Powered by Boiling Petrol.

Updated: 29 Dec 2008

Crabtree comments added

Or boiling alcohol.

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The Yarrow Zephyr: 1888
The Escher Wyss Launch: 1890
The Ofeldt Launch: 1897 Updated
Conflagrations & explosions
Historical Notes
Naptha launches in fiction
Thermodynamics: Carnot efficiency (different page)

Incredible as it may seem, around the end of the nineteenth century, small boats really were powered by boiling petrol and using the vapour to drive a sort of "steam" engine. The "petrol" was more often called "naptha" at the time, and was a mixture of low-boiling point hydrocarbons distilled directly from crude oil rather than the sophisticated brew we know as "petrol" nowadays. The literature of the day used both terms pretty much interchangeably, and I have done the same here.
The naptha was boiled by burning a certain proportion of the working fluid, ie naptha. At first I thought that the designs below were merely optimistic proposals, but further research has shown that "naptha launches" really did exist, though in what numbers I cannot presently say. Certainly they were recreational craft for the rich rather than working boats.
I initially thought that naptha was adopted as a working fluid because it boiled at a lower temperature than water, and so was thought to be more efficient. (This is actually wrong thermodynamically, but let's not get into Carnot's Law just here; see the thermodynamics page) The real reason, at least in the case of the Ofeldt boat, was quite different. It was simply to get round a law that required every steam-boat to carry a licensed steam engineer. Another motivation was that they could get up working pressure faster than a steam engine.


As reported in the French journal Nature for 21 July, 1888.

The launch Zephyr was the first boiling petrol boat. It was built by Mr Yarrow of London, who gave a talk on its design before the Institute of Naval Architects. Its length was 11 metres and the beam was 1.8 metres. It carried 40 gallons of petrol, which was both the fuel and the working fluid. The petrol vapour from the engine was recondensed in longitudinal chambers on each side of the hull.

Above: The Zephyr Boiling-Petrol Launch.

The machinery and operation of this vessel appears to be very similiar to that of the Ofeldt launch described in detail below, and I will not describe it again here. The latter design is apparently not as original as I once thought.

One of the advantages that Mr Yarrow claimed for his power plant was that it could be started from cold in only five minutes. Nature made it very clear that they understood that reducing the operating temperature range would reduce cycle efficiency, not increase it, as one might at first suppose.


From the French journal Nature for 21 July, 1888.

Left: The Escher Wyss Boiling-Petrol Launch.

The most striking thing about this boat is its very close resemblance to the Ofeldt system which is described in detail below. It looks as though Mr Ofeldt bought a licence from Escher Wyss.

Note the condenser pipes Q at the bottom of the picture.

The company of Escher Wyss still exists, as a moment's Google will demonstrate.


This section shows the bizarre and frightening arrangements of the Gas Engine and Power Company of Morriss Heights, 185th St, New york City. It was called the Essh system; that may be some sort of contraction of "Escher Wyss".

The information in this section comes from The Scientific American Supplement No 1104 of Feb 27, 1897, and No 1118 of June 5, 1897. It was supplemented on 7 Mar 2008 by info from "The Automatic Control of Small Boilers", a paper read to the Newcomen Society by J A Crabtree on 10 Mar 1971.

The main motivation for this system was to evade the USA regulations that required even the smallest steam launch to carry a qualified steam engineer; this stipulation was not lifted until 1912. Other countries had no such regulations , and the use of boiling petrol outside the USA was minimal.

Above: Cross-section of the Boiling-Petrol Launch.

Note that the petrol tank is at the front, well away from the boiler. This was probably not purely a matter of weight distribution as the tank would have been empty at times; it was probably a safety-measure. The "condensing pipes" for petrol vapour leaving the engine are not easy to see, but they pass downwards from the front of the engine, run aft to just in front of the propellor, then double back to the fuel tank in the bows.

This thing was probably expensive to build: there is no such thing as a free launch.

Above: The Boiling Petrol System.

Petrol is pumped from the tank in the bows by air pressure, generated by a hand pump, and passes through a coil boiler. Part of the petroleum vapour issuing from the boiler is fed to the burner that heats the boiler, and the rest drives a three-cylinder engine. The long U-tube at the bottom is the condenser.

Note the whistle top right, I thought at first it blew with petrol vapour, (which might have somewhat hazardous if any one on board was smoking) but Ken Helmick points out that on the diagram above, the whistle is connected to the compressed air line that pressurises the fuel tank.

An interesting feature of this boiler-engine combination is that there is no throttle valve. With small steam launch engines with flash boilers it was quite practical to operate just using the reverse gear and the burner control, as the amount of working fluid in the boiler was very small, and the response to burner modulation therefore reasonably quick. The same applied to the boiling-petrol system.

Above: Another View of The Boiling Petrol System.

Petrol is pushed into the boiler by pump P, through pipe R. (This pump needed to be larger than in steam practice because of the low specific volume of the petrol vapour) When vapourised, it enters B, where most of it descends through pipe D to the engine valve chest. The valves C were said to be slide valves, but the drawings here do not make it clear how they were oscillated; probably by some sort of cam action. Note the peculiar ball-joints at the upper ends of the connecting rods.
A proportion of the vapour is diverted from B through tube T, and is squirted through injector P, entraining air from the funnel shaped thing A and driving the petrol/air mixture down pipe H to the ring-burner K, which heats the boiler tubes.
The exhaust petrol vapour, on leaving the engine, was condensed in "tubes outside the launch" that were under water, and returned to the tank in the bows. Condensation did not create a vacuum, and the back-pressure on the engine pushed the condensed petrol forward and up into the bow tank.

The wheel M controlled the valves to allow forward and reverse running.

The boiler pressure varied between 14 and 70 psi, regulated by the burner control valve attached to injector P. There was no throttle between boiler and engine.

Petrol consumption was said to be between 17 and 20 pints per hour, generating 6 horsepower at 233 rpm. The launch would carry two people at about 5.5 knots.
The petrol acted as lubricant as well as working fluid, and it was said that "the density of the petroleum employed should be between 0.68 and 0.70. Below the former figure the petroleum does not lubricate satisfactorily, and above 0.70 it does not evaporate sufficiently rapidly." This seems like a very small range of density to specify in an age when the refining of petrol was very much in its infancy.

The dangers of this system hardly need enumerating. Most steam engines have little puffs of steam coming out of various crevices, such as the piston-rod packing. I see no reason why a petrol-boiling sytem should be any more leakproof, so it would seem to be only a matter of time before escaping petrol vapour was ignited by the nearby flame on the boiler, with dire consequences. J A Crabtree, writing for the Newcomen Society, was more optimistic, pointing out that there was a relatively small amount of petrol actually in the boiler, and the main risk was in starting without adequate pre-heating, when burning liquid fuel might run into the bottom of the burner casing and spill into the bottom of the boat. Crabtree states that anyone familiar with flooded vaporisers in paraffin-fired steam boilers would have been aware of the risks; this seems unduly complacent to me, as petrol and paraffin are very different in their flammability. Crabtree also says "It was hardly possible to apply these power-units for anything but marine work because of the need for infallible condensing arrangements." ie an ample supply of cold water. Crabtree's comments are reproduced in full below.

Turning to the possibility of excessive boiler pressure, a steam boiler explosion is quite bad enough; a petrol boiler explosion would add conflagration to detonation and would be considerably more dangerous and destructive.

Left: External View of The Boiler, with the engine under it..

A is a sight-hole to allow inspection of the flames.

E is a hand air-pump used to pressurise the petrol tank for starting up.

The whistle can be seen just to the right of the base of the chimney.

The Scientific American said:

"These little boats have won for themselves an astonishing record. They seem to be as absolutely secure from accident as any kind of power driven craft can be. Every possible precaution is adopted..."

This seems an extraordinary conclusion to draw. There are many questions about how such a perilous technology came to get even limited acceptance. A sea-going experiment with ether as a working fluid came to a fiery end in 1855, long before the naptha launches appeared.

Left: A relatively modern view of the petrol launch and its safety problems.

This is an excerpt from an article on automatic boiler control in the journal of the Newcomen Society. The plate XVIII referred to is essentially the same as the picture just above.

From an article by J A Crabtree in the journal of the Newcomen Society, Vol 43, 1970-71, p93.


Left: News of naptha launch explosions at Henley and Cowes: 1891

Well, that makes it clear that at least three of them blew up, which should come as no surprise. There is no information on the number of casualties. It is not obvious why anyone would want to import this perilous technology into Britain- so far as I am aware there was no requirement in Britain to carry a qualified engineer in a steam launch, as there was in the USA.

An extract from a letter by someone known only as 'JHS of Portsmouth' to Industries in 1891. The rest of the letter is not relevant.

Extract from a letter to Industries, 28 Aug 1891

Left: A naptha launch goes up in 1910

Explosion in Long Island Sound, probably with at least one fatality.

From The New York Times, 5th September 1910

Left: A naptha launch goes up in 1904

Conflagration at the New York Yacht Club. No casualties this time...

From The New York Times, 26th July 1904


This is taken from a 1965 article called "Naphtha Launches" by F L Herreshoff in the journal Rudder, from the USA:
"Certainly as we look at the naphtha launch today it seems a most infernal machine. Strange to say, however, these launches had few explosions or fatal accidents 'though most of them blazoned up occasionally. Many were copper sheathed in the engine compartment so these blaze-ups were rather laughed at or thought to be part of the game... The real, and possibly the only reason for the naphtha launch was to get around the law that required a licenced engineer on a steam launch... The genius who worked up the naphtha power plant to evade the law was a German named F W Ofeldt of New York and I class him as a genius because he arranged or designed launches that had few serious accidents and because the power plants were novel and built at little expense... The naphtha launch was smaller, lighter, cheaper and, of course, much quicker starting than the steam launch. They sold like hot cakes right up to around 1900 when the internal combustion engine began to be reliable and lighter than the naphtha ones."
Hopefully that extract is short enough to avoid copyright issues. I'm not at all sure about "few serious accidents".

From the Eagle Harbour website:
"The commentary on the smaller boat hulk was very interesting. My father who began to spend time at the Harbor in about 1905 always told the story that this boat was a "naptha launch" that exploded and burned at a dock on the west end of the Harbor with several fatalities. It was later towed to the east end and sunk by the coast guard. As I recall he said that the boat was owned by a prominent copper country family."
Which sounds like the sort of accident that would be all too likely. Clearly this "blaze-up" was not a laughing matter.

An extract from a news report in 1900:
"July also featured the Larchmont Yacht Club "Race Week." Thursday, July 25th, was a scheduled break for the big sailing yachts and raceabouts. Rowing contests and three events for powered craft were scheduled in their place. No gas engine launches raced but the naphtha launches were divided into two classes, those over 21 feet and those 21 feet and under; Intrepid took the over 21' title and Trochilus took the 21 and under title. The third race was for Alco-Vapor launches, launches powered by alcohol vapor.
The development of the camp and cottage life which is now the great feature of the river has been made possible largely through the introduction of the older types of pleasure craft, first, the primitive steam launches, then the "naphtha launch," and the "Alco-vapor launch," and more recent years the gasoline launch with explosion motor."

This gives us a tantalising glimpse of another forgotten technology- the alcohol vapor motor. This would presumably have been safer due to the lower flammability of alcohol vapour compared with naptha. The Alco-Vapor engine was also invention of Frank W Ofeldt, after the naphtha engine; it burned kerosene and boiled alcohol. No doubt a ride in an Alco-Vapor launch with a few leaky joints was an intoxicating experience. The Museum of RetroTech now has a page specialising in alcohol motors

Mr Olfeldt was clearly an enterprising man. Details about him are scarce, but here is his obituary:

"Frank W OFELDT - The Rev. Dr. H. C. A. MEYER. of St. James Lutheran Church, conducted the funeral services today over the remains of Frank W Ofeldt at his late residence, 173 Twenty-third street. Mr. Olfedt died on Wednesday. He was 68 years old and was a native of Sweden. He was the inventor of the first naphtha launch and the first alco-vapor launch. He was engaged with his sons, Frank and Ernest, in building automobiles and launches at the foot of Twenty-fifth street. (ed: in Brooklyn) Two other sons, Walter and George, also survive him. The interment was in Greenwood Cemetery."

The Ofeldt company also built a few steam cars in Brooklyn, NY from 1899 to 1900 and Newark, NJ from 1901 to 1902. Serious automobile production was not undertaken, though the company was still producing parts for steam cars as late as 1905.

One of the users was Leo Hendrik Baekeland, the Belgian inventor of Bakelite. He was a keen yachtsman, and in 1899 purchased a gasoline launch. He successfully cruised from Yonkers up the Hudson, through the connecting waters to the St. Lawrence and back.
(Information from volume xxiv - eighth memoir of LEO HENDRIK BAEKELAND 1863 - 1944 by Charles F. Kettering)

This museum in the USA has what is said to be the only surviving Naptha Launch: The Antique Boat Museum.


This is an extract from Tom Swift Among The Fire Fighters by "Victor Appleton", 1921. Our boy hero has been cruising around in his own airship, as you do, and lands to rescue the occupants of a sinking boat...

"But Tom Swift was too skillful a pilot to cause his craft to sustain much of a crash. He made an almost perfect "three point landing," and there would have been no unusual shaking, except for the fact that the field was a bit bumpy, and the craft more heavily laden than usual.

"Good work, Tom!" cried Ned, as the Lucifer slackened her speed, the young inventor having sent her around in a half circle so that she now faced the lake. Then Tom and Ned climbed from the cockpit, throwing off goggles and helmets as they ran to the shore where there were several rowboats moored.

"And a little old-fashioned naphtha launch! By all that's lucky!" cried Tom. "I didn't think they made these any more. If she only works now!"

There was a little dock at this point on the lake, and the boats appeared to be held at it for hire. But no one was in charge, and Tom and Ned made free with what they found. They considered they had this right in the emergency.

The naphtha launch was chained and padlocked to the dock, but using an oar Tom burst the chain.

"Get one of the rowboats and fasten it to the back of the launch!" Tom directed Ned. "I don't believe this craft will hold them all," and he nodded toward those aboard the sinking boat -- for it was only too plainly sinking now.

"All right!" voiced Ned. "I'm with you. Can you get that engine to work?"

"She's humming now," announced Tom, as he turned on the naphtha, and threw in a blazing match to ignite it, this act saving his hand. Naphtha engines are a trifle treacherous.

A few moments later, though not as quickly as a gasoline craft could have been gotten under way, Tom was steering the small launch out and away from the dock, and toward the craft whence came the faint calls for help. Behind them Tom and Ned towed a large rowboat.

Tom speeded the naphtha craft to its limit, and, fortunately for those in danger, it was a fast boat. In less time than they had thought possible, the young inventor and his chum were near the boat that was now low in the water--so low, in fact, that her rail was all but awash."

Note that "Naphtha engines are a trifle treacherous", if only when you light them up. There was a long series of Tom Swift books, written by ghostwriters and all credited to the publisher's house name of Victor Appleton.

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