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 Technology

Rig 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 Layout

Puts 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 Trim

RIG 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.

RAKE

The 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.

PreBend

Static 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 Trim

Basic 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 Trim

Light 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 Trim

Heavy 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