A Brief History of the Propeller
An Article originally by Kevin Desmond. Edited by Roy Cooper
It is ironic that the only boat to be given the name ‘The Propeller’ was in fact an 1840 Thames paddle-steamer. It was not until the paddlesteamer had reached a high degree of efficiency, that the screw propeller was generally adopted. In 1836, Frank Pettit Smith, a farmer from Middlesex, patented a single-threaded screw propeller with two complete twists, resembling part of a large cork-screw, which spun in a recess at the stern of the ship. Smith’s early successful experiments were with a clockwork model that frightened the geese on the pond at his farm. But soon a 6-ton steam launch, called the ‘F P Smith’ was built at Wapping and tried on the Paddington Canal in 1837. During one of her trials half the wooden prop snapped off and to the surprise of the crew, the launch went faster. So Smith designed a metal screw consisting of one complete turn instead of two.
The revised ‘F P Smith’ reached a speed of 8mph and Smith amended his patent. His screw was described as consisting of a double thread with two half turns; thus, the two bladed prop was born. Farmer Smith was knighted for his services in 1871.
We all know of the SS Gt Britain, designed by Brunel and built in 1844. She was fitted with a sixbladed prop of 15ft 6in diameter with blades 6in thick. Her prop was not cast but built of wrought iron plates riveted together. After a failure of the six-blade, it was replaced by a four-bladed prop.
After the valuable work of the early pioneers, a type of prop design came into general use, which was known as ‘the common screw’. This design had two disadvantages: the portions of the blades nearest the small cylindrical boss were always weak as the boss was always made as small as possible. The wide, fan-shaped tips of
the blades absorbed a large amount of power without adding to the thrust of the screw.
So, in 1849, Robert Griffiths began a long series of experiments and six-years later the Griffiths prop was born in which the blades tapered towards the extremities and were separately attached and adjustable for pitch.
The correlation of all the qualities that combine to make the ideal prop is a task involving great technical skill and has been developed over many years. For example, a prop acts on water that is not at rest. A ship or boat carries some water with her as she moves forward, and the shape of the hull aft materially affects the props performance because of its influence on the way the water approaches the prop.
Next we come to cavitation. A problem first noticed by Sir John Thorneycroft and W S Barnaby in 1893. Sir Charles Parsons constructed the first ever cavitation tunnel, to test and improve the speed of his steam-turbined ‘Turbinia’. The results of these tests led Parsons to replace the single prop shaft with nine props of 18 inches, spinning at 2,200rpm, increasing Turbinia’s speed to around 30 knots.
When Fred Cooper and Hubert Scott-Paine designed the racing hydroplane, ‘Miss England I’ for Sir Henry Seagrave in 1929, they risked the daring and unprecedented concept of coupling a 900hp Napier Lion to a single screw at no less than 6,800rpm; with this a maximum speed of 93mph was reached. So with ‘Miss England II’, Fred Cooper took the idea one logical step further, so that two Rolls Royce ‘R’ types, each developing 1,800hp would drive forward to a single gearbox, which would multiply their revs by four and drive that power down a shaft to a prop spinning at no less than 12,550 –
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13,000rpm. Such a prop would need to be strong enough to stand the strain but small enough to avoid torque.
Cooper ordered seven props from Saunders-Roe Ltd and a prop from Rolls Royce, who, for the first time, used aircraft propeller principles. Its construction took over three weeks and used a solid billet of Stan Royal – high-speed steel –instead of being forged. This billet was carved down to nine-tenths of its original size, then final machining and heat treatment took place. To finish, the prop was polished so finely that it could cut the finger of the highly skilled operator who carved it.
Conventional screw propellers are designed to operate fully immersed below the water's surface, but the nature of propeller design - and in fact any pump operating in water - can cause it to become exposed to cavitation conditions. For racing purposes, the surface-piercing propeller drive offers reduced drag over traditional stern drives and outboards, with the (possibly most critical) advantage that they do not suffer from the problems associated with cavitation. This alternative solution functions with the propeller semi-submerged, operating aerated, meaning it is not exposed to cavitation. You will instantly recognise a surface-piercing drive by its rooster tail and the separated sheets of wake caused by the propeller repeatedly entering and exiting the water's surface.
Unlike conventional propellers, surface-piercing drives operate with their low-pressure face completely aerated - there are a number of different phases of operation before the face of the blade is completely covered with an air cavity. These propellers therefore rely on creating large amounts of lift from the positive pressure face due to loss of thrust on the suction side.
Numerous profiles have been explored to create maximum thrust in this ventilated condition. According to one theory, the most efficient foil shape offering the greatest lift:drag ratio has all its lift concentrated at its trailing edge. If you look closely at the trailing edge of some high-speed
propellers you will notice heavy cupping, which improves thrust by increasing the effective pitch of the propeller, and therefore supports this theory. Also, the distinctive trailing edge offers an attachment area for the air cavity, whilst helping to maintain blade strength and maximise blade area.
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A 3-blade LAK prop for OSY400
4-blade LAK prop for F2 and F1
A Mercury racing 5-blade cleaver prop
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Miss England II with her simple 2 blade prop drive by two supercharged Rolls Royce aero engines
Three blade prop on Bob Spalding’s JPS Velden Johnson V8. Photo: Simon Scott
Rolla Propellers was founded in 1983 by Philip Rolla and based on his previous 20 continuous years of race winning competition propellers. Custom made on a small scale. From the start in 1963 for about 10 years these were known as ‘Record’ propellers. For an unprecedented period of time, every major international racing category was won with Rolla propellers.
Philip Michael Rolla was born in 1938 in Madrone, a very small agricultural town in the farm country outside of San Francisco. His family were of Italian origin and all farmers; his grandparents immigrated to California from Italy’s Piedmont area in the years 1910 -1916. Thanks to his father’s commitment to his children’s education, he graduated from Santa Clara University with a degree in engineering and economics.
Although his work was in engineering, his economic studies would take on an important role; above all in the creation of his future company. Phil Rolla has nurtured a passion for racing boats and cars, and has been fascinated by their technical and aesthetic aspects, since he was a boy. After having worked, in order to complete his studies, for a company that carried out resistance tests on materials, he understood that his destiny did not include working for a large American company, and he decided to move to Europe.
At the end of 1962 he went to Norway and then to Turin. In Turin he could count on the help of two of his father’s cousins, but his decision to stay there was also due to the presence of the Hungarian automobile manufacturer Frank Reisner. Phil, who worked for Reisner as an apprentice until 1965, considers the experience fundamental
both professionally and personally. Following Reisner’s advice, and for personal reasons, he moved to Canton Ticino in 1966. The region’s three large lakes and the presence of Como boat builder Angelo Molinari, whose friendship and instruction were fundamental, rendered it the perfect place to further develop his interest in marine propulsion.
Rolla rented a garage and began contacting people in the United States who might be interested in his ideas about production of competition propellers. He received a response from Bill Harrah, an ardent follower of motorboat racing and the official importer for Ferrari in the United States, with a cheque for $1,600 to build three innovative propellers, one of which turned out to be very important for future discoveries in hydrodynamics. Thus the company Record was born, which in turn became Rolla SP Propellers. From this moment on Phil Rolla’s ascent was assured due to his talent and passion for his work and to his successes in racing motorboats, along with his interest in contemporary art.
His propellers are objects of remarkable beauty and Rolla has stated that if he hadn’t been familiar with conceptualism and minimalism he
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Phil Rolla – Prop Wizard
never would have had certain intuitions that were realised in his commitment to functional aesthetics, and that would be decisive in industrial research.
1972: The crucial need for more advanced casting than can be done by existing factories leads to Rolla setting up an in-house facility.
1977: Tullio Abbate sets new diesel World Record at 140.6 kmh, with a four-point hull, Iveco Aifo engine and Rolla props.
1978: Rolla launches 4-blade surface props, characterised by two sets of two blades with different diameters. Fabio Buzzi sets new diesel record using Rolla props.
Phil Rolla driving his inboard hydroplane, class LV (1300cc) Coppa Campione d’ Italia, 1968.
In his quest for prop perfection Rolla broke barriers in almost every sphere of manufacture. Listed below are some of the landmarks achieved by Rolla and his Swiss-based company.
1963: American Unlimited Hydroplanes employ Rolla 2-blade supercavitating cleaver-type propellers, with race-to-race modifications.
1964: Interests and activities expand to include circuit race boats.
1965-66: Two years of advanced research on a clever-type prop conclude with optimising the 3blade solution. Rolla designs various props for Angelo Molinari’s racing catamarans.
1967: Collaboration with Don Shead on propulsion system and semi-submerged props for Telstar, in which Tommy Sopwith won the Cowes-Torquay race.
1969: Rolla props are top winners in several circuit racing classes.
1970: The 4-blade cleaver-type is conceptualised.
1979: Abbate raises the World Record for diesel to 182.8 kmh using Rolla props.
1982: Chris Kaye sets new Diesel record at 199.9 kmh with Rolla props.
1983: 5-blade cleaver-type props undergo testing.
1984: Pre-series Mach IV 4-blade props are designed and manufactured; later produced by Second Effort. The first 6-blade models are designed and constructed in investment cast steel.
1985: Jeanneau assigns Rolla the role providing props for their Kevlar circuit boats.
1987: Rolla props win the Class 1 World Championships with Cougar; the Superboat World Championships with Gentry Eagle and across the board in circuit racing.
1988: The first 8-blade props, in steel, are tested on a variety of boats including military and fast pleasure craft.
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Kevin Desmond remembers
"My friend and mentor Leo Villa and I first heard of Ken Warby in 1976 when he was building what he was not allowed to call "Spirit of Anzac" in his garage. In the days before WhatsApp etc, Ken began to send me cassette-audio tape-recordings of his progress which I would then painstakingly transcribe on my electric typewriter, most information ending up in published books and articles. Leo and I were over the moon when Ken notched up a new world water speed record of 288.60 mph (464.46 km/h), breaking the record of Lee Taylor by a little over 3 mph (4.8 km/h). I was living in Cricklewood, London NW at the time and one day the doorbell rang and there he was, beard and all with a bottle of Australian Riesling white wine which he told me to immediately put in the fridge. He also gave me a patch which read "Spirit of Australia. The World's Fastest Boat". While he was staying with us, Ken sat down in our 1950 frayed red canvas deckchair and which gave way underneath his great weight (he always said it helped him keep down the nose of the boat) and I extricated the fastest man in the world on water from its aluminium framework. Later, when his friend and film-maker Rob
McCaulay visited me, he at once declared that he had been advised to ‘not use deckchairs at the Desmonds'!
Ken and I went up to Coniston to place a wreath on the water in memory of our hero Donald Campbell. We stayed in Donald's old bedroom at the Sun Hotel. Separate beds of course! Ken had a strange prophetic dream that night about Bluebird K7
When Ken raised his record to 317.6 mph (511.1 kmh) on Blowering Dam, he rang me up and announced his disappointment that due to an itchy foot, he had broken both the 300mph and the 500 km/h barrier at the same time. Despite building Aussie Spirit, Ken (an MBE) and his son David never managed to increase that record.
A mechanical engineer by trade, Warby financed and built the power boat Spirit of Australia in the early 1970s. On November 20, 1977, he set the world water speed record of 288.60 miles per hour (464.5
12 Ken Warby MBE May 9th , 1939 – February 20th, 2023
kilometres an hour) on Blowering Dam, south of Tumut. Then with a sponsor on board and more money to spend on his boat, he broke his own record, again on Blowering Dam, on October 8, 1978.
Even 45 years later, that mark of 317mph (510.2kph) has never been beaten. Close friend John Reid said it was not surprising Warby still held the record. ‘He just had nerves of steel and he was just focused,’ he said. ‘It didn't matter what he did, whether it was racing vintage power boats at high speed, he just always went at it.’
In 1980, Warby was invited by then-Prime Minister Malcolm Fraser to take Spirit of Australia on a tour of the United States, to help promote Australia. He remained there until his death at the age of 83.
Over the past decade, Warby has collaborated with his second son David, who is behind the development of the boat Spirit of Australia 2.
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Ken with son David, Who is continuing in his dad’s footsteps
Grand Prix in verse
Kevin Desmond
From Paris, London, Belfast, Brussels –
Aspeed crusade,
Acavalcade of cars and vans and caravans
Aconvoy of tankers and trucks and trailers
Loaded with tarpaulin-covered powerboats
Parades its way
Up motorways and over winding roads
To Windermere, Westmorland
At the approach of winter.
It is a gusty, frosty, rusty and lateAutumn
Of leaves left in the even of their lives.
Valleys, vales, fells, hills, dales
Look like some hand-tinted sun-glinting
Landscape painting
Filled with small whirlwind windfalls
Of multi-coloured leaves:
Dead red, oranges, ochre, copper, purple, Dappled green and gold:
Foliage in old age.
Leaves left in the eve of their lives
OnAmbleside hillsides, Lancashire lakesides
Mellowing near Backbarrow village
And all round Lake Windermere, Westmorland
In approaching winter.
Windermere Lake:
Long ten miles, wide one mile, Deep two hundred feet
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And old many millenniums.
Mountains:
Langdale Pikes, Scafell Pike
Dove Crag, Hart Crag
Allen Cragg and Crinkle Craggs.
Streams:
Trout Beck, Cunsey Beck
Brathay and Rothay.
Islands:
Blake Holme, Silver Holme, Grass Holme, Ling Holme, Ramp Holme and Belle Isle.
Fish:
Perch and pike, trout and char
Trees:
Birch and oak, hazel and pine.
Flotsam and jetsam float along the sloping shorelines:
Rotting sticks and rocks and rubble and reeds and then boats:
Neolithic dugouts and Roman galleys
Viking longships and Victorian steamships Powerboats.
Pilots and mechanics
Prepare their power-heads and hulls in calm and in panic.
Sweating and swearing at petrol and plugs and pistons
With frustrations of wires and fears and exhaust
And exhaustion.
Oil and grease, toil and fuss
Starboard and stern annoyance and Buoyancy.
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Smiles and cylinders.
Good manners and spanners
Pedals and muddles
Organisation and lubrication
Ignition and superstition.
Trailers, trucks and rope
Hope and luck or failure and despair
and prepare, repair, prepare and repair again!
Midnight.
Astill white full-moon light floodlight
Soon finds and fills
the woods, the hills, the heights, the dells.
In his hotel room,
One pilot sleeps calm and sound.
Others sit silent, sleepless, thinking
Perversely mocked by a sarcastic universe of stars
Fixed static within the watching and waiting shine
Of Windermere Lake
Fearing to face the break of dawn
On their own
Alone
Without the stars, without the moon
But knowing that the morning cannot come too soon.
Trailers clank and crunch across the grey-brown gravel
Trucks rev, then reverse
Winches revolve and wind wheels
Down the corrugated concrete ramp
Weighed down by boats
Which begin to float in the wash of waves.
Rough troughs of lakewater
The wake of boats that are breaking through
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The wake of other boats that are splaying
Spray and splash and spume.
The booster exhaust plume of a roostertail
Single, double, triple ripples
Wake and wash, splash and spray
Aballet of boats
That bounce and bump cut corners
Swerve and swing round buoys, past quays
in curves
Veering, steering
Testing on trial runs.
Stony silences
Nervy movements
Glimpses, glances, gestures.
The wind has dropped.
The autumn leaves flop limply.
The flag is up
Is followed by the forty boats.
The sun shines
The flag drops
The race begins.
The first boat forges forward
Leaving a wake that breaks the icy lake-glass surface.
Speed feeds backfire backwards
Then forwards waterborne
Fibre-glass vibrates
Brass screws and steel shafts gyrate
And spin near rudder fins that judder
At the altering of the angle of trim
For skimming the water.
Wedge-shaped water-sledges begin to chase, to race,
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Water-wasps with hornet hulls begin to drone
Delirious from the sting of speed
Engines to roar and reverberate
Accelerate, decelerate, accelerate.
Round and round and round the ragged rocks
The ragged rascals run
Raring, raging, roaring, revving, Razor-propellers ploughing flower-petals into
Out of the water
Adding steam to streams of spray.
Exhausts joust with exhausts
Heraldic acrylic orange helmets
Heave helms down hard, pull hulls round
And round again.
Ablue boat overtakes a yellow boat
Which overtakes an orange boat
And is overtaken by a white boat
While a red boat breaks down
And a blue boat crashes.
Death by drowning.
Death by broken bones
Death at speed
Swift death, slow death
Unexpected, unprotected
Crashing, smashing
Dead leaves, widow’s weeds.
The fearful ghost of the grey horse
Galloping
Silently galloping across Lake Windermere
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From shore to shore
Is an omen for terrible events.
Superstition.
Supernatural signs and symbols
Luck and unluck
Warlocks and witches
Touching wood, good and evil
Do’s and Don’ts and days and dates
Numbers and colours - and Fate.
Adinky-toy boat becomes a toy boat
Becomes a model boat becomes a small boat
Becomes a boat becomes a powerboat
Becomes a restless, ambitious, obsession.
The sun shines.
They see the glaze of cellulose, varnish finish
Glimpse the glint of steel
Watch catamarans run past tunnel boats
Run past catamarans.
The sun shines on a shower of rain
Its rainbow bends.
Achain of chasing boats rend their way
Around its silent struts.
The wind lifts some leaves off a tree.
Round and round and round the ragged rocks
Revving, racing, soaring, rearing, revving - living!
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(« Keith More » my pseudonym 1973)
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