A naphtha launch
, sometimes called a "vapor launch", was a small motor launch
A launch in contemporary usage refers to a large motorboat. The name originally referred to the largest boat carried by a warship. The etymology of the word is given as Portuguese lancha "barge", from Malay lancha, lancharan, "boat," from lanchar "velocity without effort," "action of gliding...
, powered by a naphtha engine. They were a particularly American design, brought into being by a local law that made it impractical to use a steam launch for private use.
By the 1880s, the small steam engine was well established as a power unit for small steam launches, as well as for large boats. However US law, prompted by some past boiler explosion
A boiler explosion is a catastrophic failure of a boiler. As seen today, boiler explosions are of two kinds. One kind is over-pressure in the pressure parts of the steam and water sides. The second kind is explosion in the furnace. Boiler explosions of pressure parts are particularly associated...
s, required that all
steam boats carry a licensed engineer at all times. Although this was no difficulty for a commercial craft, it prevented small steam launches being used for personal, recreational use. Becoming such an engineer required an apprenticeship of two years beforehand. One of the few amateurs to achieve this and to become their own engineer was Rosamund Burgess, wife of boat designer Starling Burgess.
A more popular alternative was the naphtha launch, and its alternative power source to the steam engine. Advertisements of the period used the deliberate phrase, "Every Man His own Engineer!" to highlight this legal restriction.
The first naphtha launch appears to have been British, reported in the French journal Nature
in 1888. This launch, Zephyr
, was the invention of Alfred Yarrow
Sir Alfred Fernandez Yarrow, 1st Baronet, of Homestead was a British shipbuilder who started a shipbuilding dynasty, Yarrow Shipbuilders.-Life and career:...
, a well-known builder of steam launches for some years previously. Similar launches were produced in the same year by the Swiss company Escher Wyss AG. One of these was Alfred Nobel
Alfred Bernhard Nobel was a Swedish chemist, engineer, innovator, and armaments manufacturer. He is the inventor of dynamite. Nobel also owned Bofors, which he had redirected from its previous role as primarily an iron and steel producer to a major manufacturer of cannon and other armaments...
's graceful aluminium
Aluminium or aluminum is a silvery white member of the boron group of chemical elements. It has the symbol Al, and its atomic number is 13. It is not soluble in water under normal circumstances....
A sloop is a sail boat with a fore-and-aft rig and a single mast farther forward than the mast of a cutter....
, of 1892. Another, also of aluminium, was the Aluminia
The first American naphtha launches recorded were those of the Ofeldt company of New York, who would later become well known as makers of naphtha engines. They described this as the 'Essh' system, and may have been licensees of the Escher Wyss patents. As well as Ofeldt, complete launches were also offerd by the Gas Engine and Power Co. of New York. By 1890 they claimed to have sold over 500.
The typical naphtha launch was an open launch of around 24' length. These were pleasure craft for use on fine weather excursions. After all, a commercial boat with a professional crew would not have the regulatory problem that led to their invention. Naphtha launches appeared in the finest circles, in the best yacht club
A yacht club is a sports club specifically related to sailing and yachting.-Description:Yacht Clubs are mostly located by the sea, although there are some that have been established at a lake or riverside locations...
s and under the ownership of some celebrated names.
The naphtha engine is an external combustion engine
An external combustion engine is a heat engine where an working fluid is heated by combustion in an external source, through the engine wall or a heat exchanger. The fluid then, by expanding and acting on the mechanism of the engine, produces motion and usable work...
, generally similar to the type of small steam engine
A steam engine is a heat engine that performs mechanical work using steam as its working fluid.Steam engines are external combustion engines, where the working fluid is separate from the combustion products. Non-combustion heat sources such as solar power, nuclear power or geothermal energy may be...
already in use for steam launches. The working fluid
A working fluid is a pressurized gas or liquid that actuates a machine. Examples include steam in a steam engine, air in a hot air engine and hydraulic fluid in a hydraulic motor or hydraulic cylinder...
Naphtha normally refers to a number of different flammable liquid mixtures of hydrocarbons, i.e., a component of natural gas condensate or a distillation product from petroleum, coal tar or peat boiling in a certain range and containing certain hydrocarbons. It is a broad term covering among the...
, which unusually is also used as a liquid fuel to power the boiler. Appearance is similar to a steam launch, having a small vertical boiler and vertical cylinders.
The burner for a naphtha engine uses naphtha itself, and is similar to that used for steam car
A steam car is a light car powered by a steam engine.Steam locomotives, steam engines capable of propelling themselves along either road or rails, developed around one hundred years earlier than internal combustion engine cars although their weight restricted them to agricultural and heavy haulage...
s. Although such convenient and self-regulating liquid fuel burners were also used on steam launches, most launches at the time of the naphtha engine's heyday were still using solid fuel.
To avoid problems of premature condensation, the engine and boiler units were mounted together. Engines were three-cylinder single-acting vertical simple expansion engines, with 120° crankshaft spacing, so as to be self-starting without dead centre problems.
[Other configurations would have been possible, but none are known at this time.]
The boilers were of spiral monotube form. These were single-pass water-tube(sic) steam generator
A steam generator is a device used to boil water to create steam. It may refer to:*Boiler , a closed vessel in which water is heated under pressure...
s, where liquid at one end of the tube boiled by the time it reached the end, without any looped circulation. Such boilers, although with conventional water and steam, were also used for steam cars such as the White
White Motor Company was an American automobile and truck manufacturer from 1900 until 1980. The company also produced bicycles, roller skates, automatic lathes, and sewing machines. Before World War II, the company was based in Cleveland, Ohio.-History:...
. The boiler was mounted directly atop the engine, and encased in a polished brass or copper casing with a short funnel above. The purpose of the funnel was merely to vent fumes above the heads of passengers, rather than to act as a draught to draw the fire.
Unlike coal or wood, the jet burners used did not require additional draught.
[This short chimney, compared to that of a steam launch, is an identification feature for naphtha launches in old photographs.]
The boiler was fired with a pressure jet burner, a small quantity of pressurised naptha being tapped off from the boiler. A prominent tube and funnel on the front of the boiler casing (sometimes mistaken for a whistle) is the air inlet. The fuel jet mixes with the downwards air flow in this vertical tube, then the mixed air and fuel is fed to a ring-shaped burner inside the boiler casing. For starting, a hand air pump was used to pressurise the fuel tank and encourage fuel flow, together with pre-heating of the burner coil by lighting a little of the fuel in a tray below it.
There was no throttle valve or regulator to control the engine speed. As was commonly used on single-pass spiral monotube boilers, the burner output was regulated instead with the fuel valve and the boiler responded quickly enough for this to be sufficient.
Lubrication of the engine was performed by the fuel itself, collected in an sealed wet sump
A wet sump is a lubricating oil management design for four-stroke piston internal combustion engines which uses a built-in reservoir for oil, as opposed to an external or secondary reservoir used in a dry sump design....
arrangement beneath the crankcase. The naphtha fuel
[The fuel of this period was closer to modern paraffin or kerosene than what we would know today as gasoline or petrol.]
was an acceptable lubricant and this avoided the problem of separating lubricating oil from condensed fuel vapour leaking past the piston ring seals. It did however require careful sealing of the crankcase.
The engine valvegear was simple, compared to that of contemporary steam engines
The valve gear of a steam engine is the mechanism that operates the inlet and exhaust valves to admit steam into the cylinder and allow exhaust steam to escape, respectively, at the correct points in the cycle...
. A single rotating overhead camshaft
Overhead cam valvetrain configurations place the engine camshaft within the cylinder heads, above the combustion chambers, and drive the valves or lifters in a more direct manner compared to overhead valves and pushrods...
ran above the cylinders, parallel to the crankshaft. Eccentric
In mechanical engineering, an eccentric is a circular disk solidly fixed to a rotating axle with its centre offset from that of the axle ....
s on this shaft actuated a transverse slide valve for each cylinder. The valve camshaft was driven at engine speed
[The camshaft operated at engine crankshaft speed, like a steam engine or two-stroke engine, but unlike the camshaft of a four-stroke engine that runs at half crankshaft speed.]
by gears from the crankshaft. A prominent handwheel on the camshaft allowed the engine to be reversed, in a similar manner to slip-eccentric valvegear by shifting the phase of the camshaft relative to the crankshaft.
External water-cooled condensers were used, simple pipes run under the hull, along the length of the keel. Despite the obvious risks of damage from grounding
Ship grounding is a type of marine accident that involves the impact of a ship on the seabed, resulting in damage of the submerged part of her hull and particularly the bottom structure, potentially leading to water ingress and compromise of the ship's structural integrity and stability...
, these seem to have given little trouble in service. The fuel tank was in the fo'csle of the boat, well away from the engine and risk of fire. This fuel tank was pressurised by the returning naptha, avoiding the need for a fuel pump.
Low boiling point
One of the attractive features that first led inventors to consider naptha as a working fluid was its low boiling point
The boiling point of an element or a substance is the temperature at which the vapor pressure of the liquid equals the environmental pressure surrounding the liquid....
, compared to water. This allows a relatively simple engine to be constructed, although it actually represents a limitation on the efficiency of such an engine. At the time, thermodynamics
Thermodynamics is a physical science that studies the effects on material bodies, and on radiation in regions of space, of transfer of heat and of work done on or by the bodies or radiation...
was already an advanced science and the limitations of thermodynamic cycle
A thermodynamic cycle consists of a series of thermodynamic processes transferring heat and work, while varying pressure, temperature, and other state variables, eventually returning a system to its initial state...
s were well understood by physicists, if not by all engineers. By limiting the range of temperatures between which the engine worked, this actually reduces the potential efficiency of the engine, rather than increasing it.
An earlier use of low boiling point fluids had been Du Tremblay's ether
Diethyl ether, also known as ethyl ether, simply ether, or ethoxyethane, is an organic compound in the ether class with the formula . It is a colorless, highly volatile flammable liquid with a characteristic odor...
engine of the 1850s. This was used for a bottoming cycle
as an addition to a steam engine. Waste heat rejected through the condenser
Condenser may refer to:*Condenser , a device or unit used to condense vapor into liquid. More specific articles on some types include:*Air coil used in HVAC refrigeration systems...
of the steam engine was used to boil ether and drive a second cylinder.
Frank W. Ofeldt
Frank W. Ofeldt also designed the Alco Vapor engine, sold by the Alco Vapor Launch Co. This burned kerosene
Kerosene, sometimes spelled kerosine in scientific and industrial usage, also known as paraffin or paraffin oil in the United Kingdom, Hong Kong, Ireland and South Africa, is a combustible hydrocarbon liquid. The name is derived from Greek keros...
and used alcohol
In chemistry, an alcohol is an organic compound in which the hydroxy functional group is bound to a carbon atom. In particular, this carbon center should be saturated, having single bonds to three other atoms....
(probably 'wood alcohol' or methanol
Methanol, also known as methyl alcohol, wood alcohol, wood naphtha or wood spirits, is a chemical with the formula CH3OH . It is the simplest alcohol, and is a light, volatile, colorless, flammable liquid with a distinctive odor very similar to, but slightly sweeter than, ethanol...
) as a working fluid. This may have been a measure to avoid the Escher Wyss patents.
Later Ofeldt also designed a more conventional steam-generating water-tube steam boiler. This was similar to the "Lune Valley" pattern, a central drum surrounded by coiled water tubes, but with irregular wedge-shaped coils rather than a simple circle.
The "Simplex Naptha engine" built by Chas. Willard of Chicago was more akin to an internal combustion gas engine
A gas engine means an engine running on a gas, such as coal gas, producer gas biogas, landfill gas, or natural gas. In the UK, the term is unambiguous...
with timed spark ignition. It is outside the scope of this article.
Hazards and explosions
Despite the obvious hazards and occasional reports of fires, the naptha launch appears to have worked reasonably well and safely.
The naphtha engine is not well known amongst model engineers, but at least one detailed reproduction has been constructed.
In popular culture
In the 1921 novel of the popular "Tom Swift
Tom Swift is the name of the central character in five series of books, first appearing in 1910, totaling over 100 volumes, of American juvenile science fiction and adventure novels that emphasize science, invention and technology. The character was created by Edward Stratemeyer, the founder of...
" series, "Tom Swift Among the Fire Fighters
Tom Swift Among the Fire Fighters, Or, Battling Flames From the Air, is Volume 24 in the original Tom Swift novel series published by Grosset & Dunlap.-Plot summary:...
", the hero escapes on a naptha launch, describing it as "old-fashioned". The author also passes comment as to them being "a trifle treacherous" to light.