CHAPTER V
AN ELECTRIC LAUNCH
THE little electric launch to be described is of very simple construction, and when finished it will provide the builder with a very shipshape little model from which he will be able to derive a good deal of pleasure. It has a speed of from 21/2 to 3 miles an hour when equipped with dry batteries or storage batteries. The hull is of the Sharpie type, and this offers very little trouble in cutting out and assembling.
The general appearance of the boat and hull will be gathered from the drawings. The pieces necessary to assemble the hull are shown in [Fig. 58]. Only five pieces are necessary: two side pieces, a stern piece, a bow piece, and a bottom piece. The length of the boat over all is 40 inches with a 7-inch beam. The widest part of the boat is 1 foot 10 inches from the bow.
After the pieces that form the hull are cut they are thoroughly sandpapered to produce a smooth surface. The heavy imperfections in the wood can be taken out with coarse paper, and the finishing can be done with a finer paper. It is understood that sandpapering should always be done with the grain, never across the grain. The sides of the boat are cut about 1/4 inch thick, but they are planed thinner in places where the bend is most pronounced. The side pieces are 23/4 inches deep at the stern and 21/4 inches at the stern. There is a gradual curve from the bow to the stern, which is more marked toward the head.
The stern piece is thicker than the side pieces, being made of 1/2-inch wood. It is cut to the shape shown at [Fig. 58], and beveled along the bottom edge to enable it to be fixed on the slant. The bow piece is a triangle 23/4 inches in length.
After the parts are thoroughly finished with sandpaper the stern piece is fixed in position. In making all the joints on the boat the builder should see that plenty of fairly thick paint is run in while the joint is being screwed up. This will help greatly in making the boat water-tight. Plenty of 3/4-inch brass wood-screws are used in assembling the hull. All the holes for the wood-screws should be countersunk so that the heads will come flush with the surface of the hull. Now one of the sides should be screwed to the stern piece, at the same time bending the bottom and side to meet. This is done gradually, inch by inch, and screws are put in place at equal distances. When the bow is reached, the side piece is beveled to fit the bow piece, which should already have been screwed into place. The other side of the boat is treated in a similar manner, and the young worker should take care to keep the side and bow piece perfectly square and upright. This may sound easy on paper, but it will be found that a good deal of care must be exercised to produce this result.
After the hull has been assembled it is given a good coat of paint inside and out. When the first coat is dry the holes left by the screw-heads are carefully puttied over, and the hull is given a second coat of paint. This procedure will produce a perfectly water-tight hull.
The stern tube is 3/8 inch, outside diameter. A hole is bored in the bottom of the boat to receive the stern tube. This job must be done cautiously; otherwise the bottom of the boat may be ruined. It is best to screw a substantial block to the inside of the boat. This block should be cut to fit the bottom and will act as a support for drilling. It will also help greatly to make a water-tight joint around the tube. The distance from the point where the stern tube passes through the bottom to the stern should be about 121/2 inches. The stern tube should be mounted as nearly parallel with the bottom as possible, since on this depends the speed of the boat. As the angle of the propeller-shaft increases, the speed of the boat will decrease. In drilling the hole the boat-builder should be careful to keep the drill running along the central line of the boat.
As before mentioned, the stern tube is a piece of brass tubing 3/8 inch in diameter and 8 inches long. It is filed square at both ends, and a brass plug is fastened with solder in each end. The tube is then filled with melted vaseline, which is allowed to cool. The hole in the hull around the tube is then well smeared with thick paint. When this is done, a layer of red lead or putty is placed around the joint both on the inside and the outside of the boat.
While the putty is drying the spray-hood or turtle-deck can be made. This is bent to shape from a piece of tinplate and extends half way down the boat. When the turtle-deck is finished, it is best to lay it aside, before finally fastening it in place, until the entire boat is completed.
The wooden part of the deck is made of 1/8-inch wood and scribed with a sharp knife to represent planking. This method of producing planking was described in detail in Chapter II.
Toward the stern of the boat and just behind the motor a hatchway is fitted to give access to the batteries and starting switch.
The finished Sharpie hull without its driving batteries or motor should weigh about 1 pound 3 ounces. The hull being finished, let us consider the electric propelling equipment.
A 1/8-inch cold-rolled steel driving or propeller-shaft is used. The shaft is 13 inches long and a gear-wheel 1 inch in diameter is fixed to one end of this shaft. This gear-wheel meshes with a brass pinion on the motor-shaft. This forms a 31/2 to 1 reduction gear, which produces a greatly increased speed of the boat. The other end of the propeller-shaft rests in the skeg bearing. In this present case this consists of a tube about 1/2 inch long, which is made for a revolving fit on the propeller-shaft and supported by a sheet-metal bracket. This is shown in [Fig. 63] . The end of the propeller also revolves adjacent to the bearing in the skeg.
GETTING READY FOR A TRIP
Heating the blow-torch to a point where it will burn automatically
The propeller is a three-blade affair with a diameter of 21/4 inches. It is attached to the propeller-shaft with a set-screw. The motor is a very simple type obtainable in the open market. It is similar to one shown in [Fig. 41]. As before mentioned, either dry or storage batteries may be used as a source of current. The writer strongly advises the use of storage batteries if possible. The initial cost of these batteries is greater than that for dry batteries; but, on the other hand, the small storage battery can be charged repeatedly and will outlast many dry batteries. If the boat is used much the storage battery will probably be the more economical of the two.
The steering gear of the boat is very simple. The rudder works in a bearing that is screwed to the stern piece. The end of the rudder-shaft is tapped, and a brass screw is used to clamp it in position after setting it with the fingers. The rudder-shaft is a 3/4-inch brass rod. The lower end of this rod is slit with a hacksaw and the rudder is placed in this. Solder is then flowed along the joint.
ALL READY TO GO!
A little boat with steam up, ready for a trip when her owner releases her
Of course, the builder may paint his boat whatever color he may select; but a maroon hull with a white-enameled spray-hood or turtle-deck makes a very pleasing combination. [Fig. 60] shows a rough plan of the general arrangement of the power machinery. [Figs. 61], [62] and [63] will do much to give the reader a clear idea of the method of construction which could not be gained by reading a description.
The general appearance of the boat can be improved materially in many ways. For instance, a little stack or ventilator may be added to the turtle-deck, and a little flag-stick carrying a tiny flag may be placed on the bow and on the stern.
The motor current should be turned on only when necessary, for dry-cells deteriorate rapidly when in use, and small storage batteries quickly lose their charge, although they will last much longer than dry-cells and give much better service.