CHAPTER VI
A STEAM LAUNCH
THE steam launch Nancy Lee is an attractive little craft when finished and it is capable of attaining considerable speed. It is really designed after the cruising type of motor-boats. This type of boat is particularly adaptable for simple model-making, owing to the elimination of awkward fittings. The power machinery is of very simple construction and presents no real difficulty.
The following materials are necessary to construct the Nancy Lee:
Large wood block for hull.
Thin white pine for deck, etc.
Sheet-metal tube, rod and wire for the boiler, engine, etc.
Lamp-wick, paint, screws, and brads
Miscellaneous fittings
The actual expense necessary to construct the boat is very small.
Having obtained the block for the hull, you are ready to start work. The hull, when planed on all sides, should be 30 inches long, 61/2 inches wide, and 33/4 inches deep. A center line is drawn down the length of the hull, and five cross-section lines are drawn at right angles to the center line 5 inches apart. On these lines the builder should mark off the greatest lengths of the boat, taking the dimensions from the half-breadth drawing shown in [Fig. 64]. It will be noted that the deck is wider than the L. W. L. forward and narrower than the L. W. L. at the stern. The block should be cut to the widest line on the half-breadth part.
The half-widths in [Fig. 64] are drawn each side of the center line on the block. The block will be cut out to this line and planed up as true as possible. The builder should then project the section lines with a set square on each side of the boat, mark off the profile from the sheer plan, [Fig. 65], and cut the block to this line, afterward planing it up true.
The blocks should now appear as sketched in [Fig. 66]. It is now ready for the shaping of its exterior. A plane, a chisel, and a draw-knife are the only tools necessary to bring the hull to the correct shape. The cardboard templates must be cut, one for each half-section, as shown in the body plan, [Fig. 67]. These templates serve to show the proper outside shape of the hull. The block for the hull must be cut away until each one of these templates fits properly into place. The various stages are indicated in [Figs. 68] and [69].
The interior of the board is gouged out with a gouging chisel, and if the builder desires a uniform result he should make inside templates. In gouging out the interior of the hull the chisel or gouge should be handled very carefully; otherwise it is liable to slip and spoil the entire hull.
The next job is to cut and properly fit the raised portion or forecastle. A piece of wood 11/4 inches thick, 15 inches long, and 61/4 inches wide must be prepared and laid in place on the hull. The shape of the hull is marked off with a pencil and the wood sawed along this line. The inner portion is also cut out, thus making a V-shaped piece which must be glued and screwed in place, as shown in [Fig. 70].
The oval air-vents shown in the drawing can be cut at this time. The hull is neatly finished by cutting in the sheer or curvature of the hull and sandpapering it all over. A cross-beam or support, C, [Fig. 70], is cut and fitted as illustrated. This particular piece supports the fore-deck, and also carries the main-deck, as well as bracing the boat together. This piece should be 3/16 inch thick and cut from solid oak.
The decks can be made of a good quality of white pine. The builder should select clean pieces, free from knots and blemishes. It only requires to be cut to shape and then fixed to the hull with a few brads. The edge should be cleaned up flush with the hull by the aid of a plane. The opening for the cock-pit, shown in the drawing in [Fig. 71], is to be cut in the deck. The coamings and seats are cut to the sizes indicated in the drawings. They are then glued and pinned together. When fitted to the deck the result will be somewhat as shown in [Fig. 71].
The fore-deck is prepared in a similar manner; but, since this is to be removable, two battens must be fitted to the under side to keep it in place. The openings for the hatchways can be cut and the hatch-covers made by cutting another piece of wood 3/16 inch thick to form an edging. A cover piece to go over the small pieces, removed from cutting out the hatch opening, is shown at [Fig. 72] . A coping-saw will be found very useful for this work. The covers are neatly rounded on the edge and nicely finished.
Fig. 73 will give the reader a very good idea of the appearance of the boat at this stage. It will be seen that the sketch shows the deck broken away so as to render the cross-batten visible, which also shows the fair-lead at F, [Fig. 73]. This is cut from two small pieces of 3/16-inch stuff, glued and pinned in place. The forward deck is completed by the addition of cowl-ventilators, cut from hard wood and screwed in place. The flag-mast is made from a short piece of 1/16-inch wire. The details of the mooring-cleats are shown in [Fig. 74]. They are fashioned by using a small screw-eye and soldering a short piece of brass wire through the eye. An oblong metal plate is then cut and a central hole drilled. This plate is soldered to the shank of the screw-eye and the cleat is complete. One of these devices is to be fitted to the fore-deck and two on the main-deck and stern.
The rudder and steering gear will be considered next. [Fig. 75] shows the stern of the boat with the rudder gear mounted in place. It will be noted that the rudder-blade is merely a piece of sheet brass cut to shape and soldered into the rudder-post M, which is slit to accommodate it. The rudder-post is hung in two screw-eyes on the stern of the boat. A small wheel about 1 inch in diameter, with an edge filed in it, is soldered to the top of the rudder-post. A fine cord or string, well stretched and oiled, is attached to the wheel and led through two screw-eyes on the deck. From this it is led through an opening in the coaming to a drum on the steering column, which is turned by another small wheel similar to that used on the rudder-post, but with a round edge. The steering column is merely a piece of 1/8-inch wire, held in place by two small screw-eyes fixed in the coaming and with a tube-brush soldered on to keep the wire in position. The drum is simply a hard-wood bushing driven tightly in place.
The power machinery for the Nancy Lee must be considered at this time. This is really one of the most interesting parts of the construction. The general appearance of the power plant can be seen by referring to [Fig. 77], which is a view of the complete boiler and engine mounted together on the same base. The boiler is shown at A and the safety-valve and filler at L. The base or firebox B protects the burner from stray drafts of air, and also supports the boiler.
The lamp or burner consists of a receptacle C for containing the denatured alcohol. The denatured alcohol is inserted through the filler-tube E, which is kept closed with a cork. The upright tube D is fitted so that air can go into the receptacle containing the alcohol. Three burners are necessary to fire the boiler. These are fitted as shown in F, and they give sufficient heat to produce steam enough to drive the cylinder G. The steam is conducted to the cylinder through the short pipe K. The steam-cylinder has the usual piston and rod, which drives the circular crank H. This crank is mounted on a crankshaft carried on the metal tube M. As will be noticed, the cylinder is of the simple oscillating type mounted on a standard, formed as part of the boiler casing, and stiffened by two angle-plates L.
A heavy flywheel, J, is now fitted to the inside end of the crankshaft. This wheel should be a lead casting, and as heavy as possible. A heavy flywheel contributes much to the operating efficiency of the engine. The propeller-shaft and crank are shown at N in the insert.
The boiler is made from a strong tin can about 13/4 inches in diameter and 41/2 inches long. It is cleaned inside and out, and all the seams are double-soldered. The lid is also soldered on the can. This little boiler, although not elaborately made, will be found capable of standing up under considerable steam-pressure, and so no fear need be had of accidents by explosion.
A little safety-valve and filler-plug suitable for use on the boiler are shown clearly in [Fig. 78]. A piece of sheet tin is cut out to the size and shape illustrated in [Fig. 79] at A. The piece is bent up at the dotted lines and the seams are soldered. Two angle-plates, B, are then cut and fitted and soldered in place. Next a piece of brass tube with a 1/8-inch bore and 1 inch long is cut and soldered in place for the bearing of the crankshaft. A lead flywheel 11/4 inches in diameter and 1/2 inch thick is then mounted firmly on a piece of straight steel wire 13/4 inches long, which acts as a shaft.
The shaft is made to run freely in the crankshaft bearing that was previously soldered in place. The cylinder is shown in section in [Fig. 80]. If the reader will refer back to the construction of the engine described in Chapter 4 he will readily understand the operation and construction of this particular engine.
A little crank must be cut from 1/16-inch brass, and soldered to the crankshaft after fitting a wire crank-pin to the outer edge. This crank-pin should be of such a size that the joint on the end of the piston-rod shown at A, [Fig. 80], turns on it easily. The throw should be only half the stroke of the engine, which is 3/8 of an inch.
The boiler is now fixed in place by bending the lugs B, [Fig. 79], so that they just support the boiler nicely. They are then soldered in place. Next fit the short steam-pipe K between the boiler and the steam block on the cylinder. The builder should take care to keep the steam-pipe well up to the top of the boiler.
The lamp should be built at this time. The container for the denatured alcohol is made from a well soldered tin box of suitable size. It can also be made by cutting a sheet of tin to the size and shape shown in [Fig. 81]. The corner joints are soldered and then a tin lid is soldered in place. The builder should not forget to make the filler-tube E and air-tube D, as shown in [Fig. 77], before soldering the top piece in place. The burners should be made as high as the container, and these should be made from little pieces of tin bent to shape and soldered on to a bottom pipe, as shown in [Fig. 77]. The builder should also remember to cut the holes through this pipe so that the alcohol can get into the burner-tubes, and also to solder the open end of the bottom or feed tube. Before the wicks are put into the lamps, the container should be tested by filling it with alcohol to see that it is perfectly tight at all joints. If it is not the container should be gone over again with solder to assure its being leak-proof.
Before operating the engine with steam, it can be tested with a small bicycle pump through the opening for the safety-valve. The engine should turn over briskly at every stroke of the pump, providing it does not come to rest at "dead center." If it does come to rest at "dead center," where no air can enter the piston, the crankshaft should be given a little twist and the engine will then start. Before steam is applied it will be well to experiment until the engine runs with the air-pump.
Having made the engine run smoothly with air, steam can be generated in the boiler. The wicks should not be placed too tightly in the burners. After they are in place the container may be filled with denatured alcohol, and the burners lighted and placed under the boiler. In a very few minutes steam will be up. At the first indication of pressure in the boiler the engine should be given a twist with the fingers until it starts and goes of its own accord. The constructor should remember to keep his engine well lubricated.
The propeller-shaft is merely a piece of steel wire, perfectly straight and fitted with a crank A, [Fig. 82]. This crank is similar to the one fitted to the engine, but with a small slot cut out for the crank-pin to fit into. This is done so that, as the crank-pin on the engine turns around, it also turns a slotted crank on the propeller-shaft.
A short piece of tube, C, is now fitted to a flat brass plate, D. The plate is mounted at an angle to the tube, so that when it is in place on the stern of the boat the propeller-shaft will be in line with the crankshaft of the engine.
A clearance hole is now drilled through the hull, so that the propeller-shaft can be put in place. Solder the tube to the plate, and punch four small holes in the plate, so that it can be screwed firmly to the hull. Solder a short piece of tube, as shown at B, [Fig. 82], to keep the propeller-shaft in position.
The propeller must now be made. This is easily done by cutting out a disk of brass 11/2 inches in diameter, as shown in [Fig. 83]. The shaded portions of the brass disk are cut away. The blades are bent to shape, care being taken to see that they are all alike. This done, the propeller is soldered to the propeller-shaft.
The only part of the job that remains is to screw the boiler in place under the fore-deck of the boat. This done, the Nancy Lee is ready for her trial. The fore-deck should be made removable by fitting it with pins or screws with the heads cut off, so that the deck only needs pushing into place. This little boat should be capable of attaining a speed of from four to five miles an hour if it is made carefully and according to the directions outlined in this Chapter.