SAILING HYDROFOILS by THE AYRS MEMBERS OCTOBER, 1970 Published by: THE AMATEUR YACHT RESEARCH SOCIETY HERMITAGE, NEWBURY, BERKSHIRE, ENGLAND. THE AMATEUR YACHT RESEARCH SOCJETY (Founded June, 1955 to encourage Amateur and Individual Yacht Research) Patron: HIS ROYAL HIGHNESS THE PRINCE PHILIP, DUKE OF EDINBURGH, .K.G., P.C., K.T., G.B.E., F.R.S. Presidents: British: The Rt. Hon, Lord Riverdale, o.L., J.P. New Zealand: R. L. Stewart Vice-Presidents: American: B~itish: Austin Farrar, M.R.I.N.A. Great Lakes: William R. Mehatfey Beecher Moore California: Joseph J. Szakacs Sir Peregrine Henniker-Heaton, Bt. British Committee: Chairman: Sir Perry Henniker-Heaton, Bt. Vice-Chairman: Andre Kanssen (Hon. Sec.), Bill Poole Dennis Banham, W/Cdr. Jock Burrough, o.F.c., Michael Butterfield, Tom Herbert, S. A. Coleman-Malden, Michael Ellison, Pat Morwood, Eric Thorne-Symmons, Gp/Cpt. M. D. Thunder, F.o.o.s. National Organisers: American: W. Dorwin Teague, 375 Sylvan Ave., Englewood Cliffs, New Jersey 07632. Australian: Ray Dooris, 29 Clarence St., Macquarie Fields, Sydney, N.S.W. British: Michael Ellison, Hermitage, New bury, Bucks. Canadian: P. J. McGrath, 43 Thomecliffe Park Drive. Apartment 706, Toronto, 17, Ontario. French: Pierre Gutelle, 3 Rue Jules Simon, 75 Paris (I 5°). New Zealand: T. L. Lane, 32 Michaels Ave., Auckland, S.E.6. South African: Brian Lello, S.A. Yachting, 58 Burg St., Cape Town. Sweden: Sveriges Catamaran Seglare, Mistelvagen 4, Lidingo. Area Organisers: Dennis Ban ham, Highlands, Blacks tone, Redhill, Surrey. A. T. Brooke, 75 Craiglockhart Rd., Edinburgh 11. Fred Benyon-Tinker, 49 Pillar Gardens, North field Lane, Brixham, Devon. M. Garnet, 7 Reynolds Walk, Horfield, Bristol. John R. Novak, 23100 Vanowen St., Canoga Park, California. Editorial Sub-Committee: Michael Henderson, John Hogg. Editor and publisher: John Morwood, Woodacres, Hythe, Kent, England. All A YRS publications are copyright. Extracts may only be used by permission the Editor and Contributor which will not ordinarily be refused o~ as long as proper acknowledgement is made 2 CONTENTS Page Page 5 Editorial 61 Aspect Ratio 6 The AYRS 61 Air Entry 8 Introduction 61 Methods of Prevention 62 Easy Sea Motion CHAPTER I 62 Incidence Control 10 The Nature of Hydrofoils 62 Dihedral 11 The Traditional Hydrofoils 62 Foil Area 13 Asymmetrical Hydrofoils 63 Parallel Foils 14 Inverted T Stabllisars-Morwood 64 A Hydrofoil Sailing Craft 17 The All Hydrofoil Sailing Craft Morwood 20 Miscellaneous Uses for Hydrofoils 66 Rock and Roll Boats-Julian Alien CHAPTER 11 CHAPTER VI 24 The Baker Hydrofoil Craft 69 FUN-Donald Roberuon 26 Prof. Locke's Sailing Hydrofoils 70 Trimaran Conversion Unit-Alien 28 Catafoil Design-Dumpleton 71 CfRfBUS-William H. Baur 30 A Hydrofoil Design in 1956- 73 AVOCfT-Prof. Sir Martin Ryle Morwood n PARANG-Peter Cotterill 32 ENDEAVOUR's Hydrofoils-Pearce 80 An Unusual Design-A. R. Gibbons 35 Hydrofoil Experiments-Robertson 81 A Cruising Hydrofoil Trimaran- 37 Letter-Coles Arthur Piver 38 Hydrofoils-Bob Harris 82 A Wingsail Design-William Baur CHAPTER Ill CHAPTER VII 40 JfHU 1957-John Morwood 85 GIZMO-William C. Prior 42 Hydrofoil Stabilisers-Morwood 87 The Prior Hydrofoil Craft No. 2 43 A Wave Power Device-Piver 88 FLYING WING-Erick J. Manners 44 PARANG-Morwood 91 The Aspect Ratio 92 Hydrofoil Systems-Morwood CHAPTER IV 95 Hydrofoils for a Catamaran- 47 Hydrofoil Craft-Bob Harris Morwood 48 Comte de Lambert 48 Forlanini CHAPTER VIII 48 Crocco 98 Water Bicycles-Morwood 48 Wright Brothers 99 Submerged Buoyancy 49 Richardson 99 Marine Drives 49 Guidoni 100 Hotchkiss IMPELLOR 50 Alexander Graham Bell 101 The Voith-Schneider propeller 50 Principles of Design-Height 101 AVOCfT-Ietter, Martin Ryle Control 102 The Hook Hydrofoil 51 Air Entrainment 103 A Foil Crab Design-Garnett 51 Sweepback 106 Automatic Incidence Controi- 52 Tietjens Trasenter 52 Von Schertel 53 Grunberg CHAPTER IX 53 The Hook "Hydrofin" 108 The Dibb Hydrofoil Trimaran 55 The Baker Craft 110 RYSA-John Morwood 56 Gilruth 112 Micronesian Hydrofoii-Morwood 57 The Carl Hydrofoils 11 S TRIM-Aibert J. Felice 58 Gibbs and Cox 117 Downwind Yacht Design 59 Conclusions Costagliola CHAPTER V CHAPTER X 60 The Design of Hydrofoils 121 Opinions about Hydrofoii- Morwood Ed mond Bruce 60 The Section 123 A Single Outrigger (Bruce Foil) 60 The Upper Surface Bruce 60 The Lower Surface 60 The Entry CHAPTER XI 61 Thickness 129 Hydrofoil Stabi'h~r~-Morwood 61 The Plan Form 131 Letter-Andrew Norton 3 Page Page 132 Letter-Bill Holroyd 207 ICARUS-James Grogono 135 Letter-Helge lngeberg 213 MANTIS-David and Peter G. 136 Hydrofoil Stabilisers-Bruce Clark Chinery 137 G. F. H. Singleton's FOILE.R model CHAPTER XVIII CHAPTER XII 226 A Flying Hydrofoil Craft Joe Hood 139 Don Nigg's E.XOCOE.TUS, Flying 230 SUN81RD li-Chris Rowe hydrofoil 231 A Foil Stabilised Hornet-Bren Ives 144 TRIPLE. SE.C-Paul Ashford and John Potu 147 WILUWAW-Dave Keiper 234 Learning to Sail a Hydrofoii 149 A Hydrofoil Craft-R. R. A. Bratt Cockburn 151 A Hydrofoil Design-Morwood 238 A Flying Hydrofoil Catamaran 152 WIUIWAW-Dave Keiper Philip Hansford 153 Hydrofoils for a Racing Cat Williams CHAPTER XIX 156 Hydrofoil Stabilised Craft-Feldman 241 WILLIWAW, Flying and Cruislng Keiper CHAPTER XIII CHAPTER XX 159 TRIPLE. SE.C with low A.R.-Ashford 250 "The Forty-Knot Sailboat" 161 Low A.R. Bruce Foil Cruiser- Bernard Smith Perkins 252 Foil Model Experimenu- 165 A Foil Trimaran-Henry Nason S. Wayne Wells 170 A Bruce Foli-O. Holtman 254 Dynamic Incidence Controi- 172 Hydrofoil Stabilizers-Dearling W. Morton 256 The Russian Hydrofoils- CHAPTER XIV John Morwood 175 Don Nigg's FL YE.R, Mark 11 180 A Racing Bruce Foii-David Buirski CHAPTER XXI 258 COQUI, Hydrofoil Stabillsed-Morss CHAPTER XV 262 Bruce Clark Stabilisers on 18 foot 182 Centreboard Design-Morwood Canoe 185 Hydrofoil Tank Tests-Edmond 265 Hydrofoils on a Cat Hull- Bruce Peter Westerberg 189 Low A.R. Bruce foii- George Bagnell CHAPTER XXII 268 "The Foiler"-Gerald Holtom 275 Automatic Incidence Controi CHAPTER XVI Norman Riggs 192 WILUWAW-Fiying Hydrofoii Keiper CHAPTER XXIII 195 Hydrofoil Plan Form Tests 280 The Overall Conclusions Feldman Morwood 197 SULU-Rodney Garrett 280 Hydrofoils on a C Class Cat- 204 The Squid-John Morwood Berkeley 281 To Hawaii in WILliWAW-Kelper CHAPTER XVII 282 Epilogue Design-David Chinery 206 AYRS Sailing Hydrofoil Meeting 284 The Curragh-John Morwood 4 EDITORIAL by John Morwood October, 1970 In 1955, when the A YRS was formed, the members were given a challenge. They were told that people had sailed their boats off the water, being lifted by underwater .. wings," called .. hydrofoils." We showed them photographs of the Baker hydrofoils .. flying." We also told them that it was possible to stabilise a single, narrow hull with hydrofoils and again showed photographs. This book shows how our ingenious members took up this challenge. Year after year, members tried way after way of getting their boats to fly or, where stabilisers were wanted, we had examples of non-heeling sailing craft. Slowly, the design principles were worked out and the construction improved until we now have the interesting craft shown in our closing pages. At this moment in time, we can hardly say that the hydrofoil boats which our members have produced have shown any vast improvement in speed over more conventional boats. The racing catamaran, for example, at present seems to be faster without hydrofoils than with them, even though flying. However, time will undoubtedly show still more improvement in hydrofoils in speed and, as stabilisers. Reading over the material in this book, one is amazed by the collective inventiveness of our members. They will try anything and usually make it work somehow. We have every kind of inventor from the slap-happy type (such as the Editor) to the careful one who works out the principals and theory in detail, tanks tests his idea, makes his boat with loving care and sails it-and all Amateurs. This book is a tribute to our members, showing them at their best in produc ing sailing boats which will give great pleasure to yachtsmen in the years to come. A YRS sailing hydrofoil group By the time of this publication, this Group, within the A YRS, will have had its first meeting, but it is hoped that any further members who may be interested will make contact. The purpose of the Group is to exchange knowledge on all aspects of the subject, to plan and hold at least one foil-sailing meeting each year, and possibly to combine in some of the more ambitious foil sailing developments. Could anyone in any country who is interested, contact James Grogono for information at 38, New Road, London, E. I. "Sailing on hydrofoils" Early next year Kalerghi Publications are bringing out a hard-back foil sailing volume with a wide coverage of the whole subject. The main con tributors are Dr. Alan Alexander (on theory), Don Nigg (foil-sailing develop ment in the USA) and James Grogono (current problems and applications). Many of the best foil-sailing photographs have been assembled for this volume, and the Editor (James Grogono, 38, New Road, London, E. I) would be interested to hear from any potential contributor or foil sailor who has material for consideration, in par~icular any photographs of so far •un known' foil-boats. 5 The Amateur Yacht Research Society Some people who buy this book will not previously have heard of the AYRS so it is worthwhile saying something about us. We are a Society of people who either individually or in groups of two or three, try experiments with boats or make studies of yachting performance. We do it for our own pleasure and satisfaction. It is a World Wide organisation with members in nearly every country. If therefore, anyone makes an experiment anywhere in the World, whether he is a member or not, we hear about it and publish an account in our quarterly magazine. The next thing we hear is of someone else, most often in a com pletely different country making an improvement. Our book ··self-Steering'' is another example of our members' work, similar to this one. Since 1956, we have had members making special studies of how best to make a yacht steer herself on a fixed course to the apparent wind and, in 1967 we gathered everything which we had published into a book which we brought up to date in 1970, adding the new gears which our previous work had "triggered off." The other aspects of yachting in which we are interested are as follows: I. Methods of recording completely a yachts' sailing performance on a "polar curve graph sheet." We have produced a blank sheet which simply invites people to take "the sailing figures" of their yacht and put them on it. If yachtsmen will take to this idea, we will have a method of comparing one yacht with another which is far more accurate than racing, which is more a trial of the skill of the crew than of the potentiality of the yacht. 2. We have conjectured an immense number of ways to set canvas effi ciently to drive a boat. The only way so far which has proved successful is the rig used on a .. wing mast" in the C Class catamarans but other rigs may see the light of day in the course of time. 3. We have studied catamarans, from those of Nat Herreshoff in the 19th Century right up to modern times, working out the principles of design. 4. We "Pioneered" the trimaran, suggesting that it was the logical develop ment from the catamaran. 5. We have studied yachting accidents in single hulls aud multihulls, yacht electrics and ventilation and a host of minor conveniences and efficiencies for all yachtsmen. 6. We have studied "Ocean Cruising" as best we can, giving the seaman ship of the great sailors in yachts from Slocum to the moderns in the Single handed and two-man races. The list of the publications we have produced will be found at the end of this book and many can be bought from u~ still. Our present policy is to assemble books from our members' writings, rather than to keep all the past publications in print. 6 To us, the picture which emerges from our publications and books is of a large group of highly intelligent inventors, innovators and researchers who get far more out of sailing than simple fresh air. Their imprint upon sailing will last for centuries. If you are not now a member of the A YRS, you should join us now and, though you yourself may have nothing at first to contribute, your support for those who are doing research will be of immense value to them in encouraging them to continue. From the patent files of all countries, one can find examples of yachting devices of value which have never appeared on the yachting scene. The inventor has become discouraged by the lack of comprehension of his fellow yachtsmen and allowed his idea to lapse. An example of this is an excellent idea for hydrofoil stabilisers in boxes sloped at 45 degrees at the ends of a cross beam from the US patent files of 1921. 7 SAILING HYDROFOILS Introduction The A YRS has been studying hydrofoils in all their applications for some 15 years. This book is an account of these studies. We have here, however, made a selection of the material to avoid repetition, while not being afraid to include some applications which will never be used as shown but have an application in some other direction which has not yet been developed. An example of this is the use of vertical sculling hydrofoils. These are not likely ever to be used in seriousness but a modernised version of the Chinese sculling oar would have definite value. The ultimate objectives At the moment, we are on the very verge of seeing some remarkable hydrofoil craft which fall into two classes, namely (I) the Flying hydrofoil craft where the whole boat lifts off the water, leaving only three foils to sustain it and (2) the Hydrofoil Stabilised craft, where a long lean boat is stabilised against the capsizing moment of the wind by a hydrofoil placed to leeward. The fully flying hydrofoil sailing boat may, or may not, achieve speeds of 40 knots. Due to the limitations of hydrofoils in "cavitation," ultimate speeds of more than 45 knots are very unlikely indeed. Some development is needed, however, before such a craft is seaworthy. The hydrofoil-stabilised sailing boat, on the other hand, if some 50 feet long could be ordered tomorrow. If built lightly enough such as in PVC foam and fibreglass sandwich, it will have a better .. lift to resistance ratio" than the fully flying type up to speeds of 30 knots. 1t might well do 40 knots and be a fully seaworthy craft capable of righting herself from the upside down position. The method of presentation Hydrofoils show the A YRS method of producing development most excellently. An idea is produced in one country. The inventor and the invention are more or less scorned there but the A YRS publishes it. Suddenly, insomefarremote part of the world, the idea turns up again, better made or more intimately studied. Then, it is tried in even more widely varying places, all the time getting more sophisticated (possibly even getting simpler). We therefore feel that the best method of presentation is to follow the trains of thought as shown by publication after publication which we have brought out. lt is indeed a fascinating process which assures us that we have a method which can be as fruitful of results as that of governments who will think nothing of pouring millions of the taxpayers money into schemes often to produce very modest results. Our method, though perhaps slower, produces results which we are happy to show in this book. The final fully flying hydrofoil configuration may yet be to come but, if enough people read this book, it will come very soon. Cyclical invention The A YRS studies have not, of course, been confined to hydrofoils. We have studied catamarans and trimarans at the same time, acquiring some little odium in the process. This triple study is, in fact, a unity as it is simply the quest to get rid of the ballast of the conventional yacht. Catamarans and 8 trimarans have done remarkable voyages, several having sailed around the world, e.g. David Lewis in his catamaran REHU MOANA and Nigel Tetley in his trimaran VICTRESS (a non-stop voyage). But both catamarans and trimarans have capsized in the hands of less skillful sailors. Neither is really the family man's boat, except to certain designs. The process we have been watching since 1955 is composed of three parts: 1 Spreading the buoyancy of the single hulled boat into two separate hulls, making a catamaran. 2 Spreading the buoyancy into three hulls, making a trimaran. 3 "Degeneration" of the floats of a trimaran into hydrofoil stabilisers. The end of this process is a return to a single hull with the ballast replaced by hydrofoils. A cycle of development has been completed. Both models and full sized hydrofoil stabilised craft have been made and shown to work, giving great speeds and full stability. The most amazing of all that we have seen is the little model made by Gerald Holtom sailing in a scale wind of 60 miles per hour. Time after time, the strength of the wind overpowered the foils and the model capsized and the mast and sail went into the water. But, such are the dynamics of the matter that the mast and sail went on down below the hull and the wind and waves brought them up again on the weather side and the boat sailed on. Above, we have shown a cyclical development of three items ending (where we started) with a single-hulled boat. Dave Keiper, however, has shown that by adding fore and aft foils to a hydrofoil-stabilised boat, he can sail right off the water, at the same time lifting the weather foil out. Perhaps he has the configuration which will ultimately prove to be the most seaworthy and efficient. 9 CHAPTER I THE NATURE OF HYDROFOIU July, 1955 A hydrofoil is a thin sheet of material submerged in flowing water. It has all the main characteristics of an aerofoil working in air, but, because water is thicker stuff than air, the forces produced by a hydrofoil are very much greater than the forces produced by a foil of the same size and shape in air. The value of a hydrofoil is essentially its ability to produce a force acting almost at right angles to the direction of the water flowing across it and this force is very much greater than the drag, or the resistance of the foil to the water flow. Thus, if we need a force to act on a boat which is travelling through the water, we can attach a hydrofoil to the boat and get it. The main hydrofoils which are used by sailing boats are, of course, the fin keel, the centreboard, the leeboard and the rudder. The first three of these are used to produce forces acting to windward, preventing most of the leeway. The rudder, when it is slung separately from the keel, is a simple hydrofoil which is used to guide the boat. When it is slung on the after edge of a fin keel, however, complicated forces are brought into play which need separate consideration. ------------------ ~~ --· --------------------------- '· r~., Fig. 1 is a diagram of a hydrofoil with the water flowing past it. The lines, called .. Streamlines," are the directions in which particles of water travel. It will be seen that the water flowing past is turned from its course. Now, when a moving body is turned from its course, it means that a force is acting upon it, and in this case, it means that the foil is exerting a force on the water. Since action and reaction are equal and opposite, the water is exerting a force on the foil. It will also be seen in Fig. I that above the foil, the streamlines are crowded closer together indicating that the water is flowing faster there and below the foil, they are more widely separated indicating that the water flow is slower. In the 18th century, a man called Bernouilli showed that when a fluid flowed along a pipe with a narrow part in it and, for this reason, had to accelerate, the pressure in the narrow part was less than in the rest of the pipe. Similarly, if the pipe had a wider part, the pressure there was increased. The streamlines around the foil can be thought of as indicating the boundaries of imaginary pipes because particles of water do not cross them as they move across the foil so that, where they are closer together above the foil, the pressure becomes ess and, in the opposite way, the pressure below the foil increases. Fig. 2 10