I HPVA HUMAN POMR Editor: David Gordon WilsonDesign/Layout Editor: Patricia Cummings

SIX ETERS PER SECOND, 13.5 MPH, ON WATER!

This issue of HUMAN PONER, coming at the end of thefirst decade of the IHPVA, should start new enthusi-asms in receptive minds and bodies. Just as the firstspeed trials and races with faired bicycles that ChetKyle and Jack Lambie organized caught people's imagi-nation, with invention and effort being soon joined toproduce steadily increasing speeds in land vehicles;and just as Paul MacCready and his team amazed theworld with their simple and daring approach to human-powered aircraft, and encouraged others to try to fol-low; so the achievements of the pioneers in human-powered watercraft, recorded in this journal, arelikely to start some feverish and wholly delightfulactivity.

There are obvious parallels between human-powered

land and water vehicles. Both types were crude and

painful to use for all human experience until towardsthe middle of the last century. Human power wasdeveloped primarily through straining the arms andback against almost unyielding tasks. Then, quite ra-pidly and almost concurrently, the bicycle and thesliding-seat rowing shell were invented and developedto become extremely light and very efficient, with thepower in both cases being produced principally by themuscles of the legs.

In both media, developments were discouraged byrestrictive rules. Bicycles were fitted with fair-

ings, and recumbents with small frontal area were madeand raced, but were judged inadmissible for contests,especially if riders using them beat the champions whowere riding standard machines. On the water somepedalled propeller-driven craft were made and raced at

the end of the last century, and allegedly producedsome remarkable performances, but again were disal-lowed for competition. The lightweight rowing shelland the racing bicycle ruled supreme because they wereunchallenged. But who could deny that each was in its

way surpassingly beautiful, produced lovingly byskilled hands?

The creation of the IHPVA ten years ago also

created a multimedia arena where the restrictive rulesdidn't apply. The frequency with which records on

land were broken and rebroken and the magnitude of themaximum speeds reached astonished even the enthusi-asts. Although the Kremer rules for human-poweredaircraft competition must be credited in part for the

amazing performances of the Gossamer team, we baskedin the reflected glory and in our connection with ourpast-president and present international president,Paul MacCready.

Only on the water was progress difficult to discern

almost until this year. Suddenly all has changed.Jon Knapp has been delighting spectators with hischallenges in his Saber Proa. And now Alec Brooks andAllan Abbott, holder of the paced speed record forbicycles, former speed-trials record holder, andformer IHPVA president, have designed, developed andridden a pedalled hydrofoil that appears to be sub-stantially faster than the single-sculling record

speed in its initial trials, and could be faster thana champion rowed eight. Their stories of theirtrials, tribulations, and triumphs are recorded here.

But lest we be condemned for being speed-crazy,read further! There are delightful articles byPhillip Thiel, on his Dorycycle "workboat"; by PhilBolger, who shows his interest in boating for fun andrelaxation quite strongly, on Madeline, a pedalledside-wheeler; by Dick Ott, who produces the Water-Strider screw-propelled pedalled catamarans and thecomponents for sevral other HPBs, and who has been apioneer in the application of human power to manyother tasks; Hartley Rogers, Jr., giving a niceintroduction and background to rowing; and GeneLarrabee, whose propeller-design method has brought astep increase in efficiency in human-powered aircraftand boats.

Read on and revel in the beginning of a new phaseof human power.

Dave Wilson(David Gordon Wilson, editor)

2

HISTORY OF ROWING

Organizing Committee for the Games of the XXIOlympiad, Montreal 1976

Oars have been used to propel water craft sinceancient times but competitive rowing is believed tohave its origins in the races Thames River boatmenheld among themselves four hundred years ago. Howev-er, it was not until 1829 that rowing was introducedto the world of sport when crews from Oxford andCambridge Universities competed in a race on theThames between Putney and Mortlake on a course measur-ing 6838 meters, the course that is still used bycrews from the same universities in their annualclassic. Great Britain hosted the first internationalrowing event, the Royal Henley Regatta, which has beenattracting the best crews since 1839.

Boats have been evolving through the ages, and thecraft used in the original competitions on the Thameswere scarcely the trim craft we have today. Onechange came in 1843 with the introduction of outrig-gers, which enabled oarsmen to work their sweep oarsin oarlocks extended from a narrow boat. That led toslim boats used in modern competitions.

Then in 1856 came racing boats without keels, flatswift craft that could be propelled at much fasterspeeds. About the same time, oarsmen and scullersdiscovered the advantages of using their legs andsliding forward and backward as they rowed. At firstthey greased the panel on which they were sitting andsat on sheepskin. Sliding seats were introduced in1871.

Other developments over the years came in the typeof boats and oars. Sculls are those shorter oars usedby single rowers with one for each hand. Sweep oarsare longer and are used with both hands, so the oars-men alternate.

Britain continued as a world leader in the sportfor nearly a century. Professional scullers fromEngland and the British Empire taught all the leadingcountries of Europe how to scull and how to row in theyears before the Second World War. It has been repor-ted that there was no money available for their ser-vices in Britain so they went to the continent.

They were so successful in their teaching that thedominance in rowing and sculling shifted to the conti-nent and in the 1936 Olympic Games in Berlin, Germanswon five of the seven gold medals. Britain won onlythe double sculls.

In 1960 the German Ratzeburg eight, coached by KarlAdam, won the gold medal in the Rome Olympic Games andwent on to dominate competition for years. The keywas Adam's system of teaching rowing by placing empha-sis on sculling training, small boat work, and

extensive weight training.

CONTENTS

Editorial: SIX METERS PER SECOND, 13.5 mph, ON WATER!

HISTORY OF ROWING page Z

A THEORETICAL STUDY OF ROWING page 3by Hartley Rogers, Jr.

MADELINE: A PEDALLED SIDEWHEELER page 9by Phillip C. Bolger

THE WATER STRIDER HPBs page15by Richard Ott

THE FLYING FISH HYDROFOIL page by Alec N. Brooks

THE DORYCYCLE: PEDAL POWER AND SCREW PROPULSIONIN A TRADITIONAL WATERCRAFT page

by Philip Thiel

PROPELLERS FOR HUMAN-POWERED VEHICLES page 9by E. Eugene Larrabee

HUMAN AUXILIARY POWER IN A TRANSATLANTICSAILING RACE page1Z

by David Gordon Wilson

-

A THEOFRET I CAL STUDY OF FROW I NGby Hartley Rogers, Jr.

(Editorial notes Hartley Rogers is a professor of ma-thematics at NIT and a keen and accomplished oarsman.He is working on a model of rowing that gives insightsinto boat design and rowing and sculling technique.He gave me permission to publish the introduction tohis draft paper, which I think gives a nice perspec-tive on the sport of rowing. At one time 1, too,sculled on the Charles, though inexpertly, and withtwo friends started the firm of Hilson Davis &Zimmerman, producing single rowing shells having alu-minum tubular frames and foam-and-fiberglass hulls.)

Rowing at present serves a variety of practical,recreational, and competitive athletic purposes. Thepractical uses of rowing will continue, and the recre-ational and competitive aspects of rowing have the po-tential for major growth. Burgeoning interest in row-ing is evident: (i) in the marked increase in rowingactivity across the nation and in traditional centerslike Boston and Philadelphia where the demand for par-ticipation and equipment far exceeds existing facili-ties; (ii) in the rapid yearly increase in the numberand size of competitive regattas; (iii) in the recentsharp increase in competitive rowing for older agegroups; (iv) in the increased number and size ofcollege programs; (v) in the extraordinary enthusiamfor rowing on the part of many women athletes; and(vi) in the recent increases in the manufacture andsale of rowing equipment (and in the number of manu-facturers). Rowing is found by many to be a healthfuland aesthetically pleasing form of exercise that isopen to all age levels and that leaves the participantless vulnerable to joint and muscle injury than someother forms of comparably vigorous sport.

In the discussion that follows, we shall concen-trate on competitive rowing. As with automobile andsailboat racing, improvements in technology andtechnique that occur in the competitive area can havemajor and direct influence on the broader recreationalarea as well. Rowing is America's oldest intercolle-giate sport. (For a time, in the 19th century, it wasAmerica's most popular spectator sport.) Equipmentand technique have evolved steadily over the pastcentury and a half. By 1900, racing equipment hadreached approximately its present general shape andform. The sliding seat, the external rigger, and theswiveled oarlock had been developed, and dimensions ofboats and oars were not far from what they are today.Nevertheless, from 1900 to 1950 important changesoccurred, including the introduction of longer slidesand of altered styles to go with them and the develop-ment of lighter and stronger boats and oars through

the increased use of plywood.In the period from 1950 to 1980, change has oc-

curred at a more rapid rate and has led to major in-creases in racing speed. Changes have included: (i)the use of new materials (plastics, fiberglass, Kev-lar, carbon fiber, new alloys) to help provide light-er, stronger, and more durable equipment; (ii) the in-troduction of wider oar blades; (iii) the introductionof adjustable riggers; (iv) changes in the dimensionsof rigging and slides; and (v) innovations in hullshape. Major changes in rowing styles and trainingmethods have also occurred. These include: the de-layed recovery and faster slides of the modern inter-national style; increased attention to rigging dimen-sions and to the adjustment of rigging for specificconditions and individual physiques; and the use ofweight training, interval training, and a variety ofother training methods. At the same time, as insailing, new materials and technology have led to newforms of recreational equipment, which in their turnhave led to new classes of competitive activity.

Despite this growth in numbers and activity, anddespite the recent rapid progress in technique andtraining, there does not appear to have been a compar-able development of theoretical understanding of themechanics (and physiology) of rowing. We believe thatthe thoretical study described below can be an impor-tant step towards filling this gap.

MODELS FOR ROWING

A successful theory of rowing would develop modelsand principles from which one could do the following:

(i) obtain an explicit and rational foundation forthose current coaching beliefs and practices whichare, in fact, correct;

(ii) calculate in numerical form the consequencesand trade-offs that will occur when equipment ortechnique is modified;

(iii) deduce (from theory) the approximate optimalform and dimensions of racing equipment;

(iv) provide useful new coaching insights and prin-ciples;

(v) suggest directions for the development of newforms of rowing and training equipment; and

(vi) develop better instrumentation for measuringperformance (in boats and on training equipment).

In what follows, we shall describe, in some detail,a first step toward such a theory and indicate furthersteps that we plan to take. We shall, in this exam-

ple, consider the eight-oared racing boat in its con-ventional present form. The mechanical system con-sists of boat, oars, rowers, and the water and airthrough which the boat and rowers move. There arethree distinctive features of this system that giveunique quality and importance to rowing style andtechnique. These are:

(i) the non-linear relationship between boat speedand boat drag;

(ii) the non-linear relationship between slippage(speed through the water) of the oar blade and theforce of the blade on the water; and

(iii) the impedance match between rower andequipment (the extent to which motion of equipment andmotion of the human body are adapted to each other topromote the flow of power from body to equipment).

We note in passing that if the relationships in (i)and (ii) were in fact linear, rowing would lose muchof its distinctive character. In engineering terms, asimple superposition principle would hold, and rowingstyle would have no purpose other than helping toachieve a good impedance match for each rower. Eachrower would make his or her own independent contribu-tion, regardless of style, to the speed of the boat.These contributions would directly add, and the speedof a boat would be directly proportional to thecombined efforts of its rowers. In other sports, suchas bicycle racing and track and field events, styleand technique are almost entirely concerned with theachievement of good impedance match. In rowing, it isthe central role of the non-linearities in (i) and(ii) that give the sport much of its distinctive char-acter. Many rowing coaches are conscious of thenon-linearity in (i). Fewer, however, appear to beaware of (ii). As we shall see, (ii) is more impor-tant than (i) in determining the essential character-istics of good rowing style. Cont. on Page 6

IN THE NEXT ISSUE OF HUMAN PONERI

We have been promised a paper from Johnthe MIT Team's success with the onarchwinner of the third Kremer prize forflight.

Langford aboutHPAircraft -human-powered

Dr. To of The Airplane Company will be reporting onhis inflatable aircraft.

A review of human-powered boats is promised fromShields Bishop.

Submissions for Human Power should be sent to:David Gordon WilsonEditor, Human Power15 Kennedy Rd.Cambridge, MA 02138

The deadline for the Spring 1985 issue, and composi-tion recommendations, may be obtained from the aboveaddress.

3

THt 73"R YC YCL E DOR YC Ce : PEDAL POWER AND SCREWPROPULS I ON I N F TRFAD I T I ONAL WTECRA FT

by Philip Thiel

ABSTRACT

The Dorycycle was designed as an experiment in theuse of "lo-tech" components for the application ofpedal power and screw propulsion to a traditionalseaworthy watercraft. The goal was to develop a rec-reational cruising boat of moderate cost and reason-able performance, within the construction capabilitiesof a competent layperson.

The Dorycycle weighs 1300 Newtons (300 lb) on awaterline length of 3.96m (13 ft), and powered by asingle "healthy adult" will carry 890 Newtons (200 lb)at 2 m/s (4.5 mph) in smooth water for one hour. Thecost of materials and parts was about $800.

INTRODUCTION

To live in the Pacific Northwest and not have aboat is certainly unnatural and possibly immoral. Butwhat does one do if one does not care to cope with thewhims of the wind, suffer the noise and odor of amotor, or deal with electrical complications? Humanpower is the obvious answer - the original "lo-tech"and most biologically benign means of motion.

Paddles and oars have been used for locomotion onthe water since the beginning of time, and have muchto recommend them for simplicity and economy. Butjust as in the use of the wheel in land transporta-tion, with a similar moderate increase in complexityand cost, the conversion of muscle power into motivethrust may be more effectively and agreeably accom-plished with the use of pedal power and the screw pro-peller. The advantages result from the fact that inthis case the user operates the boat while comfortablyseated, facing forward, with hands free except for anoccasional rudder correction, and converts the torquefrom leg-muscle power to the uniform and continuousthrust of the efficient submerged screw propeller.

The purpose of the present investigation was totest the use of conventional mechanical components anda simple hull-form to produce a pedal-powered andscrew-propelled seaworthy recreational craft ofmoderate cost and reasonable performance, within theconstruction capabilities of a competent layperson.

HULL

A New England background suggested the advantagesof the traditional (Grand) Banks dory, a time-testedcraft well-proven in deep-sea work-boat service

(Chapelle, 1951; Gardner, 1979). This easily-con-structed model has a single-chine simplified form witha narrow flat bottom, flaring sides, raking ends, anda strong sheer. The Dorycycle is 4.9m (16 ft) longoverall, and 1.3m (4 ft, 3 in.) maximum beam. It is3.96m (13 ft) on the waterline and 0.76m (2 ft, 6 in.)maximum width on the bottom. Atypical appendages area cutaway skeg providing directional stability, later-al plane, and propeller protection; and a galvanizedwelded-steel stern frame bolted to the hull and theskeg. The draft aft is 530mm (21 in.). Sides andbottom are constructed of fir marine plywood, 6mm (1/4in.) and 9mm (3/8 in.) respectively, and the framingand trim are of oak. The outboard rudder is providedwith a yoke, and controlled by lines carried forwardthrough oarlocks to an elastic cord under the seatingstructure. Flotation in the form of foam is fittedbelow the seats at the bow and stern, and also provi-ded by plastic fenders lashed along the sides amid-ships (Fig. 1 and 3). Total weight, including onepair of emergency oars, power train, and seating, is1330 Newtons (300 lb).

POWER TRAIN

The propelling mechanism (Fig. 2) is carried ontwin fore-and-aft wooden members parallel to theinclined shaft, and consists of a transverse pedalshaft in ball-bearing pillow-blocks carrying two230mm- (9-in.-)diameter die-cast V-belt pulleys, onekeyed to the shaft and the other bronze-bushed as anidler. A standard v-belt runs over them with a twistto a 63.5mm- (2.5-in.-)diameter bronze-bushed idler onan adjustable take-up shaft in a slotted vertical woodstrut, and to a similar-size driven pulley keyed tothe 19mm (3/4 in.) bronze propeller shaft. A flangedthrust-and-steady roller-bearing in a second verticalstrut carries the forward end of the shaft, which runsaft through the hull in a standard bronze shaft logand stuffing box to a bronze rubber-bushed bearing inthe stern frame. The pulley ratio is 1:3.6, so thatat 60 pedal rpm the propeller turns at 216 rpm.

PROPELLER

The propeller is three-bladed, 406mm (16 in.) indiameter and 610mm (24 in.) in pitch, with a devel-oped-area ratio of 0.53 and a blade-thickness ratio

Cont. on Page 6

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Continued from Page S0.0625. Intended as a temporary expedient, it wasbuilt up from laminations of 12mm (1/2 in.) fir marineplywood, epoxied together and finished with threecoats of the same. After four seasons of use it hasshown no signs of deterioration (Fig. 5).

SEATING

The driver's seat is molded fiberglass, mounted ona plywood deck uniting the fore-and-aft pulley frameswith a transverse member chocked into the sides of thehull. The seat can be adjusted in fore-and-aft posi-tion, and in angle of inclination (Fig. 4).

PERFORMANCE

Progressive trials were run on a windless day on a60m (200-ft) course of still water about 2m (7-ft)deep. Ten runs were made, alternating in direction,each at a different constant pedal speed, ranging from20 to 70 rpm. The results are represented by thenearly straight line shown in Fig.? . Also plotted isa propeller power curve calculated from the Troost(1950) charts for the nearly-equivalent three-bladedmodel of 0.50-developed-area ratio, assuming a wakefactor of 0.10.

At the sustainable cruising speed of 60 pedal rpm,the boat speed is 2 m/s (4.5 mph), for a speed-lengthratio of 1.08. The true slip, based on the assumedwake factor of 0.10, is 17.5%. At this speed thepropeller power is about 144 watts (0.194 hp), and as-suming that the one-hour sustained power input for a"healthy adult" at 60 pedal rpm is 205 watts (0.275hp) (DeLong, 1978: Fig 6), the mechanical efficiencyof the power train is 70. But the belt drive isquiet, reliable, and inexpensive.

As for handling, the Dorycycle tracks steadily on astraight course, yet is responsive to the helm and

maneuvers well ahead and astern. When in heavy chop,or in a wind and tide rip, even when loaded with threepeople it performs creditably and inspires confidencein its seaworthiness.

The cost of materials and parts, during 1980-81,was about $800.

IMPROVEMENTS

The most obvious deficiency is the low efficiencyof the twisted v-belt drive. This could be improved,at increased expense, by the substitution of moresophisticated "hi-tech" belt and/or bevel gears. Thepropeller shaft stuffing-box might also be replaced bya long tube extending along the shaft to above thewaterline. These changes could raise the mechanicalefficiency to about 90%. The present propeller has anefficiency of about 77%. A two-bladed propeller witha lower developed blade-area ratio, and running ataround 600 rpm would have an efficiency of about 85%.But since the boat presently is cruising near itslimiting "hull speed", it is not certain that eitherof these two changes would produce a significantincrease in speed.

Cost and weight, however, could be bettered by thesubstitution of a wooden stern-frame bolted outboardof the transom and secured to the skeg, for thepresent welded-steel arrangement; and a wood and/orcloth seat would weigh and cost less than the heavyfiberglass seat now fitted. Also, the plastic fendersmight be eliminated in favor of more foam flotationinboard along the sides.

ACKNOWLEDGEMENTS

The author would like to express his appreciationto Shields Bishop, Larry Hahn, and E. Eugene Larrabeefor their advice, assistance, and encouragement.

REFERENCES

Chapelle, Howard I. American Small Sailing Craft NewYork: Norton, 1951

DeLong, Fred DeLona's iGuide to Bicycles and BicvclinqRadnor, Pennsylvania: Chilton, 1978

Gardner, John The Dory Book Camden, aineInternational, 1979

Troost, L. Open Hater Test Series with ModernPropeller Series, North-East Coast Institution,1950-51

Philip Thiel4720 7th Ave NESeattle, WA 98105

A THEORTICAL STUDY OF ROWING

Continued from Page 3Most previous attempts to analyse the mechanics of

rowing have attempted to construct a single mathemati-cal model that would reflect the full complexity ofthe mechanical system under consideration. Ourapproach will be different in that we shall begin witha relatively simple model and then go on to constructa series of more and more complex models. At eachstage, the model under consideration will illuminate anew aspect of rowing style and will supply us withboth qualitative and quantitative information. Thefirst and simplest of these models gives informationabout the most fundamental feature of rowing style;the need for a long and smooth stroke. Subsequentstages and models will concern the role of weight (ofrowers and equipment), the need for a hard, fastcatch, the form and pace of the recovery, the need forsimultaneity of the rowers (especially at the catch),and the achievement of a good impedance atch betweenrowers and equipment through appropriate dimensions,rigging, and timing.

(At this point I a cutting in and will leave you,dear reader, hanging. I will try to let you know whenand where Hartley Rogers publishes his completetheory. I will encourage him or Alec Brooks or anyoneelse to publish the complete theory of huaan-poweredhydrofoils. It is, though, complex. - Ed.)

6

DORYCYCLE

THE FLYZNS FS HYDRFOIL

Continued from Page 7AeroVironment, Inc. The final design has a diameterof 406 mm (16 in.), advances 690 mm (27 in.) perrevolution, and is 88 percent efficient at the designpoint.

CONSTRUCTION

Construction of the Flying Fish was fairlystraightforward, but rather time-consuming. The wingwas constructed using a wet-layup of carbon fiber andepoxy in a styrofoam female mold. This was fast, butthe surface finish out of the mold was rough, andrequired extensive filling and hand-sanding. The pro-peller blades were built by laying up carbon fiber andfiberglass in a fiberglass female mold. Steel rodsembedded in the blades were clamped into an aluminumhub, and carbon fiber was added to the outside for re-inforcement.

The front wing and strut assembly, not as highlystressed as the rear wing, was carved out of mahoganyand covered with a thin layer of carbon fiber.

The main vertical strut that mounts the wing to thebicycle frame was fashioned from a piece of aircraftstrut tubing. The wing was glued into a fitting onthe leading edge of the strut, and reinforced withcarbon fiber. The strut was covered with a stream-lined foam-and-fiberglass fairing to reduce drag.This whole assembly bolts into the bicycle frame.

The bicycle frame is nearly stock - the onlymodification was to extend the head tube forward about600 mm (2 ft) to reduce the pitch sensitivity. Thepropeller is driven by a long 6.3 mm- (0.25 in.-)pitchchain that runs through the vertical strut. The90-deg. rotation of the motion is done in the chain.The chain was assembled with a half-twist to make it a'Mobius loop.' This makes it naturally hang with aperfect 90-deg. twist. The overall ratio between thepedals and propeller is about 4 to 1.

Styrofoam flotation was added to the frametriangles to prevent the 'Fish from sinking at the endof each flight. The weight of the completed vehicleis 18 kg (39 lb).

The launching ramp was made by screwing several 6m-(20-foot-)long pieces of wood together to form channelsections. A wooden dolly on skateboard wheels rollsin the channels. The 'Fish attaches to the dolly atthree points, and employs a release mechanism thatholds it firmly to the dolly until the dolly reachesthe end of the ramp. At that point, a rope pullstight, actuating the release mechanism, and stops thedolly. The ramp is tied at one end to a convenientdock. The other end is supported by simple floats.Ropes through pulleys at the front of the ramp allow aperson on the dock to pull the dolly forward forlaunching the 'Fish.

FLYING

The Flying Fish has performed veryfew 'teething' problems with the very

well, after asmall 12-tooth

sprocket on the propeller shaft. It has gone fasterevery time it has been run.

Judging speeds on water is quite difficult. Ourinitial experiences in the motorboat were that wewould consistently overestimate the speed (e.g. whatseemed like 14 or 15 mph was really only 8 mph.) Toget an honest speed indication, -we built a simplewater manometer out of brass and clear plastic tubing.The speed can be directly calculated from how high thewater is forced up the tube by the ram pressure on thePitot tube underwater. The top of the manometer was1.8m (6 ft) above the water surface, corresponding toabout 6 m/s (13.5 mph), well above the speeds weexpected to see.

Allan was the pilot for the first run with themanometer. His plan was to sprint straight out of thelaunching ramp to try to achieve the highest possiblespeed. The launch went smoothly, but it was immedi-ately apparent to observers on the dock that a hoseclamp at the bottom of the manometer was dragging inthe water, creating a large rooster tail. This wassurely causing considerable drag and would limit thespeed.

Meanwhile, Allan was intently watching the waterlevel in the manometer. Out of the launching ramp,the speed was about 3 to 3.6 m/s (7 or 8 mph). Soon,the water level was indicating 4.9 m/s (11 mph). Hebore down harder on the pedals, and watched the levelrise to 5.8 m/s (13 mph). He accelerated again in afinal effort, and saw the level rise until water shotright out the top of the manometer! With the mano-meter removed, and with a champion sprinter riding,speeds of 7.2 m/s (16 mph) are foreseeable.

What's a ride on the Flying Fish like? You beginby carefully climbing on, after it has been mounted onthe launching dolly. Pull the toe clips moderatelytight, and try spinning the pedals. You immediatelynotice that it takes very little effort to turn thepropeller. After signalling 'ready' to the launchcrew, a countdown begins at 5. At a count of 1, youstart pedalling fast. At 0, you feel a tremendousacceleration as the dolly surges forward. Thensuddenly everything is very smooth and quiet. Thereis not a great sensation of speed, because your eyesare 2m (6 ft) above the water surface and there isn'tmuch splashing. But by watching the shoreline go by,you know that you are moving along pretty quickly. Itnow takes considerably more force to turn the propel-ler, as it gets a better 'bite' on the water. Balan--cing is very easy. In fact, it seems to only want togo straight. Lots of body English and a littleopposite rudder are required to start a turn. Afterturning around, a mild sprint sends you shooting pastthe cheering spectators on the dock. Now it's timefor some low-speed work to test out the minimum powerrequirement to stay up on the foils. As the speeddrops off, pedalling becomes much easier. Suddenlythe front foil is out of the water, and all controlvanishes. Splash!! You're in the water, victim of oneof Flying Fish's few vices.

As the speed decreases, the rear wing sinks deeperand deeper into the water and its angle of attackincreases. The front foil, controlled by the surfacefollower, rides at a constant depth. As a result, the'Fish tilts back and shifts its weight entirely ontothe rear wing. The front wing, still lifting, unloadsand shoots up out of the water, resulting in a near-certain splash. The rider can prevent this only byleaning far forward at low speeds.

WHAT'S NEXT?

In the near future we hope to make attempts on the2000m single rowing record of 6min, 49sec; 4.89 m/s(10.94 mph) and on the IHPVA 50m sprint record of8.95sec; 5.59 m/s (12.5 mph). The future for unlimi-ted human-powered water vehicles is very exciting.Carefully optimized single-rider vehicles might beable to break the 8-man 2000m record of 5min 32 sec;6.03 m/s (13.5 mph) and exceed the 9 m/s (20 mph)'barrier' in sprints.

Alec N. Brooks678 S. Oak KnollPasadena, CA 91106

a

IHPVA BIBLIOGRAPHY OF PREVIOUS HPB ARTICLES

DESIGN OF HUMAN-POWERED BOATS, Randy Danta,HUHAN POWER vol #1 Winter 1977-78

NO BOATS ABOUT IT, Lonnie CopeHPV NENS vol 1 7 December 1983

DESIGN OF HP BOATS, Norman BenedictHPU HENS vol 1 #7 December 1983

WATER DIVISION NEWS, anon.HPV HEWS vol 1 #9 March 1984

NOTES ON BOATS, Norman BenedictHPV NEWS vol 1 #10 April-May 1984

HPBs GET WARM ATTENTION AT COLD NEWPORT EVENT(Newport Boat Race), David Wilson

#PU NEWS vol 2 #1 August 1984

NMAD£ L I N a F F:DLLE I I eD S I DEWIEE:L E:F

by Phillip C. Bolger

For a long time I've deliberately cultivated ahabit of looking at any device with an eye to makingit cruder, if possible with a minimum sacrifice ofperformance. I like oars and paddles because they'recrude, not only in the sense that they're primitive inprinciple, but also in not being demanding in use.They can be buried in mud and bounced off rocks, andstroked in ice or weed. They are extremely handy formanuevering, and I tend to shy away from any improve-ments that degrade that quality. Even ordinary out-

riggers strike me as out of keeping with what rowboatsdo best, namely to go where power and sailing boatscan't. The double paddle does this better still, andthat's what I've used most myself in recent years.The single paddle is best of all, and I'm thinking ofchanging to that.

My attitude about propellers is that they'resomething you have to put up with if you want to use amotor. One of the leading advantages of a rowing boatis that it will work without a propeller. Now andthen I've toyed with the idea of a reciprocating pro-peller on the scull or yuloh principle, but I've neverworked out a clear idea of an experiment worth tryingin this direction.

When Peter Hoe Burling asked me about a pedal boatI didn't give him much encouragement, but I let himbribe me into just having a look at the problem. Theassumption was that it would be a sternwheeler, but Icame up with nothing that was of much interest in thatdirection. I was intrigued to find that if the wheelwas about three feet (about a meter) in diameter, itdid not need any gearing; it could be pedalledstraight on to the wheel shaft. This led to the ul-tra-simplified sidewheeler, Madeline.

I thought she could be steered and maneuvered bylisting her, the crew leaning away from the intendedturn, to lift the wheel on the inside of the turn moreor less clear of the water, and give the outside wheelmore bury. The twin steering oars were partly on asuspenders-and-belt principle, to allow the boat to berowed around, pushed sideways, or ferded off of ob-structions. As with numerous other atempts I've madeto use steering oars, the owner and everybody elsedisliked them, and required me to design a rudder forthe boat.

Barring the steering oars, Madeline got enthusias-tic reports from everyone concerned. Dynamite Payson,the builder and an experienced boatman, had beenskeptical of her performance, but said flatly that hecould pedal her much faster and farther than he couldhave rowed a similar hull. He has rowed hulls of asimilar type, a lot. He estimated her flank speed asseven knots (3.6 m/s), which I'm diffidently skepticalabout, having hoped for five knots, and being resolvednot to apologize if it was three. The hull is easilydriven, and apparently the wide wheels, giving consid-erable blade area on a small dip, are fairly effici-ent.

I haven't heard of any trials she may have had inchoppy water and strong winds. It's possible that thecontinuous thrust might compensate for the wind resis-tance of the paddle boxes to some extent. She must bepractically as good as a rowing boat in dealing withobstructions in the water. The wheels were given aslight dip below the bottom of the hull to allow herto "walk" in shallow water.

Though Madeline is considered a great success,there has not been a great rush to duplicate her, ifonly because her "machinery" was very expensive com-pared with a couple of pairs of oars. If there's im-proved performance, it's not of much consequence forthe usual uses of human-powered boats, whereas thedegradation of handiness and compactness is substan-tial.

My personal interest in increasing speeds by minuteincrements is slight. I hope nobody will take that asa slur on anyone else's taste; the statement is notmeant to mean more than it says. If I had to try toget more speed out of a human-powered boat and couldcount on calm conditions, I would at least have a lookat what might be done with very large paddle wheelswith a proportionately small dip; I would also look,of course, at feathering wheels which get the sameeffect with much less wind resistance.

Phillip C. Bolger250 Washington St.Gloucester, MA 01930

FFDOELLER FOF HUMAN- FOWEFED £%E I CLES

by Prof. E. Eugene Larrabee

The puny output of the human animal - between 200 W(hard work) and 800 W (heroic effort) - requires effi-cient propellers if pedal-driven watercraft are toachieve useful speeds or if aircraft are to fly atall. The, general shape of highly efficient propellersis seen on the best piston-engine airliners of the1930s; by contrast the geometry of motorboat andsteamboat propellers is driven by practical con-straints on diameter (always too small), and low per-missible blade loading (cavitation damage). Tradi-tional marine propellers are seldom more than 75%X e-ficient, but good air propellers may approach 90X ef-ficiency. Therefore the designer of human-poweredboats should look for guidance to the vast body ofaeronautical propeller theory; it is based on a vortexmodel of blade operation similar to that for airplanewings.

VORTEX PROPELLER THEORY

Vortex propeller theory is the next step up insophistication from the actuator--disc or oventustheory of Rankine and Froude, developed in the 19thcentury. In actuator-disc theory, the propeller isassumed to create a uniform slipstream flow devoid ofrotationl such a slipstream would have minimum kine-tic-energy loss for a specified boat speed, propellerdiameter, and thrust. Vortex theory takes the more

realistic view that a practical propeller has a finitenumber of blades rotating about a central shaft tocreate a cyclic, swirling slipstream. This flow willcontain more kinetic energy than a uniform slipstreamfor a given thrust because of swirl and non-uniformvelocity componentsl nevertheless, there is a certainradial distribution of blade lift that minimizes slip-stream kinetic-energy loss for a specified number ofblades, vehicle speed, shaft speed, propeller diame-ter, and thrust. This radial loading is called mini-mum-induced-loss loading, and is related conceptuallyto the elliptic span loading of a monoplane wing thatminimizes the kinetic energy of wing vortex wake flowfor a specified flight speed, wing span, and lift,thereby minimizing the induced drag. Vortex propellertheory, like vortex wing theory, was developed byLudwig Prandtl and his circle at ioettingen duringWorld War I(

The vorticity in wing and propeller theories hasits origin in the lift of airfoil (or hydrofoil)surfaces. According to the 1911 Kutta-Joukowsky(3YKOBC(NhKA theory of airfoils in spanwise uniformflow>

), the lift per unit span (or radius), N/in, is

given bys

dL/dr =p W r (1/2)pW cCi (1)

Cant. on Page 09

FOPELLERE3 FOR H UMAN--POWERED VE"4 HI CLES

wh ere p is the fluid density, kg/m3; W is the fluidvelocity, m/s; r is the vorticity, m/s; c is theairfoil chord, m; and c is the lift coefficient. Thevalue of , the bound vorticity, is determined byviscosity in the airfoil boundary layer, which alignsthe flow with the airfoil trailing edge.

Since the blade lift must vanish at the tips andat the shaft centerline, Stokes proposed a theoremrequiring that trailing vortices, aligned with thelocal flow, be shed by the individual blades in such away that the change of bound vorticity between bladeelements at radii r and r dr appears as trailingvorticity, as shown in Figure 1. The entire array ofradially varying vorticity, bound to the blades, andtrailing vorticity, arranged in helicoidal vortexsheets, may be modelled by a geometrically similararray of current-conducting wires. The magnetic field"induced' by such an array, and calculated by the

Biot-Savart law() is in every way analogous to thevelocity field induced by the vortex array; at theblade elements in particular, the velocity field oper-ates to change their angle of attack. This is theessence of vortex propeller theory.

Fig. Relation between bound and trailing

vorticity (Stokes' La).

INDUCED VELOCITIES FOR MINIMUM INDUCED LOSS

For the special case of minimum-induced-lossloading, the induced velocities have the simple formshown in Fig. 2. All of the resultant velocities, W,at each of the blade elements (which depend on theinduced velocities w), appear to focus on a centralvelocity V+ v'/2. The velocity v' is called thedisplacement velocity; its half-value can beidentified with the slip of traditional, pre-vortex,marine-propeller theory. The blade-element angle ofattack, B, is given by the difference between thegeometric blade angle, B

3 , and the helix angle of thelocal relative velocity, .

Figure 3 shows some radial bound-vorticitydistributions corresponding to minimum-induced-lossloading, which give rise to radially constant dis-placement velocity. They are functions of the advanceratio, V/fR (where fn is the shaft speed and R the tipradius), and the number of blades, B. The quantity 6= B2Vv' (G for Goldstein ) not only is adimensionless measure of the bound vorticity r (B, theblade number; n, the shaft speed; V, the flight speed;and v', the displacement velocity; are all constants),but G is also approximately equal to the ratio ofaverage axial velocity increase in the slipstream tothe displacement velocity; in other words, by makingthe tip helix angle small and the blade number large,the induced losses approach those of an actuator disk.Note that Fig. 3 contains two estimates of G: theapproximate ones of Betz and Prandtl" and the improvedones of Goldstein.

(3) If the perpendicular spacing ofthe helicoidal vortex sheets at their outer edges isless than the propeller radius, the much simpler Betz-Prandtl estimate can be used, except near the hub. Mypropeller-analysis methods exploit this idea.(4)

Continued from Page 9

PROFILE LOSSES -- PROPELLER DESIGN

Individual blade elements have profile drag (mostlyskin friction) which keeps the resultant blade loadfrom being normal to the local helix angle by theglide angle - arctan (co/cA). The efficiency of ablade element can be shown to be:

= [ tane/tan(+)] tj[(-a')/(l+a )]

= [tan0/tan ( -*) 1/ l+(v'/V)/21])(2)

where aV and a'R are the axial and swirl components,respectively, of the induced velocities at the bladeelements. The quantity tano/tan(0+E), the profile ef-ficiency, has a maximum if 0= ft/4 -/2; therefore themost heavily loaded part of the propeller, near 80Xradius, should operate at this helix angle to minimizethe profile losses. This result is in conflict withminimizing induced losses, so a propeller of highestefficiency must incorporate some kind of compromise tominimize the sue of induced and profile loss.

To design such a propeller by my method, firstchoose a design point characterised by a certainvehicle speed, shaft speed, and shaft power. Nextselect a reasonable diameter, say that given by:

P -= 2P/pV 3ftR 2 0.2

(where P is the shaft power in watts),a suitable number of blades. Two or

(3)

and then choosethree usually

Fig. 2 Induced and resultant velocities forminimum induced loss. 11ll the resultant veloci-ties Hn, appear to focus on a comon axial velo-

city ( + v'/2 v' is the displacement velocity.

I _ o I 1

f

27r V J 'I B = umber

blades

L V or rl - --L

Fig. 3 Bound-Vorticity distributions forminimum induced loss, according to Betz andPrandtl - - --. ccording to Goldstein

(0

i(5:/0)

[~,~

V

f,C 7. v 1 4

--

j I

Qr,

will be best. Next calculate the corresponding mini-mum-induced-loss bound-vorticity distribution, G.Also, it is necessary to have a radial variation ofprofile--drag/lift ratio, D/L, say 1/50, correspondingto a design lift coefficient of 0.50 and a profile-drag coefficient of 0.01. Then four simple integrals,suggested by Goldstein, can be evaluated numerically:

I, 4G(1-L) doX

12 = 2:6(1-PL )(1/ lX) dtx

J, 46(1+ D/L x) d

JZ e 256(1+ D/L x)(X 1+X ) d

where , a r/R and x rr/Vintegrals the displacementcalculateds

2JLv J a 1and the overall efficiency:

'2 = (It, - I;)/Pc

(4)

(5)

(6)

(7)

- / (V/AR). With theset velocity ratio can be

(8)

(9)

If the efficiency is satisfactory, theangle at any radius can be calculated,

helix

0 - arctan (V/1LR ) (1 + /2) (10)

the blade angle (dC$is the design angle of attack),

(11)the lo velocity ratio,

the local velocity ratio,

i -x + - (S cos0/2)2

V

and the local chords

c/R - 4 ( V/nR) .B W/v FC:

(12)

(13)

This preliminary blade geometry allows c.alculationof the radial variation of Reynolds number( to see ifestimates for D/L, c, and 0D have been reasonable andif the blade is structurally practical. Experiencethen shows how to change the design assumptions toimprove the propeller. The theoretical basis for thisanalysis is more fully discussed in reference 4.

EXAMPLE: PROPELLER FOR A HUMAN-POWERED BOAT

A practical human-powered boat might have anoverall length of 4.5 m (14.76 ft), a beam of 1.2 m(3.94 ft), and a keel draft of 75 am (3 in) for adisplacement of 120 kg (265 lb). A shaft power of200 W (0.27 hp) should keep a canoe-like hull of thesedimensions moving at about 3 m/s (5.83 knots). Apropeller radius of 177.8 mm (7 in) leads to a powercoefficient of:

Pc - 2(200)(1000)(3)3 (ft)(0.1778)

- 0.149 170

which is most satisfactory.blades, a D/L of 0.02 over mostlets the advance ratio be 0.25,

11 = 1.143 72

If one choosesof the radius,

the integrals ares

twoand

I = 0.095 28

J1 = 1.214 07 J2 = 0.506 45

The displacement velocity ratio v'/V is 0.117 14,

Fig. I N.Z.L. propeller for human-powered boat.

the efficiency is almost 90X, and the propeller lookslike Figure 4 if all the blade elements operate at adesign lift coefficient of 0.5. If the profiles arecambered to support this lift coefficient at zero an-gle of attack, the geometric pitch/diameter ratio is0.831. The propeller must turn 645 rpm at this designpoint. A sketch is given for a suitable drive line;it is important that the propeller axis be nearlyparallel to the flow since efficiency declines approx-imately as the cosine-cubed of the misalignment angle.

REFERENCES

1. Luftschrauben it geringsten Energieverlast, AlbertBetz; with an appendix by Ludwig Prandtl. Reportsof the Aerodynamics Research Institute atGoettingen, 1919. Also included, in nearly completeform, in NASA Reference Publication 1050, edited byR. T. Jones. NASA Reference Publication 1050contains a reprint of NACA Technical Report *116,written by Prandtl in German about 1921, andpublished in English translation about 1923. Thisanonymous translation is one of the few good onespublished by the old NACA.

2. Theoretical Aerodynamics, L. N. Milne-Thompson.Reprinted by Dover publications (no. 0-486-61980-X,1973), NY.

3. On the Vortex Theory of Screw Propellers, SidneyGoldstein. Proceedings of the Royal Society, SeriesA, Vol. 123, London, 1929.

4. Five Years Experience withPropellers - Part I Theory;E. Eugene Larrabee. SAE840027, 1984.*

Mini mmPart II:Preprints

Znduced LossApplications,

840026 and

E. Eugene LarrabeeEmeritus Professor,Aeronautics and AstronauticsMassachusetts Inst. of Technology

* These two papers may be obtained, for US$6.00,from the SAE or from E. E. Larrabe, 12 S. MontgomeryAve., Apt. 1, Atlantic City, NJ 08401, USA.

I I

H-MI IN AUi X II I FLI FRY WE I P OWE S L I NG RFACE:

Continued from Page 13

cessful pedal-power rig, which tired him out too fast,forcing him to give up on it. I am trying to imaginesomething I can comfortably sit in to pedal two hoursa day in fifteen-minute intervals. Another require-ment is that the unit should be light and not take uptoo much space ....

I instantly referred Bill to Steve Loutrel, asuperb sailor and designer who every year used to takehis wife and hardy students to northern Labrador orinto Hudson's Bay among the ice-floes in a smallsloop, and who had designed a pedalled generator. Buteven he had not succeeded in producing a device thatdid what Bill Doelger wanted.

Bill collected me one blustery day in June, droveme to Marblehead, and took me for a sail in Edith, hisVal. It was thrilling. I had just purchased asecond-hand Tornado, a fast Olympic-class cat, andwanted to learn all I could. (Alas, others felt thatthey had more right to my Tornado than I, and strippedit in the boatyard before I had my first sail. I tookup sail-boarding as an interim solution before I couldhave my dream of a fast HPB.) A trimaran has, ofcourse, three hulls (or, if you are fussy, a hull andtwo aas), and in one of 10m overall length the mainhull has a small cabin and cockpit. But there washardly room to stand or sit, let alone pedal and steersimultaneously.

I added "the design and construction of a sailboatpedal-powered generator" to my list of undergraduateprojects at MIT, and this was noticed by CarlNowiszewski, a tall, muscular, friendly, capable mech-anical-engineering senior. He also had great tact andperseverance, and, with Bill and me, went through manyiterations before arriving at a folded-backsemi-recumbent two-stage design that would just fit atan angle in Bill's cramped cockpit. I hope that I caninclude some illustrations.

Bill had told me he was not a practical type, buthe contributed greatly to the final design. He wasthrilled with it. He sailed over to Britain just intime for the race, and crossed the start line amongthe last of the contestants. When 160km out, a "heftyocean-going chase boat" with press photographers

circled him "as I pedal on my generator and actphotogenic." "I discovered that the solar panel I hadsimply did not provide enough power for myself-steering and instruments. The (pedal) generatorworked both ways across the Atlantic. It kept my bat-tery up and kept me warm and healthy in addition tooccupying me from one to two hours every day." Butall did not go well when he encountered some of theAtlantic's storms when nearly across.

"Seeing a near-vertical wall of water the height ofa two-story building moving down on me at 40 mph maybe exciting, but I am not interested....It isdifficult to be objective about bad waves unless oneactually capsizes, but I cannot help think that I came

close to going over." Then, south of Newfoundland,"in the very early morning of the 27th (of June,1980), I am doing well. For the first time in severaldays, I am making my charted course and doing acomfortable 7 knots (3.6 m/s) under a moonlit sky and10 knots (5.2 m/s) of wind. Then a big "BANG". Ilook all over the boat, but I can see nothing wrong.I sit back on my generator and begin pedalling,reasoning uncertainly that I must have hit something.At 0326, another bang, and like a big tree the mastfalls down easily onto the starboard aa."

The story of how Bill Doelger, still single-handed,

got the huge broken mast stepped two days later andsailed into Newport as number 31 out of 88 starters,16th in his class, is a saga that, unfortunately, doesnot belong here, but it totally disproves Bill's claimthat he is an impractical type. His was a personaltriumph. He also participated in a wider triumph:that of multihulls in a race previously dominated bymonohulls. The race was, in fact, won by a 67-year-old Massachusetts publisher, Phil Weld, in anotherDick Newick trimaran, at a time when younger folk weretrying to make those of us over 30 feel we should beunseen and unheard. So there was a third triumph, ofa very young sexagenarian. And a fourth triumph hasbeen very little celebrated until now: CarlNowiszewski's pedalled generator. My aim has been togive Carl some of the credit he deserves.

Dave Wilson15 Kennedy RdCambridge, MA 02138

14

CARL NOIJISZEWSKI'S PEDALLED GENERATOR FOR A SAILBOAT COCKPIT

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