Chapter V: Part I: I (3)

It was found necessary to brace the ribs in order to keep them in line. Thin pieces of lath were tacked on the tops to hold the ribs the proper distance apart, and longer and stronger strips of wood were used for bracing the boat sideways. These were nailed to the joints in the ceiling or high up on the walls of the boat house.

MAKING A MOTOR LAUNCH

"All the Nails Required for the Boat Were of Copper, Because That
Metal is Less Likely to Corrode Than Iron or Steel"
]

At noon the boys had the skeleton of the boat well advanced, and to one standing in front of the bow, it presented an appearance like the sketch shown at Fig. 25.

The launch might be called "carvel ribbon built," or nearly so, and it would have a displacement of 14 or 15 hundred-weight when fairly loaded. This weight would bring her down to the third W. L., as shown in the end sketch. To load her to the fourth W. L., would give her a load far beyond these figures. The sections had to be closely spaced, and the ribbons or slats let into the temporary section moulds before the outside boarding could be put on, the edges of the boarding being clinch fastened, as shown in the ribbon carvel, Fig. 26. Other styles of sheathing boats, as shown, are often used, but the _Caroline_ was "ribbon carvel."

It is usual to lay off the sheer profile on a suitable floor, and line in the rebate line, scarf of stem, deadwoods, fork timbers, etc., making thin moulds of each member to be lined off, sawn, and bolted together. The section moulds, from which the boat derives its shape, are also laid off, and the planking, 3/8-in. thick, deducted when making them.

The stem, of crooked oak, was 2-1/4 in. thick by about 3 in., shaped as shown in Fig. 24. The fore deadwood was 2-1/2 in. thick, moulded about 3 in., and through-bolted to the stem and keel with 3/8-in. copper bolts; and the stern-post, 3-1/2 in. thick, was wrought to shape, as shown. The centre line of the shaft, as shown, is subject to alteration, since different makes of motors have different sizes of propellers and flywheels. The fork timbers were let into the stern-post, and carried the transom, wrought out of a flitch of elm 3-1/2 in. thick. The planking, of 3/8-in. cedar, was closely jointed and varnished, and secured to the ribbons. The timbers were of rock elm, 7/8 in. by 1/2 in., steamed and bent or sawn to shape, and through-fastened at the top and bottom edges of the planking. These were spaced on 7-1/2-in. centres, with two clinch nails into the ribbons between them. Three or four solid floorings should be worked into the motor space; fitting of the motor bed thwartships gives great support to the boat.

The thwarts were of oak, 8 in. wide and 1 in. thick, with the side seats, 7/8 in. thick, supported by turned legs of oak. The decks at each end should be of 1/2-in. oak or cherry reeded into 3 in. widths, and filled with marine glue. The covering board, 2-1/2 in. wide, with a nosing worked on the edges, and 1/2 in. thick, was carried by a clamp or binding stake, 2-1/2 in. by 5/8 in., through-fastened at every timber. The knees were of oak, 1 in. thick, about 10 in. on the foot by about 3 in. at the head, and through-fastened. A breast hook 2 in. thick should be fitted. The floor boards may be of 3/4-in. spruce, elm, or ash grating, as preferred. The centre of the motor was at No. 6 section, as indicated, the gasolene being stored in a strong tank under the forward deck, just high enough to feed by gravitation. After being cleaned off and sandpapered, a coat of good shellac varnish, may be followed, if desired, by three coats of best yacht varnish. The spacing of the sections was: No. 1, from face to stem, 1 foot 2 in.; No. 2, from No. 1, is 1 ft. 2 in., the other sections to No. 11 each 1 ft. 6 in.; No. 12 was 1 ft. 1 in. from No. 11 (see Fig. 25). The water-lines were 5 in. apart, and the buttock-lines, A and B, 1 ft. and 1 ft. 9 in. respectively from the middle line.

The boys followed these directions, and with the help of the following table, managed to get the boat ready to varnish and finish up. The following table, which refers more particularly to the section shown in Fig. 25, shows the sheer lines, counting from L W L (low water line). While all the work and calculations regarding the plan had been already done, Mr. Gregg, who had watched the work's progress for a week, thought they should know the principles on which the craft was being built, and therefore advised them to examine the illustration and table, so that they would have some knowledge of the science required to build a boat intelligently. Fred and George did this, and were helped along by Walter, who seemed to have mastered the subject pretty thoroughly.

TABLE OF OFFSETS

===============+=========+=========+=========+=========+=========
| |
| _Stem_ | _Section Numbers_
---------------+---------+---------+---------+---------+---------
| | 1 | 2 | 3 | 4
---------------+---------+---------+---------+---------+---------
|_ft. in._|_ft. in._|_ft. in._|_ft. in._|_ft. in._
| | | | |
Sheer heights | | | | |
above L.W.L. | 1 7 | 1 6 | 1 5 | 1 4-1/8| 1 3-1/4
| | | | |
L.W.L. to | | | | |
rebate line | | 7 | 8-3/4| 9 | 9-1/4
| | | | |
Half-breadths | | | | |
at gunwale | | 8-1/4| 1 3-1/8| 1 9-1/2| 2 1-1/8
| | | | |
Half-breadths | | | | |
at 4 W.L. | | 6-7/8| 1 1-1/2| 1 8 | 2 0-1/2
| | | | |
Half-breadths | | | | |
at 3 W.L. | | 5-7/8| 11-5/8| 1 6-3/8| 1 11
| | | | |
Half-breadths | | | | |
at L.W.L. | | 4-3/8| 9-3/8| 1 3-5/8| 1 8-3/4
| | | | |
Half-breadths | | | | |
at 1 W.L. | | 2-1/2| 5-3/4| 10-1/2| 1 3
| | | | |
Buttock A | | | | |
from L.W.L. | | | 5-1/2| 4-1/8| 6-3/8
| | | | |
Buttock B | | | | |
from L.W.L. | | | | | 3/8
---------------+---------+---------+---------+---------+---------

===============+=========+=========+=========+=========+=========
|
| _Section Numbers_
---------------+---------+---------+---------+---------+---------
| 5 | 6 | 7 | 8 | 9
---------------+---------+---------+---------+---------+---------
|_ft. in._|_ft. in._|_ft. in._|_ft. in._|_ft. in._
| | | | |
Sheer heights | | | | |
above L.W.L. | 1 2-3/4| 1 2-1/4| 1 2-1/8| 1 2-1/8| 1 2-1/2
| | | | |
L.W.L. to | | | | |
rebate line | 9-1/2| 9-7/8| 10 | 10-1/2| 10-3/4
| | | | |
Half-breadths | | | | |
at gunwale | 2 3-1/2| 2 4-1/2| 2 4-3/8| 2 3-5/8| 2 2-1/8
| | | | |
Half-breadths | | | | |
at 4 W.L. | 2 2-7/8| 2 4 | 2 3-7/8| 2 3-1/4| 2 1-3/4
| | | | |
Half-breadths | | | | |
at 3 W.L. | 2 2 | 2 3-1/4| 2 3-1/4| 2 2-1/2| 2 0-3/4
| | | | |
Half-breadths | | | | |
at L.W.L. | 2 0 | 2 1-1/2| 2 1-1/2| 2 0-5/8| 1 9-1/2
| | | | |
Half-breadths | | | | |
at 1 W.L. | 1 6-3/4| 1 8-1/2| 1 8-1/2| 1 6-1/2| 1 0-7/8
| | | | |
Buttock A | | | | |
from L.W.L. | 7-5/8| 8 | 8 | 7-1/2| 5-1/4
| | | | |
Buttock B | | | | |
from L.W.L. | 3-3/8| 4-3/4| 4-3/4| 3-1/2| 3/8
---------------+---------+---------+---------+---------+---------

===============+=========+=========+=========+=========
| | _End of_
| _Section Numbers_ |_Transome_
---------------+---------+---------+---------+---------
| 10 | 11 | 2 |
---------------+---------+---------+---------+---------
|_ft. in._|_ft. in._|_ft. in._|_ft. in._
| | | |
Sheer heights | | | |
above L.W.L. | 1 3 | 1 3-5/8| 1 4-1/4| 1 6
| | | |
L.W.L. to | | | |
rebate line | 11 | | |
| | | |
Half-breadths | | | |
at gunwale | 2 0 | 1 9-1/2| 1 6-3/4|
| | | |
Half-breadths | | | |
at 4 W.L. | 1 11-3/8| 1 7-1/4| |
| | | |
Half-breadths | | | |
at 3 W.L. | 1 9-1/4| 8-1/2| |
| | | |
Half-breadths | | | |
at L.W.L. | 1 2-1/8| | |
| | | |
Half-breadths | | | |
at 1 W.L. | 5-3/4| | |
| | | |
Buttock A | | | |
from L.W.L. | 1 | 6 | 11-3/4|
| | | |
Buttock B | | | |
from L.W.L. | | | |
---------------+---------+---------+---------+---------

It was necessary, before installing the motor, that a foundation should be laid for it, so varnishing and the final finish were left over until the engine and propeller should be put in and tried.

The engine was brought to the boat house from Newark, and the expert, engaged by Mr. Gregg some time previous, came along with it, bringing such tools as he might want. He examined the bed for the engine, and saw that all was properly fastened and in good condition to place the engine and the propeller shaft. Mr. Watts (the machinist) laid off a line for the propeller shaft and with a long auger bored a hole from the engine bed through to the stern-post, large enough to permit the shaft of the propeller to revolve in it easily. A bearing, or "box," was adjusted to the stern-post in which the shaft ran, and the "box" was made water-tight to prevent any inflow. The propeller was made of bronze, had been nicely fitted to the shaft before it came, and had a set screw in its hub to hold it firmly on the shaft. The diameter of the propeller wheel measured 15 inches and it had two blades. The shaft and wheel being properly adjusted, the next thing was to place the engine, which weighed about 200 lbs. The blocks and tackle used in taking down the old barn were rigged up to the ceiling by cutting a hole through the floor, laying a short timber across the joists, hitching a rope around the timber, and letting a loop hang down through the hole made in the floor. The hook of the upper block was attached to the loop, a sling was fastened to the engine, the whole was hoisted by Nick with the greatest ease, and the machine dropped on its bed. As it did not lie quite level, it was raised again and held suspended until the bed was trued up, when it was permanently lowered into place and fastened down. Two views of the engine are shown in Figs. 27 and 28.

In "shop talk," the engine may be described as follows--Bore of cylinder 4-1/2 in. Stroke 4-1/2 in. Crank shaft 1-3/8 in. Revolutions per minute from 60 to 750. Propeller shaft one inch. About 15 or 16 horse-power. A float-feed carburetor, Fig. 29, was installed at the same time. This carburetor is an excellent one. It insures a regular supply of gasolene and air, in proper proportion, and prevents trouble when the motor is in use. The float guarantees an even level of gasolene in the float chamber at all times. The proper balance of the cork float closes the supply of gasolene automatically when it reaches the proper level. This prevents waste of fuel, every drop being thoroughly vaporized and mixed with the proper amount of air. The spraying nozzle is higher than the gasolene in the float chamber, and prevents the gasolene from getting into the engine, unless it is running. The throttle valve on the carburetor gives the operator the power to change instantly the speed, without changing the timer, and affords him absolute control of the engine.

When all the machinery was in place, and the propeller attached, Mr. Watts told the boys that he would finish up the work of installing the next day, and would then run the engine "dry" for an hour or two, to get everything working nicely before declaring the _Caroline_ ready for sea.

It was just two weeks from the day the stuff arrived when the engine was finally installed.

"That's pretty quick work," declared Walter, "and if the boat were varnished, we could have her in the water in a couple of days."

In the evening, as all the Greggs were seated on the veranda, Fred tried to explain to his father the installation of the engine, but he failed to make himself quite clear.

Mr. Gregg said to him: "You seem to have grasped the theory of the matter, but I see you don't understand some important points, so I think a few suggestions may be of use to you. I will not confine myself to marine motors altogether, as gasolene engines are used for many purposes, more and more every day. With regard to installing an engine in a boat, the first question is the bed, as you have seen in your own case, where your foundation is made good and solid.

"Small engines may be supported upon a single cross piece at each end of the bed, but this method should be employed only for the smallest sizes.

"The heaviest, and in most cases the hardest, pipe to fit up is the exhaust. It runs from the exhaust nozzle on the engine to the muffler and thence outboard.

"The muffler is commonly placed in the stern with the outlet directly outboard. It may, however, be in any convenient position, like under the seats in the standing room, and the piping led outboard. In any case, the piping for the exhaust should be as direct and as free from sharp bends as possible.

"When the motor is near the middle of the boat, a good practice is to lead the exhaust pipe out through the bottom, and along it to a point near the stern, where it again enters the boat and connects with the muffler. The outlet from the muffler then leads directly outboard as before. This method, especially on a large cabin boat, avoids much loss of space and the disagreeable heat of the exhaust pipe. The surrounding water quickly cools the exhaust, reduces the pressure and makes the exhaust almost noiseless.

"The particular function of the muffler is to afford a comparatively large space into which the exhaust may pass and expand, greatly reducing the pressure. The gas, under the reduced pressure, then passes out with little disturbance. The muffler need be of no particular shape, as long as the volume is sufficient. It is usually made of cast iron in the smaller sizes and of sheet iron in the larger. In many cases a long piece of rather large pipe will answer the same purpose.

"The muffler may be dispensed with and much space saved by carrying the exhaust directly through the bottom of the boat and exhausting under water. Although this is a very convenient and many times satisfactory way, great care must be used or poor results will be obtained. When the exhaust leads directly out, a certain amount of pressure is used in displacing the water. This pressure is, of course, supplied by the piston and is a 'back pressure,' retarding the piston and decreasing its power.

"A small expansion chamber or muffler should be provided between the engine and the outlet, in order to break up the violent pulsations and make the flow fairly constant. Some form of shield should be fitted over the outer end of the exhaust pipe to guide the stream of the exhaust aft and prevent the water being forced into it by the movement of the boat. Several forms of these are on the market in the shape of brass castings which bolt on to the outside of the hull and have a thread on the inside to take the exhaust pipe.

"When the under water exhaust is fitted, a pet cock should be put in the exhaust pipe near the engine. This is opened when the engine is stopped, thus preventing the water from being drawn up into the cylinders by the vacuum caused by the cooling of the gases in the pipe and cylinders.

"The under water exhaust is a very neat and simple method, when correctly installed, as all noise and heat from the exhaust pipe are avoided. The exhaust may be considerably cooled and the noise reduced by dispersion.

"With regard to stationary engines, used for domestic or other purposes, any old place is considered good enough to put them in. Now, this is one of the biggest and most expensive mistakes one can make, for as soon as some small screw gets loose in the far corner, the engine, salesman and manufacturer are unjustly blamed, simply because the present owner has not left enough room to make the small adjustments necessary in every engine and piece of machinery. Therefore, it pays always to install the engine in a light, dry place, easy of access and with sufficient space all round to enable all parts to be reached and to give plenty of room for turning the fly wheels in starting. Whenever possible, place the engine on the ground floor. On an upper floor, the necessary provision should be made to avoid vibration; if installed in the basement, place it in the best light.

"Without a good foundation, an engine may be expected to give more or less trouble from vibration, since it is subjected to forces, suddenly and repeatedly exerted, which produce violent reactions. Care should be taken to excavate down to good soil and to line the bottom with a substantial thickness of concrete in order to form a single mass of artificial stone. The foundations may then be built up of either concrete, brick, or stone. Anchor plates should be extended to the bottom of the masonry and fastened so as to prevent turning while the nuts are being screwed up. Place gas pipes or tubes with an inside diameter twice the diameter of the bolts around them, while the foundation is being built; this allows the bolts to be adjusted, and any variations between the tubes may be filled with thin cement after the engine is set.

"The top of the foundation should be finished perfectly flat and level with a dressing of cement, and after this is thoroughly dry the engine may be placed in position. When bolting down the engine, it is better to draw each bolt down a little at a time until all are tight and thus avoid straining the engine crank. After the nuts are drawn tight, if the crank turns unreasonably hard without loosening the main bearing caps, it may indicate an uneven foundation, which is a strain in the engine bed casting.

"When setting up large engines, for farm or other purposes, especial care must be taken to avoid straining the bed castings. Foundations hung from an upper floor, or built upon it, should be placed as close to the wall as possible. For the smaller sizes of engines it is a good plan to lay wooden beams on top of the foundations and then to place the engine on top of them so that when the frame is bolted down it beds itself into the timber. The timber cap often saves an annoying vibration when it can be overcome in no other way.

"All the connections should be as short and as free from turns as possible, and no mistake can be made by having plenty of unions, so as to disconnect with ease. The gasolene tank should be set as near the engine as is convenient, with the top of the tank, preferably, not more than a foot or two below the base of the engine. In cases where the gasolene tank must be set from forty to fifty feet away, it is necessary to place a check valve in the suction pipe near the tank. Both suction and overflow pipes must have a gradual rise all the way from the tank to the pump and should be as straight as possible to avoid the air traps, which prevent a steady flow of gasolene. It is most essential to clean thoroughly all pipes and fittings before they are put together, by hammering lightly to loosen any scale and washing out with gasolene, as solid matter of this nature may be responsible for some of the simple, but hard-to-get-at troubles common to gasolene engines.

"Shellac is best for joints in gasolene piping, but when this cannot be obtained common laundry soap will answer the purpose just about as well. Remember, also, that gasolene is a rubber solvent, and should never be applied to joints where rubber is used. In some cases it will be found advisable to use gravity feed instead of a pump, except in the case of the tank, which must be so arranged that its lowest point is slightly above the generator valve.

"The exhaust pipe must be of full size, free from turns and short as possible, since the shorter it is the more economically the engine will run. It will be found advisable to place the muffler and exhaust piping away from combustible material, and never to turn the exhaust into any chimney or flue.

"There are two general methods of supplying the water, the first being that of the cooling tank commonly used with small engines. For convenience in piping, the tank should be slightly elevated, and both pipes, having as few bends as possible, should slope from the tank to the engine, a valve being placed in the bottom pipe near the tank. By using a circulating pump, fitted to the engine or shaft, water may be used from an underground cistern or tank.

"The other method is to use a continuous cooling stream from water-works or other source. When city water is used, it is a good plan to have a break and funnel inserted in the drain pipe so that the current of water flowing through the cylinder jacket may be seen. For making joints in water pipes, either thick lead or graphite may be used with almost equal success. It may be well to place particular emphasis on the fact that it will pay to get into the habit of always shutting off the water at the tank and draining the cylinder every time the engine is stopped--not necessary in summer, but absolutely essential in winter--as a fair percentage of gasolene users know to their cost.

"The greatest care must be employed in using and handling gasolene, as it is dangerous and highly explosive. It has been known to explode when 20 or 30 feet from light, the vapours having reached the fire in the way of a gas, igniting and firing the liquid. And, now, right here, let me impress on you this warning; never handle gasolene near a fire or light under any circumstances, and be very careful with it under all conditions.

"Fortunately, there are few accidents resulting from gasolene, when we consider the large amount used since it has become almost a universal fuel for engines, and it is also used largely for domestic heating and lighting.

"It is a product of petroleum, of which in its crude form about 76 per cent. is turned into kerosene, 11 per cent. into gasolene, 3 per cent. into lubricating oils, and the balance into vaselines, paraffine, coke and so forth.

"Different petroleums produce different proportions of the various products, some of them being considerably richer in gasolene than 11 per cent.

"Gasolene is usually designated according to its specific gravity by an arbitrary measure, known as Baume's hydrometer scale. This designation is in degrees, the most common gasolene ranging between 65 degrees and 85 degrees, and the average being 70 degrees, the usual density used in engines.

"You will find it somewhat difficult at first to start up your engine when you wish to, so I will give you a few hints to show how this difficulty may often be overcome.

"There is always a reason why a gas engine refuses to obey the behest of its driver.

"In the first place, see that the compression is right and the admission valve so tight that it will admit only enough of the mixture (gasolene and air) to make a charge that will take fire from the sparker and move the piston forward. Next see that the sparker is clean, that it will make a bright spark at white heat when the contact is broken, and at the right time. 'In time' means to go if everything else is right, and 'out of time' means not to go even when everything else is right.

"The valve of the engine must be kept well ground down with emery and oil so as to preclude the possibility of a leak, as one would very seriously weaken the power of the engine even after it had started. The spark must be made when the connecting rod of the engine is on the 'up stroke,' with the crank shaft about three inches below the horizontal line of the centre of the index, and herein lies the whole secret of the greatest efficiency from the least amount of gasolene. As there is an interval of time after the spark is made until it ignites the charge, it is very evident that the movement of the machinery continues and the moment of ignition should take place when the compression is greatest. This will be when the piston is on its farthest 'in stroke,' _i. e._, in perfect line with the centre of the cylinder. But if the charge be ignited at this point the engine will not develop the greatest power, as the interval spoken of will elapse and the piston will have started on its 'out stroke', thereby not getting its full force of the expansive gases liberated by combustion of the air and gasolene.

"So you will readily see that you must allow for the interval spoken of, if you would get full returns for the energy used in propelling the motor. I have tried to make this plain, and I hope my efforts will help you out with your engine, either in starting or developing the power at which it is rated."

It was not yet late, so the boys took down from the book shelf a code of yacht flag signals, and found the following:

"There are no hard and fast rules regarding shapes and colours of yacht bunting, but the following are generally accepted by the prominent clubs in the United States and in foreign countries.

1. The "pennant" (a triangular shaped flag) is used for the club burgee.

2. The "shallow tail" is adopted for the private signal.

3. The rectangular flag is chiefly used for a flag officer's signal.

4. The shape, consequently, at once denotes whether a flag is that of a club, a flag officer, or a member.

5. The majority of flag officers' signals are coloured: Blue for commodore, red for vice-commodore, and white for rear-commodore.

6. The international code of signals enables yachts to communicate with each other, and is also used for dressing ship.

The ensign should be flown from the peak of the main-sail on a sailing yacht, when under way, and from a stern flag pole when moored.

On a yawl, it should be hoisted at the mizzen truck.

On a steamer, launch, or dinghy, it should be flown from a stern flag pole, when under way or at anchor.

_Club Burgee._--The burgee should measure in length about one-half inch for each foot of height of truck from the water; width to be two-thirds of the length. Private signals may be smaller.

The burgee should be flown from the mast-head or truck of a cutter, sloop, or cat-rigged yacht, the main truck of a yawl, the fore truck of a schooner and steamer, and from the bow pole of a launch or dinghy.

Flag officers' and private signals should be flown from the truck of a cutter, sloop, or cat-rigged yacht, the main truck of a schooner, yawl, or steamer, and from the bow pole of a launch or dinghy.

The following flags are not considered as colours:

_Night Pennant_ (_blue_).--Is hoisted at the main truck from sundown to 8 A. M.; also occasionally used as a tell-tale when racing or sailing.

_Owner's Absent Flag_ (_blue rectangular_).--Is flown from the main starboard spreader when yacht is at anchor only. It denotes owner is not on board, but should never be flown when under way.

_Owner's Meal Flag_ (_white rectangular_).--Is flown from the main starboard spreader, and denotes the owner is at meals--boarding a yacht when this flag is flying is considered bad form.

_Crew Meal Flag_ (_red triangular_).--Is flown from the foreport spreader on schooners and main-port spreader on single-masted yachts. This denotes that the crew is at meals.

_The Ensign._--Displayed on a vessel indicates distress and want of assistance.

_Flag "B,"_ of the International Code of Signals, is used for a protest flag, and is conspicuously displayed in the rigging of a yacht protesting during a race.

A yacht, on withdrawing from any race, should at once lower its racing colours, and allow yachts still competing the right of way.

This code was studied by the boys until both of them thoroughly understood its full meaning, and George became so enthusiastic over it that he exclaimed: "Fred, I am going to be an admiral of the navy!"

V

A TALK ABOUT ENGINES

Mr. Watts was early at the Gregg residence next day, and busied himself preparing the engine to start up. A big tub was taken to the boat house filled with water by a hose attached to the suction pipe, and dropped into the water. This was a mystery to George, who inquired about the use of the water and the other attachments. It was explained to him, that outside the cylinder there was a hollow space, called the "water jacket," extending over the top of the cylinder, and this had to be kept full of cold water by continual circulation. It was pumped in by the engine and forced out by the same means, a simple contrivance being arranged for the purpose. This circulation of water is necessary to keep the inside of the cylinder cool, otherwise the walls would soon become red hot, on account of the rapid explosions of gas and air employed in the cylinder to keep the piston moving to and fro.

George seemed to grasp the idea thoroughly. Mr. Watts also explained the use of the carburetor, the spark coil, the battery, and the method of contact to produce a spark at the proper moment. After some screwing of bolts, adjusting the piston, and trying the valves, the tank in the carburetor was supplied with gasolene and Mr. Watts tried the engine for a few revolutions, as gently as it could be done. It was a little stiff at first, some of the connections fitting too tight, and the piston, being new and harsh, did not work smoothly. By the judicious use of good lubricating oil and a few turns of some of the nuts on the bolts, a little more freedom was given to the machine and the starting was easy and smooth. George and Jessie were delighted with the rapid movement of the machine, the buzz of the propeller, and particularly interested in the movement of the water in the tub.

Mr. Watts allowed the engine to run quite a little while, and arranged the exhaust so as to beat regularly and to "pop! pop!" as little as possible. He then called Fred into the boat and taught him how to run the machine, arrange the contact breaker, and regulate the feeding of fuel. The engine was stopped to cool and to be examined again by Mr. Watts, who pronounced it all right. Mr. Gregg, who had arrived just before the engine was stopped, examined all its parts and watched it work for a minute or so.

Fred arranged his pots and brushes, and he and George went to work varnishing, so that before sunset the _Caroline_ looked quite smart and trim. The boys were very careful in applying the varnish to put it on light and thin so as not to let the coats lap over one another as they went along. They finished each "streak" from end to end, before starting on the next, and following this method they obtained a nice, even surface. The varnish did not look "blotchy" or patched, as it would have done had the ends of the varnish lapped. To avoid "lapping" is one of the most essential operations in varnishing, when a nice piece of work is desired.

FINISHING THE MOTOR LAUNCH

"To Avoid 'Lapping' is One of the Most Essential Operations in
Varnishing"
]

It was decided to give the little craft two more coats of shellac varnish before launching her, and the following spring to give her a good coat of marine varnish. Mr. Gregg thought that in another week, say the following Wednesday, the _Caroline_ might be launched with safety, as the varnish would get dry and hard, and the inside paint would also be hard enough. Jessie and the boys were given permission to invite a few friends each to the boat launching, and were promised suitable refreshments to be served on the new grounds, if the weather was favourable. Fred asked his father if he could not build up some temporary picnic tables and seats for the occasion, as there was plenty of material still left unused from the old barn stuff. Permission was granted, and after counting up the number that would probably be present, it was found that three tables, each about fifteen feet long, with necessary seats, would give ample room for the accommodation of the proposed guests, with a good allowance for overflow.

Just then the whistle of a small steam tug, that often plied on the river, gave warning of her approach; and all went down to the river edge to watch her pass and to see what effect her "wash" would have on the new pier and the boat house "skid" or slides. She came up stream rapidly against the tide--which was on the ebb--and there was a considerable "wash" from her wheel, but it struck the bank, the pier, and the "skids" without doing the least harm or giving any evidence that trouble would result from any reasonable wash. The little steamer's exhaust, as she passed, made quite a noise and Jessie was somewhat puzzled at this, as the exhaust from the gas engine of the _Caroline_ only made a plaintive puff in comparison. Her father promised to explain the reason after tea.

Returning to the boat house, George suggested that the name of the boat be painted on both sides of the bow, in large letters, but Mr. Gregg and Fred, thought it better to have "Caroline" placed on the second streaks of sheathing, in gold, the letters to be not more than two inches over all. This was agreed upon, and a young artist, who was a near neighbour, was suggested as the person to do the work.

After tea, Jessie and the boys followed their father into the den, where Mr. Gregg gave the children a brief history of the steam engine, as far back as known, commencing with the Colipyle, the invention of Hero of Alexandria about 130 B.C. An illustration of this is shown in Fig. 30. It was simply a pot or boiler, partly filled with water, the lid or cover being fastened down tightly. On the top of this was attached a hollow bent tube having a tap fitted to it, which supported and communicated with a hollow metal ball hung on another tube or bearing on the other side in such a manner that the ball could revolve easily. Attached to this hollow ball or sphere were four other hollow tubes, so fastened as to project from the surface two or three inches, and these were bent at their outer end, as shown in the illustration. These tubes were of course attached and bent in a direction at right angles to the axis of rotation. The tap leading to the hollow ball, when turned open, allowed the steam from the boiler to rush into the ball and fill it up. If it was closed entirely, the ball would remain still, but the steam exerting an equal pressure on all points of the inner surface, and finding the openings, escaped through with a rush and noise as it condensed in the air, which it pressed against, causing the ball to revolve in an opposite direction to the outflow of steam. This Hero engine or Colipyle, was doubtless the beginning of steam motors, but during the 2,000 or more years since Hero's toy engine was invented, great strides have been made toward bringing the steam engine to its present efficiency.

"But I do not intend," said Mr. Gregg, "to give a history of the growth and development of the machine, at this time. There are numerous works on the subject, obtainable in any fairly-equipped library."

Steam, as everybody knows, is generated by heat being applied to a closed metal kettle or boiler containing water. This boiler must be strong and properly arranged so as to admit more water--which is usually injected with a force pump--and it must have an outlet for the release of the steam to the cylinder of the engine. Generally, there is a small dome on the top of the boiler, called the "steam dome," and to this the steam outflow pipe is attached. The actual use of this dome is to hold a volume of steam that will remain unmixed with water, as it is placed considerably above water level. On the top of the dome there is an automatic arrangement called a "safety valve," so that when there is too much pressure of steam in the boiler, it will open and allow the over-pressure to escape, and thus prevent the boiler from exploding or being over strained. This valve is controlled by a simple device, somewhat similar to a steelyard. A movable weight is arranged to slide on a long arm which is loosely fixed to the valve flange by a bolt and nut, and extends some distance past the seat of the valve. The arm or lever has an iron pin attached to it directly over the valve seat, which holds down the valve and keeps the steam from escaping. The movable weight on the arm is adjusted so as to regulate the pressure on the valve. When there is too great a pressure, the valve forces up the lever, and at the same time opens a passage for the extra pressure of steam to escape. There are several other contrivances for relieving the boiler of over stress, but the one described, or rather the principle on which it is built, is most in use on this country. There are many kinds of boilers, or steam generators, but the best, and very likely the strongest, are those employed on our first-class railway locomotives. These are frequently under a pressure of 200 or more pounds to the square inch, which seems an enormous load for a hollow shell to carry, yet, so near perfection are they, we rarely hear of a locomotive boiler explosion. As there are many kinds of boilers, so also are there many kinds of steam engines, but all of these latter, with very few exceptions, have a cylinder and piston for converting the force of the steam into useful and effective motion. The manner of using this force and keeping it under proper control is somewhat complex and difficult to describe briefly, without elaborate diagrams, but Mr. Gregg explained, in his own way, how the great force was converted into motion. On the blackboard he drew a rough diagram of a cylinder and valve or steam-chest, with piston and slide-valve, about as shown in Fig. 31, which gives a longitudinal section of the whole arrangement. Here we see near each end, the opening of a double conduit aa, made in the thickness of the side; these are the openings by which the steam comes alternately to work on one end, then on the other, of the piston. These are called the steam-ports. These two open outward on a well-polished surface, and between the two a third opening, E, is seen, which serves to let the steam escape when it has done its work, and is called for that reason the exhaust port. C is the pipe by which the steam gains access to the open air or to the condenser, where it parts with its elastic force.

Here is shown by what contrivance the distribution is effected, consisting, as it does, of two partial operations; the admission of the steam and its escape, which must be repeated twice to obtain a complete phase of the to-and-fro movement of the slide-valve. There are various methods employed according to different engines--but the first described is the one represented by the illustration.

In the valve chest, BB, is seen a prismatic box, open on one side, called the slide-valve, and this is applied by its open face to the well-polished plane on which, as mentioned before, the three ports open. The space BB, is called the valve or steam chest. The steam coming from the boiler by the pipe C spreads out freely in it, but the inside of the slide-valve, on the contrary, is always closed to the entering steam, though constantly in communication with the escape pipe and also with first one then the other of the entrances to the cylinder. Lastly, the movement of the slide-valve is produced by the engine itself, aided by a rod and an eccentric fixed to the shaft of the fly-wheel.

By following the successive and alternating motions of the slide-valve, as represented in Fig. 32, we can easily comprehend the different phases of the distribution of the steam.

This is the machinery for the distribution of steam generally. There are other engines, such as rotary and oscillating, that are supplied by other contrivances, but most of these have fallen, or are fast falling into disuse, as they are not so satisfactory as the ordinary slide-valve. It will be seen upon examination of the sketch, shown in Fig. 32, how the steam enters and leaves the cylinder and the position of the piston under the various positions of the valves. The arrows show the direction of the slide, also the direction of the piston and its position when the slide covers the ports X, or leaves them open, or partly so. The ports for egress or ingress are shown at X, the slide-valve at V, and the cylinder at C. When the piston is near one end of the cylinder, the steam is admitted and forces the piston in the opposite direction, while the valve is so arranged that when the piston starts in that other direction, it begins to open the port at the other end of the cylinder through which the exhausted steam escapes. This makes the noise Jessie asked her father about. There are some engines so devised that the exhaust is made to assist in driving another engine.

Of course, there are many kinds of steam engines, but all are run on the same principle, or nearly so. As you know, steam is generated in boilers by fire being applied to the outside and the water made hot enough to raise steam. A steam engine is said to be externally heated, while gas, oil, and other similar engines are internally heated, because instead of the steam driving the piston, the gas, oil, or other explosive matter is admitted into the clearance or space between the piston and the end of the cylinder, where it is exploded by an electric spark from a battery provided for the purpose, and this is called the "ignition." The explosion causes the gas and air in the cylinder to expand, bringing a great pressure on the piston, forcing it to move toward the other end of the cylinder, and making the whole machine move. One great advantage of employing a gas engine is that no boiler is required, a very important matter, as boilers take up a great deal of space. The coal or wood necessary to keep up steam also takes space that could be used for other purposes, all of which make the use of steam objectionable when it is possible to employ suitable gas engines. Besides, the make-up of a steam engine is of such a character that it is very expensive, while the first cost of gas engines is much lower.

All gas, oil, or other explosive engines are internal heaters, because the heat is generated in the cylinder at each explosion, and this is one of the main features that distinguishes the gas from the steam engine. Of course, there are many attachments and connections to steam and gas engines that would take too long to describe, and in a great measure be unnecessary. A few items may prove both useful and profitable and it is well to know firstly: How to estimate the horse-power of an engine.

When steam engines were first introduced they were largely used to take the place of the horses previously employed for raising water from mines. Naturally people inquired, when buying an engine, what amount of work it would perform as compared with horses. The earliest engine builders found themselves very much at a loss to answer this question so they had to ascertain how much a horse could do.

The most powerful draught horses and the best of any then known were the London brewers' horses. These, it was ascertained, were able to travel at the rate of two and a half miles per hour and work eight hours per day. The duty, in this case, was hoisting a load of 150 pounds out of a mine shaft by means of a cable. When a horse moves two and a half miles per hour, he travels 220 feet in a minute, and, of course, at the speed named, the 150-pound load would be raised vertically that distance. That is equal to 300 pounds lifted 110 feet per minute, or, 3,000 pounds lifted 11 feet or 33,000 pounds lifted one foot high in one minute. That is the standard of horse-power, as we all know. It is much more, however, than the average horse can do, and therefore the builders were confident that the engines would take the place of fully as many horses as the horse-power would indicate that they should.

Of course, 33,000 pounds lifted 1 foot per minute is much more convenient for calculation than 150 pounds lifted 220 feet, and therefore the former rate has been adopted. The amount of work, or number of "foot-pounds," is the same in either case. A foot-pound represents the amount of power required to lift one pound one foot high. To find the number of horse-power in any engine, we multiply the area of the piston by the average pressure per square inch upon it; multiply this result by the distance which the piston travels per minute in feet and the result is the number of foot-pounds per minute which the engine can raise. Divide by 33,000 and the result will be the number of horse-power. The number of feet per minute travelled by the piston is twice the number of strokes per minute multiplied by the length of the stroke. This gives the amount of horse-power sufficiently accurate for all practical purposes.

It necessarily takes time to do work, but the amount of work done has nothing whatever to do with the time taken to do it.

If a man, weighing 150 pounds, walks up the 900 steps leading to the highest attainable level in the Washington Monument, 500 feet high, he does work against gravity equal to 75,000 foot-pounds, irrespective of the time taken in the ascent. Then the work done in a given time, divided by the time, is called the power of activity.

Power is the time rate of doing work. In the English gravitational system, the unit of power is the horse-power (H.P.); it is the rate of doing work equal to 33,000 foot-pounds a minute, or 550 foot-pounds a second.

In the centimetre-gramme-second (C.G.S.) system (in which the unit is 1 gramme moving at the rate of 1 cm. a second), the unit of power is the watt. It equals work done at the rate of one joule (10,000,000 ergs) a second.

One horse-power is equivalent to 746 watts.

A kilowatt (K.W.) is 1,000 watts.

It is therefore nearly 1-1/3 horse-power.

To convert kilowatts into horse-power add one-third; to convert horse-power into kilowatts, subtract one-fourth.

For example, 60 K.W. equals 80 H.P. and 100 H.P. equals 75 K.W.

The expression foot-pound is in general use among English-speaking engineers, and as explained it is the unit of work done by a force of one pound working through a distance of one foot. It is not a fixed standard of measurement, since the weight of a pound is not the same in all heights above sea level, and on this ground it is open to objection. It is the nearest constant, however, we have yet discovered, hence its general adoption.

"Dry steam" is the steam in which no condensation is visible, and it may generally be obtained at a 10-pound pressure per inch, but no exact dividing line of pressure can be defined between dry steam and wet. If care is taken in covering pipes and cylinders, to prevent condensation, a pressure of 10 pounds should make steam as dry as gas, and if the steam pipe is carried through a good, hot fire at some point, the fire will superheat the steam and render it more dry. Wet steam, of course, is steam that can be seen, through having been more or less condensed by contact with air or cold. There can be no steam without heat, but steam does not require as much heat as is generally supposed. Suppose we take one pound of water at 32 degrees Fahrenheit and apply a fixed and known quantity of heat until it boils; we will assume that it takes 20 minutes, and we have supplied the water 180 heat units, which, added to the 32 contained in the water at the start, makes 212 degrees Fahrenheit or heat units, and is the sensible heat of steam at atmospheric pressure. Now let us continue the same quantity of heat per minute until all the water has evaporated into steam, and we will then find that it has taken five and one-third times as long, or 107 minutes to do this work. Consequently we have used five and one-third times 180 or 960 heat units; or, to be exact, 966 heat units. Now the temperature of the steam is the same as the water from which it has evaporated, or 212 degrees Fahrenheit, and this 966 heat units is the latent heat of steam at atmospheric pressure. All steam has a sensible heat corresponding with the temperature of the water it has evaporated from. If you boil water under a pressure of five atmospheres, or 75 pounds pressure, the sensible heat is 306 degrees Fahrenheit, the boiling point at that pressure, but the latent heat has decreased by the same number of heat units that the boiling point increased, so the total is the same in all cases. In the first instance we have 212 degrees minus 32, plus 966, or 1,146; and in the second 306 degrees minus 32, plus 872 or 1,146 heat units. This may be considered a fair description of latent heat.

The most useful quality of steam yet discovered is its power of expansion. It follows what is known as Marriott's Law of Expanding Gases, which means one-half the pressure double the volume. So if we let steam into an engine cylinder, at 80 pounds' pressure, and cut it off at one-fourth stroke, it is at 80 pounds up to the point of cut-off. At one-half stroke, because it has doubled its volume, it is reduced to one-half pressure, or 40 pounds; while at three-fourths stroke the volume has trebled and the pressure has dropped to nearly 27 pounds, and this is why it is economical to run engines that use steam expansively. Steam at 27 pounds' pressure is very much cooler than steam at 80 pounds, and this difference in temperature has been converted into mechanical work by our steam (heat) engine.

There are many other peculiarities about steam and steam engines that a young boy should know, and the information can readily be obtained from books in any good library.