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97. (1) In wearing, the tiller is put up and the mainsheet slacked away roundly. The boat goes off before the wind, the mainsail is either gybed or taken in and shifted over (preferably the latter), and the boat is hauled up on the new tack, losing more or less ground to leeward, according to circumstances. The details of the maneuver may vary considerably according to the conditions of wind and sea and the peculiarities of the boat as to rig and trim. In a light breeze, the mainsheet is slacked away roundly until the wind is aft, then hauled in smartly for gybing and eased away steadily on the new lee quarter. In a fresh breeze, where gybing would be dangerous, the mainsail is taken in just before the wind comes aft, and set again in time to bring her to the wind on the new tack.
(2) The fore and jib sheets are shifted when nearly before the wind. As she comes to on the new tack, they are left flowing until hauled aft to meet her by the wind.
98. (1) A boom sail is "gybed" when it is allowed to swing from one side to the other, the wind being aft or nearly so, and the sail full, first on one side and then on the other. This may be done intentionally, as in wearing or in changing course, or it may come unexpectedly from a shift of wind or from the yawing of the boat. Às it necessarily involves a violent swing of the sail, it puts a heavy strain upon the spars and fittings and causes the boat to lurch more or less deeply to leeward. Moreover, the violent sweep of the boom across the stern endangers everybody in its path.
(2) In a light breeze, these dangers are perhaps not serious enough to justify the rule that a mainsail never should be gybed, but in a fresh breeze it should not be thought of; and the fact that it is often done by experienced boatmen does not make it any more seamanlike.
(3) When a necessary change of course in a fresh breeze will bring a shift of wind from one quarter to the other, the sail should be lowered or clewed up for a moment before putting up the tiller, and then set again on the other quarter. If this can not be done and it is still necessary to gybe, the peak should be dropped, the boom hauled in slowly and eased away on the new tack.
SPECIAL DUTIES OF COXSWAINS.
99. (1) The coxswain of a power boat is responsible for the whole boat and for the discipline and obedience to regulations of all men in the boat.
(2) While the engineer and fireman, so far as relate to their technical duties, remain responsible to the senior engineer officer for the proper performance of their duties, they are nevertheless, in general matters, entirely under the orders of the coxswain.
(3) The engineer of the boat, in technical matters, has general charge of the boiler and engine or motor, and is responsible that the fireman efficiently performs his duties, as he is simply the assistant of the engineer.
(4) If anything is required about the engines, such as coal, gasoline, oil, or water, or if any repairs are required which necessitate temporarily disabling the boat, the engineer will report it to the coxswain, who will report to the officer of the deck.
(5) In overhauling the boat while in the cradles the same rule prevails; while the engineer will attend to the technical details of the work on the machinery, any outside assistance necessary, not technical in nature, should be obtained by the coxswain, if necessary, by applying to the officer of the deck.
(6) Orders relating to getting up steam are given to the coxswain of the boat, who will inform the engineer. The coxswain is responsible that all reasonable efforts have been made to have steam up at the moment ordered.
(7) The coxswain of a power boat should, as soon as possible after being assigned to that duty, make a special study of his boat with the view to getting perfectly familiar with her. He should learn by practice the turning circle, the effect of the screw under different conditions. Also the amount of fuel, water, and oil usually carried, the maximum speed of the boat, the operating radius, and the amount of extra fuel, water, and oil required to cover a given distance at the ordinary speed.
(8) The general instructions for coxswains of boats apply with equal force to the coxswain of a power boat, but he is particularly warned, owing to the greater power of his boat, and the greater injury in case of a collision, to carefully study the “Rules of the Road.”
(9) In running in a fog, the coxswain should remember that owing to the presence of the machinery in the boat, more especially in a steamer, the compass will be affected. Therefore, to get a correct compass course, it must not be taken from a chart, but should be observed by reading the compass when it is in its place for steering by it, and with the boat headed in the desired direction. This gives the proper reading of the compass when the boat is headed on the desired course. Therefore, on his very first trip in and out from a landing the coxswain should always use his compass, observe and, if necessary, record the compass courses, so that he could make the trip either way in a fog.
(10) Knowledge of the effect of the screw on the steering is most essential to a coxswain. Generally speaking, the right-handed screw when going ahead tends to throw the stern to starboard; when backing, to port. In other words, the stern is dragged around in the direction the propeller is turning, and this effect is noted whether the boat itself has begun to answer the motion of the propeller or not. In attempting to turn a power boat, the rudder should be shifted when the propeller is shifted instead of waiting for the boat to lose its headway, for the rudder has the same general effect on the steering of the boat when the propeller is backing, whether the boat itself is moving astern or has not yet lost its beadway and is still forging ahead. This rule is not strictly applicable to all boats, but it is a good general rule.
NOTES ON POWER BOATS. 100. (1) In making a landing, it is a common mistake to keep too much headway on and to rely on backing the engines full speed to stop the boat. This is poor seamanship, as the engines may fail to back promptly, causing a collision or smash up, and if they do back hard, it throws unnecessary strain on them. Therefore, make landings with slow speed. This precaution applies particularly to motor boats where sudden reversals and hard backing put excessive strains on the engines and reversing gear, and will eventually result in breakdowns.
(2) In landing alongside a ship’s gangway in a strong current, do not let the tide catch your boat on the outboard bow, as this might sweep her underneath the gangway. The boat line from forward should in all cases be used, the boat being kept off a little from the side until it is fast, and then sheered in by the rudder. A boat may lie alongside safely in a strong current with a line from the inner bow, and the rudder slightly over for sheering out.
(3) In towing, the stern of the towing boat should be kept well down by shifting weights aft if necessary. This keeps the propeller well immersed, and gives it a good hold on the water.
(4) When running in a seaway, speed should be reduced somewhat not only to avoid shipping seas but to reduce the strain on the machinery due to the racing of the screw. In running into a sea, it is possible by careful nursing to make fair speed, watching the seas and slowing or even stopping for a moment as heavy ones are seen bearing down upon the boat. If the man who is running the engine has sufficient experience to regulate the speed in this way, it is convenient to leave this to him, if he can see ahead. If running more or less across the sea, it is well to head up momentarily for a heavy
101. (1) The water used in a boiler should always be obtained from the ship as this is always distilled. Fresh water from shore often contains corrosive ingredients or lime salts, and should never be used when it can be avoided. Salt water should never be used, and the water in the feed tank should be frequently tasted and never allowed to grow brackish through leaky connections.
(2) When a steamer is about to be lowered, the fires should be started promptly and steam got ready to try the engine by the time the boat is in the water. As soon as the steamer is in the water, if not before, the feed pump or pumps must be worked by steam, and the engines turned back and forth, and the whistle, safety valve, bell, and steering gear tried. Failures to work must be immediately remedied.
(3) When a steamer is alongside a gangway, never permit any firing. Attention to the fires before coming alongside will prevent the necessity of doing this, and the dirt and the inconvenience of having thick, black smoke over the ship is avoided. For the same reason the use of the steam jet is to be avoided when alongside.
(4) Steamer crews are generally inclined to carry too little water in the boiler; a third to half a glass should be the rule.
(5) In water-tube boilers the fires may be forced, or suddenly hauled, or put out with a bucket of water, without danger of seriously injuring the boiler, but this should only be done when there is more or less of an emergency.
RULES FOR CARE AND OPERATION OF POWER-BOAT
MACHINERY (GASOLINE ENGINES).
Fig. 1. 102. (1) The action of a two-cycle engine is as follows: Consider the piston at the top of its stroke with the combustible charge of gas compressed and ready for ignition. On the first stroke the charge in the combustion chămber is ignited and burned, and the resulting increased pressure forces the piston downward. At the beginning of this stroke, the inclosed crank case is full of a combustible mixture which has been previously drawn in and through ports “A,'' is compressed to about 4 or 5 pounds by the piston on its down stroke. When near the bottom of the stroke, the top edge of the piston uncovers a series of ports “C” in the cylinder wall through which the burned gases escape into the exhaust pipe, the pressure in the cylinder dropping to about that of the atmosphere. Shortly after the exhaust ports have been uncovered, the piston still moving downward uncovers the transfer ports “B” in the cylinder wall, which are situated diametrically opposite the exhaust ports. The transfer ports are connected by a passage or by-pass through which the combustible mixture in the crank case flows into the cylinder. To prevent the incoming charge from passing directly across the cylinder and out of the exhaust ports inlet and exhaust ports being open at the same time), the top of the piston is provided with a deflector or baffle plate, which directs the charge up to the top of the cylinder, thereby driving out the greater part of the burned gases remaining. On the second stroke the piston moves upward, first closing the transfer ports and shortly after the exhaust ports. The charge in the cylinder is compressed, and at the top of the stroke is ready for firing. During this stroke a new charge is drawn into the crank case.
(2) By the three-port method (used in the service engine) the charge is drawn from the carburetor into the crank case through ports “A” in the cylinder wall, located just below the exhaust ports, and are uncovered by the bottom edge of the piston when near the top of its stroke. No check valve is required.
(3) In figure 1 are shown sectional views of a Schebler carburetor and a two-cycle engine. Before the gas is admitted to the engine the gasoline passes through a carburetor or vaporizer.