forward is a better heavy air shape, keeping the leech more open to depower
Draft aft is a better light air shape, firming the leech for power
Cunningham
Zero
+ 25 mm
+ 50 mm
+ 100 mm
Outhaul Loose outhaul makesthe lower main fullerfor more power
Tighter outhaul flattenslower main and opensleech
Tight outhaul
20 mm looser
40 mm looser
60 mm looser
80 mm looser
Main Sail Trim• Light Air
– Outhaul Loose– Cunningham off– Vang Loose– Backstay, loose– Traveler up to boom
on C/L.– Mainsheet- Top
Battenparallel
• Moderate– Outhaul Max– Cunningham loose– Vang Snug, no slack– Backstay, adjust
power to keep boat flat
– Traveler, keep boat flat
– Mainsheet top parallel or slightly open
Main Sail Trim• Heavy Air– Outhaul Max– Cunningham, no
wrinkles– Vang very firm– Backstay on hard– Traveler, down, below
C/L– Mainsheet, top batten
open 5- 10 degrees
Head Sail Trim• Jib Lead– Controls Twist– Forward=more power, less
twist– Back= less power, more twist
• Jib Halyard– Entry Position– Full Entry is better for chop– Fine Entry is better for flat
water
Controls• Jib Sheet– Controls Over all shape and
depth– Inboard and Outboard
position
Head Sail TrimLight Air– Medium halyard- finer entry, looser in chop– Lead Forward– Eased Sheet
Medium Air– Tighter Halyard in flat water, looser in chop– Lead Middle– Tighter Sheet
Head Sail TrimHeavy Air– Really Tight Halyard all the time– Lead Aft– Sheet eased
Spinnaker Trim• A full shape is more
stable and good for power in chop or when pumping
• A flatter shape provides more exposed area and is most effective in flat water
Spinnaker Trim• Pole too high flattens the
luff and moves the draft aft, closing the leech
• 2. Lowering the pole moves the draft forward and opens the leech
Spinnaker Checklist
• Pole Height, Inboard and Outboard
• Sheet Tension Discussion• Pole angle• Keep sheet moving
Downwind Trim
• Too little vang allows too much twist and flattens the top of the main, depowering the sail
• Vang on decreases twist and makes the top of the main deeper and more powerful
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