CHAPTER V
A MOTOR BOAT
The first time you stepped aboard a motor boat you were impressed by thelooks of the engine and the numerous appliances which when rightlyhandled drive the craft through the water at the rate of ten, fifteen,twenty and sometimes more miles an hour. You thought it would be hard tolearn to manage the boat and know how to overcome the different kinds oftrouble that are almost certain to arise. But the task, after all, issimple and with patience you can soon master it.
In the first place let us find out the principle which governs thesmooth, swift progress of the structure. I shall be as brief and pointedas possible.
As a foundation, we need a good supply of clean, strained gasoline inthe tank. Unless the fluid is free from all impurities it is likely toclog and interfere with the working of the machinery. The tank is soplaced that its elevation is sufficient to cause the gasoline to flow bygravity through the pipe, which is connected by an automatic valve withthe carburettor, admitting just enough to answer the purpose desired. Asthe gasoline is sprayed into the carburettor a quantity of air is drawnin from the outside. The two mingle and form a highly explosive gas. Tostart, you give the fly-wheel a rapid swing, which causes the piston tomove downward. This action sucks the gaseous mixture into the cylinderthrough the inlet valve. The further movement of the fly-wheel causesthe piston to move upward, compressing the gas into small volume. Whilethe gas is thus compressed it is exploded by means of an electric spark.The violent expansion of the burning gas drives the piston downward withgreat force. The movement opens the exhaust valve, the burnt gasesescape through the exhaust pipe and the fresh mixture is drawn in againto be compressed and exploded as before. If the engine has more than onecylinder the same process is repeated in each one. This is theoperation which is continued so long as the supply of gasoline holdsout.
In the steam engine the vapor acts alternately on each side of thepiston head, but in motor boats and automobiles it acts only on oneside. The speed with which this is done is amazing and the same may besaid of the steam engine.
The swift rise and fall of the piston acting through the connecting rodturns the shaft directly below, which whirls the screw around at thestern. The electric spark that explodes the vapor is generated by a drybattery or by a magneto-electric machine driven by the motor itself.There is also the "make and break" spark, to which we need give noattention. The two ends of the wires in the spark plug which is screwedinto the cylinder are separated by a space barely the twentieth part ofan inch, across which the spark leaps, giving out an intensely hotflash.
You understand, of course, that I have given simply the principle andmethod of operation of the engine belonging to a motor boat. There aremany parts that must operate smoothly and with the minimum of friction.Lubricating oil is as essential as gasoline; the ignition battery mustbe kept dry; you must know how to operate the reversing lever, to shutoff, to start and to hold the desired speed. Except when racing or undersome pressing necessity, the swiftest progress is rarely attained, forit is trying to all parts of the engine and consumes a good deal offuel, which cannot be bought for a trifling price.
You would be confused by any attempt on my part to give a technicaldescription of all the motor appliances, nor is there need to do so. Ifyou have just bought a motor boat, you will be taught how to control andmanage it by a practical instructor, and such instruction is better thanpages of directions. To show the truth of what I have just said, I willquote a single paragraph from the description of the boat concerningwhich I shall have a good deal to say in the course of my story.
"The keel is of white oak, with specially bent elm frames. Planking ofselected Laguna mahogany, finished thickness one-half inch, in narrowstrakes and uniform seams, secured to frames by copper boat nails,riveted over copper washers, all fastenings being of bronze or copper towithstand salt water. Seams of hull caulked with special cotton payedand puttied. Outside of mahogany planking, finished in natural wood withspar varnish. Watertight bulkheads fore and aft which assist in floatingthe launch in case of accident. Decks and interior woodwork finished inselected Laguna mahogany. Steam bent quartered oak or mahogany coamingextending around cockpit."
Alvin Landon's launch was thirty-five feet long, with six-cylinder,sixty-horse power motor and a guaranteed speed of twenty-four miles anhour. The motor was placed under the forward deck, where it was fullyprotected by a hinged metal deck. To become somewhat technical again letme proceed:
All the valves were placed on the same side, the camshaft (operatingthe valves) as well as the pump shaft being mounted on ball bearings.The crankcase was of tough aluminum alloy, and lubrication was wellprovided for, being kept at a constant level in the crankcase by ageared oil pump. A gear-driven pump circulated the necessary coolingwater for the cylinders, which passed out through the copper exhaustpipe at the stern. Only one operating lever was employed and that wasplaced directly at the helmsman's left hand. The gasoline tank containedfifty gallons and was under the after deck with a pan below it forsafety's sake, draining overboard. The propeller wheel and shaft were ofbronze.
Alvin's motor boat, thus partially described, included the necessarydeck hardware, "such as brass chocks and cleats, flag pole sockets andflag poles, ventilators to engine compartment, rubber matting for floor,cushions and upholstered backs for seats, three sailing lights, oars,rowlocks and sockets, compressed air whistle with tank, two pairs ofcork fenders, bell, foghorn, boat hook and portable bilge pump, sixlife preservers (as required by the U. S. Government), a twenty-poundfolding anchor and a hundred feet of strong manila rope."
We must not forget the glass wind-shield. Passengers and crew werealways guarded against flying spray and sweep of wind and rain. Nothingthat forethought could provide for the safety and comfort of all wasforgotten.
Suppose young Captain Landon stepped on board the _Deerfoot_ with theintention of starting out on a cruise. He would first turn on the switchwhich controls the electric current for the jump spark, open the valvethat allows the gasoline to flow from the tank into the carburettor,swing around the fly-wheel and then assume charge of the lever andsteering gear. But lo! the engine refuses to respond. There is nomotion. What is the cause?
There may be a dozen of them. In the first place, the battery may beworn out; there may be a lack of compression due to leaky valves;perhaps, after all, he forgot to place the switch key in position; thespark plugs may be fouled or cracked, the gasoline shut off, the gasmixture imperfect, no gasoline in the tank, water in the cylinder causedby a leak from the water jacket, or water in the gasoline.
It may be that when the launch has covered a good many miles the enginesuddenly stops. The cause may be faulty ignition, because of adisconnected wire or a loose terminal, exhaustion of the gasoline, orderangement of the magneto, or poor carburettor adjustment.
But I have said enough to give you an idea of what the expert handler ofa motor boat must understand. It may seem almost a hopeless task, but,as I stated at the beginning of this chapter, patience and applicationwill enable you to overcome all difficulties and make the handling ofthe craft an unalloyed pleasure.