DOCSLIB.ORG

Numerical Analysis and Design of Upwind Sails

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Numerical Analysis and Design of Upwind Sails NUMERICAL ANALYSIS AND DESIGN OF UPWIND SAILS a dissertation submitted to the department of aeronautics and astronautics and the committee on graduate studies of stanford university in partial fulfillment of the requirements for the degree of doctor of philosophy Sriram Shankaran April 2005 °c Copyright 2005 by Sriram Shankaran All Rights Reserved ii I certify that I have read this dissertation and that in my opinion it is fully adequate, in scope and quality, as a dissertation for the degree of Doctor of Philosophy. Antony Jameson (Principal Adviser) I certify that I have read this dissertation and that in my opinion it is fully adequate, in scope and quality, as a dissertation for the degree of Doctor of Philosophy. Juan J. Alonso I certify that I have read this dissertation and that in my opinion it is fully adequate, in scope and quality, as a dissertation for the degree of Doctor of Philosophy. Margot Gerritsen Approved for the University Committee on Graduate Studies: iii To all things alive iv Abstract The use of computational techniques that solve the Euler or the Navier-Stokes equa- tions are increasingly being used by competing syndicates in races like the Americas Cup. For sail configurations, this desire stems from a need to understand the influ- ence of the mast on the boundary layer and pressure distribution on the main sail, the effect of camber and planform variations of the sails on the driving and heeling force produced by them and the interaction of the boundary layer profile of the air over the surface of the water and the gap between the boom and the deck on the performance of the sail. Traditionally, experimental methods along with potential flow solvers have been widely used to quantify these effects. While these approaches are invaluable either for validation purposes or during the early stages of design, the potential advantages of high fidelity computational methods makes them attractive candidates during the later stages of the design process. The aim of this study is to develop and validate numerical methods that solve the inviscid field equations (Euler) to simulate and design upwind sails. The three dimensional compressible Euler equations are modified using the idea of artificial com- pressibility and discretized on unstructured tetrahedral grids to provide estimates of lift and drag for upwind sail configurations. Convergence acceleration techniques like multigrid and residual averaging are used along with parallel computing platforms to enable these simulations to be performed in a few minutes. To account for the elastic nature of the sail cloth, this flow solver was coupled to NASTRAN to provide v estimates of the deflections caused by the pressure loading. The results of this aeroe- lastic simulation, showed that the major effect of the sail elasticity, was in altering the pressure distribution around the leading edge of the head and the main sail. Adjoint based design methods were developed next and were used to induce changes to the camber distribution of the main sail. The goal of the design process was to reduce the leading edge suction peaks that were considered to be detrimental to the growth of the boundary layer. The deflected shape of the sails obtained from the aeroelastic simulation were used by the design process. The design process re- sulted in an camber distribution that allowed smooth entry of the flow through the leading edge of the main sail thereby, reducing the leading edge suction peaks. vi Acknowledgments vii Contents iv Abstract v Acknowledgments vii 1 Introduction 1 1.1 Design Requirements of Racing Yachts . 1 1.2 Models of Fluid Flow . 3 1.3 Analysis with CFD . 5 1.4 Aeroelastic Analysis . 8 1.5 Optimum Design . 10 1.6 Aerodynamic Shape Optimization . 12 1.7 Outline of this study . 16 2 Discretization of Governing Equations 19 2.1 Overview of the Numerical Scheme . 19 2.2 Finite Volume Discretization of the Flow equations . 21 2.3 Spatial Discretization . 23 2.4 Staggered Meshes . 24 2.5 Implementation of the Cell-Vertex Scheme . 29 2.6 Artificial Diffusion . 29 2.7 Analysis of Artificial Compressibility . 30 2.8 Time Integration . 31 viii 2.9 Multigrid Acceleration . 32 2.10 Parallel Implementation . 35 2.10.1 Domain Decomposition, Load Balancing . 35 2.10.2 Parallel implementation of the multigrid algorithm . 38 2.10.3 Speedup of the Parallel Implementation . 39 2.11 Governing equations and analysis of the structural model . 39 2.11.1 Structural Model of the Sail . 41 2.12 Aeroelastic Coupling and Mesh Deformation . 42 3 Analysis of Sail Configurations 46 3.1 Low Mach number, high angle of attack simulations with a compress- ible flow solver . 47 3.1.1 Multi-Element airfoils . 47 3.1.2 Sail simulations . 47 3.2 Effect of Numerical Discretization and diffusion on artificial compress- ibility methods . 48 3.3 Validation of the parallel implementation . 49 3.4 Single and multi-element sail computations with artificial compress- ibility methods . 50 3.4.1 Characteristics of the main sail . 50 3.4.2 Characteristics of the Head and Main sail combination . 52 3.5 Aeroelastic simulations for single and multi-element foils . 54 4 Aerodynamic Shape optimization 76 4.1 The general formulation of the Adjoint Approach to Optimal Design . 77 4.2 Adjoint and Gradient formulations . 79 4.2.1 Adjoint Equations for the Euler equations modified by artificial compressibility method . 83 4.2.2 The need for a Sobolev inner product in the definition of the gradient . 84 4.3 Analysis of the Optimization Procedure . 86 4.4 Mesh movement . 88 ix 4.5 Parallel Implementation . 88 5 Validation of the Optimization Procedure and Results 89 5.1 Shape optimization for airfoils in compressible flow . 90 5.2 Shape optimization of airfoils in incompressible flow . 90 5.3 Three dimensional shape optimization of wings in compressible flow . 95 5.4 Inverse design of wings in incompressible flow . 96 5.5 Inverse design for sail geometries . 96 6 Conclusions 107 6.0.1 Aerodynamic and Aeroelastic analysis . 107 6.0.2 Aerodynamic design . 108 Bibliography 110 x List of Tables xi List of Figures 2.1 Dual mesh representation of the control volume . 25 2.2 Nodal formulation of the finite volume scheme . 25 2.3 Evaluation of fluxes in three dimensions . 26 2.4 Control volume for cell-vertex schemes in three dimensions . 26 2.5 Staggered arrangement of flow variables . 28 2.6 Half-staggered arrangement of flow variables . 28 2.7 Interpolation coefficients for use in the multigrid cycle . 34 2.8 Transfer of solution, residuals and corrections between the fine and coarse mesh . 35 2.9 Domain decomposition of a rectangular region using a bisection method 36 2.10 Halo nodes and the distribution of edges along processor boundaries 37 2.11 Speedup from the parallel implementation . 37 2.12 Boundary conditions for the main sail . 42 2.13 Boundary conditions for the head sail . 43 3.1 Grid and Pressure distribution over a multi-element airfoil geometry at a M = 0.2 and α = 8.2 degrees . 56 3.2 Cp distribution at two sections and convergence history of the com- pressible flow solver . 57 3.3 Potential flow solution from FLO1 at 0,1 and 3 degrees . 58 3.4 Flow over a NACA 0012 airfoil at 0,1 and 3 degrees using a cell-centered scheme . 59 3.5 Flow over a NACA 0012 airfoil at 0,1 and 3 degrees using a nodal scheme 60 xii 3.6 Flow over a NACA 0012 airfoil at 0,1 and 3 degrees using a half- staggered scheme . 61 3.7 Total Pressure losses on the airfoil surface at 0o . 62 3.8 Total Pressure losses on the airfoil surface at 1o . 62 3.9 Total Pressure losses on the airfoil surface at 3o . 63 3.10 Total Pressure losses on the airfoil surface at 5o . 63 3.11 Sail geometry . 64 3.12 Pressure distributions along sections at 1, 25 and 85 percent of the height of main sail . 65 3.13 Spanwise force distributions . 66 3.14 Variation of Lift and Drag with wind incidence . 66 3.15 Effect of mast on variation of Lift and Drag with wind incidence . 67 3.16 Effect of heeling angle on variation of Lift and Drag . 67 3.17 Twist,camber and chord distribution of the head sail . 68 3.18 Twist,camber and chord distribution of the main sail . 68 3.19 Pressure distributions along sections at 1, 25 and 85 percent of the height of head sail . 69 3.20 Pressure distributions along sections at 1, 25 and 85 percent of the height of the main sail . 70 3.21 Spanwise force distributions on the head sail . 71 3.22 Spanwise force distributions on the main sail . 71 3.23 Pressure distribution over the pressure and suction side of the head and sail combination . 72 3.24 Original and deformed sail sections for the head sail . 73 3.25 Original and deformed sail sections for the main sail . 73 3.26 Pressure distributions along sections at 1, 25 and 85 percent of the height of head sail after aeroelastic analysis . 74 3.27 Pressure distributions along sections at 1, 25 and 85 percent of the height of main sail after aeroelastic analysis . 75 5.1 Comparison of the gradients from SYN75 and SYN82 . 91 xiii 5.2 Comparison of the first co-state variable from SYN75 and SYN82 . 91 5.3 Comparison of the second co-state variable from SYN75 and SYN82 . 92 5.4 Comparison of the third co-state variable from SYN75 and SYN82 .
Load more

Recommended publications
  • Aerodynamics of High-Performance Wing Sails
    Aerodynamics of High-Performance Wing Sails J. otto Scherer^ Some of tfie primary requirements for tiie design of wing sails are discussed. In particular, ttie requirements for maximizing thrust when sailing to windward and tacking downwind are presented. The results of water channel tests on six sail section shapes are also presented. These test results Include the data for the double-slotted flapped wing sail designed by David Hubbard for A. F. Dl Mauro's lYRU "C" class catamaran Patient Lady II. Introduction The propulsion system is probably the single most neglect­ ed area of yacht design. The conventional triangular "soft" sails, while simple, practical, and traditional, are a long way from being aerodynamically desirable. The aerodynamic driving force of the sails is, of course, just as large and just as important as the hydrodynamic resistance of the hull. Yet, designers will go to great lengths to fair hull lines and tank test hull shapes, while simply drawing a triangle on the plans to define the sails. There is no question in my mind that the application of the wealth of available airfoil technology will yield enormous gains in yacht performance when applied to sail design. Re­ cent years have seen the application of some of this technolo­ gy in the form of wing sails on the lYRU "C" class catamar­ ans. In this paper, I will review some of the aerodynamic re­ quirements of yacht sails which have led to the development of the wing sails. For purposes of discussion, we can divide sail require­ ments into three points of sailing: • Upwind and close reaching.
    [Show full text]
  • Pennsylvania
    Spring 1991 $1.50 Pennsylvania • The Keystone States Official Boating Magazine Viewpoint Recently we received a letter suggesting that we were being contradictory in Boat Pennsylvania. According to one reader, we suggested that boaters wear personal flota- tion devices, but that the magazine photographs don't always show their use. Obtaining photographs for a magazine can be a difficult proposition. Sometimes we stage situations and take the photographs ourselves. More often, we rely on photographs submitted by contributors. Photos that depict the general boating public often do not show people wearing PFDs simply because the incidence of wearing them is so low. If we were to say that we would only use photos that showed boaters wearing PFDs, we would have a difficult time fmding acceptable photos. Generally, we try to show people wearing PFDs in small boats in situations in which devices should obviously be worn. On large boats, people most often do not wear their PFDs. Should people wear PFDs? Statistics show that wearing a PFD can save your life. Are PFDs needed all the time? Because accidents happen when they are least expected, wearing a PFD all the time is a good idea. Practically, however, as comfortable as the newest PFDs are, they can be excruciating on a hot July day. Many boaters also want to get a little sun. We accept this and our statistics show that the chances of having an accident where a PFD would have been a factor are much lower in the summer months. Ofcourse, circumstances do exist in which wearing a PFD,even on the hottest day, is warranted.
    [Show full text]
  • Performance Prediction for Sailing Dinghies Prof Alexander H Day
    Performance Prediction for Sailing Dinghies Prof Alexander H Day Department of Naval Architecture, Ocean and Marine Engineering University of Strathclyde Henry Dyer Building 100 Montrose St Glasgow G4 0LZ [email protected] 2nd Revision Feb 2017 Abstract This study describes the development of an approach for performance prediction for a sailing dinghy. Key modelling issues addressed include sail depowering for sailing dinghies which cannot reef; effect of crew physique on sailing performance, components of hydrodynamic and aerodynamic drag, decoupling of heel angle from heeling moment, and the importance of yaw moment equilibrium. In order to illustrate the approaches described, a customised velocity prediction program (VPP) is developed for a Laser dinghy. Results show excellent agreement with measured data for upwind sailing, and correctly predict some phenomena observed in practice. Some discrepancies are found in downwind conditions, but it is speculated that this may be related at least in part to the sailing conditions in which the measured data was gathered. The effect of crew weight is studied by comparing time deltas for crews of different physique relative to a baseline 80kg sailor. Results show relatively high sensitivity of the performance around a race course to the weight of the crew, with a 10kg change contributing to time deltas of more than 60 seconds relative to the baseline sailor over a race of one hour duration at the extremes of the wind speed range examined. Keywords sailing; dinghy; velocity prediction program; performance modelling Performance Prediction for Sailing Dinghies 1 Introduction 1.1 Velocity Prediction Programs Velocity Prediction Programs (VPPs) for sailing yachts were first developed more than thirty-five years ago (Kerwin (1978)) and a wide variety of commercial software is available.
    [Show full text]
  • OWNERS MANUAL Introduction
    OWNERS MANUAL Introduction his user manual is designed to help you to get the most from your Neil Pryde sails. Whether Tyou are a cruising or racing sailor, investment in sails is an important aspect of your sailing program. We want you to have all the information you need to get top performance. Neil Pryde operates from a centralized loft. We rely on an extensive worldwide network of sail consultants to service our customers needs. Our consultants will help you get the most from your relationship with Neil Pryde. If, after reading this booklet, you have further questions, please don’t hesitate to contact either your local Neil Pryde consultant or the International Design and Sails Office at: Neil Pryde Sails 354 Woodmont Road #18 Milford, Conn. 06460 U.S.A. Tel: (203) 874-6984 FAX: (203) 877-7014 On-Line E-Mail: [email protected] On The Web: http://www.neilprydesails.com Neil Pryde Terminology n this discussion we use many technical terms with very specific meanings, While most are Istandard terms, other sailmakers sometime use alternative terms. Glossary of Terms Halyards and cunninghams Halyards are lines used to pull the sails up and to adjust the position of the draft (sail camber, curvature Figure 1 or “fullness”) fore or aft in the sail. They don’t significantly alter whether the sail is more full or less full. More tension on the halyards brings the draft of the sail forward; less tension drops it back. (figure 1) Cunninghams are down haul lines for fine tuning luff tension after the halyard is tightened and cleated off.
    [Show full text]
  • Terminology N This Discussion We Use Many Technical Terms with Very Specific Meanings, While Most Are Istandard Terms, Other Sailmakers Sometime Use Alternative Terms
    Neil Pryde Terminology n this discussion we use many technical terms with very specific meanings, While most are Istandard terms, other sailmakers sometime use alternative terms. Glossary of Terms Halyards and cunninghams Halyards are lines used to pull the sails up and to adjust the position of the draft (sail camber, curvature Figure 1 or “fullness”) fore or aft in the sail. They don’t significantly alter whether the sail is more full or less full. More tension on the halyards brings the draft of the sail forward; less tension drops it back. (figure 1) Cunninghams are down haul lines for fine tuning luff tension after the halyard is tightened and cleated off. It has the same effect on the draft as the halyard. Mainsail outhaul Halyard tension moves Line used to flatten or make fuller the bottom third of the sail. Tightening the outhaul flattens this part of draft forward and aft, the sail and makes the aft section (exit or leech) straighter. Loosening the outhaul makes the sail fuller in with little effect on how the bottom so the leech becomes a rounder, fuller exit, providing more power. (figure 2) full the sail is. Main sheet Figure 2 Line giving control over the movement of the boom. Upwind, it is used to control sail twist (tighter mainsheet reduces twist, looser mainsheet increases it). Downwind it is used to control the lateral position of the boom in and out. (figure 3) Boom vang Outhaul tension effects how full the draft is, with A line at 45 degrees from bottom of mast to underside of boom.
    [Show full text]
  • Faster Reaching and Down Wind Strategy - by Alan Gillard
    Faster Reaching and Down wind Strategy - by Alan Gillard Most people concentrate on upwind speed and trim but ask little about down wind and reaches. SAIL TRIM Close reaching. Use your telltales the same as for upwind. (Leech tell-tales flying all the time). Use your kicker to set the overall fullness of the sail, let the outhaul off a little bit (but not too much), and let the downhaul off until the front of the sail starts to wrinkle (speed ripples). The mainsheet is then used to control the angle of the sail to ensure the tell-tales are all streaming. If you start to become overpowered on a close reach try pulling on more downhaul, this will have the effect of opening up the leech and so de- powering. As you come off the wind more, ease the outhaul to power up the sail. Broad reaching. On a broad reach it's more difficult because the boom and sail are limited in how far out they can travel by the shrouds. Let the outhaul nearly right off (i.e. make the sail really full low down), and the downhaul fully off. The top tell-tales are the most important on a broad reach and the kicker is the most important control. On a broad reach the bottom of the sail is generally stalled because the boom can't go out far enough. But if you let your kicker off a bit, the sail will twist so you can still get some flow over the sail and keep the top telltales streaming properly.
    [Show full text]
  • Design of a Generalized Tool for the Performance Assessment Under Sail Based on Analytical, Numerical and Empirical Results
    Departamento de Arquitectura y Construcción Navales Escuela Técnica Superior de Ingenieros Navales Universidad Politécnica de Madrid PhD Thesis DESIGN OF A GENERALIZED TOOL FOR THE PERFORMANCE ASSESSMENT UNDER SAIL BASED ON ANALYTICAL, NUMERICAL AND EMPIRICAL RESULTS. A GLOBAL SAILING YACHT META-MODEL By Manuel Ruiz de Elvira M. Sc. in Naval Architecture Supervisors: Prof. Luis Pérez-Rojas Ph.D. in Naval Architecture Prof. Ricardo Zamora Ph.D. in Naval Architecture 2015 This page intentionally left blank ii ABSTRACT The assessment of the performance of sailing yachts, and ships in general, has been an objective for naval architects and sailors since the beginning of the history of navigation. The knowledge has grown from identifying the key factors that influence performance (length, stability, displacement and sail area), to a much more complete understanding of the complex forces and couplings involved in the equilibrium. Along with this knowledge, the advent of computers has made it possible to perform the associated tasks in a systematic way. This includes the detailed calculation of forces, but also the use of those forces, along with the description of a sailing yacht, to predict its behavior, and ultimately, its performance. The aim of this investigation is to provide a global and open definition of a set of models and rules to describe and analyze the behavior of a sailing yacht. This is done without applying any restriction to the type of yacht or calculation, but rather in a generalized way, capable of solving any possible situation, whether it is in a steady state or in the time domain.
    [Show full text]
  • Flag Notes- Holiday Edition 2018
    Flag Notes Holiday Edition LPOYC Flag Notes- Holiday Edition 2018 Flag notes are back again, after a short haitus by yours truly…and not much has happened since the Annual Dinner and Storm session last October. For those of you who missed it, we met at Cedars, Lake Coeur d’Alene’s version of the floating patio…and as in the past, we were greeted with heavy rains, high winds and most of us lurching back and forth, not from drink, but rather from the ups and downs of the restaurant. Awards were handed out for the racers, a new slate of officers was elected (with some hang-overs or hold overs, if you prefer) and in general, a great social time for member who attended. Check out the website for more information www.lpoyc.org The first board meeting of the new year will be held on the 18th of January with lots of things on the agenda…as our esteemed Commodore has lined out several items for discussion that may have an effect on upcoming activities…some of the items to discuss are: • Social Functions for the season…how many, when, participation…last year most social and cruising events were poorly attended…what can we do to increase participation and what would the club like in the way of themes? • The website- how may folks use it, what can we do to improve it and increase viewership • Education- maybe a knot tying seminar for the fingerly challenged, or as Dennis Connor once said “If you can’t tie a good know, tie a lot”…how about seminars on anchoring for the cruisers (pinpointing conditions at LPO), talking about sail twist or other “technical subjects” that will improve performance of your boats • Schedules- the folks up north (SSA) have several members what crew for LPOYC boats…so looking at some Saturday races so they can come down and crew with us and we can have some members go to the far northern reaches and participate with their boats and members.
    [Show full text]
  • Advanced Sail Trim (Trim Your Sails for Speed) Most of the Clinic Will Be Limited to the Mainsail
    Advanced Sail Trim (Trim Your Sails for Speed) Most of the clinic will be limited to the mainsail. With a quick-learning class, once they have mastered the main, you can include the outhaul on the jib and its control of both draft and twist. On the White Board: (10 Minutes Max) • Use the sailboat model as well as the white board to show where the cunningham, boom vang, outhaul, and backstay are. • Draw an overhead view of the mainsail, showing different amounts of draft and explain how draft affects power. On the Boat: • Position the boat so that you can raise the main at the dock. Show the effects of tightening and loosening all of the controls. Try and have the mainsail filling slightly to better see the effects on draft. • Have the students stand amidships and show them how tightening the backstay bows the mast, drawing the area around the spreaders forward and reducing draft aft of the spreaders. • Show how the outhaul affects the bottom half of the sail’s draft. • Show how the cunningham flattens the luff, reducing draft and bringing it forward. • Demonstrate the effect of the vang on leech tension and sail twist. Discuss how the mainsheet will act as a vang on a close haul. • Go sailing, allowing the students to analyze the weather conditions and choose whether we want a full sail or a flat sail. • Discuss what effects reefing has on sail controls. How the reefing line acts as a replacement cunningham and outhaul, since they will no longer be working.
    [Show full text]
  • The Explorer 16 Handbook
    THE EXPLORER 16 HANDBOOK Explorer 16 Association Inc. A001539C First published 2003 Revised and reprinted February 2005 Revised and reprinted March 2006 Revised and reprinted August 2009 Revised and reprinted June 2012 Revised and reprinted September 2014 Revised and reprinted July 2016 © Explorer 16 Association Inc. 2003-2014 This work is copyright. Apart from any use as permitted under the Copyright Act 1963, no part may be reproduced by any process without written permission. Compiled and edited by Brian Adeney. Typeset in Verdana 9 pt. FOREWORD For some time there had been suggestions that we should have some sort of guide for new (and existing) Explorer 16 owners on the best ways to set up their boat, sail it, and care for it, based on the experiences of Explorer owners. There have been many articles written over the years on these subjects, and it is from these that we have made selections and combined them with articles from other sources. This handbook does not set out to cover general seamanship, navigation, weather, safety equipment and regulations, radio operating, race rules, and other aspects that are more than adequately covered in other publications - what we have intended to cover are those subjects that are especially applicable to Explorer 16s. The basis for this handbook was a booklet prepared by Andrew Jeffs in 1989 when he was a youngster crewing for his father, Philip, on 'Resolute' (Number 59). This was prepared as a school project, and as well as his own authorship he drew on articles that had been written by well-known Explorer sailors and published in the Association’s 'Newsletter' and its successor 'Discovery'.
    [Show full text]
  • Optimist Tuning Guide from UK Sailmakers
    Optimist Tuning Guide from UK Sailmakers There is no precise answer to how your new Optimist sail has to be trimmed. It depends on several factors, among others; � The sailors weight � The sailors psysical strength � The sailors technique Below is a detailed review of the different trim options, and our suggestions for setup under different conditions. On the Optimist you have the following trim options: � Sail ties in luff and foot � Luff tension � Sheet � Outhaul � Kicking strap � Bridle � Sprit � Mast rake All of these things can be trimmed on the water, but it´s a good idea to set up the trim when you´re preparing the boat on land. Remember that there are almost always more wind on the water than on land! Sail ties in luff and foot Normally you don´t need to adjust the sail ties in the foot. Tie them leaving about 9 mm between the sail and boom – this way the sail will easily pass the boom fittings. Remember that the sail must not be more than maximum 10 mm from the boom and mast! In the luff we recommend that you run your sail ties twice around the mast – this makes tuning more accurate. The following measurements are indicative and not appropriate for all types of masts. 0­6 Knots Your sail is designed with very little luff curve. When sailing in light wind you will have no mast bend because of the light sheeting. Tie your sail 9 mm from the mast all the way – this way you get your sail as far from the turbulent area behind the mast as possible.
    [Show full text]
  • Enterprise Boat Speed
    ENTERPRISE BOAT SPEED Written by Philip Kirk It doesn’t matter weather you are a keen racer or a Saturday afternoon cruiser, most of the time you want to get the best out of your boat. The following sailing guide tells you how to sail your boat faster in a range of wind conditions. The tables below divide the conditions you are likely to see into three areas Drifting (very light winds), Powering up and Overpowered. Please remember that these wind speeds given are a guide and a light weight helm and crew will become overpowered in less wind than a heavier pair. Upwind Conditions Drifting Powering Up Overpowered (0-4 Knots) (5 –15 Knots) (16+ Knots) Boat Trim Trim forward to lift tran- Trim level to maximise waterline length som Boat Heel 5° to leeward to fill sails Upright – 5° to windward Centreboard Down Raise 50-150mm Jib Sheet In firm In tight In tight (move fairleads aft 25mm) Main Sheet Ease boom to corner of Bring boom to centreline Ease sheet to spill wind transom in gusts. Kicker Take up slack Pull on to flatten main sail. Outhaul On tight Ease 12mm On tight Cunningham slack slack Use to depower Pointing/ Jib Tell-Tales Don’t pinch, tell-tales hor- Pinch but maintain speed, windward tell-tale lifting izontal 45° to vertical. Depowering Options: Settings in the right hand column such as raising the centreboard, moving the fairleads back and pulling on the cunningham may be used separately as depowering options in heavy weather. It is very likely that the kicker will be on tight before this point.
    [Show full text]