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3rd Diagram. Ship’s head NE (Cor. Mag.)

M represents the quadrantal deviation. When the ship's head is placed NE or SW, the North point of the compass is drawn to the right as in the diagram ; but when her head is NW or SE, the North point of the compass is drawn to the left.

In our diagram the box of soft iron (a) draws the North point back towards the left, and the box (6) draws the South point to the right, and consequently turns the North point also to the left.

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HEELING ERROR.

The fall lines in P and represent the ship when upright, and the dotted lines represent her when heeled 10° to starboard, the ship's head having been placed at North when she was on an even keel, and the ship is supposed to be in North latitude.

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In P, the North point of the needle is drawn to windward, which is most frequently the case, then the errror is compensated by a magnet placed vertically under the centre of the card with its North pole upwards.

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In Q, the North point of the needle is drawn to leeward, in this case the magnet must be placed with its South pole upwards.

3rd Diagram. Ship’s head NE (Cor. Mag.)

M represents the quadrantal deviation. When the ship's head is placed NE or SW, the North point of the compass is drawn to the right as in the diagram ; but when her head is NW or SE, the North point of the compass is drawn to the left.

In our diagram the box of soft iron (a) draws the North point back towards the left, and the box (1) draws the South point to the right, and consequently turns the North point also to the left.

M

HEELING ERROR.

The full lines in P and Q represent the ship when upright, and the dotted lines represent her when heeled 10° to starboard, the ship’s head having been placed at North when she was on an even keel, and the ship is supposed to be in North latitude.

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In P, the North point of the needle is drawn to windward, which is most frequently the case, then the errror is compensated by a magnet placed vertically under the centre of the card with its North pole upwards.

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In Q, the North point of the needle is drawn to leeward, in this case the magnet must be placed with its South pole upwards.

CURRENT SAILING. Given a current acting on some part of your ship and its drift, also the ship’s rate in the current, to find the direction she must steer to reach her port.

If the current is on the port beam, starboard beam, port bow, starboard bow, port quarter, or starboard quarter, then the ship will drift to leeward, as in the following figure.

Where S is the Ship, and P is the Port. The line SP is called the Port Line.

P

f

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e

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d Current on Port Beam, Ship drifts towards a Starboard

6 Port Bow Starboard

d Port Quarter Starboard

f Measure off on this line the amount of the given drift. With a pair of dividers measure on the same scale the ship’s rate. Place one leg on the current point, and the other on the Port Line; then the edge of a pair of parallel rulers placed against the legs will be the required direction, if brought back to the centre of the ship.

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