Islander 36 Fleet San Francisco Bay Sail Shaping for Performance Sailors Sail Trim Lecture Presented by Michael Whitfield April 14th, 2007

Sail Shaping for Performance Sailors

Sail Shaping for Performance Sailors First Module      Overview of Objectives Foundational Concepts Trim Fundamentals Sail Controls Upwind Headsail Shaping

Sail Shaping for Performance Sailors Second Module  Mainsail Shaping  Rig Control  Shifting Gears for Conditions

Sail Shaping for Performance Sailors Third Module  Trim Loops  Helm/Sail Feedback  Spinnaker Shaping

Goals

 You will be able to shape sails effectively in a wide range of conditions using all available tools.

 You will recognize and manipulate sail shape with onboard tools; enhancing boat speed, maintaining comfort, and capturing more wins!

Photo & Graphics credits: Islander 36 Class Association website, Lat38, North Sails, Max Ranchi, Volvo Ocean Race, Quantum Sails, Jboats Int., C&C Yachts, Chris Ray, Sail Magazine, Harken, All the IAC Teams, UK Sails and Sailnet

Sail Shaping for Performance Sailors First Session      Overview of Objectives Foundational Concepts Trim Fundamentals Sail Controls Upwind Headsail Shaping

Foundational Concepts

 The Basic Laws of Physics  Flying the Boat  Systems Thinking Approach  Power Generation and Management  The One Wing Concept  3 Dimensional Sail Shaping

Basic Laws of Physics

 Newtonian versus Bernoullian Physics  Lift  Drag & Displaced Hull Speed = 1.41 x Sq Root WL  Wing Shape - Chord Length and Depth  Aerodynamic-Attached Flow  Horsepower to Weight Ratio

Flying the Boat

 Sailing – We are a Vertically Oriented Airplane Flying in Two Mediums  Two Wings  One Wing in the Air  One Wing in the Water  Aerodynamics  Hydrodynamics

Low Speed Lift – 767 with Flaps Down

Boeing 747 with Winglets

High Speed Lift Mach 2+ F22 Raptor

Boeing 767 Sailing?

IAC Boats That Drive Like Airplanes

IAC Boats Flying – You Bet!

Lift Diagram

How Lift Works

Sailing Forces Diagram

Drag and Displacement Hull Speed

Drag and Displacement Hull Speed

Drag and Displacement Hull Speed

Low Drag Hydrofoil Trimaran

Wing Shape Diagram

Sailing Wing Shape

Systems Thinking Approach Power Generation and Management  How Much Power is Enough?

 How Much Heel is Enough?

 How Important is Helm Balance?

 How Important is Pointing?

 Islander 36 Example  2 Boats Sail 1 Mile Upwind at the Same Speed  1 Boat Points 1 Degree Higher  150 Feet of Gain = 4+ Boat Lengths!!!

Power Generation and Management Speed Pointing Power Generation Leeway

5 Things I Want to Know Prior to Leaving the Slip  Wind/Current Direction  Right-hand or Left-hand Propeller  Does the Prop Wash Hook-up to the Rudder  Vessel Displacement  Underwater Profile

Islander 36 Hull Shape Keel & Rudder

The One Wing Concept

 Jib or Genoa Combined with the Mainsail Create One Wing Shape!

 Starts at the Leading Edge – Jib Luff  Ends at the Trailing Edge – Mainsail Leech!

 Two Sails Nest Together to Create One Wing!

 Start at the Front of the Wing, Set-up and then Move Aft to Finish the Job!

Sailing Forces Diagram – One Wing

Farr 40 Worlds One Wing Concept

IAC - Two Nested Sails Create One Wing

3 Dimensional Sail Shaping

 X, Y & Z Axes  Horizontally – Fore and Aft  Depth – Beam to Beam  Vertically  Aids – Draft Stripes, Boom, Mast, Forestay and Backstay  Jib & Main Leeches

Sail Shaping for Performance Sailors First Session      Overview of Objectives Foundational Concepts Trim Fundamentals Sail Controls Upwind Headsail Shaping

Trim Fundamentals

 Definitions  Anatomy of a Sail  Sail Choice  Initial Set-up  Pointing Modes  Full and Bye  Power Mode  Point Mode

Definitions & Anatomy

 Those Darn Corners  Those Darn Sides  All the Rest  Overlap/Headsail Size  Materials

Headsail Parts

 Head  Tack  Clew  Luff  Foot  Leech  Leech & Foot Lines  Cunningham Cringle

Typical Jib Features

Angle of Attack & Draft

  Angle of Attack— The angle of the sail and boom to the apparent wind flow. In essence, angle of attack is controlled by the mainsheet and the boat’s heading.

Draft (Depth) Amount—This is the depth of the sail and the position of the greatest depth. This measure is technically known as Sail depth and is Depth divided by Chord Length. Thus, a one foot draft (Depth) in a ten foot long sail would have a 10% Sail Depth. In general fuller shapes will generate more power and flatter shapes less.

Draft Placement

 This critical measure is viewed fore and aft along seams and draft stripes (dedicated stripes normally found midway up the sail) and conveys information, in percentage terms, about the draft’s placement aft of the luff. Typically you will want to place your point of maximum draft in headsails about 40 - 45% of the way aft of the luff. Normally, it is enough to simply get the “draft forward of middle” and that is the phrase you will hear aboard performance boats.

Head Stay/Luff Sag

 Sails and the stays are supported only at the top and bottom. As a result, the head stay and luff sag considerably to leeward in moderate and heavy winds.

Twist

 This is varying angle of attack that the top, middle and bottom portions of a sail require to accommodate decreased wind strength near the surface relative to higher in the rig. Twist in headsails is a function of the fairlead position and the degree of sheet tension. Given a properly set up lead position, the sail’s telltales will lift (break as sailors refer to it) evenly along the entire luff of the sail.

 Twist is used as a powering-up or de-powering action.

Wind Shear

 The wind at the top of the mast has a greater velocity and is traveling in a different direction than the wind at the deck level.

 Remember That This is Only Noticeable on Boats with More Than 40ft. Rigs!

Overlap – Headsail Sizes

The Sail’s Size - Many Bay Area sailor’s have only rarely, if at all, used the large overlapping sails called genoas. Alternatively, you may hear these large sails being discussed as a number one, or even as light and heavy number ones. The most obvious characteristics of a Genoa are its size and shape. Sailors measure genoas by the length of their LP, or luff perpendicular. To construct an LP, draw a line from the sail's clew to its luff, intersecting the luff at a right angle. The length of the LP divided by J (the distance from the forestay to the front of the mast) equals the overlap of the sail. LP divided by J = Overlap (%) On older boats, the largest headsails usually have a 150% overlap; No. 2s have a 130% overlap; No. 3s have a 98% overlap, and so on.

Sail Materials

 Jibs/Genoas/Mains  Dacron & Stabilized Dacron  Mylar  Kevlar  Aramid  Spinnakers  Nylon  Dynac  Mylar

Sail Choice

 Example: I36 Headsails for Specific Wind Ranges  Light & Heavy #1 Genoa (150%): 1 - 15 Knots Apparent  #2 Genoa (135%): 16 - 25 Knots Apparent  #3 Genoa (100%): 25 Knots + Apparent  More Than That – Let’s Go Home!

Initial Set-Up

• • • • • Pick and set the proper sized headsail.

Adjust draft position with halyard tension. Be careful if you are using a sail built of low stretch fibers, Kevlar/Mylar sails are easily destroyed by overzealous hoisting.

Adjust the fairlead to provide wind appropriate range of draft & twist adjustment.

Adjust sheet tension to get proper draft amount and twist. Continuously adjust angle of attack and other parameters as needed.

J24 Italian Nationals – Check Set-up with Your Telltales

Sail Shaping for Performance Sailors First Module      Overview of Objectives Foundational Concepts Trim Fundamentals Sail Controls Upwind Headsail Shaping

Sail Controls Tools for Shaping Jibs/Genoas  Halyard  Sheet  Jib Fairlead Position – Fore and Aft  Barber Hauler – Inboard and Outboard  Cunningham  Leech and Foot Lines  Backstay Adjuster

IAC One World – Genoa Trim

Sail Shaping for Performance Sailors First Module      Overview of Objectives Foundational Concepts Trim Fundamentals Sail Controls Upwind Headsail Shaping

Upwind Headsail Shaping

 Sail Controls – How We Use Them  Sail Trim Feedback and Boat Feedback  When, How and Why to Change Trim  Wind Speed  Chop/Waves  Point Mode or Power Mode Needed  Twist Impact

Trim Model - Diagrams

Trim Modes – Full & Bye, Power and Point Full & Bye Mode - Light Airs

Sail Trim and Boat Feedback

 Wrinkles  Luff Scallops Between Hanks  Distance the Leech was, and now is, from Spreader  Heel  Helm Balance or Lack There Of

Jib Luff Wrinkles

Luff Tension – Light Scallops

Islander 36 Jib Trim in Breeze

J24 2002 NAs – Scallops

Islander 36 – Genoa Trim

IAC Genoa Designs

5 Key Factors for Success

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Think of the Jib and Main as One Wing!

Set-up the Front of the Wing First, Jib Luff Tension/Draft Position and Sheet Trim Finish with the Back of the Wing, Main Draft Position and Leech Tension Set-up Luff Tensions with Small Wrinkles, then Adjust to Conditions Use Telltales Vertically Sync’d to Confirm the Position the Lead

Sail Shaping for Performance Sailors First Module – Q&A      Overview of Objectives Foundational Concepts Trim Fundamentals Sail Controls Upwind Headsail Shaping