Navigation NAU 102 Lesson 36

Vessel Grounding

Magnetic Compasses Disadvantages Deviation No digital output

Gyrocompasses Disadvantages Expensive Difficult and expensive maintenance Requires stable power and backup Takes a long time to stabilize

New Advances Flux Gate Magnetic Compass Ring Laser Gyrocompasss No moving parts Digital output Low power requirements Rapid start-up Self correcting

Flux Gate Compass Two harmonic coils wrapped around a magnetic core. Earth’s magnetic field changes the core’s magnetic induction. The coils sense the changes. Electronics calculate the magnetic field necessary to cause the change.

Flux Gate Compass To minimize deviation, the sensor is placed at the top of the mast. Residual deviation is automatically calculated as the ship changes course 360°. It makes its own deviation table! Deviation is automatically applied.

Flux Gate Compass Operator can input the variation. Resulting true direction is sent to digital equipment.

Ring Laser Gyrocompass Two laser beams travel in opposite directions around a fiber-optic ring. When the compass (the ship) isn’t turning, the beams are in phase. When the compass turns, the beams are out of phase. The quicker the turn, the larger the phase differences.

Ring Laser Gyrocompass

Exam Review! A ship is proceeding on course 240° at a speed of 18 knots. The apparent wind is from 040° relative at 30 knots. What is the true wind. True Wind Calculation

Wind Step 1: Plot ship’s course & speed.

Wind Step 2: Convert relative direction of apparent wind to true direction, if necessary. A ship is proceeding on course 240° at a speed of 18 knots. The apparent wind is from 040° relative at 30 knots. R + S = T 040° R + 240° = 280° T

Wind Step 3: Draw the apparent wind from the tip of the ship’s course & speed vector. (Remember, draw the direction the wind is blowing towards!)

Wind Step 4: Complete the triangle. Result = True wind. Direction = 315 °T Speed = 20 knots

Slip The propeller on a vessel has a diameter of 24.6 feet and a pitch of 26.1 feet. What would be the apparent slip if the vessel cruised 462 miles in a 24 hour day at an average RPM of 72?

Slip The propeller on a vessel has a diameter of 24.6 feet and a pitch of 26.1 feet. What would be the apparent slip if the vessel cruised 462 miles in a 24 hour day at an average RPM of 72? Distance = Pitch x RPM x Time (in minutes) x Efficiency 6080 feet/nm

Slip The propeller on a vessel has a diameter of 24.6 feet and a pitch of 26.1 feet. What would be the apparent slip if the vessel cruised 462 miles in a 24 hour day at an average RPM of 72? 462 nm = 26.1 ft x 72 RPM x (24 hr x 60 min/hr ) x Efficiency 6080 feet/nm Efficiency = (103.8%)

Slip The propeller on a vessel has a diameter of 24.6 feet and a pitch of 26.1 feet. What would be the apparent slip if the vessel cruised 462 miles in a 24 hour day at an average RPM of 72? Slip = % = -3.8% Slip = 100% - Efficiency

Fuel Consumption While steaming at 19.5 knots your vessel burns 297 barrels of fuel per day. What will be the rate of fuel consumption if you decrease speed to 15 knots?

Fuel Consumption While steaming at 19.5 knots your vessel burns 297 barrels of fuel per day. What will be the rate of fuel consumption if you decrease speed to 15 knots? New Consumption = New Speed 3 Old Consumption Old Speed 3

Fuel Consumption While steaming at 19.5 knots your vessel burns 297 barrels of fuel per day. What will be the rate of fuel consumption if you decrease speed to 15 knots? New Consumption = barrels New Consumption = 135 barrels

Fuel Consumption Your vessel has sufficient fuel to steam 812 nm at 15 knots. At what speed must you proceed to reach your next port, 928 miles distant?

Fuel Consumption Your vessel has sufficient fuel to steam 812 nm at 15 knots. At what speed must you proceed to reach your next port, 928 miles distant? New Consumption = New Speed 2 x New Distance Old Consumption Old Speed 2 x Old Distance

Fuel Consumption Your vessel has sufficient fuel to steam 812 nm at 15 knots. At what speed must you proceed to reach your next port, 928 miles distant? x nm = New Speed 2 x 928 nm x nm 15 2 x 812 nm kts = New Speed

Introduction to Navigation Questions?