CatalystJournal of the Amateur Yacht Research Society

Number 7 January 2002

JANUARY 2002 1

Contents

AYRS John Hogg Prize 20013 Report of the Judges

5 Introducing the Swing-Sail rigDavid Duncan

9 A fundamental theory of sailing and itsapplication to the design of a hydrofoilsail craft

Stephen Bourn

16 Description of a Wind LoggerBob Spagnoletti

19 AYRS John Hogg prize rules for 2002

News and Views20 Autism & sailors, meginhufers, planing

foils,Hydrofoil control, AYRS BoatCompound, etc.

Design26 Swifgig

Roger Collins

Regulars29 Precision of results for a small wind

tunnelFrank Bailey

32 Catalyst Calendar

On the Cover —

David Duncan’s Swing-Rigged Wayfarer

Photo: Alan DuncanEnhanced by Paul Brierley,Firefly Design Ltd.

2 CATALYST

CatalystJournal of the

Amateur Yacht Research Society

Editorial Team —Simon FishwickSheila Fishwick

Dave Culp

Specialist CorrespondentsAerodynamics—Tom SpeerElectronics—David Jolly

Human & Solar Power—Theo SchmidtHydrofoils—George Chapman

Instrumentation—Joddy ChapmanIceboats & Landyachts—Bob Dill

Kites—Dave CulpMultihulls—Dick Newick

Speed Trials—Bob DownhillSteam Power—Lord Strathcona

Structures—Keith BurgessWindmills & Turbines—Jim Wilkinson

Catalyst is a quarterly journal of yacht research,design, and technology published by the AmateurYacht Research Society, BCM AYRS, LondonWC1N 3XX, UK. Opinions expressed are theauthor’s, and not those of AYRS. AYRS alsopublishes related booklets.

Contributions are welcome from all. Email themto Catalyst@fishwick.demon.co.uk, or send (atyour risk) disks or typed copy with illustrationsto the Society’s office. AYRS can take noresponsibility for loss or damage.AYRS subscribers receive both Catalyst and thebooklets. Subscription is UK£20 or US$30 perannum for a Full Member, £10 or $15 forstudents and retired members. Subscriptionrequests and all other queries to be sent to theAYRS Office, BCM AYRS, London WC1N 3XXUK, phone/fax +44 (1727) 862 268 or email:ayrs@fishwick.demon.co.ukAYRS is a UK Registered Educational Charity(No 234081) for the furthering of yacht science.

Website: http://www.ayrs.org

© 2002 Amateur Yacht Research SocietyBCM AYRS, London WC1N 3XX, UK

All Rights ReservedISSN 1469-6754

AYRS John Hogg Prize

2001 saw the launch of the AYRS John Hoggmemorial prize, established in memory of one of AYRSdistinguished early members, to be awarded for the mostmeritorious contribution to innovation in yacht sciencemade by an amateur researcher. The prize has beendonated by his family to celebrate John’s life and work.

Six entries were received before the closing date, andone too late to be included, from which the judgesselected a shortlist and the eventual winner. Catalystcongratulates them all. The winner will be presentedwith a cheque for £1000 on the AYRS stand at the 2001London Boat Show on 3rd January by Rodney Hogg,John’s son, and chairman of Spinlock Ltd.

The prize will be awarded again in 2002. The Ruleshave changed a little from 2001, but not in spirit, onlyin detail to eliminate some of the problems experiencedduring this year’s judging. We look forward to seeingyour entries.

Proa rules

The AYRS Proa Symposium on December 4th was afaciniating occasion pulling in proa devotees anddetractors alike, albeit more of the former! It is clearthat there is much more experience of proa sailing withinAYRS than is generally realised. Not all of this is insheltered waters with small dayboats – there is clearly abody of experience that would put the lie to the opinionexpressed in a distinguished UK yachting magazine thatproas are unfit for open ocean sailing, thereby writingoff 1000 years of tradition!

It is however clear that there are no established design“norms” for modern proas in the way that there are forcatamarans and trimarans. If proas are to take their placeas the third kind of modern multihull, then they needsuch norms as a basis for sorting the safe designs fromthe way-out. AYRS members led the way in setting suchnorms for cats and tris. We need to do it again.

Simon Fishwick

JANUARY 2002 3

John Hogg Prize

AYRS - John Hogg Memorial Prize 2001.Report of the Judges.

Six entries were received by the due date, of which three were short-listed.From them David Duncan has been selected as the winner of the £1000 prize.

The other two short listed entrants receive ayear’s free AYRS membership, and all three willreceive certificates at the 2002 London BoatShow presentation.

David Duncan’s novel Swing-Sail rig is bestunderstood from the photos and drawings. Itcould be described as an 85 degree crab-clawsail hoisted on a freely rotating mast, with apoint on the boom at the foot of the sailsupported by a telescopic swing-boomgoosenecked to the mast. A normal sheetcontrols the sail in use. The photo shows thesail afloat on Duncan’s Wayfarer on PlymouthSound. This sail exploits the lifting property ofan inclined sail and additionally keeps fullcontrol, in particular of helm balance and fordownwind sailing when it should be possibleto minimise the risk of broaching.

His modelled, but not yet full-size, schemeis the ‘Twin-Surfer’, which will seat the crewon a forward extension of the swing-boom. Thisshould provide an interesting and exciting newway of sailing where one plays the sail with one’sfeet.

Stephen Bourn (Australia) submitted a paper “A Fundamental Theory of Sailing and itsapplication to the design of a Hydrofoil Sail Craft”. The paper “presents a general comprehensivebut succinct theoretical framework for analysing the forces acting on a sail craft and the resultantsail craft performance” to quote the abstract. Much of this will be familiar to those who haveread, for example, Edmond Bruce’s and Harry Morss’ works, but this paper carries their (andothers’) work forward with the clearest exposition yet of the need for the smallest possible apparentwind angle if you wish to sail fast, and the deleterious effect if you incline the sail (to gain liftupwards) too much. The paper as presently written concludes with a graphical presentation ofthe variation of the relevant parameters as the hydrofoil’s angle of action relative to the horizontalis varied.

David Duncan’s swing rigged Wayfarer onPlymouth Sound

4 CATALYST

John Hogg Prize

The second part of Bourn’s entry is the design of a ‘speed machine’. The way it will be operatedis fully described in his November 1998 patent application, which was sent as part of the submission.

Bourn’s scheme for a fast sailing machine is not a totally new idea, looking at first sight not sodifferent from J.G.Hagedoorn’s ‘Ultimate Sailing’ craft of 1971, reprinted in AYRS 114, January1994. But the string is replaced by a beam, and the hapa by a lifting foil. Jonathan Howes’ design,of which there is a conceptual sketch in the October 1998 AYRS Newsletter (pp 8 & 9), is similarso there is now an exciting race on to get from the model stage, at which both are, to full size.Bourn sent a short video which shows that his radio-controlled model can get under way oneither tack, stop and tack, but so far ‘flying’ the ‘hull’ clear of the water so that it can aerodynamicallyweathercock does not seem to have been achieved.

Bob Spagnoletti’s Wind Data Logger was nominated by Bob Downhill, who hasbeen one of the beneficiaries of this device, which provided a continuousrecord of wind speed and (magnetic compass) direction during SpeedWeeks 2000/1. This compact instrument - which would havebrought joy to John Hogg and maybe helped the UK to anAmerica’s Cup win - recorded the data every 10 seconds atWeymouth for over 10 hours at a time. Recording as frequentlyas every quarter of a second, or up to once every 5 minutes ispossible with an inversely proportionate duration. The formercan show much more of the detail of wind, and a ‘field’covered with such instruments could provide data to keepa meteorologist busy for weeks and earn him/herself a PhD.More detail is on the Speed Sailing web sitehttp://www.speedsailing.org.

The other entrants were (“40 knot”) Bernard Smith(USA), nominated by Robert Biegler (Norway), DidierCostes (France) who submitted ‘Mes Bateaux’ – publishedin Catalyst No 5 - and Peter A. Sharp (USA) who submittedhis ‘Power Alternating Sailing’, described in Catalyst No 3.

We are grateful to all the entrants whose ideas have givenus much food for thought. We have provided some feedback,which we hope will be useful for future work, as indeed wehope the prize itself will be in furthering currentdevelopment. We have learnt that the rules need to be moreclosely specified to help both the judges and entrants: alsothat electronic transmission of words and of diagrams inparticular has its hazards, so that future submissions will becalled for in hard copy, by post, or in one of a limited rangeof formats.

The next award will be made at the London Boat Showin January 2003. The closing date for entries will be15 October 2002.

John Hogg takingwindspeed measurements

JANUARY 2002 5

John Hogg Prize

Introducing the Swing Sail-rigDavid Duncan – Winner,

2001 John Hogg Prize

This new swinging sail rig is designed to reduce heeling moment and to produce a verticallifting force. This helps to reduce a vessel’s displacement, reduces water drag, and therefore increasesthe boat’s speed.

The lifting force is obtained by tilting the sail vertically, as is the case with jib sails and spinnakerswhich both produce a vertical lift when inclined.

Tilting sails have been used successfully at varies times in the past but have not been easy tohandle. The Arab dhow’s lateen is an efficient sail that produces some vertical lifting force but isslow to tack about, and Kites produce lift but are not easy to control.

The unique arrangement of this rig, with its swinging boom, allows it to be easily controlled.

of the swinging boom. This allows the sail to betilted at an angle to the vertical as it moves with theswinging boom from one side of the vessel to theother. See drawings.

Changing from one tack to the other is easilyachieved by moving the swing boom from side toside. As the swing boom moves aft the sail assemblybecomes upright and automatically passes behindthe mast and out onto the other tack.

How it worksThe rig consists of a wing sail assembly, which swingsabout a short mast with the aid of a swinging boom.

The boom is pivoted at the bottom of the mast sothat it can swing horizontally about the mast.

There are two pivoting points on the Swing-sailrig, axis “A-A” and axis “B-B”.

The sail pivots about the mast axis, “A-A”, as in aconventional rig, and it also pivots about an inclinedaxis, “B-B”, between the top of the mast and the end

6 CATALYST

David Duncan

The angle of attack of the sail is controlled by amainsheet in the normal way and lee or weatherhelm can be easily adjusted by moving the sail foreand aft.

On a run the tendency to broach or to pitchpoleis reduced by moving the sail assembly ahead of themast. In this position the sail area is more evenlybalanced side to side and the decreased heelingmoment or lift helps prevent pitchpoling.

Raising, lowering or reefing the sail is achieved inthe normal way while the sail is held in the uprightposition.

The photographs show a prototype version of therig, mounted on a standard Wayfarer dinghy. Thephotographs were taken during trials in PlymouthSound. The angle of tilt of the sail is less obvious inthe pictures, but if a line is drawn from the top ofthe mast to the end of the swing boom, it becomesmore apparent.

The boat has also been tested at a “Winds ofChange” AYRS event at Harwich.

Apart from some teething problems the rigperformed very well with a noticeable reduction inheeling moment.It also proved to be very easy to control.

JANUARY 2002 7

John Hogg Prize

Force DiagramsThe essential requirement of a sail is to produce a

driving force component and it cannot do this(except on a dead run) without producing a heelingforce. In a conventionally rigged yacht sailing closehauled the driving force is roughly one-fourth toone-third of the heeling force. In other words forevery kilogram of driving force generated on the sail,three to four kilograms of heeling force are producedwhich have to be counteracted by the boat’s stability.

A Keelboat has to heel for the keel to produce anyrighting moment. The following diagrams show theforces acting on sailing vessels in a typical heeling

condition when sailing to windward with a conventionalrig on the left and the new rig on the right.

As can be seen in the two diagrams, the heelangle, sail area, keel area and driving forces are thesame for each vessel. The underwater forces and thehorizontal components of the sail forces are thesame.

The vertical component of the sail force howeveris negative on the conventional rig and positive onthe swing-sail rig. This reduces the heeling momentby about 50%.

The reduction in the heeling moment means thekeel weight can be reduced; or, for the same keelweight, the sail area can be increased.

8 CATALYST

David Duncan

Introducing “TWIN-SURFER”

Performance.The boat is fitted with a “Swing-Sail” rig, which

produces a vertical lift, reduces heeling moment, andallows a larger sail to be used.

Control.The sail angle is controlled with a mainsheet but

with less load than a conventional sailing dinghy.One sail is used so the boat can be sailed single-handed. Boat direction is controlled by rudders or bythe helmsman moving the sail position using theswinging boom.

Comfort.The helmsman can sail the Twin-Surfer sitting

down comfortably on a raised seat. His raisedposition keeps him drier than many sailing dinghies.

Transport.Although the Twin-Surfer is larger than a

standard wind-surfer it is still light enough and smallenough to be carried on a car roof.

“Twin-surfers do it sitting down”. In this versionof a wind-surfer, the helmsman sails and steers theboat sitting on a seat. The surfer is twin hulled andis fitted with a “Swing-Sail” rig.

The seat is fitted on a swinging boom, whichrotates about the mast and is suspended from themasthead.

The swinging boom extends out from both sidesof the mast base with the bottom of the sail assemblyattached at one end of the boom and the seat at theother end.

The seat can be moved in and out on the boomand also raised and lowered.

The sail assembly is rotated about the mast by thehelmsman moving the boom with his feet. The boatcan be steered in the same fashion.

The “Swing-Sail” pivots between the top of themast and the end of the swingboom so that it movesfrom an upright position when tacking to a tiltedposition when sailing.

The boat can be sailed with one hull out of thewater so that water drag need not be any greaterthan a standard wind-surfer.

The Twin-Surfer is easier to sail and offers severaladvantages over a standard wind-surfer.

Stability.Because the surfer is twin hulled it is far more

stable than a standard wind-surfer. The helmsmandoes not have to carefully and continually balancehimself on a board but can relax and move about thetwin-surfer.

JANUARY 2002 9

John Hogg Prize

A Fundamental Theory of Sailing and itsapplication to the design of aHydrofoil Sail Craft

Stephen BournOctober 2001

This is a (very) condensed version of Stephen Bourn’s full paper, which presents a general comprehensivebut succinct theoretical framework for analysing the forces acting on a sail craft and the resultant sailcraft performance. An innovative type of hydrofoil sail craft, whose design was guided by the theory, isdescribed. This type of craft should have superior performance to all existing types of high performancesail craft on all courses in most conditions. The theoretical analysis shows that the system of forces actingon any sail craft at equilibrium can be reduced to an equivalent system of three forces acting in avertical plane. The resultant forces represent the net aero, hydro and gravitational forces. The geometricalrelationships between these forces and the air/water/craft velocity triangle in the horizontal plane leadsto a fundamental equation governing the limits of sail craft performance. Consideration is given to theimplications of the theory regarding the necessary attributes of high performance sail craft in general.The particular type of hydrofoil sail craft described in the paper would be almost fully airborne whenin use. A single inclined aerofoil and a single submerged inclinable hydrofoil would generate the mainaerodynamic and hydro forces that would support and propel the craft.

10 CATALYST

Stephen Bourn

IntroductionThe full paper analyses the problem of the

fundamental limitations on ultimate sail craftperformance. The general attributes required forhigh performance sail craft become apparent fromthe analysis. Guided by the analysis a novel hydrofoilsail craft has been designed, and is described.

A few well-understood basic principles are appliedto the problem. The primary principles come fromsimple Euclidean geometry and statics, that branchof engineering mechanics that deals with rigid bodiesat equilibrium under a system of forces. Resultsfrom aerofoil theory, which is equally applicable tofoils operating submerged in water, are also used.Basic results from the hydrodynamic and hydrostatictheory applicable to the motion of a hull on thewater surface are also needed. The principal initiallyused from aerofoil theory is the simple fact that lift,a force component perpendicular to the direction offlow, can be generated.

An innovative approach is taken to the analysis ofthe complete system of forces acting on a sail craft.The system of forces acting on a sail craft at equi-librium is reduced to an equivalent system of threeresultant forces with concurrent lines of action lyingin a vertical plane. The resultant forces represent thenet aero, hydro and gravitational forces. Thegeometrical relationships between these forces andthe air/water/craft velocity triangle in the horizontalplane leads to a fundamental equation governing thelimits of sail craft performance. The equation relatesthe apparent wind angle to basic parametersassociated with the net aero and hydro forces.

The approach taken in reducing the system of forcesobviates the need to give independent considerationto heeling, pitching and righting moments.

The theory is applicable to all sail craft. Thisincludes displacement yachts, dinghies, multihulls,sailboards and kite powered craft. The theory can beapplied to ice and land yachts, with appropriatesubstitutions for references to water. While thetheory may apply to all sail craft, the emphasis is onhigh performance, meaning high speed relative tothe true wind speed, and high absolute speed.

The hydrofoil sail craft described in the paperwould be almost fully airborne when in use. Asingle inclined aerofoil and a single submergedinclinable hydrofoil would generate the mainaerodynamic and hydro forces that would supportand propel the craft. The craft should have superiorperformance to all existing types of high performancesail craft on all courses in most conditions.

Section outlineThe full paper is structured as follows. Section 2

introduces the velocity triangle and the arc ofconstant apparent wind angle. The dependence ofvarious performance measures on apparent windangle is presented. An expression is given for avelocity ratio that changes and must beaccommodated as course changes.

In Section 3 the horizontal components of the netaerodynamic and hydrodynamic forces are examinedand their geometric relationship to the velocitytriangle.

In the next section the full three-dimensionalsystem of forces is considered. These are reduced tothree resultant forces, representing the net aero,hydro and gravitational forces. The aero and hydroforce to weight ratios are expressed as functions ofthe force elevation angles. An equation relating theapparent wind angle to the drag angles and the forceelevation angles is derived. This is the fundamentalequation determining sail craft performance. Therelatively low hull drag at low Froude number isdiscussed. The basic equations for fluid dynamic liftand drag are introduced and discussed in relation tothe velocity ratio variation that accompanies changesin course. Finally in this section the relevantliterature is reviewed.

In Section 5 the general principles are consideredregarding the relative locations of the centre ofgravity and the aerodynamic and hydro centres ofpressure, and the elevation angles of the resultantforce lines of action. The attributes required forhigh performance and for stable equilibrium arededuced. The design implications of aspect ratioand induced drag are discussed. Finally the designsof a variety of existing types of sail craft are reviewed.

Finally in Section 6 the novel hydrofoil sail craftdesign is presented. Cavitation is discussed.Alignment of the craft in response to the course,apparent wind and net forces is shown. Theresultant forces and lines of action in the verticalplane are shown. The craft geometry isparameterised and an equation derived relating theresultant force elevation angles. Representativevalues are assumed for the craft geometry and dragangles, and a full analysis of relative craftperformance is undertaken. Finally specificperformance measures are derived for a particularexample craft weight, aerofoil area and true wind.

[Since the full paper is overlong for a Catalyst article(21 pages) , we print here just Section 6. AYRS hopesto print the full paper in a booklet in due course – Ed.]

JANUARY 2002 11

John Hogg Prize

A high-performance hydrofoilsail craft

The author has designed a novel type of hydrofoilsail craft, which should be capable of sailing at veryhigh speeds and small apparent wind angles. It isfully described in the patent application [9]. Aperspective drawing taken from that publication isreproduced at Figure 6. The numbered parts aredescribed in [9].

The design goal was a craft of minimumnecessary complexity that was capable of highperformance over a wide range of true wind speedVT and course angle γ. This capability was requiredon both tacks and in unsheltered waters.

All of the general principles for high performanceand stability of equilibrium were considered andgenerally accommodated. The design choice processled to selection of the following general features.The locations for center of gravity CG, and centersof pressure CPA and CPH are fixed. In use a singleaerofoil and a single submerged hydrofoil generatethe main aerodynamic and hydro forces, respectively.Only the hydrofoil, together with its supportingstruts and stabilisers, remains submerged, the rest ofthe craft being airborne. The main aerofoil andhydrofoil have fixed areas SA and SH.

The craft must be able to accommodate a range ofprojected drag angles εIA and εIH, and it must becapable of providing a range of force elevation anglesφA and φH, and coefficients of lift CLA and CLH.This can be achieved as shown in Figure 6 byproviding three degrees of freedom in the gimbalassemblies supporting the aerofoil and hydrofoil.Yaw rotation about the vertical axes maintainsalignment with the air and water flow respectively,keeping the foil lateral axes transverse to therespective flows. Roll rotation about the horizontalaxes controls the lift elevation angles φLA and φLH.Finally pitch rotation about the foil lateral axeschanges the incidence angles αA and αH, therebycontrolling the coefficients of lift CLA and CLH.

In addition the hull is free to rotate, about avertical axis, with respect to the main beamconnecting the aerofoil and hydrofoil assemblies.Yaw rotation combined with rolling φL through π/2,that is rolling the foil to be horizontal and thenbeyond on the other side, allows the craft to sail oneither tack. Furthermore the foils can be thick andasymmetric. This is necessary to provide a widerange in the coefficient of lift while maintaining lowdrag.

Since the ratio of foil areas SA to SH is fixed, it isdesirable that the force ratio FA to FH remainsreasonably constant as the force magnitudes change.This is achieved if CG is close to midway laterallybetween CPA and CPH. Fortunately this is notinconsistent with other requirements.

Recall that each foil has three degrees of freedomassociated with it. Yaw can be controlled automaticallyby provision of fins to maintain alignment with thefluid flow. The pilot must control roll and pitch.This could be achieved by provision of a joystick foreach foil. Steering is achieved by generating

Figure 6 Perspective drawing of a hydrofoilsail craft [9].

12 CATALYST

Stephen Bourn

β

εIH εIA

Vm g

γ

V T

VA

V S

εIA

F IA

L IA

D A

F IH

εIH

L IH

D H

VAVH = -V S

εIA

εIH

β

Figure 7 Plan view of craft with forces and velocities overlaid.

W

F A

FIA

F H

F IH

L VA

L V H

W

C PH

C PA

C G

F A

F H

φH θ

W

C PH

CG

FH

F IH

ω b

b

L V H

Figure 8 Net forces in their vertical plane.

JANUARY 2002 13

John Hogg Prize

Figure 9 Angles, velocities, forces as functions of φH .

transient net lateral forces by coordinatedadjustment of the aerofoil and hydrofoil.The foil assemblies should be reasonablywell balanced about their axes, both withrespect to fluid dynamic pressure andinertial mass. The wind velocity gradientmust be accommodated to fully achievebalance.

Further discussion and detail regardingthe design and variations may be found inthe patent application. The topicsdiscussed include control and operation ofthe craft, including take off from rest andchanging tack, stability, the use ofstabilisers and elevators, and choice of foilsection shapes and properties.

Use of a single submerged hydrofoil isvirtually mandated by the stated designgoals and the principles governing highperformance. There are additionalbenefits. Hydrofoils have superior lift todrag ratios compared with planingsurfaces. A submerged hydrofoil avoidsthe problems associated with the roughstate of the water surface. It also avoidsventilation that can affect surface piercingfoils. A disadvantage is the dragassociated with the supporting struts.Ventilation may further increase drag onthe struts.

CavitationThe pressure distribution over a foil

may be expressed by ½ρV2Cp where Cp isthe coefficient of pressure and varies overthe surface. The pressure distributionchanges as the incidence angle α changes.When the magnitude of the pressure dropat some point on a hydrofoil surpasses theambient fluid pressure, cavitation occurs,and performance is impaired. Forexample water at VH=28 kn has dynamicpressure

atm12

1 2 ≈HH Vρ .

Cavitation could be a performancelimitation, and foil shape for high speedshould be carefully selected to controlCPH. This requirement limits the foilthickness and reduces the maximum valueand range of CLH. Although control ofCLH is limited, equilibrium can still be

14 CATALYST

Stephen Bourn

achieved by adjusting CLA, φLA and φLH.Ultimately further increases in speed will require theadoption of super-cavitating hydrofoils, but thesehave markedly inferior lift to drag ratios.

Force geometryFigure 7 is a plan view of a hydrofoil sail craft.

Superimposed on it are vectors representing thewater flow and apparent wind. Also superimposedare the horizontal force components. For simplicitythe forces are shown acting at the aerofoil andhydrofoil gimbal centres. This is equivalent toassuming negligible drag on the main connectingbeam and hull. Finite drag would slightly offset thecraft total aerodynamic centre of pressure. The insetdiagram shows the velocity triangle. The velocitiesand forces shown in Figure 7 are identical to those inFigure 1 [not shown here - Ed]. Notice that the mainconnecting beam is aligned with the forces and liesin the resultant force plane, under the assumptionsof negligible beam and hull drag. A bonus of thisdesign layout is that the main structural component,the beam, tends to be in tension, rather thancompression. This allows it to be a comparativelylighter structure, although there may be bendingmoments that it must withstand.

Figure 8 shows an offset frontal view of ahydrofoil sail craft. In fact it is a view normal to theresultant force plane. The waterline is represented inthe figure, and all but the lower part of the hydrofoilassembly is airborne. The resultant forces and theirlines of action are superimposed. The resultantforces and their lines of action are reproducedwithout the craft but with the force componentsshown, and the elevation angles φA and φH marked.To complete the force analysis the craft must becharacterised by two further parameters. These arethe elevation θ of the aerodynamic centre of pressureCPA with respect to the hydrodynamic centre ofpressure CPH, and the lateral position of the centreof gravity CG expressed as a proportion ω of thelateral distance from CPH to CPA. These parametersare shown in the figure. Also shown in Figure 8 is apictorial representation of the vector sums of theforces and their components.

The condition of concurrency of the force lines ofaction is equivalent to the algebraic constraint

θφωφω tantantan)1( +=− HA(11)

This determines the relationship between theelevation angles φA and φH. The ranges of φA andφH are limited by

AA επφθ −≤≤2

, and (12)

HH επφθ −≤≤−2

.

The elevations φA and φH are related by (11),and so the upper bounds are determined bywhichever is the most restrictive of these twoconditions. Recall from the previous section thathigh performance requires a craft to be relativelywide. For the hydrofoil craft described in thissection that is equivalent to requiring small θ. Thisis confirmed by (12), which states that φA isbounded below by θ.

Performance analysisA hypothetical example will now be given to

predict the performance that could reasonably beexpected in practice. Modest parameter values thatshould be achievable are assumed. Let θ =30°,ω =0.45 and εA = εH = 7.5º. As shown in Figure 9,φA can be plotted as a function of φH, usingequation (11) and the assumed values for θ and ω.Next the necessary corresponding force to weightratios FA/W and FH/W can be plotted using (7) and(8). Also the resultant projected drag angles εIA andεIH and the required lift elevation angles φLA andφLH can be plotted using (3), (4), (5) and (6), andthe assumed drag angles εA and εH. Following this,the apparent wind angle IHIA εεβ += can beplotted. Finally the expressions dependent on b inTable 1 for relative speeds on various courses can beevaluated. In Figure 9 the relative speeds TS VV

maxand Tmg VV

max , and their corresponding courseangles, have been plotted.

Now suppose the example craft has a gross weightof 175 kg, so W=175 kgf, and is operating in truewind VT =10 kn. If the craft could sail withapparent wind β =20° then from Figures 2 and 9 itcan be seen that a maximum speed maxSV ≈30 knwould be possible, and the best speed made goodupwind would be

maxmgV ≈10 kn on course γ ≈55°.The elevations φA ≈50° and φH ≈15° are required toachieve β =20°. From Figure 9 it can be seen thatthis would require FA slightly greater thanW=175 kgf. On course γ ≈55°, with β =20°, theapparent wind would be VA ≈25 kn. Suppose thecraft has an aerofoil area SA =15 m2. Assuming acoefficient of lift CL=1.2 and applying (10) givessufficient lift LA ≈180 kgf.

In winds too light for the craft to becomeairborne, there are niches in which existing craft may

JANUARY 2002 15

John Hogg Prize

have an advantage. For displacement mode sailing,longer craft have a Froude number advantage. Craftthat can deploy massive light air rigs may be able toachieve a force to weight ratio advantage.

Conclusion

The full paper shows that the system of forcesacting on any sail craft at equilibrium can bereduced to an equivalent system of three forcesrepresenting the net aerodynamic, hydro andgravitational forces. The resultant force lines ofaction lie in a vertical plane and are concurrent.These are sufficient conditions for equilibrium, it isnot necessary to give separate consideration toheeling, pitching and righting moments. There is adirect geometrical relationship between the resultantforces and the velocity triangle. This relationshipleads to the fundamental equation (9),

+

=

H

H

A

A

φε

φεβ

cos

sinarcsin

cos

sinarcsin

which seems to be new, relating the apparent windangle β to the drag angles εA and εH and the forceelevation angles φA and φH. This single equationencapsulates the factors controlling performance,namely the aerodynamic and hydro lift to drag andforce to weight ratios. Note that equation (2)

IHIA εεβ += relates the apparent wind angle β tothe projected drag angles, not the drag anglesthemselves.

Equation (1),

ββ

sin1

sin1

minmax

2

2

2

2

−+==

mgmg VA

S

VS

A

V

V

V

V

which also seems to be new, indicates the extremes tobe encountered in the 22 / SA VV ratio as course γchanges. Sail craft must be able to accommodatethese extremes. A benefit of decreasing apparentwind angle β is a corresponding reduction in thevariation of this ratio.

The achievement of high performance and stableequilibrium imposes certain general designrequirements on the relative locations of the centreof gravity CG, the aerodynamic centre of pressureCPA and the hydro centre of pressure CPH, and theelevations of the aerodynamic lift φLA and the hydrolift φLH.

A hydrofoil sail craft has been designed withminimal necessary complexity that generallyaccommodates all of the attributes required for highperformance and stability of equilibrium. The craftis designed to operate on both tacks in unshelteredwaters over a wide range of true wind speed VT andcourse angle γ. The craft should have superiorperformance to all existing types of highperformance sail craft on all courses in mostconditions. The feasibility is demonstrated byexample calculations showing exceptionalperformance.

References1. Beer, F P and Johnston, E R, Vector Mechanics forEngineers – Statics, McGraw-Hill, Fourth Edition 1984.2. Thompson, Sir William (Lord Kelvin) andTait,PG, Principles of Mechanics and Dynamics, firstpublished as Treatise on Natural Philosophy by CambridgeUniversity Press in 1879, last revised 1912, DoverPublications unabridged and unaltered edition 1962.3. Bethwaite, F, High Performance Sailing,International Marine, 1993.4. Larsson, L and Eliasson, R E, Principles of YachtDesign, Adlard Coles Nautical, London, Second Edition,2000.5. Lanchester, F W, Aerodynamics, Vol 1 p 431, AConstable and Co, London, 1907.6. Marchaj, C A, Aero-hydrodynamics of sailing,Adlard Coles Nautical, London, Second Edition 1988,reprinted 1993.7. Barkla, H M, Physics of sailing (EncyclopaedicDictionary of Physics - Supplementary Vol 4) PergamonPress, 1971.8. Perry, J, “AYRS Meeting at Weymouth, October 98”,p 7, AYRS Newsletter, October 1998.9. Bourn, Hydrofoil Sail Craft, PCT internationalpatent application, priority date 2 November 1998,publication number WO 00/26083, 11 May 2000.

16 CATALYST

Bob Spagnoletti

Hardware: The hardware consists of thesensors, cup anemometer and compass, and the datalogger board. The compass and the windspeedcounter are built on a separate printed circuit board,firstly to allow flexibility, and secondly to cram allthe electronics and the battery into the waterproofcase. The case its self is a 300ml food storage tubfrom Woolworths at £ 0-99.

The compass is a pre-assembled module fromPrecision Navigation http://www.precisionnav.com

and is available in the UK through WillowTechnologies. It gives the compass heading toaround 2 degrees accuracy in ~ 200ms provided it iskept level. A version with a mechanical gimbals isalso available but it is probably less robust and thusless suitable for my later developments.

Two 16 bit counters are also included, one forwind speed and a spare for later developments. Thewhole lot is interfaced to a Stamp 2 processor. TheStamp is also connected to a battery backed CMOS

Description of Wind Logger

Bob Spagnoletti

Weymouth Speed Week is about having a good time; it is also about getting some performancedata for the boats and boards to help with future developments. This project fits with the latterobjective.

Project Objectives:To record wind speed and direction throughout the day for later analysis in conjunction with

the boat / board speeds. The Joddy timing system used at Weymouth Speed Week already providesspot windspeeds at the start and finishes of each run, however this is only averaged over a shortperiod of time and does not give direction. Clearly we have to record the course direction to makebest use of the data. Ideas for later developments came out of some very useful conversations withPeter Martin.

JANUARY 2002 17

John Hogg Prize

RAM (32k x 8), with a clock. The upshot of al thissilicon wizardry is that the device can log 8 bit statesof the two counters, the compass heading and thetime (hh:mm:ss) 4000 times.

The Stamp 2 processor is manna from heaven to acyber-challenged individual like myself. It is a simpleprocessor with built in EPROM memory and anRS232 programming port that allows you to writePBASIC (a BASIC like language, ideal formanipulating bits and bytes) programs and runthem as soon as the power is switched on. It ismanufactured by Parallax Inc. www.parallax.comand available in the UK from Milford Instrumentshttp://www.milinst.com

Mechanics: All the components, theanemometer, the data logger and the tail plane aremounted on an aluminium channel. This has avertical bearing assembly in the middle so the wholeassembly points into the wind.

I had intended to use an optical sensor on the cupanemometer but I did not complete it in time so Iused a magnetic read switch device from Autonic.This had two problems in my application; firstly it isheavy and secondly it has a magnet in it so it mustbe kept away from the compass. These to problemsmeant that the overall device was bigger and heavierthan I first envisaged. When mounted on top of awooden pole (18 mm x 18 mm) in a strong wind itmade the pole swing about violently!

Calibration: In order to calibrate theanemometer it is necessary to find a known steadywind speed. This is where the other counter isuseful. I will fix the wind logger to a “bow sprit” onmy bicycle and connect the spare channel to thefront wheel sensor. On a windless day (or still frostynight) I can now calculate the speed with a fairdegree of accuracy and check this against theanemometer. Until this is done I will rely on themanufacturer’s figure.

User Experience:The device is straightforward to use: Simply

switch it on and mount it on its pole. It will takereading every 10 second until it runs out of memoryspace. At the end of the day it is connected up to aPC by the RS232 port and switched on, it nowoffers the chance to download the results to the PC.When this has been done the memory is cleared,ready for the next set of results.

The RS232 port and on/off switch are visible onthe bottom of the module, the battery is behindthese.

The prototype was used for real for the first timeat Weymouth Speed Week 2000. It performedreliably for the 7 days of competition. Excel let usdown when it came to plotting out the results so wewere not able to post wind speed results as quickly aswe would have liked. The mechanical layout needs

The electronics with the lid removed (actually the bottom of the upside down food storage containeris removed) The compass module’s printed circuit board is outlined.

18 CATALYST

Bob Spagnoletti

improving, it is currently too heavy and has toomuch inertia. These problems are being addressed.

The results show fairly dramatic changes of windspeed over a short period of time, this initially ledme to think that the device was not workingproperly. Discussions with Joddy Chapman and alook at some data published else where suggestedthat this was expected. There is far more structure inthe wind than I had ever expected! The changes indirection are probably exaggerated due to themechanical problems mentioned earlier.

What is good? In a word, flexibility. The Stamp iseasy to programme and the hardware will allowlogging results at 0.25 sec to 5 minute timeintervals. Power consumption is modest, a PP3battery should do for 15 hours logging, it would bepossible to programme it and the compass to go tosleep to save power and extend the recording time.

Dirty LinenThe Stamp software needs tidying up and

additional features adding. Presently the compass

takes a single reading every 10 seconds, in order toaverage out the swinging due to the mechanicaldeficiencies. It would definitely be better to takereadings every 0.5 seconds or so and then average.

Further developments: During my earlythinking on this project I had a number ofdiscussions with Peter Martin, who suggested that itcould also be used as a performance log for a dinghyor sailboard. Joddy Chapman has published anumber of articles on this subject in AYRS Catalystand elsewhere, but here was an opportunity to getsome information about sailboard performance.

A basic sailing boat performance log has to recordwater speed, apparent wind angle and speed. Mylogger has a spare counter for water speed. By fixingthe compass relative to the boat and using a windvane with a magnet in it, I can measure apparentwind angle. With this data it is possible to get usefulinformation about the craft. I have not yet resolvedwhere to mount it on my sailboard but a bowsprit ismy present favourite.

I will keep this up to date as and when I makeprogress.

Amended 14/02/01

JANUARY 2002 19

John Hogg Prize

AYRS John Hogg Memorial Prize – Revised RulesThe AYRS announces the second award of a Prize to be awarded in memory of John Hogg, the

distinguished yachting researcher and amateur, who died on July 24th 2000.

The prize of £1000 has been donated by his family to commemorate John’s life and work.

The aim of this international award is to encourageand recognise important amateur contributions to theunderstanding and development of sailing performance,safety and endurance. Preference will be given to currentwork where the prize money is likely to benefit furtherdevelopment. It is expected that an award will be madein a subsequent year.

Nominations, whether of oneself or another, shouldbe submitted to The Secretary, Amateur Yacht ResearchSociety, BCM AYRS, London WC1N 3XX, to arriveby 15th October 2002. Nominations may be madeby or for anyone, whether or not a member of AYRS.Those nominating someone else must obtain thewritten agreement of the nominee before forwardingthe entry.

Submissions must be made in English, preferablyin hard copy sent by post, to arrive by the due date. Itwill be appreciated if submissions are made in triplicatesince a copy is needed for each of the three judges.Since under some circumstances electronic transmissioncan lead to errors, poor reproduction and confusion,the format of all material sent by email or on disk mustbe agreed in advance with the AYRS Secretary.

‘Amateur’ in this context means work done as apastime and largely self-funded. Details of any grantsor other funding received should be given. Work carriedout as part of normal employment is not eligible, butsubsequent commercial exploitation of research neednot debar work carried out originally as a pastime.Those with ongoing projects are as eligible to apply asthose whose work is completed.

The submission should cover the following:–

• A summary, of not more than one page, identifyingthe nominee, and the work submitted, and includinga short statement of its merits justifying its submission.

• A detailed description of the work itself, its novelty,its practicality, its degree of success to date, and (briefly)hopes for the future. The use of already publishedmaterial, whether or not peer reviewed, is welcome.Diagrams, graphs and photographs may be used, andvideo material on VHS PAL system may be helpful.Reference to web sites in support of the nimination isnot acceptable, however material from websites maybe transcribed into the submission document.

• A brief biography of the the nominees should beincluded, and his/her amateur status and qualificationsshould be explained.

Nominees may care to say for what they will use theprize should they win.

AYRS will wish to publish brief summary accountsof winning entries, and also that of other entrants, andmay also seek further articles from entrants about theirwork, using their submissions. Grant of permission topublish such articles is a condition of entry. Howeverinformation received as part of a submission will betreated ‘In Confidence’ if so marked.

The winner and runners-up will be announced atthe London Boat Show in January 2003. All short-listed entrants will receive one year’s free membershipof AYRS and a certificate.

The Judges, whose decision shall be final, will co-opt experts as required. Submission of an entry will betaken as signifying the entrant’s acceptance of theserules.

Requests for copies of the definitive set of rules, andqueries concerning possible entries may be made byphone or e-mail to the AYRS Honorary Secretary, SheilaFishwick, on tel/fax +44 (1727) 862 268, e-mail:ayrs@fishwick.demon.co.uk.

20 CATALYST

News & Views - Letters

I'm talking about the kind of sailor who is onlyreally happy when he is sailing. He is dependable,organised and logical. He is usually not too worriedabout the kind of boat that he is sailing; but, evenwhen he is on a powerboat, you will often see a juryrig or steadying sail.

I know of what I speak, because I fit theparameters that I have just listed. It was firstcommented on by friends who said things like "Inever saw you smile until we went sailing". I havespent a great deal of my life in around and on top ofboats, especially sailboats. I have been lucky enoughto have had the experience of a diverse number ofboats, and there have always been rational reasonsfor the absolute satisfaction and enjoyment that I getfrom them. Whether it was that aggressive win bythe thickness of the headstay fitting whilst teamracing at college, or slowly drifting to within a fewfeet of a resting heron, or my first transatlanticlandfall, or even sailing a hundred foot schooner rail-down in the Caribbean with pilot whales alongside.All of this is heady stuff, but always there seemed tobe an indefinable extra to my enjoyment. The factwas that I liked any boat no matter what; and even ifI thought rationally about all the reasons for myliking boats, there was always a synergistic effect.

Others seem to have the same affliction: captainsof industry, who are delighted to be invited for a sailin a Bequia "two-bow" boat; Wall Street financiers,who spend their Winter weekends racing tiny, badly-designed, dinghies in freezing conditions. Maybeeven you, the reader who spends a disproportionatepart of your income on a sailboat. In fact the wholesailing game seems an irrational waste of moneywhen looked at in a logical way.

Seven years ago my son, who was three at thetime, was diagnosed with P.D.D. autism. After I hadgotten over the shock and denial phase, I studied theproblem in depth, and especially the hereditary issue.It all seemed remarkably familiar. When theoccupational therapist came back from testing myson, and stated "Mr. Hughes, your son likes being insmall spaces and also likes being rocked", light bulbs

started to illuminate in my head. She did not seemto catch the implication of my reply, which was;"Isn't that strange, I've enjoyed living on sailboatsfor ten years".

Autism is described as a symptomatic disease;which is the medical profession's way of saying thatthey don't really know what causes it, but they canand do parcel the symptoms together. Some of thesymptoms include;

An inability or unwillingness to communicate well.Insistence on sameness, resisting change in routineNo real fear of dangerLittle or no eye contactUnresponsive to normal teaching methodsSustained odd playPreferring to be aloneNoticeable physical overactivity or underactivityTantrumsInappropriate attachment to objectsUneven gross and fine motor skillsThinks in picturesLearns by doing rather than watching

Now the preceding list pertains to almost everyobsessive sailor that I know. Now, I am not makinglight of this situation – as the parent of a child withPDD Autism, I live the reality every day. Nor am Isaying that every sailor fits somewhere on whatdoctors call the PDD Autism spectrum. I am,however, saying that probably I fit there, andprobably so does my wife, and that Autism is aninherited condition. I know that sailing is beingused as an educational tool more and more. Myhope is that it can be recognised for its therapeuticvalue in the case of Autism.

For the time being, my son and I love to gosailing together. As a baby he would fall into a deepsleep almost as soon as we got on the boat. Now hesleeps maybe half the time. I distinctly remember theincremental improvement in his demeanor one daywhen we chartered a boat and sailed out toDamariscove Island in Maine. It had been a tenseSummer with our business, and our son seemed to

Autism and Sailors

We all know the type of sailor I'm talking about, the words we normally use don't reallydescribe him (it's almost always a him), we use the words “diffident”, “loner”, “solitary”. We evenhave single handed races especially for this type of sailor, although there are always a sprinkling oftruly gregarious competitors in single handed races.

Your Letters

JANUARY 2002 21

News & Views - Letters

have no outlet for his frustrations,and was often close touncontrollable. He had an after-lunch nap, and just stood in thecompanionway as we slowly sailedand drifted back to ChristmasCove. He was animated andinterested, but totally selfcontrolled – the perfect child – anunusual occurrence in those days.

I am now in the process ofhelping set up a charitable sailingschool in Portland, Maine. Youcan find details on the Web at<http://friendsinternational.org/sailing.html>.

I spent some time this pastSummer (2001), offering sailing toother Autistic children. By thevery nature of this population, it istough to measure success. Theonly measure that I have is thatparents and caregivers were wildlyenthusiastic; and that they sawtheir children reacting andparticipating in a positive manner,even though that might not beobvious to an observer who wasnot aware of their "normal"benchmark demeanour. I know ofoccupational therapy only as anobserver. I know also that there isa field called recreational therapy. Ifeel that the foregoing fits underthe aegis of recreational therapy,and that probably many membersof AYRS have been self-administeringrecreational therapy for years.

I would urge readers to seek outautistic children and offer to takethem sailing. Please listen tofeedback from parents and caregivers.Let's hope that the new crewmemberbecomes a delighted and delightfuladdition, but most parents of thesechildren would be happy withdescriptions such as "a little moreenthusiastic" or "more engagedthan usual".

Please send your reactions toCatalyst or to

Gareth Hughestriatic@yahoo.com

1) At low speed there is nodifference as compared to normalkeel boats.I have experience onmany types.

2) When you have enoughwind the lateral resistance starts toincrease and is very good .But thiscould be from my chine.

3)Once there is good wind, thehull surfs and is very stable on itscourse. I trim the sails and with alittle bit of shock cord it keepsvery steady.

4) The added advantage is thatin tidal waters it sits upright anddraws very little water ....My boatweighs about 6 tons and draws 65cms.

Having a double skin bow tomake the lift off hump has otheradvantages, like when you draganchor and go on the rocks.

I would recommend it toanybody thinking of building afast boat, it’s a very practical idea.But do not use a dagger board as Ihave in the bow. Move the rig aftand use lee boards.

all the bestKen Upton

<cyberlifeboat@wanadoo.es>

DIY BoatbuildingHas anyone who has built

DIY boats in the UK set upweb pages about their projects?

I am planning a page of UKboat project web links and wouldlove to know about any such linksyou may have please!

This is not a commercialventure - it’s intended to be usefuland fun for boat nuts in the UK.

Gavin AtkinGAtkin@ubminternational.com

MeginhufersA few years ago I read a long

article that the Vikings got to theUSA and went down the coast asfar as Florida. I think the articlewas in TIME magazine.

The keel on my boat is similarto the meginhufers. I got the ideafrom old drawings. It is like a surfboard on top of a rowing skiff, andon the very bottom, I have a longsteel section to give lateralresistance and easy beaching.(This was a galvanised railwayoverhead power cable support.)

Also I put a hump in the bowpart of the hull to give me lift.

My experience, after 18 yearsof using the boat, is:

The bow of Ken Upton’s boat

22 CATALYST

News & Views - Letters

Ref: Kennebunk Weekend 1999My hydrofoil having turned

into a craft with four wavepiercing planing foils; one at eachcorner; necessitated that I shouldspeak about it. The planing foilshave not been developed to anygreat degree as of yet but thefundamental fact of having aplaning boat that does not smackthe waves has been demonstrated.My thanks to Simon for hisperspective on the planing foilsrelative to the base air-entrapmenthulls. (I should have contributedto the wine)

Of some interest to people wasthe makeup of two of the planingsurfaces which incoroporated thestruts and lifting surface from onepiece of 1/4" by 6" aluminum 4"long. The relative lengths of thesections and the angles used arearbitrary for now.

The majority of the 4' piece isfirst milled to a foil shape with aflat bottom. This can be accomplishedby chamfering the top two cornerswith a carbide blade on a table sawset at about a 5 degree angle.These cut surfaces are then cleanedup and rounded using 36 gritpaper on both a grinder and a beltsander. Files made for aluminumare good for a rest from the noise.

To be able to bend thealuminum where you want

without it cracking and withoutbending equipment is worthy ofnote. What I do is reduce thethickness of the 1/4" thickaluminum where the bend is to bemade. This can be started with afile but if a sharp notch is left thealuminum will crack when bent. Iuse the side corner of a belt sanderto make a rounded depression. Tomake the bend secure the aluminumjust below the depression and pullthe other end by hand; with thedepression on the inside of thebend. Once a 45 degree bend hasbeen made the aluminum at the45 degree bend can be furtherreduced in thickness by using thebelt sander on the outside of thebend. The piece can then befurther bent by hand to form anacute angle.

The bend one inch back fromthe end is made first by laying the4' piece on a board sitting on aconcrete floor with the one inchsticking out over the end; kneel onthe aluminum and beat the endwith a sledge hammer. This isafter having notched the inside ofthe bend.

Happy planing,Rob Fraser

rfraser@accesscable.net

Sails in no windDear Editor,(Enjoying Catalyst No. 5. Keep

up the good work!) Whileresearching something, I wasbrowsing through some oldA.Y.R.S. newsletters and ran acrossthe 18 January 1986 issue whichmight be of interest to ourmembers.

If anyone is familiar withwhirligigs, they might have runacross a whirligig which consists offour, say catboats, mounted onhorizontal rods about one footlong with mainsheet arranged sothat the boats rotate about avertical central axis in a breeze.Other whirligigs arewoodchopppers with bellcranks tochop wood, etc, farmer milking acow, etc.

Anyway, in the newsletter oneGiusseppe Gigliobianco, with amodel, connected the rotatingboats masts (I assume) to "smallblades in the water" so that themodel could sail directly into thewind. This is perfectly believable.

Here is the point of all of this:Consider doing away with theblades in the water and power thefour rotating sails through theVoith-Schneider linkage system.Thus, with power, the boat couldmove without any breeze. If thereis a breeze, then of course the sailscould be oriented to power theboat a la wingsail.

I wonder how this arrangementwould compare with a rotor shipwhich cannot move when there isno wind. I did no text research tosee if this has been mentionedsomewhere else in AYRS pubs.Here is another point. There islots of neat information in the oldAYRS newlstters. Don't discardthem. Ideas beget ideas.

sincerely,F. BaileyCatalyst owes Robert an apology over

this letter. It was sent in 1999, but lost inthe files, and has only now been found.

Rob Fraser at speed

S FI

SHW

ICK

An Exposé of my Planing Foils

JANUARY 2002 23

News & Views - Letters

Solar Boat Race, 2002It is with regret that I am

writing to notify you of thecancellation of the Solar &Advanced-Technology Boat Racefor 2002. This great event hasbeen one of the highlights of theAustralian Science Festival for thelast six years but sadly we have hadto make the decision not to runthis event in 2002, due to lack ofadequate sponsorship for theevent.

Unfortunately, the move of theAustralian Science Festival andNational Science Week to Augusthas meant that the race cannot berun during the festival in 2002 asthe weather in August is notsuitable. We have explored manyavenues for funding throughgovernment organisations andcorporate sponsors over the last sixmonths to run the race as a stand-alone event in April/May or aspart of the Canberra Festival(which is held in March eachyear). Sadly, we have been unableto raise adequate sponsorship forthe event.

We will certainly considerrunning the race again in 2003 ifenough funding can be found.However, for 2002, we have nooption but to cancel the event.The decision to notify raceentrants and stakeholders of the2002 race cancellation was madeas soon as it was realised thatsponsorship would not beforthcoming. We apologise for anyinconvenience, but hope youunderstand that the cancellationhas occurred due to events beyondour control.

Rob Simpson Project ManagerASF Limited PO Box 193, Civic

Square ACT 2608Email: boatrace@sciencefestival.com.auURL: www.sciencefestival.com.au

decends which actuates the trimtab which negatively inclines thefoil: hydro-foil descends towardsthe best height.

• When the hydrofoil is at thebest height, the free floating devicekeeps the trim tab in a neutralposition.

I offer it as a suggestion forothers to try. Maybe no one hasthought of this yet? I would begrateful if you would pass it on.

Thanks,Mark R. Tingley

Hydrofoil ControlDuring the speed week

symposium, the subject ofhydrofoils flying at the best depthbelow the water was dicussed.Apparently people have triedvarious mechanical linkages tosense the wave surface and havethese alter the depth of the foils.However the delegate [EmileLautier] felt they were not quick/reliable enough, and their presencecreated extra drag. His preferedsolution was to use a computer tocontrol the depth via a servowithin the vertical shaft.

This sparked off a debate aboutanother method – drawing in airdown the vertical shaft to inducecavitation above the wingedsurfaces. Theoretically, this wouldcause the hydrofoil to go lower inthe water, until the vent hole inthe vertical shaft submerged.However, according to GrahamWard, in practice it is not sensitiveenough.

Rather than trying any of thesemethods, I have thought ofanother way. Whilst it is amechanical approach, it would becontained within the vertical shaftand so cause no extra drag. Itrelies on the principle that wateralways finds its own level, andemploys simple technology thathas already been used with ruddersto make them self-steer.Essentially, it is to have enclosedwithin the vertical shaft a freefloating device to actuate a trimtab on the trailing edge of thehydrofoil. For this to work seawater must be permitted inside thevertical shaft. The way I imagineit working is:

• A wave crest passes thevertical shaft; free floating devicerises which actuates the trim tabwhich inclines the foil: hydo-foilclimbs towards the best height.

• A wave trough pases thevertical shaft; free floating device

Computer RowingModel (ref Catalyst No 2)

I finally have my webpage up:<http://www.atkinsopht.com>

William C. (Bill) Atkinson343 South Avenue, Weston, MA

02493-1948, USAwatkinson@compuserve.com

Another view comes from LeoLazauskas at the University ofAdelaide, who has investigated theeffect of dynamic sinkage and trimon rowing shells and kayaks. Thereis a draft paper on the Universitysite that might be of interest.

“The effect of fore-aft asymmetry onthe squat and resistance of kayaks” ison the Web at <http://www.maths.adelaide.edu.au/Applied/llazausk/hydro/kayak/kaysquat1/kaysquat1.htm>

Although the (draft) paper dealswith kayaks, there are similartrends for rowing shells. Forrowing shells there is of course theadded complication of the rowermoving in the shell which canamplify the sinkage and trim atsome stages of the rowing cycle; atothers it can attenuate thedynamic movement.

24 CATALYST

News & Views - Letters

Many AYRS members like meare interested in making boats sailfaster, and in UK we are now veryfortunate to have two excellentannual events where speeds can bemeasured, Winds Of Change andSpeed Week. However myenjoyment of these events isreduced by the way they show sobrutally that windsurfers usingstandard sails and boards are muchfaster than any of ourexperimental boats.

This is not true at world recordlevel, where as illustrated byRichard Boehmer’s diagram onp24 of Catalyst No.6, craft likeYellow Pages and Longshot haveachieved speeds in the 40-50 knotrange which challenge the world’sbest sailboarders. But the 2001Speed Week results summarised onp 4 of that issue confirm thiscomplete domination of UK speedsailing by windsurfers, withnumerous runs in the 30-35 knotrange while no boat reached 20knots.

Since Crossbow’s retirement 20years ago I think there has beenliterally only one timed boat runabove 30 knots in UK, JohnLindley’s standard (American-built!) Hobie Trifoiler in 1998.

I feel a major reason for thissorry state of affairs is that thelogistics of developing a fastsailing boat in UK are so difficult,and that a big factor here is ourlack of a permanent site whereexperimental craft and theirsupport boats can be kept safelyashore near a stretch of watersuitable for fast sailing, and whereAYRS members without boats canvisit to help with testing.

I have discussed this problemwith Bob Downhill, who thinks it

could possibly be solved byarranging for AYRS to have areserved compound on Phil andSandra Gollops’ Weymouth andPortland Sailing Academy site(WPSA), where the last two SpeedWeeks have been held. This wouldoffer permanent outdoor storagefor experimental craft (rigged) andsupport boats, with launching intoPortland Harbour from a nearbyslipway.

Indoor storage for sails and gearcould probably also be madeavailable, and of courseWeymouth and Portland are verywell supplied with overnightaccommodation which nowincludes the excellent YouthHostel described by Mark Tingleyon p 27 of Catalyst No.6.

Before discussing the detailsand financial arrangements of thisproposal with the Gollops we needto know

(a) how many boat-owningAYRS members might beinterested in keeping their craft atWPSA, and what charges theywould consider reasonable,

(b) whether non-owners wouldbe prepared to visit Weymouth tohelp with sailing trials, e.g.launching and recovery, providingand driving support boats,crewing, on the assumption thatan efficient internet or telephonesystem is set up to announceactivities at the site and matchowners with helpers.

Please contact Bob Downhill(tel: 01323 644 879, emailrobert@speedweek.demon.co.uk),Slade Penoyre (tel: 01276 472 208,slade@penoyre.freeserve.co.uk) orCatalyst@fishwick.demon.co.uk withyour views.

Slade Penoyre

AYRS boat storage compound at Weymouth? New WingsailIn September 2001 Dynawing

launched a range of doublesurfaced, soft wing sails for thewindsurf market. These sails areclaimed to point higher, producemore power and produce lessheeling than any other windsurfproduct on the market today.

The Dynawing product line-upstarts with a 4.5m (48square foot)sail designed for the beginnerboard rider and used in windsurfschools to reduce the number ofsails required per student. This sailis very easy to uphaul, planes earlyand sails directly into the wind [itsays here - Ed].

The 6m, 7m and 8m wings aredesigned for the more advancedriders who can handle this size ofrig. Recreational riders enjoy theDynawings as they can ghost alongon the plane long after the othershave fallen off as the puffs dieaway. Dynawings are a great dealsmoother to use than a traditionalsail as the torquing force is greatlyreduced. This same reducedheeling force generated by thewing when compared to atraditional sail, means it is not sotiring to rideall day long.Dynawings enable the board topoint higher going upwind, so it isa lot easier to go where you wantto go.

The 9m custom produced sail,is a big rig and designed for thestrong, out-and-out performanceenthusiast. Experienced riders lovethe Dynawing’s increase inperformance over traditional sailsand the ability to use a smaller finto greatly improves top end speed.

Contact: Peter Bell -Dynawing, Inc. 4601 Langland Rd- Suite 106, Dallas, Texas 75244 USA.Email:Peter.Bell@dynawing.comhttp://www.dynawing.com

JANUARY 2002 25

Advertisment

International Multihull Design Competition, 2002Issued 26/10/01 by Norway ’s Multihull Association (NFS) www.flerskrog.org

To Everyone with Ideas on Boat Design:

Your Mission:

Design a new multihull on these basic lines :• a fast &&exciting sailing multihull for 2-4 people.• some onboard comfort::2 bunks,cooking space,space for hygiene.• easy &&economical to build (price range self-built boat $10,000-16,000.)• cool &&sexy appearance.For anyone who wants fun,fast sailing,with a little comfort !

Everyone can enter (except the judges!).

Easy to Enter! Just basic drawings required.

June 1,2002 deadline for all entries.

General Goals :To promote the creation of a small or mid-sized sailing multihull which offers very high

performance sailing and a little cruising comfort, on a modest budget.A new design to fill the gap between the classic beach-cat (i.e.Hobie 16,Tornado) and most

current cruising designs,which for many sailors can be too expensive and complicated to build– or not sporty enough!

General guidelines :• The winning design should be unusually fast-sailing and visually attractive.• The winning design should feature a minimal accommodation, enough to provide shelter,onboard vacationing and some privacy when in harbor for 2-4 people.

• The winning design should be possible to self-build for between 10,000 and 16,000 US$,ready-to-sail.

Entry deadline and address :The deadline for mailing or handing in entries is 1 June 2002.

Mailing address:Norsk Flerskrog Seilklubb2002 Design CompetitionP.O.Box 53,1324 Lysaker,Norway.

See http://www.flerskrog.org/Flerskrog/design%2026_10_01.pdf

1000

0 N.K

R PRIZ

E!

(ABO

UT US$

1100

)

26 CATALYST

Design

SWIFGIG

Roger Collins <bluejacket@cytanet.com.cy>

Long term offshore cruising imposes special requirements for yacht tenders. .

A yacht tender may have to become a lifeboat that can be sailed to a port of choice, and heave-to when the weather dictates. For instance, on entering Indonesian Waters, the BA Pilot tells youthat ‘There are no rescue services in Indonesian Waters”. Going round in circles in a liferaft withno chance of rescue is not sensible.

If you want to avoid annual services, you need a hard tender that doubles as a lifeboat. Liferaftservices do exist in Asia and Africa, but after seeing one liferaft canister open up full of Taiwanesetelephone directories and no liferaft, and observed ‘experts’ mixing critical two part liferaft adhesivesby guesswork, it seems smarter to eliminate liferaft service altogether.

These are some important yacht Tender imperatives:· Stowage for water and food for 4 people

for five days.· Can be stowed in 2.3m (7’8”) on the

mothership.· Hull-form that can handle moderate

waves.· Enough space for a crewman to be able

to stretch full length off watch.· Dry enough to keep stores in perfect

condition after shopping trips.· Can be launched off the mothership

inside 30 seconds.

· A sailing rig that can be rigged and un-rigged at sea inside four minutes.

· A fast boat that can be sailed with orwithout a cover erected.

· Able to heave to in bad conditions withsail and spars stowed.

· On capsize, not to remain inverted.· Positive buoyancy, especially near the

gunwales so when awash it floats upright.· A fast balanced boat that can be motored,

sailed, rowed or sculled.· Lightweight hull weighing under 45kgs

(99lbs) and strong.

OCTOBER 2001 27

Design

To achieve these aims practical research withmany trials has been undertaken. It was discoveredthat a small boat with adequate freeboard LOA ofabout 3.2m (10’3”) could handle quite rough waterand still remain near the target weight of 45 kg(99lbs).

A shorter boat did not handle conditions so well;a longer boat ran into weight and stowage problems.

Inflatable boats do not like sunlight and coral; itis difficult to get them to sail fast too. Against that,inflatable boats are cheaper to build.

Requirements pointed towards a hard dinghy inmodern composites including waterproof resin andan aramid outer skin that will resist abrasion andpenetration. This is a more expensive option, but thecorrect solution.

Polyurethane injection molding was considered,but rejected on the grounds of excessive weight andappearance.

A 3.2m joining boat was settled on, leading tomany trials as to joining methods and materials.

Stainless Steel Joiners, even 5mm plate, bent. AB1(Aluminium bronze) was strong enough, but washeavy, and became a damage nuisance to themothership.

Acetyl joiners were settled on. Sheer tests onjoining components averaged at 1768kgs beforesheer on three test components. Acetyl is unaffectedin water. Stainless Steel is unreliable immersed andwhen deprived of oxygen in conventional fixings cancause unexpected sheer. For example, the writerrecently had six out of eight halyard winch studssheer during a passage in heavy air in the Gulf ofAden.

Swifgig - The BoatLength LOA 3.2m (10’ 3”); waterline LWL 3m

(9’ 8”). Construction is honeycomb coredmultiaxial e-glass, with an outer layer of aramid fibrefor abrasion, and impact resistance. Vynelester resinis used exclusively. Design parameters were to befour times stronger than a 3mm-ply laminate. Thehull shape will plane in the right conditions. Drag isonly 5kg with two up under outboard at 4kts.

FlotationThere is 444kgs (980lbs) of positive flotation. It

was found that four separate air chambers wereeffective and the lightest option. There is backupclosed cell foam flotation in each chamber. There arefour Holt waterproof hatches for stowage access.Swifgig floats the right way up if awash; and if not

overloaded, will automatically empty out until youhave enough freeboard to complete the job yourself.The self-bailer will get the last remnant of water outwhen you are off sailing again.

Joined Boat.For those yachts that cannot take a full length

Swifgig, the joining version stows in 2.3m (7’8”) –less stowed length and weight than the best selling3.1 inflatable RIB.

Dodger.More than fifteen years in the tropics tells us that

orange liferaft covers are counterproductive to theoccupants. The sun heats up the interior space somuch, thirst becomes a real issue, so fresh waterconsumption goes up. Swifgig’s cover is white. Overthe crown of the dodger is aluminium foil materialthat reflects heat, and cold. There may be some radarreflective element in this too. On the joins are largeborders of Red reflective tape that can be seen atnight from air or sea if light is applied. During theday, the large red squares can be seen from air andsea.

The result of this arrangement is a cooler workingand resting environment.

The cover is held by boltropes in Aluminiumtracks to keep as much water out of Swifgig aspossible. There are heavy zipped escape hatches foreand aft.

In a recent Tasman rescue a (well-known make inservice) Liferaft dodger was swept away by largewaves. The occupants suffer massive heat loss – inone case a survivor spent six days in hospitalsuffering from hypothermia after just six hoursexposure.

Swifgig’s dodger is very low profile, mounted onunbreakable flexible polycarbonate battens to takewave action in heavy air. The dodger is depressedinto the hull form and erected by lifting withfingertip pressure. There are no structural airbagsthat need to inflate in an emergency. There are twoairbags on top of the dodger than can be inflatedfully after launch. These provide further anti-capsizemeasures and provide further insulation andstiffness. The boat can heave-to with a small float atthe masthead to assure self-righting.

The mast is small enough to stow inside the boatin one piece.

The boat can be sailed with the dodger erected.This is important for survival, exposure even after afew hours in an open boat can be extremelydebilitating.

28 CATALYST

Design

Sailing

The RigImagine a squall coming with thirty knots in it,

and you in a dinghy. It can be a frighteningexperience, especially being led by a 3-metre wall ofspray. At sea, you need to able to get the sail off theboat and under the cover inside four minutes and adrogue out to hold the boat head or beam to wind.

Swifgig’s Mast is short, unstayed, in one piece andless than 2m length. Construction from a matrix ofcarbon fibre and glass provides a very stiff spar. TheMast to deck joint is a double start thread and withthree turns the mast is seated in a slot in theforedeck. The head of the mast is a machined Acetylinsert that takes a quick release hook to which thehalyard block is attached. The halyard hoist startsround a Holt block/jammer at the foot of the mastjust above the deckline. Extremely simple to rig andunrig at sea. The mast and sail can easily be takenoff, or just the sail.

Swifgig sail spars are of varying widths in glassand run the full length of each luff edge of the sail.Many trials were necessary before the finalarrangement was settled.

Each sail spar demounts into two sections. Whenthe sail is taken down at sea, the spars are simplydrawn apart; the sail folded lengthwise down theboat and stowed in the sail bag complete with spars,and stowed inside the dodger.

Swifsail.The sail is completely different in the way it

drives the boat. Sail shape is very specific, and theresult of many trial sails and different rigs.

Reading the sail is hard at first because habitmakes us treat the sail like a conventional foil. Theintention is to form two strong vortex flows on theleeward edges of the sail. This is quite different froma normal airfoil effect. Swifsail acts like a Concordewing. Very low heeling force is evident. Weatherhelm needs to be controlled, so you must beattentive not to impede flow by creating excess hullturbulence.

The sail is of varying aspect ratio. By easinghalyard tension, the sail lower luff is graduallymoved nearer to the surface of the water as you sailfurther off the wind and the heading angle increases.This is the fast way to sail the boat.

Swifgig daggerboard is a strong cored e-glassNACA foil with low wetted surface. It’s fast andgives good lift.

The sail is de-powered by bringing the luffstoward each other, thus breaking down the vortexflows.

SteeringThe boat is steered with an oar. This works well,

and creates less drag than a rudder when you aresailing Swifgig correctly, so is faster. Australian andNew Zealand surfboats use this method of steering,it is practical and the oar is easy to ship on reachingthe beach.

Specifications:LOA 3.11m (10ft 2.5”)BOA 1.25m (4ft 1.5”)LWL 3.05m (10ft 0”)

Draft 8cm (3”)Draft (Centreboard down) 0.7m (2ft 3”)Hull weight 44kgs (97lbs)Sail Area 4.48m² (51ft²)

JANUARY 2002 29

Notes from Toad Hill

The apparatus isshown in the sketch.The beauty of thisarrangement is thatthere is no frictioninvolved in takingany readings. Acommercial handheld windspeed meterwas used to measureairflow velocity. Thecritical item in thearrangement is thesmall spring. Thespring constant, lbs.per inch of stretch,was arrived at usinggram weights up to15 grams and about1.6” stretch. Fromthe graph of extension versus grams you will see thatit is not a linear arrangement but if you put someinitial stretch in the spring, we are working in thelinear area. The hanging platen has transverse andlongitudinal fins on the bottom to act as damperswhen they are immersed in a tray of oil. The wholeapparatus, other than the windspeed meter costpractically nothing and was mostly assembled usingmasking tape and scrap material.

The well know drag formula for immersed bodieswas used to calculate the coefficient of drag if youknow the force on the body and of course the other

constants andvariables in theformula. I point outhere the formula usesvelocity squared over2 so that we do notmisunderstand thatthe 2 is in the dragcoefficientsomewhere.

The results areshown in the tableoverleaf. Theexperiment was donefor three windspeedssimply because myfan had threeavailable speeds. Asyou can see, theexperimental drag

coefficients developed here are not in particularlygood agreement with standard handbook valuesexcept perhaps in the case of the spheres. In general,they seem to be low. I don’t think any of myreadings could be off by more than 10% and maybemuch less so there is something inherently unknownhere. I speculate the problem might be with thesurface roughnesses and the limited outlet area of thetunnel. However, it appears all the calculatedcoefficients are about the same order of magnitudewhich at least might tell you my arithmetic is correct(maybe) and the methodology is fairly sound.

Precision of Results For A Small WindTunnelAnd A Failed Downwind Experiment

Frank Bailey

In A.Y.R.S. Journal No. 125 was described a small wind tunnel with an exit opening of aboutone foot square. This article attempts to ascertain how any results one could obtain with thissmall size tunnel might be compared to those obtained by an establishment with a very largetunnel. Actually, this exercise was done in order to see if there is some unusual downwind sailconfiguration which might have a benefit over what is now normally used. Unfortunately, bothresults were disappointing but the thought processes may have some merit.

30 CATALYST

Notes from Toad Hill

You might also conclude from these results thatthe wind tunnel could be used to find order ofmagnitude differences. A lot more tests could be runto pin down more unknowns but why bother.

Now for the failed experiment.We are interested in two phenomena described in

your standard hydraulics textbooks. I will describeeach one. First, envision two older ladies incrinolines seated on a shaded porch in CharlestonSouth Carolina in summer fanning themselves in theintense heat of that town. Their fan moves the airand their hand encounters a resistance. Or, the otherway around, move the air against the fan, and thefan feels a force on it. Secondly, consider a turbine.Some fluid emerging from a jet of a certain area witha certain velocity impinges on a curved blade ofanother area that may also be moving away from thejet thus causing a force to push the blade. Now

wouldn’t it be advantageous in downwind sailing ifthe two forces noted here could be generated at thesame time and could be additive? That is, could wefigure out some sail arrangement that might causethese two forces to complement each other? It couldbe two spinnakers, one port and one starboard plus acouple of staysails. This is why the previousdeterminations of drag coefficients were attempted.(On the other hand, we could merely stay with theforces generated and dispense with most of thetedious calculations.) To test this hypothesis, anidealized sail rig was constructed on a 5” by 7” flatplate as shown in the sketch. It was constructedwith a certain drag area, 5” x 7”, on one side and onthe other side with vanes added to approximate a jeton a vane arrangement. It was put in the tunnel airstream both forward and backward. To make a longstory short, there was no appreciable difference inthe drag force or the coefficient of drag eitherforward or backwards. This tells you that drag forcesand changes of momentum forces do not add, whichyou might have guessed at the start consideringrelative speeds, etc. Basically, in downwind sailing,you should hang out all your sails that you can butof course we knew that already.

Air Speed Feet/sec.Drag Coefficients 4.55 10.12 12.30

Flat Plate 3.7”x 5.7” .83 .50 .52Book Value ? ? ?Reynolds Number N.A. N.A. N.A.

Flat Plate 5”x7” .83 .54 .54Book Value ? ? ?Reynolds Number N.A. N.A. N.A.

Ping Pong Ball 1.48” dia. 1.01 .31 .44Book Value .40 .40 .40Reynolds Number 3530 7860 9630

Plastic Ball 2 ½” dia. .64 .32 .32Book Value .40 .40 .40Reynolds Number 5990 1331016300

Long Cylinder ¾” dia. 1.14 .60 .63Book Value per foot .90 .90 .90Reynolds Number 1800 4000 4890

Long Cylinder 1” dia. 1.04 .53 .54Book Value per foot .90 .90 .90Reynolds Number 2390 5320 6520

Flat Disc 4” dia. 1.29 .68 .66Book Value 1.00 1.00 1.00Reynolds Number 9570 2128026060

JANUARY 2002 31

Notes from Toad Hill

All is not lost however because please considerthis. In the April 2001 issue of “Discover”magazine, page 21 and 22, there is an articledescribing a new book by David Anderson and ScottEberhardt titled “Understanding Flight”, McGraw-Hill, 2001. Mr. Tom Blevins also tipped me off to acondensed version of this book when he madeavailable to me an article by these two individualstitled “A Physical Description of Flight”. They havea new outlook on lift and drag. So why cannot wehave a new outlook on downwind sailing? Is justplain drag the only answer? Of course there hasbeen I suppose somewhere experiments ondownwind sail shapes, Marchaj, etc. But have theybeen made in the light of the Anderson andEberhardt material? Is this an area for fruitfulfurther research or to add an apt phrase, is this justanother straw in the wind?

A Boat Building Day

A day of discussion on boat-building theory and poracticewill be held in the ThorpeVillage Hall (between Stainesand Chertsey, Surrey, UK) onSunday 17th February 2002from 9.30am to 5pm. (Followthe signs towards Thorpe Parkthen enter the village.)

Bring your project along, orif you cannot bring it, bringsome pictures (OHP or 35mmslides for preference) and beprepared to talk about it!

Details from Fred Ball, tel:+44 1344 843690; emailfcb@globalnet.co.uk

32 CATALYST

Catalyst Calendar

This is a free listing of events organisedby AYRS and others. Please send detailsof events for possible inclusion by postto Catalyst, BCM AYRS, LondonWC1N 3XX, UK, or email toCatalyst@fishwick.demon.co.uk

January 2002

3rd - 13th London InternationalBoat ShowEarls Court Exhibition Hall.Those who can give a day or two,from 16th December onwards,to help build/staff the AYRSstand (reward - free entry!)should contact Sheila Fishwicktel: +44 (1727) 862 268; email:ayrs@fishwick.demon.co.uk

12th AYRS Annual General Meeting19.30 for 20.00hrs at theLondon Corinthian SailingClub, Upper Mall, London W6.Contact: AYRS Secretary, BCMAYRS, London WC1N 3XX; tel:+44 (1727) 862 268; email:ayrs@fishwick.demon.co.uk

February

5th AYRS London meetingDownwind faster than the wind.19.30 for 20.00hrs at theLondon Corinthian SailingClub, Upper Mall, London W6.Contact: AYRS Secretary, BCMAYRS, London WC1N 3XX,UK; tel: +44 (1727) 862 268;email: ayrs@fishwick.demon.co.uk

17th Boat Building Day9.30am - 5pm, Thorpe VillageHall, Coldharbour Lane,Thorpe, Surrey (off A320between Staines and Chertsey –follow signs to Thorpe Park, thento the village). Bring your projectalong, or if you cannot bring it,bring some pictures (OHP or35mm slides) and be prepared totalk about it! Details from FredBall, tel: +44 1344 843690;email fcb@globalnet.co.uk

March

5th AYRS London meetingPatents. 19.30 for 20.00hrs atthe London Corinthian SailingClub, Upper Mall, London W6.Contact: AYRS Secretary, BCMAYRS, London WC1N 3XX,UK; tel: +44 (1727) 862 268;email: ayrs@fishwick.demon.co.uk

April

2nd AYRS London meetingHydrofoils. 19.30 for 20.00hrsat the London Corinthian SailingClub, Upper Mall, London W6.Contact: AYRS Secretary, BCMAYRS, London WC1N 3XX,UK; tel: +44 (1727) 862 268;email: ayrs@fishwick.demon.co.uk

28th Beaulieu Boat JumbleNational Motor Museum,Beaulieu Abbey, Hampshire, UKemail: events@beaulieu.co.uk

September

28th (to 4th October)Weymouth Speed WeekPortland Harbour, UK. For entrydetails etc contact: Nick Poveytel:+44 (1342) 825292; email:nick@speedsailing.com

Catalyst — a person or thing acting asa stimulus in bringing aboutor hastening a result

On the Horizon . . .

Amateur Yacht Research SocietyBCM AYRS, London WC1N 3XX, UK

Printed by Direct Image Systems& Communications, London N1 6DL

Electric Propulsion Design — Theo SchmidtProa Foil Sections — Tom SpeerThe Maximum Speed of Yachts — Bob DillAlerion Electric Auxiliary Conversion — Charles HoughtonKCat70 —a High Performance Motor Sailer — G CoombsMore Sunshine — Chris EvansMore sources and resources: reviews, publications and

Internet sites