Hovering Craft & Hydrofoil Magazine August 1967 Vol 6 No 11 · 2018. 7. 25. · HOVERlNG CRAFT &...

HOV-G CRAFT & HYDROFOIL

THE INTERNATIONAL REVIEW OF AIR CUSHION VEHICLES AND HYDROFOILS

KALERGHI PUBLICATIONS

can your defence strategy succeed without the world's latest hovercraft weapons system ?

. . . the BH.7 which brings a new dimension t o your defence planning. This 40-ton pacesetter is now on offer w i th f i rm delivery dates and prices. Already the British Government has announced its intention to order both the fast attack

version (FAC) and the logistic amphibious version (LAC). BH.7 has a lot to offer. With its 3,400 s.h.p. Rolls-Royce Marine Proteus gas turbine, BH.7 is a completely integrated weapons system carrying formidable fire power at a cruising speed of 75 knots, by day or night from

mobile, easily-concealed shore bases or from mother ships at sea. Only BHC hovercraft have been used in combat. On operations with both British Defence Forces and the U.S. Navy they have proved themselves in every climate from tropical jungles to the frozen arctic.

BRITISH HOVERCRAFT- WORLD LEADERS I N THE HOVER TRANSPORT REVOLUTION

BRITISH HOVERCRAFT '& CORPORATION LIMITED I S A S U B S I D I A R Y OF

LIMITED A'RCRAFT

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HOVERlNG CRAFT & HYDROFOIL

FOUNDED OCTOBER 1961

First Hovering Craft & Hydrofoil Monthly in the World l1

AUGUST 1967 VOL 6, No 11

Editor : JUANITA KAURGHI

HOVERING CRAFT AND HYDROFOIL iis produced b y Kal~rghi Publications, 50-52 Blandford Street, London, PVI. Telephone WELbeck 8678. Printed in Great Britain by Villiers Publications, London, NW5. Annual subscrip- t ion: Five Guineas U K and equivalent overseas. USA $ 1 5 There are twelve issrres ann~mlly,

Contents o f thi,s i swe are the copyright of Kalerghi Publications. Permission to reproduce pictures and text can be granted only under written ugreement. Extracts or comments may be made with due acknowledgement to Hovering Craft and Hydrofoil.

ADVERTISING REPRESENTATIVE L . Temple Rosswick Ltd, 3 Queens Court, Queensway, London, W 2 . Telephone BAYswater 5812

PAINS HAT will the Ertimates Committee of the House of Commons be saying in ten years' time about hover-

craft research and development? The question, impossible though ~t may be to answer, is worth asking in the light of the recent Estimates Committee report on the British space programme.

The Committee sharply criticised the Treasury for un- willingness to consider space research as a whole. It proposed that one Ministry, the Ministry of Technology, should be made responsible for all space research. Too many Ministers, the Committee clearly felt have had their fingers, in the pie up in the sky. There had been wasted opportunities, lack OPI purpose, an absence of cohercnt organisation.

With any luck there should be no such strictures on the hovercraft programme when the Committee of Estimates reports in 1977. The industry and the Government can congratulate themselves that hovercraft development has, at an early point after its successful launch, been brought under the central control of a single Ministry, Mintech. There may be wasted opportunities ahead, but alniost cer- tainly not lack of purpose or organisational incoherence.

Many people in the industry have voiced grumbling suspicion about the "take-over" by Mintech of Hovercraft Development Ltd. The scientists and engineers at HDL are, in particular, concerned about their new status and conditions as civil servants. Both the suspicion and the

concern are natural. But the soundness of establishing Ministry superv~sion over the whole hovercraft field, in- cluding the hovercraft respons~b~lities that used to be borne by the old Ministry of Aviation, is not open to serious question. Overlapping, duplication of effort, financial waste-curses of the space and other technological programmes - should be largely averted.

There will of course be a period of uneasy adjustment by HDL and the hovercraft officials from the Aviation Ministry on the one hand and Mintech on the other. Technologists do not Ilk* the idea of becoming bowler- hatted bureaucrats, even with civil servlce security of tenure. They prefer more pay, less formality and even the r i ~ k of the sack. Established civil servants, for their part, are not always sensitive to the individual quirks of gifteci "boffins". Willingness to make the marriage work is needed by both parties to the match.

Fortunately Mintech is young and supple. There is a long way to go before arteries harden. And Mr Wedgwood Benn is the unstuffiest of Ministers. There is good reason to expect that he will know how to work the HDL men smoothly into h ~ s team.

The discontent expressed at HDL over the terms of their joining Mintech will not last long, if the Minister acts wisely. They will forget their suspicions once they see how much they stand to gain from central, purposive direction. The troubles at HDL are growing pains but there is more growth than pain ahead.

IN THIS ISSUE

The Hovercraft Pioneers 4

People and Projects 6, 23, 30, 32 Power for Hydrofoils 8

Moving Day 14

Improvement in Foilborne Navigation 19

Expo 67, Canada 20

Hydrofoil Boats or Hovercraft ? 24 Hovertravel 28

COVER PICTURE : Waiting t o take to the water for the first time, the US Navy hydrofoil gunboal, PG(H)2 "Tucumcari", hangs suspended during its oFcial launchirtg and christening ceremony. More than 500 g u e ~ t s witnessed the launching of the Navy',, newest hydrofoil, which is designed to cruise cct a speed o f more than 40 knots. The launching took place at Seattle, Washingtort, jocilities of the Boeing Company, who designed and built the hydrofoil boat (See People and Projects, page 6, for further details)

In 1963 thrs group of enthusrasts schemed out a proposal whrch ultimately led to the formulatron of the Hover- marrne 30-seat craft - the companys first "brochure" srdewall project. A common determrned Interest was apparent and eventually Hovermarrne Ltd was formed rn September 1965 The founder members wele N D. Prper, G. C. Hodgson, H M Watson, E G Tattersall - J D. C. Stone was company secretary and IS now the financral Dlrector At the end of 1965 Tattersall left WDL so as to get the new company's projects under way. Chrrstopher Coclterell pro- vrded a very sympathetic ear and was a source of frrendly advlce at this rather crrtrcal trme. Although Cockerel1 drd not agree wlth all the Issues, he accepted that Tattersall was determrned to do somethrng about sldewall craft

At thls stage Hovermarrne had no headquarters; Ted was workrng at home In the spare bedroom and board meetrngs were held at weekends Among the toprcs discussed at these cornpany meetrngs was the need to ~ncrease sea- going capabrlrty and to elrmrnate the flat bottom of present hovercraft, whrch 1s lrmlted In cushron herght partly by stabrlrty consrderatrons. From these d~rcussrons Ted evolved the deep-cush~on concept, rn whlch the payload IS carried wrthln the srdewalls, together wrth the propul- slon system and fuel Thls allows the cush~on to be ralsed, provrdlng greater over-wave clearance wrth negllgrble effect on centre-of-gravrty helght. Tn March 1966, Hovermarme appl~ed for patcnts for the deep-cushron srdewall craft, rn several countries, Edward Gunston Tattersall is clted as the lnventor

On one occasion a board meeting was combined with a family picnic on the Hogsback, but disastrous weather

drove the prcnlc party ~ n t o a packed transport cafe. There "wrth the julte box In full swmg" Hovermarrne's directors declded to spend therr "last few bob" on enterrng Hover- show 66. Aboutthrs trme, Tattersall had recelved temptrng offers of jobs In the Un~ted States; and he mrght well have gone but for thrs Hovershow declsron, whlch "turned the corner for Hovermarrne". Here, the company met rts first major shareholder, who put rn sufic~ent money to start the company on rts own "garret" premlses in August 1966- two 18 feet square attrc rooms rn Southampton ult~mately housrng erght people.

Among the early team was Davrd Nicholas, now per- sonal assrstant to Ted Tattersall. HIS enthusrasm, en- couragement and sheer hard work has been an essentral factor In spurrrng the project along. Davrd came from HDL and was a key member of the s~dewall team there. Peter Hrll, the company's productron manager, jorned a t this tlme and has consrderable experrence rn rernforced plastic structures. He was prev~ously employed by Walmatlc Ltd. Another "volunteer" was Shlrley Fellows, who pro- v~ded all the secretarral work. Shlrley was prevrously Mr Cockerell's secretary at HDL.

By December 1966, Hovermarlne had promrse of a further major shareholdrng whlch enabled Tattersall and hrs desrgn team lo embark on the detall desrgn of the first Hovermarrne product~on vehicle, the 60 passenger HM 2 now under constructron In Halmatlc's workshops. At this trme, Tattersall brought In Bob Tr~llo from HDL as chref development engineer "to think of tomorrow's products" and to take the deep-cushlon concept further.

"This concept, we feel, is as important a step as the introduction of flexible skirts," says Tattersall, who is determined that "development of the idea to fruition shall take place within these shores". To get development under way, the company must raise the not-so-very-large sum of 2250,000 and Tattersall says categorically "The country should support this". Some monies were allocated to the defunct Denny D.3 project and "1 feel we should inherit the right to use this money".

One of the attractive characteristics of Ted Tattersall is his reluctance to "oversell". Speakrng of the 60-passenger craft he says "it won't revolutionise anything", but on the rrght routes it should prove profitable. With unlimited funds, Tattersall would have concentrated on a larger craft - "the sooner we get on wrth the deep cushion concept, the better" and the current 25 ton HIM 4 deep-sidewalI project, although a useful craft in its own right, he sees primarily as a half-scale model for a high-speed 1,000 ton freighter craft for containerised cargo, wlth a 16 ft wave capability, probably powered by combined dresel and gas turbine installation. He also sees the deep-cushion sidewall configuration as a "natural" for hoverships and large transatlantic vessels.

Ted Tattersall has great confidence in the future for British hovercraft - and in his own contribution towards the future. He has had need of that confidence in the immediate past when Hovermarine's efforts to acquire a licence continually came up against a solid wall of frus- tration; and he will probably continue to need it to lift over the potential obstacles that lie ahead: but there is plenty of cushion power and directional stability in this young man and his co-directors.

Each and every member of Hovermarine's team was initiated at an interview which in the first instance was aimed at discovering their voluntary enthusiasm. Each has accepted the challenge; each is determined to make the project a success.

Champagne foamed over the bow of the Un~ted States Navy's newest hydrofo~l vessel in launch~ng ceremonles at the Boeing Company, July 15th, In Seattle, Wash~ngton. Seconds later the gleam~ng steel fo~ls of the PG(H2) (patrol gunboat hydrofoil) dlpped Into the water for the first tlme

Mrs P h ~ l l ~ p B B~dega~n, spon\or of the vessel for the Navy, chr~stened the advanced 71-ft craft Tucurntavi for her New Mexrco hometown wh~le more than 500 guests watched

Pr~ncipal speaker was Rear Adm~ral John D Bulkeley. A PT boat sklppei and Medal of Honour winner dur~ng World War 11, Adm~ral Bulkeley recently was appointed pres~dent ot the Naval Board of Inspect~on and Survey rn Wash~ngton, DC

Guests were welcomed to the launch~ng by Boeing Prestdent Wlll~am M Allen Lysle A Wood, Eoe~ng's Group v~ce-president - Aerospace, served as master of ceremonles

The launching guests Included Navy representat~ves. New Mex~co drgn~tar~es, representatives of the Pac~fic Northwest marine industry, Boe~ng executives, and the Boerng employees who designed and bu~l t the advanced craft

Leading the New Mex~co delegat~on was Congressman Thomas C. Morris Mrs Morr~s was Mrs Bldega~n's matron of honour.

In contrast to most s h ~ p launch~ngs, the Tucun~curl hydrofoil entered the water as a nearly completed vessel ~ n s ~ d e and out Tt will undergo dockslde testing and hullborne manoeuvvzk,, followed by ~ t s first "fl~ght" on ~ t s folls In September at qpeeds of more than 40 knots

Des~gned and bu~l t by Boeing, the Tucurncarl represents a s~gn~ficant development In hydrofo~l des~gn. The craft has no conventional propeller and will use a unlque system of waterjet propuls~on Its foil system acts as underwater "wlngs", l ~ f t ~ n g the craft's hull above the water, enabl~ng ~t to ach~eve high speeds and great manoeuvrability In almost any type of sea.

I t will undergo extensive fo~lbarne tests prior to dellvery to the Navy late t h ~ s year. * * *

Textron's Bell Aerosystems Compariy has announced that it has successfully flown an airplane that lands and takes off without wheels on an air-cushion landing gear.

The flight took place recently at Niagara Falls lnter- national Arrport.

The airplane in which the Air Cushlon Landing Gear (ACLG) concept was proved was an LA-4 "Lake" amphi- bian that Bell engineers modified and equipped with an air-cushion system.

With Bell test pilot David W. Howe at the controls, the craft took off, circled the airport and landed on its air cushion. The plane behaved much as it would with wheels. Howe said later that the air-cushion take-off and landing were "smooth as silk". During the flight, Howe radioed the words: "Bag down and inflated." This phrase may someday join "gear down and locked" as the standard airplane-to-tower commullication just before landing.

When it is inflated, the ACLG looks much like a 2 ft thick black doughnut on the plane's underside. In flight, the ACLG hugs tightly and aerodynamically to the aircraft.

T. Desmond Earl, project director and co-~nventor of the ACLG, expla~ned that the a~r-cushion bag is activated by a fan that Bell engineers Installed In the hollow rear fuselage of the airplane. T o prepare for landing, the pilot starts a small, four-cylinder englne that powers the axial fan. When he 1s ready to Inflate the ACLG, the p~lot pulls a lever to ~ t s "inflate" position. The "rnflate-deflate" Lever controls two sets of louvres in the aircraft's fuselage. In the "inflate" position, louvres lead~ng lo the ACLG are opened and louvres on the s ~ d e of the fuselage are closed. When the lever is In the "deflate" position, the louvres reverse the~r positions The side louvres are designed to give the airplane forward thrust when the ACLG is in the "deflate" mode w ~ t h the fan englne on.

The most dist~ngulsh~ng feature of the ACLG is its landing gear "bag". When ~t is inflated, alr from the fan engine escapes through hundreds of jet nozzles that circle the bag's undersrde. These jets of air feed inward toward the "hole" of the ACLG doughnut, producing an air cushion under the alrplane that holds ~t off the ground.

Bell developed a special material for the ACLG bag. I t cons~sts of layers of nylon cloth sandwiched between layers of rubber. T h ~ s material stretches easily to triple its width, but can't be stretched lengthwise a t all. [n land- Ing with the ACLG, the plane's forward speed is checked by reversing the propeller pitch. For final braking, the air- cushlon bags rubber rrbbed tread 1s brought into contact wrth the ground by a braking control.

Because the ACLG bag 1s flexible, ~t conforms to ground contours and can pass over obstacles. Bulldozers, in an emergency, could rough-grade an airstrip and giant cargo planes fitted with ACLG could begin landing immediately.

Earl said one of the best features of the ACLG is that rt does not need a hard-surfaced runway.

"The weight of the plane is spread out over the relatively Large area covered by the bag," said Earl. "Because of this, only a small amount of air pressure is needed l o hold the craft off the ground."

In Bell's test airplane, this air pressure totals 50 Ib/sq ft, or less than ) Ib/sq in. In contrast, a wheeled airplane puts all its weight on the small surface where its tyres touch the runway. Thus, the ACLG airplane can use open water, ice, snow, swampland, sand or dirt for most run- ways. Only its actual debarking, service and terminal area would have to be surfaced with concrete for use by service vehicles.

The test aircraft IS propelled by a standard 180 hp prston engine. Gross weight of the craft, w ~ t h the ACLG, is 2,400 Ib. The ACLG fan engine weighs 72 lb and turns the 2 ft dranieter fan a t up to 4,100 rpm.

Earl said the test ACLG weighs little more than a standard landing gear. ''In a larger airplane," s a ~ d Earl, "the weight of the ACLG might even weigh less than conventional gear."

In flight, the ACLG has no effect on the performance of the alrplane On landing and take-off, Howe sa~d it was impossible to tell just when the air-cushion support left off.

Bell has patented the ACLG concept (US Patent No 3,275,270). Co-inventor with Earl, and named in the patent, is Wilfred J. Eggington, Bell's air-cush~on vehlcle derign technology chief.

Earl said Bell will continue to modify and lmprove its ACLG airplane, wlth additional flights planned for later this year. The Initla1 ACLG airplane is a test bed intended to prove the air-cushion landing gear concept and lead the way toward its application in military, commercial and cargo airplanes.

Last year Bell received a $99,000 contract from the Fl~ght Dynamics Laboratory at Wright-Patterson Air Force Base, Dayton, Ohio, to do wind-tunnel tests of ACLG models. More recently, Bell received a $98,700 contract from Wright-Patterson to build a ground test model to study the possible use of the ACLG on a C-119 "Flying Boxcar" cargo airplane. * * *

The prlnclpal character~st~cs of the two types of hydrofoil boat produced by Seaflight S.p.a. of Messina (see page 1 %of thls ~ssue) are as follows :

"P.46" "H.57" (30 pass.) (60 pass.)

Length 0.a. 46 ft 6 ~n 57 ft 1 ln Breadth over fo~ls 16ft 51n 26ft 3 ~n Draught (float~ng) 5f t l11n 8 f t 1 1 n Draught (on folls) 2 ft 6 ~n 3 ft 8 ~n D~splacement :

Full load -tons 12.5 26 D~esel englnes - hp 2 x 3 7 0 2 x 6 5 0

Cummlns Flat-Carraro Take-off speed --knots 20 20 Crulse speed up to --knots 35 35 Max~mum speed - knots 4 1 3 9 Range - naut~cal m ~ l e ~ 270 270 Sea-state - No 2 - 3 3 - 4 Wave-helght - ft 3 5

* * * Formation of Air-Go Inc, a new firm which will develop and manufacture air-cushion devices, has been announced by a group of prominent Seattle businessmen.

The Seattle corporation will produce a variety of materials-handling equipment designed to "float" over ground and water surfaces on a frict~on-eliminating film or cushion of air.

Officers of the new firm are Stanley B. McDonald, president; Kenneth G. Wood, vice-president and general manager; Fred Kimball, treasurer; Wheeler Grey, secretary; and WiI Anderson, assistant secretary. All except

1

Anderson are members of the hoard of directors. Other directors are M. Lamont Bean, Robert J. Behnke,

W~lliam Caswell, Robert Halliday, Rogers P. Holman, William S. Leckenby, Gregg C. MacDonald, Phillip S. Padelford, Rlchard C. Philbrick, James C. Pigott, Hugh A.

1

Smith, and T. Evans Wyckoff. Air-Go Inc IS being created with co-operation of the

Roeing Company. whose Associated Products Divislon is largely responsible for preliminary development of the major air-cush~on component the new company will perfect and market. Boeing has licensed Air-Go operations and will retain a financial investment in the firm.

Two Air-Go pr~ncipals, Kenneth Wood and inventor Walter A. Crowley, will direct design and development. They have been associated in air-cushion research at Hoeing for several years and are experts in technology of the field.

Crowley is inventor of the first US man-carrying air- cu~hion vehicle, now displayed in the Smithsonian Insti- tute, and holds several other a~r-cushion patents. As a design engineer, he has specialised In research on ground effects devices for the past eleven years.

Wood was head of various facility engineering functions

at Boeing from 1955 to 1960. Following that he was D~rector of Search and Evaluation for Boeing Associated Products.

Wood said Air-Go's product development will exploit the numerous uses of a flexible, inflatable air bearing which lifts objects from the ground and holds the trapped bubble of air pressure on which they float. The bearing will be an integral part of both self-propelled devices, and of pallets which w~l l float heavy objects by the use of air pressure from a self-contained or outside source.

"We intend to make commercial applications of this new air-cushion technology where ever possible," Wood sa~d . "There are promising opportunities for Air-Go to achieve a leading position in the air-cushion industry. We feel the company can become an important economic factor in this reglon."

Wood said the firm wlll conduct design engineering, development and marketing with a small Initial staff in its offices at 2447 Sixth Avenue South. Construction of product components will be sub-contracted to local firms.

While attempts at commercial exploitation of air-cushion devices have been under way for some time, Air-Go is the first-known company established to concentrate its total effort in the field.

The firm's initial objective will be the perfection of small devices, such as materials-handling pallets, rather than the better-known "hovercraft" types of vehicles.

First potential customer for such pallet systems is the aircraft industry, Wood said, with airplane assembly the first probable use. A set of five 8 ft by 10 ft pallets, each supporting up to 45 tons, can move sections of a plane as large as the 350,000 1b Boeing 747 through final assembly, he said.

Air-Go will also proceed with tests on air-cushion pallets designed for loading airl~ners with cargo and food galleys. Standard aircraft cargo pallets would be fitted w ~ t h flexible air bearings. Compressed air from a source outside the plane would be fed into an inflatable plenum distribution system built into the pallet.

Wood said the air bearing invented by Crowley has substantial advantages over those developed for previous air-cushion devices. "It allows you to float and move objects with a lower coefficient of friction, greater stabil~ty, and much smaller air requirements," he said.

"This bearing is compact, light in weight, and tremen- dously efficient," Wood said. "Attached to a pallet measuring about 3 ft by 4 ft and inflated by a small blower, it can easlly float a 2,000 1b load which a person can control by hand."

There are numerous other possibilities for use of the Air-Go bearing in industrial materials handling. They include the floating of retail displays, moving merchandise in warehouses, and loading and unloading of truck-trailers and ships.

"We also see air-cushion applications in the consumer household field," said Wood.

One is a pallet designed to move large household appli- ances and furniture during cleaning, painting, and moving. A standard household vacuum cleaner supplies enough air to easily float a refr~gerator weighing up to 1,000 Lb.

Air-cushion vehicles offer some of the most interesting possibilities for both civilian and military use, Wood said. They include land and amphibious sports machines, Aying- pallet riding toys, amphibious commuter vehicles, and sub-sonic transit trains capable of all-weather safe speeds of 200 mph and above.

* * x * (Continued on page 231

Range of engines available-con-

SURFACE PiERCfWG CBWBIWEll

COMBlllED SURfbCE PIERCING AN0 SURFACE PLARlMG SUBMERGED

Figure I . Table gives a comparison between the pricipul Figure 2. Variations on submerged and surface-piercing foils. characteristics of high-speed diesels and gas turbines. Photo Of the two basic types8, submerged foils have better riding l e f t shows Proteus-powered PC(H)I rising on its foils qualities in high seas than the surface-piercing type

Lightweight marine gas turbines have already become strongly established in high-speed. displacement vessels and hovercraft. A third role of growing importance is that of power- plants for hydrofoil craft. In this article Mr Connor discusses some of the problems involved in the design of hydrofoils and summarises the Rolls-Royce Industrial and Marine Gas Turbine Division's participation in the supply of gas turbines for these vessels. Much of the information contained in this article originally appeared in Navy, with whose permission it is reproduced here.

H YDROFOIL craft themselves are not new; the first was built and operated before the turn of this century, and through the early decades of the century various experimenters constructed and "flew" hydrofoil craft, some- times with amazing performance. These craft had a wide variety of hydrofoil strut configuration.

However, the full scale sf this concept of craft has awaited the development of several new technologies, namely : I . Engines with very high power-to-weight ratio. 2. High-speed, high-efficiency foils. 3. High-speed, high-performance propellers. 4. Gear transmission systems of very light and unusual

capabilities. 5. Water-jet propulsion. 6. Boat hulls of aircraft-type construction.

All of the required new technologies have been developed to a very promsing state and a summary is given below. Powerful Engines

The hydrofoil, like all high-speed craft, requires a reason- able low specific engine weight. It was realised that as the size of the craft increased, the power of the largest existing high-speed diesel engine would not be suitable in larger vessels, neither would conventional marine diesels, steam turbines or steam engines because of their high weight. This left only the lightweight marinised aero-type gas turbine. Gas turbines for foilborne operation make possible large craft and high speeds. They develop more power per unit space and weight than any other engine.

Lightweight diesel engines are available today only up to approximately 3,000 hp continuous rating. Marine gas turbines are available up to approximately 20,000 hp continuous rating.

The availability of high-power gas turbines is a very important factor in designing larger craft where greater powers are needed. Multiple amounts of smaller engines normally add complexity and weight. Fig 1 gives a comparison between high-speed diesels and gas turbines.

The Foils Fig 2 presents variations of the two different types of

foil configurations, surface-piercing and submerged. Of the two basic types, the surface-piercing configuration has poorer riding qualities in high seas than the submerged foil configuration.

Craft with a surface-piercing foil system react to wave action with a change in the amount of foil area exposed to water, thus automatically adjusting the foil's lift. This tends to increase the craft's altitude when entering a wave and decrease the altitude when leaving it.

Craft with a submerged foil system cut through smaller waves that otherwise come into contact with the hull. To accomplish this contouring, however, such craft need control equipment. ?'he result is an inherently more expensive system implying as it does, sensing, comparing and servo elements which are naturally sophisticated, but it also results in a greater potential for sea-keeping. Most of the commercial craft in service today use surface-piercing foils.

Present-day experience indicates that submerged-type foils with automatic control will excel the surface-piercing types. However, a hybrid system now under investigation, namely surface-piercing with automatic controls, may approach the performance of the all-submerged types.

Propellers The marine propeller becomes a marginally satisfactory

thrust producer under the high speed and power requirements of hydrofoil craft. Speeds above 45 knots will normally dictate the use of supercavitating propellers. Problems in the design of supercavitating propellers include blade strength and losses, due to cascade effects. Some recent failures were of a fatigue nature. It is thought that thicken- ing the sections or using better material may solve the current problems. A great deal of work needs to be carried out to enable the use of supercavitating propellers with complete confidence. li

Figure 3. Wuter jets huve been studied as an ulternutrve tlzrust- producing system to tonventional propellers. Tlze simplicity o f wnter jet propulsion i~ very attractive

Gear Tra~~smission Most of the early hydroforl boats used an rncllned pro-

peller shaft. The drive to the shaft has been accomplished by such means ar an inclined engine, an angle drive by means of universal couplings or by Vee-drive gearboxes.

However, the extension of this drive into larger vessels, with higher speed and with the ability to operate in the Atlantic Ocean, poses some very serious engineering problems. Zt is hard to get a craft of this type high enough off the water to accommodate high waves. The propeller thrust is not in the proper direction for the highest propulsion efficiency. The long-drive shaft from the power source to the propeller Is a vibration hazard. Furthermore, it 1s impossible to retract the inclined propeller type of drive. For most efficient cruising in the displacement condition or operation in shallow harbours, or for cleanlng the foil system, a retractable drive is necessary.

A perpendicular drive with two 90" power gearboxes offers the opportunity of considerably extending the use of hydrofoil boats. 77he strut and foils that contain the main drive gears can be readily retracted without affecting the integrity of the transmission system.

Since the hydroforl craft is analogous to an aircraft, ~t is necessary that all major structural elements be very light in werght. Gear materral that does not contribute to the performance and rellabillty of the transmission must be eliml- nated. Because of thrs the welght of hydrofoll gearing 1s of the order of one-fifth to one-tenth of conventronal marine gearlng. However, rt must be realrsed that transmlttlng 10,000 to 20,000 hp by meails of such gearing from a gas turbine rotatlng at 5,000 rev/mln presents formidable engineering problems

Water Jet Propulsion Because of the difficulties experienced on propellers

operating in the cavitating reglon and by transmission of high powers to propellers, other schemes of thrust have been studled, such as arr propellers, straight jet engines and water jets. The most promising of these schemes appears to be the water-jet system. Fig 3 shows a schematic layout of such a system. Water is taken through an inlet at the bottom of the strut and up to a gas-turbine-driven water pump. The water is then expelled through nozzles in the transom of the craft. The srmplicity of this system is very attractive.

Velocih (Knots)

Figure 4 . Typical ef iciencie~ o f various meikods of thrusl production. T h e wrrfer jet is con~paruble with the supercccvitatiing propeller between 65 and 100 knots

Flg 4 compares the typlcal eficlencles achreved by varlous methodr of thrust production. The water let has a fairly constant efficrency at speeds above 50 knots; ~t 13 comparable w ~ t h the supercavrtat~ng propeller at speeds from 65 to 100 knots

The water-jet system wlll weigh less than a comparable supercavltating propeller system and should be cheaper rn r n ~ t ~ a l capltal cost, more relrable and easrer to operate and malntaln. There IS no complicated power transmission system and no lubrlcatlon problem associated with keeplng hundreds of moving transmrsslon parts running smooth The water-jet englne I? connected darectly to the h~gh-speed pump The installation 1s compact and eaqily accessible.

Boat Hulls of Aircraft Type Atrcraft technology has understandably had a strong

rnfluence on the recent developments In hydrofoll craft. The techn~ques of aerodynamic design have been applied dlrectly to hydrofoil systems. Apart from alrcraft gas turbrnes mentioned above, aircraft autop~lot technology has been used to deal wrth problems of hydroforl c r a f i control. Aircraft structural deslsn techniques here had a strong influence on hull and foil construction Alrcraft concept? of equ~pment and machinery I~fe, rel~abllity a i d malntenance are influencrng hydrofoll operating concepts which In turn exert a strong influence on deslgn

It is, therefore, not surprrslng to find alrcraft companies deeply lnvolved rn the development of hydrotolls

State of the Art Without doubt, the Unlted States Government IS at the

forefront in the development of such craft Both the Marl- trme Admlnistration (Crvil) Authority and the United States Navy have been spending considerable amounts of money in research and development. About seven years ago the Navy accelerated lts programme of hydrofoll development The reason for thls increased emphasis was related to the des~re of the Navy that the hydrofoll would provide a more effective s h ~ p for dealrng wlth the hrgh- speed nuclear submarine

Therefore, the emphasls moved to hydrofoll craft able to perform In open seas and to lncreaslng speeds beyond the conventional limit of approx~mately 50-60 knots

Figure 5 . Arrnrlgemel~t of the maclr~nery in PC(H)Z. Power Figure 6. General fllrflG'ement o f the foils and propeller~ in slzafts lecrd f o r~ ,u rd and drive via bevel gears to counter- PC(H)l. TO meet foilbort~e requircmertts the craft uses u sub- rotating propeller J. Ethaust is dischtrrged directly uft merged foil system with aictomutic controls

USS High Point In 1958, the Bureau of Shlps began the deslgn of the

first Unlted States Navy operational hydrofoil patrol boat, USS Nzgh Poznt PC(H)l. This s h ~ p was to perform rn- shore anti-submarine duties and, in addition to ~ t s ability to go at hlgh speed in rough waters on its foils, it was required to have a fairly long range and excellent sea- keeplng ablllty In the hullborne mode of operation. The contract for thls 108-ton craft was placed on the Boeing Alrcraft Company and the speed requirement was stated as 40 knots

The follborne sea-state requirements were so stringent tor a craft of the slze contemplated that it was declded that only a submerged foll system wlth automatic controls could provlde the performance demanded.

For hullborne operation the struts In the foil system retract vertically ~ n t o the hull, thus reduclng draught. Inspection, cleanlng or other maintenance of the folls and struts can be done ollly by divers or by dry-docklng.

The automatic control system for High Point receives craft motion input from a sonic height sensor at the bow and from roll and pitch gyros and vertical accelerometers. The computer portlon of the control system then transmits signals to control the hydraulic actuators, which move the flaps on the forward and after foils to maintain height, pitch and roll attitudes within very close limits. The control system also limits the vertical accelerations and orders contouring of waves too high lo avoid hull contact. It also permits banking in turns to reduce side loads on the struts.

Power is supplled by two 4,250 hp Marine Proteus gas turbine engines which are located aft, taking air down the trunks used to house the retracted strut and discharging exhaust directly aft through the transom. The power shafts lead forward to right-angle bevel-gears a t the top of each strut, down each strut with a single shaft to right-angle gears in a propulsion pod and then to counter-rotaing propellers at each end of the propulsion pod. Counter-rotating propellers were selected to reduce the gear size and hence the pod diameter. Figs 5 and 6 show a schematic machinery layout and the craft at full speed.

The Marine Proteus (Fig 7) is a development of the Proteus turboprop which powers the Britannia airliner, in which it has gained a remarkable record of reliability based

on more than 4,000,000 hours of service running. The marine version of the engine has proved extremely successful in fast patrol boats and motor gun boats, and more than 110 Marine Proteus have been delivered to, or are on order for, seven of the world's navies. The most recent order for the Royal Navy is for the frigate E x m o u t h , which will use two of these engines for cruising. Qpera- tional experience with the Marlne Proteus at sea now exceeds 30,000 hrs and is increasing a t the rate of 7,000 hrs per year.

Because it is a development of an aero'gas turbine the Marine Proteus is light and compact for the power developed. It incorporates a free-turbine layout in which the turbine which drives the power shaft is independent of the compressor system, so that the engine delivers extremely high power at low and medium propeller speeds. This allows rapid acceleration and gives great flexibility of performance. The engine gives full power in less than two minutes of a cold start.

Gecrnali Navy -Hydrofoil Plans The German Navy are extremely interested in this new

concept of craft and have bought two Marine Proteus engines to power a prototype Supramar-designed hydrofoil of approximately 160 tons. All other information on this project is restricted at the time of writing.

US Navy's Hydrofoil Grinboats Gas turbine propulsion plant has also been designated

to power the United States Navy's new hydrofoil gunboats. Two craft are at present under construction. The first, known as PG(H)l, has been designed by the Grumman Aircraft Corporation and is powered by a Tyne engine. The second craft, designated PG(H)2 (Fig 8), will be powered by a Marine Proteus engine driving a revolution- ary water jet propulsion system. The designers of this craft are the Boeing Aircraft Company of Seattle.

PG(H)2 will fly on three fully-submerged foils similar to those on H i g h Point . Water is drawn into the rear struts by the Proteus-driven pump and is discharged at high speed through stern nozzles which are above the water line. The ship will have a speed in excess of 40 knots and will be the first of its kind designed for Navy service.

Figure 7. 3ectior.t drawing of the 4,250 lzp Marine Proteus gas Figure 8. T h e PG(H)2, one of the 7Jnited States Nuvy's r?ew lurbine, operc~tional experience with which itow) exceeds l?ydrofoil gunboats, will be powered by a Marine Proteus 30,000 hours in fast patrol bocrts mzd gurt boats driving a water jet propulsion systeirr

Figure 9. Studies indicate that hydrofoil ships with displacements between 500 and 3,000 tons are feasible. Marine Olyn.lpus irzstallation would be s~iitable for such vessels

Principal data on the two craft are : Grummutz Boeing

Length 74 ft 01n 71 f l 10 in Beam 21 ft 0 in 19f t61n Draft Foils extended 13 l't 5 in 13 ft 11 in Folls retracted 4 ft 3 ~n 4 f t 5 in D~splaccment-

full load 57 tons 58 tons Maximum speed Move than 40 knots More than 40 knots Foil configurat~on Conventional Canard Fo~lborne Rolls-Royce Brlstol S~ddeley

propulsion Tyne Proteus Supel cavltatlng Water Jet

pi opeller Hullbol ne Two General Motors One General Motors

propuls~on diesels (320 bhp) dlesel(l60 bhp)

On completion these craft will commence evaluation trials and ~t is expected that one of the two will be chosen as a possible production unit for the US Navy.

Ultimate Size Studles indicate that hydrofoil ships with displacements

between 500 and 3,000 tons are feasible. These studies assume that a ciegree of engineering effort is put into large designs which is comparable to that given to larger transport aircraft.

Frg 9 shows an rnstallation of a Marlne Olympus 22,300 hp englne whrch would be sultable for such large h ydrofolls

T h e Olympus is one of the world's most powerful turbo- jets. I t has established a first-class reputation for relrabilrty since ~ t s rntroductron to the RAF in 1956, and rs the engine chosen for the Concorde.

In the marine verslon changes have been made rn materral t o guard agalnst salt corrosion, and the fuel system and controls have been adapted for operation on d~esel fuel. I t can be used as a boost englne In conjunction wlth tradl- tional rnachlnery or as the sole means of propulsion.

The Marrne Olympus has been ordered for trials in the converted Br~trsh frlgate H M S Exn~outh I t 1s also desrg- nated powerplant for the Royal Navy's new Type 82 destroyer T h e Frnnrsh Navy has also ordered the Marrne Olympus and the Germans have had a n engrne on teqt srnce 1964 T h e Marrne Olympus has also been ordered by the Malaysian and Iranran navles

I t 1s a strarght-flow hrgh-pressure-ratro unit wrth a five- stage low-pressure compressor, and a seven-stage hrgh- pressure compressor each drlven rndependently by rts own single-stage turbrne through coaxral shafts. T h e compressors a re niechan~cally ~ndependent and each runs a t rts own optimum efficiency, grvrng the engine exceptronal flexib~llty a n d rapid acceleratron T h e specific fuel consumpt~on 1s low and full power is avarlable wrth~n two mlnutes of a cold start under any cl~matic condrtloas.

l 'be development and b~nlding costs of hydrofoil craft a re high compared to those of conventional craft. There a re many interestrng detail problems to be solved rn con- nectron with the hydrofoil whrch offer a n extremely fasci- nating field fo r both engrneer and shlpburlder, wrth a mrnd for hlgh speeds and unconventronal desrgn

With crckno+vlcdgrnent to "Bristol Siddeley lor~rnol"

LEOPOLDO RODRIQUEZ SHIPYARD

MESSINA - ITALY

Licensed by Supramar A.G. Zug-Switzerland

The Greatest Experience

in Hydrofoil Boat Building

RODRIQUEZ

Hydrofoil Boats Across

The World's Seas

A in 21 Countries

ANY KIND

of

SHIP REPAIRS

One air set, ductiizg and t ~ n k . The tow rope connecting

the ussemhly can be seen. Other ropes support the

extremely flexible ducting. T h e men provide scale

NG DAY by R. A. Cole

An application of the air cushion principle makes light work of moving two 300,OQO- gallon storage tanks

OVING day always presents problems and thls is M particularly so when the items to be moved are either bulky or delicate. The Esso organisation were pre- sented with qulte a problem recently when it was decided to re-arrange their storage site at Mode Wheel Terminal, Manchester.

For reasons of efficiency in site management the new plan required that two 300,000 gallon (1,363,790 litres) storage tanks were re-positioned some 350 yards (320 m) away from their existing position. This short journey involved crossing rough ground with a slightly increasing level, a road, two railway tracks and then another stretch of rough ground. At the same time it was necessary for the tanks to be orientated through 180 degrees. The size of the operation may be judged from the fact that the tanks have a diameter of 50 ft (15.24 m), a height of 30 ft

(9.14 m) and weigh well over 50 tons. They were moved quite quicltly and easily by application

of the hover cushion principle and at a lot leqs cost than if convent~onal methods had been applled. This waq the first time that such an operation had been carr~ed out on a commercial basis.

Without this unlque method the removal of these tanks would have posed problems and difficulties that could have bcen ~urmounted only a t a high cost. Tn fact ~t may well have been that the cheaper proposition would have been to scrap them and build two new ones. A major difficulty that arose when considering conventional methods of removal lay in the fact that the water table was just a few inches beneath the ground surface. This would have meant that special preparations for the use of jaclts and rollers or bogies.

Methods and Details T o use the arr cushron method one first of all has to

convert the storage tank to a rudrmentary hovercraft Thrs 1s done slmply and effect~vely by clamp~ng two steel bands around the tank near rts base. Separated vert~cally by a few feet the bands carry attachment points for the segmented sli~rt wh~ch 1s of nylon rernforced neoprene A few of the segments carry an entry facrlrty wh~ch accepts light flexlble ductlng through wh~ch the alr 1s fed. The sketch dragram shows the basrc form of the Inflated skrrt and the fixing details.

Iletcril of segmented sicirt. T h e photograph tciken during

the moving sequence shorvs absence o f d u ~ t largely due

o water dampenirag. The skirt is cros~ing a17 open gulley which hcr~ been filled with

baulks of timber crnd covered by tarpaulin

The tank and one air set. T w o light pel ible ducts deliver air to the skirt. Aiz unused duct entry can be seen orz the skirt

Air for the operation is supplied by centrifugal fans of a type that are widely used for industrral purposes and these are powered by diesel engines. In this case two fans were employed and each delivered 26,000 cubic feet of air per mlnute (736 cubic metreslminute) at a pressure of 60 lb/sq ft (293 kglsqm). Each being powered by a Ford diesel engine of 130 bhp and mounted on a rubber tyred trader which was hitched to the tank by a wi:: rope. Thus as the tank moved the two air sets were automatically towed behind it. The pull was provided by a w~nch mounted on the back of a lorry.

Sketch diugrcrm slzows inflated form o f segrneizted ~ k i r t (1s well ns the lnethod of uttochment to tank. Ground clecirarzce is measured from the underside of the tank

DETAIL O F 1

Amongst the list of prelimtnaries for this type ot operation one finds the necessrty to cover open culverts and drains so that air from the cushron cannot escape down them. This rs readily achreved by layrng tarpaulins over them. In the case of gulleys they must be filled wrth baulks of timber prror to coverlng so as to grve a fairly even load bearing surface. For everyone's comfort a fire hose to tiampen down dry earth and surfaces and so prevent a dust storm, comes as a final requirement.

Because these tanks had been in position for many years and had sunk several inches rnto the ground they were rather reluctant to lift. They eventually moved after about half an hour of blowing and this part of the operation may be likened to an initial prising-off job. After this they lifted very quickly once the air was being pumped and as much as 10 inches (25 cm) of clearance could be obtained.

Backgsoul~d This application of the hovercraft principle was devised

by the National Research Development Corporatron through ~ t s subsidiary, Hovercraft Development Ltd. An inltial and completely successful trral was carried out using a much smaller tank at a milrtary establrshment. General contractors for thrs rnltial exper~ment were Pynford Ltd., a concern whrch specralrses rn jacking-up and movlng awkward loads and in the art of underprnnrng buildings.

As a result of their efforts and the experrence they have garned they have been granted a licence by HDL which allows them to apply the hovercraft prrnclple to this type of work 'The Esso job was their first commerc~al under- taking in this field and obviously it is not golng to be their last. We understand that they are currently negotlat~ng the removal of several other tanks by thrs method.

Reporting as rndependent observers of part of the moving operation we can say that it is hard to imagine how such an awkward itern could have been traversed more quickly, cleanly or efficiently.

T h e tank being winched forwcird from tlze back o f a

(.ry. Dust has been suppressed by watering the ground

rovemen orne Navi A Report on Foil Systems Fitted up by the

ding Company "Sea ight" of Messina Giuseppe Giuffrida Technical Manager, Seaflight

F OILUORNE navigation can be split into two basic systems : The system of partly submerged foils or surface-piercing foils; the system of totally submerged foils.

In princ~ple the main advantages and disadvantages regard~ng each system have been indicated as follows

The surface-p~ercing foll 5ystem has its major advantage in that ~t automatically ensure\ the three required equi- l~briums; that is to say altitude (clearance) equilibrium or stability, lateral equilibrium or stability, and longitudinal equil~brium or stabil~ty

The word "automatically" has been used just to mean

that no electron~c means of control or complicated mech- anlsms are necessary In order to resolve the problems of in-fl~ght stability. But while the system is up to requirements In a perfectly smooth seaway, its results are q u ~ t e different In a rough seaway.

In fact, owlng to the orbital motions of the waves acting over the submerged surface of the foils and ch~efly In con- sequence of the waves, there is a continuous variation of the lift, which causes audden motions of the craft: more accentuated in the direction of roll. but less dangerous and less accentuated in the d~rection ~f pitching, but more dangerous, in as much as any variation In the longitudinal

trim when the craft is golng head downwards entails an equal var~ation of decrease In the fo~ls' ~ncidence (since they are fixed to the hull) and consequently a loss of lift even total or d~rectly an increase of heaviness wlth a loss of clearance and violent clashlng agalnst the sea.

The totally-submerged foll system presents the advantage of d~sengagrng the foils' surface from the water-level and conseq~~ently from the waves, yet remaining subject to the orbital motions of the waves, w ~ t h correspond~ng varlat~ons of the llft Conversely t h ~ s system presents the great dis- advantage of not having - in ~ t s conception - elther altitude stabil~ty or lateral or long~tudinsl stability

In order to make up for this serious gap, ~t is necessary that the lift produced by the submerged foils may be varied both 111 the lateral and loilgitudinal directions by means of movable flaps and an electronic flight-control system.

Sonars, pendulums or gyroscopes and accelerometers are the sensors of the electronic flight-control station; a hydraulic station and a serles of valves of the hydraulic network electromagnetically dr~ven and a certain number of hydraulic cyl~nders are the servo-mechanisms of the electronic flight-control station.

There IS no doubt that when nav~gat~ng in a calm seaway the task of the electronic fl~ght-control statlon 1s enor- mously fac~litated and the results wlll be very good, whereas the problem of counterbalanc~ng -in a perfect manner ancl wrlh the necessary promptness - the causes of perturbation due to the wavy mot~ons (of the seaway) 1s more difficult

Wlth regard to that, one can observe : The sonars used for stabrlis~ng the hull's clearance, I£ placed forward, are the only sens~tive organs to per- ceive ahead of tlme (a small fraction of J. second) the causes of perturbat~on All the other sens~tive organs intervene w ~ t h some delay after a removal from the posit~on of equ~l~brium has become evident Another delay 1s due to the flow of the Auld in the hydraulic clrcuit In order to obta~n the required varla- tions In the angle of the foil flaps It 1s not suficrent that the removal from the posltron of equlllbr~um alone be taken into account, but rt should be necessary that the accelerat~on at wh~ch such an alteration takes place be taken into account too; and if such a movement cons~sts in a removal from, or a nearing to, the posit~on of equrl~br~um

011 an average, one wave crest and cavlty wlll be met durrng each ~econd of t~me, that is to say two var~atrons per second, to whlch two openings of valves should correspond for each second - and 7,200 openlngs of valves per hour

From the frequence of the movements one can real~se the huge wear on the mater~als, valves, hydraulic cyl~nders, and the~r correspond~ng packlngs Moreover, one must bear in xn~nd that some mater~alr subject to rapld wear and tear are placed in inaccessible places, and therefore the craft will have to be l a ~ d up for their substitution.

The promptness of intervening through a variation in the incidence of foil-flaps is of a fundamental importance, but it is just as much important that the correct angle be obtained for an exact quantity of time.

The diflerent factors taking part In the problem are too many to be taken into proper account ind~vidually.

Since the problem of obtaining with necessary promptness a certain variation in the flap incidence in order to balance a certain cause of perturbation of a certain equilibrium is already a difficult one, it is more difficult to harrnonise the movements of the foil-flaps to control not

a single equilibrium, but three equilibriums at the same time: lateral, longitudinal and altitude.

The sufefy of navigation (taking for granted a perfect operation of the electronic brains governing the craft's flight) relies on the perfect efficiency of all the electric circuits and the hydraulic installation; for any average whatsoever will be detrimental to the possibility of navi- gating on foils.

This is a very important factor, especially in the case of military employment.

From a hydrodynamic viewpoint, it must be also ob- served that a flap not aligned with its foil reduces the hydrodynamic efficiency of the foil itself.

The Shipbuilding Company "Seaflight" have introduced of late into practical application some new foil systems "with pre-set constant lift and self-adjustable incidence".

Such foil systems belong to the surface-piercing foil system and have the following features:

They are not rigidly connected with the hull but with an axle, supported by bearings, transversal to the hull. Consequently the whole foil system can make rotary oscillations around the said axle. The effect due to the rotation is a variation in the angle of attack by which the foil surface meets the water flow. The foil surface develops for the most part slightly abaft of the axle of rotation and the lift produced by it tends to rotate the foil backwards. Similarly also the resistance to its advance tends to rotate the foil backwards. The movement of backward rotation is opposed by the force from a spring, or any other device, acting at the extremity of a lever, inside the hull, and united with the axle of the foil system.

The system is in equilibrium when the active moments of the lift and of the resistance to advance equal in value the reactive moment of the spring.

Some of the causes of perturbation of the equilibrium and of its re-establishment, automatically, in a chrono- logical succession of fractions of a second, are indicated as follows:

W h e n Crossing a Wave-crest Larger forl-surface submerged, greater l ~ f t produced, Increase of the active moment of the 11ft. The major value of the actlve moment as compared with the reactlve moment of the spring determines the beginning of a rotatlon of the f o ~ l baclcwards and a gradual redkctlon of the angle of attack. The excess of the lift produced by the wave-crest 1s thereby progressively annulled and the rotatlon of the foil will end as soon as the equ~libr~um is re-established between the two moments -active, and reactive.

Everyth~ng takes In a fraction of a second and the rotation of the f o ~ l system, naturally accord~ng to the height of the waves under cons~deration, hardly reaches 1 degree. The l ~ f t produced by the foll remalns practically constant wh~le negot~atlng a wave-crest.

When Crossing a Wave-cavity This case is like the previous one, but with contrary

effects and movements.

W h e n the Craft's Bow goes Downwards That may happen when negotiating - from the crest

towards the cavity - very long oceanic waves or sea about to become a swell.

A certaln angle of bow-lower~ng determines, in the craft w ~ t h foils rrg~dly fastened to the hull, a reductron of the angle of attack of the hydrofoil, havlng the same value; and a loss of lrft

W ~ t h the Seaflight's fo11 systems, the follow~ng wlll have place chronolog~cally

Reduct~on of the ~ncidence, lesser llft, lesser actlve moment of the llft The reactlve moment of the sprlng exceeds the actlve moment and a rotatlon of the foil begrns forward, thus gradually reinstating the angle of attack necessary in relat~on to the water flow. The rotatlon ends when the equ~llbr~um IS re~nstated between the actlve and react~ve moments and therefore as soon as the ~nrtial 11ft has been reinstated

When the Craft's Stern goes Downwards This case is like the previous one, but with contrary

effects and movements.

When the Speed increases The resistance to the advance of the foil system increases, thus Increasing the resistance active moment. The greater value of the active moment as compared wlth the reactive moment gives way to the beginning of a rotation of the foil backwards and gradually, through the further compression of the spring, to an Increase of the force exerted by the spring and an increase of the reactive moment until the equilibrium is reinstated with the active moment. During the rotation, a reduction of the angle of attack takes place, which is necessary, in consideration of the speed increase, In order to keep the specific lift un- altered and consequently also the in-flight clearance.

When the Speed Decreases This case is like the previous one, but with contrary

effects and movements. Until now we have examined schematically the advant-

ages and disadvantages of the foil systems, both the surface-piercing and the totally submerged ones, but rigidly fastened to the hull, and the undiscussed advantages repre- sented by the Seaflight's rotarily oscillating hydrofoil, which contributes positively in the progress of foilborne navigation, especially with reference to its extreme simplicity and thereby its extreme safety of operation.

For a more detailed examination of the problem, the following additional specifications are herewith supplied: (a) 'The oscillating fore-hydrofoil is divided into two single

independent complexes : one on starboard and one on port-side, thus eliminating almost totally the movements due to roll.

(b) The hydrofoil surface develops in such a way that the centre of lift of the submerged part gets away from the vertical plane passing through the axle of rotation (lever of the lift) as gradually as the foil emerges and vice versa. Such a feature is very important in as much as it reduces the variations of the lever (arm) of the lift by effect of the rotation of the foil and the variation in the submerged surface of the foil. as two movements in opposite direction are determined by the centre of lift.

(c) The reacting springs have such features as to determined variations of the reactive moment slight superior -- in absolute value - to the variations of the active moment, with reference to a determined oscillation of the foll.

(d) Usual helical springs with a constant pitch can be used or incidentally with a variable pitch, having a com- pressive force (stress) per mm of excursion equal to about 0.4% of the load weighing on the hydrofoil, capable of reaching maximum values of compression equal to 15 + 25% of the load weighing on the foil.

(e) During the take-off, owing to an expansion of the spring, the foil assumes its maximum incidence, limited by a fit buffer-stopper, to which an angle of attack must correspond ensuring the highest lift resistance ratio in relation to take-off speed. In such a way, take- off becomes easier and will take a shorter time. As gradually as the hull is lifted and its speed increases, the foil reduces automatically its incidence.

(f) The continuous equalisation of the foil, in terms of incidence, to the instantaneous conditions and the continuous production of a lift almost constant do reduce vertical accelerations and consequently they reduce stresses both on the foils and the 11~111.

(g) In very big buildings it is possible to reduce - when having equal values of the stresses -the weight of the hull by having it supported not on two points (after foil and fore-foil), but on a third point or more points, with as many foils or couples of foils (starboard and port-side) oscillating automatically ; with the certainty that the supports of the central hydrofoils will absorb a certain share of deadweight independently from the waves and direction of the stream lines. While the fore-foil will remain a surface-piercing type, in order to ensure lateral and altitude stability, the intermediate hydrofoil might be a totally- submerged type, also this oscillating rotarily, as it is required that it should bear only a share of the deadweight and should automatically equalise its angle of attack with the direction of the water flow which- as it is known - can be considered horiz,ontal only with regard to the fore-foil ; and it is deviated by it (ie the fore-foil) in a different manner, according to speed, backwards. The problem can be solved easily by adopting oscillating hydrofoils while with the foils stiffly fastened to the hull one cannot obtain a constant and well determined lift, but a variable one in relation to the speed and the angle of the water flow.

Conclusion The comparrson between the two basic systems of foils,

whrch made one prefer the former or the latter ~n conse- quence of the cons~deration glven to the s~mplic~ty and safety of the surface-prercing system (yet w ~ t h the Inconveniences of the sudden movements of roll, wlth the limltatlon of navigat~ng with stern-sea not over a certain wave-he~ght and wlth the remarkable stresses derlv~ng from sudden falls ahead), or to the totally-submerged fo11 system (freed from the perturbations of the surface of the seaway, but still a slave to an electronic b ra~n and to the electric- magnetic-hydraulic servo-mechan~sms, wlth the unknown poss~bil~ty of a perfect operation in a variously perturbed seaway, both as regards its technical respondence and as regards ~ t s safety of operatrve durat~on) now appears to be decidedly In favour of the system w ~ t h partly-emerged forls due to the contribution of the new foil complexes adopted by the Seaflight, hav~ng "pre-set constant llft and self- adjustable ~ncidence", whrch add a further automation to the system and el~minate those defects Inherent to the surface-p~erclng foil system, w ~ t h the folk stlffly fastened to the hull, also emphas~sing 11s srmplic~ty in ensurlng a solutlon of the varlous problems of equrllbrlum and opera- tive safety - hav~ng a bas~c value for those who go by sea

Captain Jacques Robitaille of Quebec, the first Canadian to quali fy as a commercial Itovercraft opcrrrtor, is sllown above (right) reviewing Expo 67 hovercraft charter route maps with Captain I Peter Ayler of Ryde, Isle of Wight

C A N A D A Hovercraft's Internationa

Shop Window by G. Ray Gibson

ONTREAL'S one thousand acre Expo 67, if measured M in terms of area, of National participation, of interest and entertainment for the individual visitor, stands out as the largest and finest event of its kind to date. Indeed there has never been an exhibit~on such as Expo 67. The Canadian Federal Government, the City of Montreal and the Province of Quebec have co-operated magnificently to make possible not just the event of the year but the wonder of the century.

Cons~der the one thousand acre exhibition site which is lald out in four main areas. The first area was the former Mackay Pier breakwater which had over four million tons of new land added. Second 1s the upstream end of the original Ile Sainte HClkne (named by the French explorer Jacques Cartier in 1535 after his wife HitlBne). 'Third is a new island, Ele Notre-Dame, bordering on the Seaway and fouith the downstream extension of Ile Sainte HBlBne known as La Ronde. In all some 30 million tons of earth and equipment, more weight than all the Egyptian pyramids, were moved to create the overall site.

Most world fairs of International standing have at least seven years to build their site on solid ground. The Canadian planners of this exhibit had less than four years to get their show on the road and on an area partly beside and partly beneath the St. Lawrence river. This extravaganza is the only "first-category" exposition ever to be held on the North American Continent. It meets the rigid standards of timing, scope and operation as established by the world today regulating such international exhibitions.

At London's Crystal Palace Exhibition in 1851 the world first accepted iron and glass architecture. At the Paris Exhibition in 1904 structural steel and steam engineering made their debut. Today at Expo 67 advanced forms of transportation will no doubt be one of the major points by which this exposition will be remembered. Space craft, hydrofoil ships and hovercraft are on show to the greatest international audience ever to assemble at any time. From April 28th, when the show first opened, until October 27th, some 70 nations will exhibit to visitors from around the world. These visitors will have the opportunity of travelling to the Expo 67 site in British built hovercraft operated by Hoverwork Canada Ltd.

Expo Hoverservice Canada's first commercial hovercraft operation is now

in full swing carrying visitors to the exposition. Two radar equrpped 35 passenger, 50 miles per hour SR.N6 amphib~ous craft are running regular transportation services between specially constructed terminals at La Ronde and the parking lot on Ile Charron, and along the river between La Ronde and Citi: du Havre. A th~rd route carries passengers on a thrilling sight-see~ng trip around Ile Sainte Hi.lkne over the fast running waters and rapids and under the bridges of the St Lawrence. Special charter trips are also available for private groups. These hovercraft trlps of the Expo 67 islands is probably the most convenient and spectacular way of viewing the overall exhibition. Trips between Citi! du Havre and La Ronde run every hour on the hour from 1100 hours in the morn- ing until dusk. The Ile Charron-Expo service runs from 0915 hours to 2100 hours. The sight-seeing trips start a t 1130 hours and run continuously until 2030 hours.

Roverwork Canada Ltd, the company that operate these craft, is very positive and agressive in their efforts to make hovercraft work out on this side of the Atlantic. The company is owned on an approximate 50-50 basis by the British company Hovertravel Ltd and a Canadian com-

The hovercraft of ice at Ci t i du Havre i5 onc o f tlzree sucl~ portable buildings of modern design ~ , h i c h serves a dual purpose as radio control centre for tlze i lCVs N I Z ~ passenger ticket ofice

pany Andrew German Ltd. Ultrmate control of vehicles and the~r operat~on remalns wlth the more experleiiced Brltish Hovertravel management Anthony German, vlce- pres~dent and general managcr, Hoverwork Canada Ltd, controls the servlce from an operatlonal headquarters at the La Ronde slte, and from adrnln~stratlon ofices at Place Vllla Marle In downtown Montreal. I vls~ted wrth Mr German early In July to revlew his companys opera- t ~ o n and to report back to the readers of thls publ~cat~on. I was very much ~mpressed, not just w ~ t h the efficiency and fr~endly manner In wh~ch the company was operat~ng, but with the factual stat~st~cs on the operatlonal success of the servlce

With the Russian pavilion on the Ile Notre Dame and Con- cordia Bridge as a background, a IzXovercraft negotiates the ,St Lawrence River in a strong cross wind

T o meet Port of Montreal reg~llutions for water craft, all On li f t-off the craft Poats down the rainy on lo the river clear are req,Lir.ed lo curry gr.uppli,lg of the special loc~ding plutform above on eitlzel. sicle o f the forward hatch

On the day I v~slted the Expo, Wednesday, July Sth, some 130,000 passengers had been carr~ed from the tlme of the falr's openlng In Apr~l. I enqulred of Mr German what the~r buslest slngle day had been. Thls was Monday, June 26th when some 4,356 passengers travelled on the craft An all up record for hovercraft operation anywhere In the world. Down tlme durlng the over 1,000 hours' servlce fly~ng has been less than 1%, a remarkable ach~eve- ment Sklrt repalrs to date have been mlnor wlth s~ngle panel sect~on replacement as the maximum problem en- countered T h ~ s excellent servlce record can be attributed to planned n~ght maintenance operatlons, by a ground englneerlng staff of SIX englne and a~rframe operators and two sk~r t repalr mechan~cs. Head~ng up the englneerlng operatlons team IS Mr R~chard Stratton, chlef englneer of Hoverwork Ltd, one of the most exper~enced men In the hovercraft operatlons field.

Hoverwork's senlor captaln, Peter Ayles, of Ryde, Isle of W~ght, heads up a fl~ght crew of five p~lots. CBptaln Jacques Rob~ta~lle and Bert Mead are Canad~ans, wh~le Capta~ns Arthur Phlll~ps and Ben Goldsmith are Br~ t~sh , mak~ng up the very busy group runnlng t h ~ s 7-day a week service The logrst~cs of such an operation calls for some 16 beach staff to handle passengers and control services. All beach staff were tra~ned on the job p r ~ o r to the openlng of Expo and are In the most Unlvers~ty students on summer vacatlon from Canad~an Un~vers~tles. A pre- employment requlslte for all beach personnel IS a knowledge of both Canad~an languages, French and Engl~sh. MISS Kathleen Foley, on leave from post-graduate work at Montreal's McG~ll Unlverslty, was selected as Hostess and works dlrectly wlth Mr David Seatle, Hoverwork Canada's traflic manager, In keep~ng the operat~on runnlng to schedule

It would be impossible to l ~ s t all the famous people who have used the Expo Hoverservice. For example, Britain's Princess Alexandra and her husband Angus Ogilvie used the service while visiting the exposition in June. My Christopher Cockerell, British inventor of the hovercraft, and Monsieur Bertin, the French ACV inventor, were also among the early vis~tors. The American stateswoman, Clair Booth Luce, chartered a craft on two separate occasions for entertaining friends. Dr J. Herbert Holler- man, US Under Secretary of Commerce, had the craft demonstrated for him. Of noted Canadians, Mrs Pearson, wife of the Prime Minister, and Mr Phill~pe Gayliardi, Minister of Highways for British Columbia, were early users. lndeed Mr German's list of noted visitors reads somewhat like a very special copy of Who's Who.

If the international transport Industries have, in the past, held any reservations about the reliability of such craft, Hoverwork Canada Ltd has now removed all possible doubts by demonstrating these craft under maximum operating conditions. As stated by Mr German during my recent visit "Expo provides a spectacular shop window for hovercraft. The public is already showing a tremendous interest in the vehicles and are using them to commute across to the Expo site rather than for pleasure trips. We believe this to be just the beginning of our company's commercial operations. Canada has plenty of tough transportation problems which require solving, Hoverwork is ready with two excellent craft to go to work on these problems." Mr German also polnted out that BP Canada Ltd was a co-sponsor of the service. BP have collaborated closely in the operat~onal and commercial development of the hovercraft and have played an important role in most of the hovercraft "firsts" in the United Kingdom, Europe, Africa and North America. BP Canada are also at this

A group of typical Expo 67 visitors loading on board for tlze trip out to Ile Sainte Hhldne. Their baggclge, ir~cl~ldirlg picnic baskets, prams, etc, always manages to be .stored on board

time ~~ndertaking all the fuellrng and lubricatrng arrange- m e n t ~ for the Expo 67 hovercraft servrce.

After meeting Mr German and his very talented associates I am sure that hovercraft transportation is here in Canada to stay. Providing this young company is given proper support and an opportunity to show what they can do on a commercial basis there is no reason, in the view of thrs writer, why they should not be successful on the long term baas.

Wlzilc approaching the Cite du Havre at speed, a hovercraft prepcrres to arrest on the special meiul-fcrced ramp developed by I fover~vork Carzada Ltd for far: Po~ling oper.cltions

PEOPLE AND PROJECTS continued from page 7 The Navy's newest Hydrofoil gunboat and the nation's

latest research submarme will make West Palm Beach, Fla, their test port under the terms of an agreement concluded by Grumman Aircraft Engineering Corporation of Beth- page, NY, and the Port of Palm Beach.

According to Willlam T. Schwendler, Chairman of the Executive Committee at Grumman, the Florida port will be the test and operational base for both the Grumman- Piccard submersible PX-15, now being constructed in Switzerland, and the hydrofoil gunboat "Flagstaff", being built by Grumman at Stuart, Florida. Present plans call for the Flagstag to be launched on or about November 15th and to be berthed at the Port of Palm Beach two or three weeks later.

Schwendler said that West Palm Beach was chosen after detailed surveys of several other East Coast ports. The Gruniman support facilities at Stuart, the nearness to deep ocean waters, and specified technical mechanical capabilities at West Palm Beach led to a determination in favour of that location, Schwendler asserted.

Under the terms of the agreement, Grumman will occupy some 9,600 sq ft of a building to be erected in Riviera Beach, at the intersection of Route 1 and South Road. An additional slir, measuring 50 ft bv 150 ft will be reserved for the ~ r u h m a n hy&ofoil and submarine vehicles, as well as dockside storage areas totalling some 9,450 sq ft. The lease arrangements continue for one year with options available to Grumman.

For the PX-15, the base will mark the port of departure for its proposed 1,500-mile submerged journey in the Gulf Stream, from Florida to Nova Scotia. The 50-ft, 130-ton submarine will drift silently at depths of 300-2,000 ft, with its crew of six performing visual and instrumental measure- ments of deep ocean phenomena during the six-week journey which is scheduled for the summer of 1968. Dr Jacques Piccard, who provided the basic design of the PX-15 and is supervising its construction, will lead the Gulf Stream Drift Mission.

In December of this year, West Palm Beach will become the base of the Flaprtaff for the rieorous sea trials that - u ,d ., must be completed prior to formal acceptance by the US Navy. The 75-ft, 60-ton, turbine-powered vessel is expected to reach foilborne speeds in excess of 40 knots in heavy seas. The Flagstag will be turned over Lo the Navy in early 1968.

The Council of the Institute of Marine Engineers has decided that a Sectron of the Institute for the d~scuss~on of miscellaneous craft and ocean englneerlng shall be formed. The rnterests of the new sectlon will lnclude fishsng vessels and their mechanical equipment, hydrofoils and hovercraft, small ferrres, lifeboats and slmllar craft of thrs order of size: ocean engineering wrll rnclude the mechanlcal and structural aspects of offahore drillrng equipment, the mech- anrcal aspects of laying plpel~nes under the ocean, manned and unmanned craft for underwater experrments, welding and simllar processes underwater, methods of locating objects under water, and mechanlcal and electrical engineering aspects of any future developments rn ocean engineering

It IS the Intention that from t ~ m e to tsme special meetlngs for the discussion of these aubjects shall be arranged and a Sub-Commsttee has already been formed with this Intention

-k * r * (Corztinued orz pc~ge 30)

Hydrofoil Boats or Hovercra

An extract from the 1965 Annual Report of the

Norwegian Institute of Transport Economics

BGULAR hydrofoil boat services have been run in R Norway since summer 1960. The Stavanger and Sandnes Steamship Companies at that time acquired a Supramar PT-50 hydrofoil boat which was put into service between Stavanger and Bergen. One year later the company acquired another PT-50 which was also run on this route. Sometime later the Stavanger Steamship Company commissioned a smaller hydrofoil boat, the Supramar PT-20, to cover a route between Stavanger and various centres in the Ryfylke Fjords. The same type of boat is used by the Hardanger-Sunnhordlandske Steamship Com- pany on a route between Bergen and Sunnhordland. These services are normally operated from MarchIApril to the end of November.

In Oslo Fjord a hydrofoil service was started in 1964 with two boats of the PT-20 type. This service was operated throughout the year and has recently been granted a provisional permit for operating in the dark. Thus, six hydrofoil boats are now being operated in Norway. Westermoen Hydrofoil AIS, Mandal, are producing hydrofoil boats for the Scandinavsan market. Altogether approximately 80 hydrofoil boats of different Supramar types are now In operation throughout the world.

Operational expersence wlth hovercraft in Norwegian waters is based on the use of two Westland SR-N6 hovercraft at More and Romsdal in summer 1965. This service was operated from June 28th to September 25th. In the course of this period the two vehicles were in operation for a total of approximately 1,150 hours. From October 1965 to February 1966 these vehicles were put into service between Aarhus and ICalundborg in Denmark where, at times, they were tried out under very dificult operating conditions. At present approximately 25 Westland SR.N5/6 hovercraft are in service. Services are operated in the UK, USA and Japan. Another hovercraft is in service in Brunei and the British forces in Borneo have operated two hovercraft for approximately one year.

Both hydrofoil boats and hovercraft have the advantage that they are considerably faster than ordsnary boats. In view of the fact that the hulls of these vehicles are

lifted off the water during operation, the propulsion resistance is much less than in the case of ordinary boats. Other common features of the two types of craft are that their mode of construction and their machinery is rather different from the equipment normally available to ship- ping companies. Also, a more comprehensive maintenance and special knowledge is required than for ordinary vessels. As opposed to hydrofoil boats, the majority of hovercraft are independent of water depths and can also travel over land. However, hovercraft must primarily be considered as being means of sea transport.

Any choice of "high speed vessels" will in most cases be between hydrofoil boats and hovercraft. Even though the two types of vessel may have roughly the same performance, one type may possibly have obvious advantages of an operational or economic nature.

Of the existing hydrofoil boats the greatest chance of success lies with models Supramar PT-50 or PT-20. Other available types are less suitable or too expensive. The example glven below has been drawn up with a view to servsclng a possible route at Meire and Romsdal is based on Model PT-20 with accommodation for approximately 70 passengers. In this area the PT-50 (100 passengers) will probably be too large.

At present only the Westland hovercraft SR.N5 and SR.N6 appear to have any commercial value. Because of its larger passenger capacity model SR.N6 appears to be the most sustable craft for passenger traffic, the extra operational and initial cost as compared with model SR.N5 being much lower than the difference in passenger capacity (37 as against 17 seats). I t would appear that during the service in summer 1965 the available accommodation on model SR.N6 was most suitable for the route in,question.

SR.N6 has a cruising speed of approximately 50 knots as compared with 34 knots for PT-20. However, the work- ing capacity for IT-20 will be 301% higher than for SR.N6 because of the greater passenger capacity. The hydrofoil boat passenger cabin is relatively larger, measuring approximately 0.7m2 per passenger as compared with 0.5 m2 on the SR.N6.

Travelling Time In coastal districts the use of hydrofoll boats or hover-

craft w~l l give considerably shorter travelllng tlmes than conventional shipplng routes. In most cases the tlme-savlng

\ as compared to bus/ferry and pure bus connection will also be cons~derable This, as a rule, 1s due to the fact that sea travel distances are shorter than road connectlons between correspondlag places In the coastal areas In the event of the express boat connectlons berng qurte parallel to the bus routes, the time-savlng wlll, In most cases, be inslgnlficant. Model SR N6 has a crulslng speed of approxl- mately 50 knots, but experlcnce gamed in regular servlce operations lndlcates that, for practical purposes, the average speed 1s In the region of 40-45 knots. For hydrofoil boats of the PT-20 type a crulslng spced of 32 knots is expected. T h 1 ~ mcans that the travell~ng tlme on high- speed boats could be reduced by 50 to 70% as compared with parallel shlpplng routes.

The travelllng tlmes on h~gh-speed boat servlces at More and Romsdal are cons~derably shorter than when travelling by bus and ferry Wlth hovercraft the travelllng tlmes wlll be reduced by up to a quarter or one-thud over "favourable" distances The travelllng trme by hydrofoil boat wlll be from 35 to 45% of thc usual present-day travelling time Even though the hovercraft is 20 to 30% faster than the hydrofo~l boat over most sectlons, thls means relat~vely llttle In terms of shorter travelllng tlmes on the shorter routes applicable to More and Romsdal. O n the major~ty of routes the tlme d~fference 1s in the reglon of 10 to 15 mlnutes.

The route which will give the most favourable result for high-speed boats is between Molde and Vigra airport. However, the hydrofoil boat must land its passengers a greater distance from the airport than a hovercraft and, consequently, involves longer bus times. In the event of a future hovercraft service being planned, it is possible to avoid this additional changing by moving the vessel right up to the airport. This, however, requires considerable planning work between the airport and the beach. If this can be put into practice, it will be possible to reduce the travelling time by approximately 5 minutes.

Regularity A satisfactory regularity is a prerequisite for commercial

operation. The users' confidence will suffer greatly if the services are cancelled and delays occur, even if this hap- pens to a limited extent only. Regularity will depend on the seaworthiness of the craft and their operational reliability. Particularly the latter may give rise to problems when starting a new service with a new means of transport. Teething trouble must be expected, but the ability to overcome such trouble is decisive for the future of the service.

Wind and Weather As far as regular services are concerned, the sea-

worthiness of PT-20 and SR.N6 will be roughly the same. I t is possible to run a PT-20 with 4 ft waves without speed reduction and with approximately 6.5 ft waves with reduced speed. This, however, depends on favourable wave types and directions. With waves from the rear, for example, the seaworthiness will be reduced. SR.NG may be operated with waves up to 4 f t high in Norway (5 ft abroad), but in the course of several experiments it has been found that the craft can negotiate considerably higher waves. The craft can be driven at a speed of 50 ltnots in waves approximately 3 ft high. Under unfavourable conditions,

ie, with wave lengths from 314 to 1.5 times the length of the craft, the speed must be reduced to approximately 42 knots.

Even though there 1s no l~mltation on hydrofoll traffic, 4 ft waves wlll so much reduce passenger comfort that, m practice, the servlce must be stopped Both types of craft are, therefore, sultable for servlce only on narrow waters Hovercraft are, at present, not permitted to travel In wlnds exceeding 20 knots, le, w ~ n d force 5. This indrcates that the regularity mlght be lmpalred durlng winter operation Wlnd observations talten on Rundo from 1941-50 lndlcate that the wlnd force 1s In excess of 5 for about 15% of the perlod from October to May As Rundo 1s much more exposed than the actual servlce route for high-speed boats, lt is to be expected that the servlce can be operated somewhat more regularly than the figures ~nd~cate . I t should also be mentioned that AB Sundfart who operated the hydrofoll boat servlce over the Oresund w ~ t h two PT-20 and one PT-50 close down their service in w~ndforce 5 and wave heights of 4ft , le, as In the case of hovercraft.

Durlng the trial service wlth the SR.N6 at More in summer 1964, only five journeys were cancelled because of bad weather from 2816 to 1219. The day before the service was opened, however, the craft was weatherbound. Of almost 1,600 actual passengers only 4'% suffered delays in excess of ten minutes. Approximately one-third of these delays were due to bad weather. The hydrofoil service between Stavanger and Bergen, which covers relatively highly exposed sea sectlons over Roknfjorden and Sletta, had to cancel only 5-6 passages per craft in 1964. The PT-50 boats used on thrs service are, however, more seaworthy than the PT-20. The PT-20-express boat- operating over the Ryfylke Fjords during the same period was cancelled for one day only.

Operational Safety and Maintenance The number of technical irregularities wlll largely

depend on the accuracy and programme of the maintenance service. In order to avoid any unnecessary operational delays it has proved necessary to malntain a com- prehenslve spare parts store. The hydrofoll boats have, among other thlngs, been troubled by propeller and propeller shaft d~ficulties. With preventative maintenance such as, for example, inspection or replacement of propellers after a certain number of operating hours it has been possible to reduce this problem. In addition to propeller cavitation, the propellers and foils can also be damaged by floating objects.

The main maintenance problems in connection with the hovercraft used at M0re were due to oil leakage as well as damage to the sklrt and, particularly, the centre keel. Trouble in the hydraulic system gave rise to approximately 25% of all passengers cancelled. There was also motor trouble, possibly due to contamination of the fuel when tanking up from barrels. The other problems were of a more incidental nature and normally negligible. Approxi- mately two-thirds of all cancellations at M0re occurred durrng the first 14 days of the service. At present the hydrofoil boats appear to be able to ensure a better technical regularity than hovercraft. This, however,, must be assumed to be a transition phenomenon. There is nothing to indicate that hovercraft should not become equally reliable as the hydrofoil boats.

Both types of craft require specially trained maintenance mechanics, but there is no reason why the operating companies should not bek able to train their own technical staff to carry out maintenance and daily inspec-

Andalsnes-Molde Molde-Vigra a~rport 3 h 40 min Molde-Alesund Andalsnes-Alesund Alesund-Hareid Alesund-Gvsta 2 h 0 min

tions. Hovercraft engine overhauls, however, must be carried out In special workshops, but engine replacement can be carrled out within one day so that the craft does not have to be kept

Hovering Craft & Hydrofoil Magazine August 1967 Vol 6 No 11 · 2018. 7. 25. · HOVERlNG CRAFT &...

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Transcript of Hovering Craft & Hydrofoil Magazine August 1967 Vol 6 No 11 · 2018. 7. 25. · HOVERlNG CRAFT &...