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The University of Southampton

SESS3027 Yacht and High Performance Craft

Module Overview

This module covers the performance and design of a variety of high performance small craft: namely planing craft, sailing yachts, hydrofoils and hovercraft. It will examine the basic mechanics and fluid dynamics associated with their performance and allows you to understand and utilise design principles related to each type. It will expose you to the latest techniques associated with yacht and small craft experimental techniques taught by leading engineers from the Wolfson Unit for marine technology and industrial aerodynamics.

Aims and Objectives

Learning Outcomes

Knowledge and Understanding

Having successfully completed this module, you will be able to demonstrate knowledge and understanding of:

  • The mechanics and performance of each craft type considered (sailing, hovercraft, hydrofoil). This involves an appreciation of force balance, drag breakdowns, resistance approximations, stability considerations and theoretical/experimental methods.
  • Demonstrate a knowledge of the most common types of full scale trials used to determine a vessel's performance
  • Have an understanding of the physical and mechanical processes involved in routine model test procedures for both sailing and power craft
  • Have an understanding of the process by which model test data can be used for performance prediction
  • The mechanics and performance prediction of high performance craft
  • Appreciate how the basic mechanics in each case are applied in simplified design scenarios through more complex engineering design orientated worked examples presented during the timetabled tutorial periods.
  • The mechanics and performance of powercraft. This involves lectures on force balance, drag breakdowns, resistance approximations, stability considerations and theoretical methods/mathematical idealisations
  • The stability and performance of powercraft.
  • Determine appropriate test methods to evaluate different aspects of power craft design.
  • Understand the procedures for extrapolating model tests data to full scale.
  • Appraise the dynamometer and transducer types appropriate to particular model test arrangements
  • Perform analysis of model tests in order to undertake performance prediction studies.
Subject Specific Intellectual and Research Skills

Having successfully completed this module you will be able to:

  • Formulate and resolve analysis necessary to assess stability and performance of high performance craft. This involves the lecturing of worked examples, supported by self-study using example sheets.
  • Understand the mechanics, performance and design considerations relevant to a range of highspeed power craft
  • Be able to specify appropriate model test programmes in support of a new vessel design.
  • Be able to critically appraise and utilise results from model tests carried out by commercial facilities.
Transferable and Generic Skills

Having successfully completed this module you will be able to:

  • Appreciate technical publications related to basic analysis and design of vehicles considered.
Subject Specific Practical Skills

Having successfully completed this module you will be able to:

  • Apply the understanding of the mechanics and performance prediction to approximate the performance and stability.


Overview of Hovercraft and Surface Effect Craft: Hovercraft types: skirt configurations. Heave, Roll & Pitch Stability mechanisms. Thin jet theory and thick jet theory (equilibrium case). Plenum chamber and orifice flow theory. Simple stability analysis. The influence of internal ducting losses and fan characteristics upon the powering requirements. Hovercraft over water. Wavemaking, trim and C.G. rise, theoretical data, experimental comparison with wave pattern measurement. Hydrofoils: Principal characteristics of existing craft. Surface piercing and submerged foil systems. Stability in heave, pitch and roll. The effects of free surface and depth immersion on foil performance. Two dimensional lift and drag characteristics and impact on hydrofoil design. Spanwise loading on surface piercing struts, interference between foils in tandem. Cavitation and ventilation characteristics and their impact on hydrofoil design. Overall craft performance: lift/drag ratios over a range of speeds. Sailing Performance: Basic aerodynamic and hydrodynamic axes, apparent and true wind vector diagram, conditions of equilibrium, the beta-relation between apparent wind angle and the aerodynamic and hydrodynamic drag angles. Overall yacht performance polar diagram. The rig polar diagram and proper sail settings in moderate weather. Sail interference effects (slot effect). Overall drag breakdown for hull. Centres of effort and lateral resistance from wind tunnel and towing tank data, sailing balance. Semi-Displacement Round Bilge Forms: Changes of hull form as flow regime changes with increasing Froude Number. Sinkage and trim characteristics of semi-displacement forms. NPL round bilge series and other data sources. Planing Hull Forms: Flow conditions under planing surface: spray root, spray sheet and fully wetted regions. The use of steps and spray rails. Forces and conditions of equilibrium. Design data and formulae. The effects of appendages and propellers. Dynamic stability of planing craft; longitudinal stability and porpoising. Roll stability and broaching behaviour. Craft behaviour in a turn. Advanced performance prediction: comparison between experimental data and predictions from fluid finite element programs. Loading - slamming phenomena, classical methods of assessment, empirical methods. Catamarans and Trimarans: Relations between wetted area, deck area, displacement and length for monohull, multihull and SWATH types and implications for power requirements. Aspects of wave and viscous drag interference as a function of craft configuration. Data sources and scaling procedures.

Learning and Teaching

Teaching and learning methods

Teaching methods include : - lectures ( with pre-prepared lecture note handouts) . - tutorials carrying out analysis in a design context. - laboratory class (4 hours each), made up of the actual laboratory time, prepatory taught material and a post-experiment analysis tutorial. Student would then prepare a detailed assignment based around powercraft performance. - Example sheets and directed self-study in the areas of hovercraft, hydrofoils, planing craft and sailing performance and semi-displacement craft. Learning activities include: - Reading recommended publications. - Expertise in carrying out hydrodynamic testing with a full understanding of instrumentation systems and error analysis. - Understanding inclusion of simplified analyses in design context. Feedback and student support during module study: Formative assessment: - Questioning students on their understanding. Through design applications and via marked example sheets. Interaction throughout laboratory experience and provision of feedback on assignments during module. Relationship between the teaching, learning and assessment methods and the planned learning outcomes: - Theory alone provides understanding of theory not necessarily its application. Experiments and tutorials are essential to the synthesis of different related analyses being combined in a design context. This is achieved through specifically designed examples.

Practical classes and workshops4
Completion of assessment task125
Total study time150

Resources & Reading list

Technical papers. principally in Transactions of RINA and SNAME or ISP, JSR etc



MethodPercentage contribution
Continuous Assessment 20%
Final Assessment  80%


MethodPercentage contribution
Set Task 100%


MethodPercentage contribution
Set Task 100%

Repeat Information

Repeat type: Internal & External

Linked modules

Pre-requisite: SESS2020

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