# 1 3 Dynamic Stability

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## Presentation Description

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By: Hunterye (143 month(s) ago)

Great Explanation. Thanks

## Presentation Transcript

### Slide1:

DYNAMIC STABILITY LT Tom DeNucci (860) 444-8672

### Slide2:

G Station Coos Bay 47’ MLB training Nov 1999

### Dynamic Stability Objectives:

Dynamic Stability Objectives Understand heeling moments Determine dynamic stability Determine max roll from righting and heeling moment curves Understand the Navy Criteria for dynamic stability

### Heeling Moments:

Heeling Moments Moments of forces are what cause a ship to heel, list, return to equilibrium or capsize. A righting moment tends to rotate a vessel towards its initial position A heeling moment tends to rotate a vessel away from its initial (stable) position. Causes of heeling moments Off-Center Weights Beam Winds Off Center Weights (Weights over the side) High Speed Turns Crowding of passengers Icing

### Heeling Moment Curve:

Heeling Moment Curve Plot of the Heeling Moment versus angle of heel, for any externally applied force. Heeling Moment curves usually start at a maximum value, and then decrease to zero at 90 degrees of heel.

### Slide6:

Angle of Heel Heeling Moment Curve (From - wind, turns, etc.) Moment

### Static Stability Curve:

Static Stability Curve Area under the curve represents work performed to heel the ship and stored energy available to return the ship to 0.

### Righting Moment Curve:

Angle of Heel Righting Moment Curve Righting Moment Curve Moment

### Slide9:

Angle of Heel Heeling Moment Curve Moment Righting Moment Curve

### Slide10:

Angle of Heel Moment Excess Heeling Energy

### Slide11:

Angle of Heel Moment Excess Heeling Energy Excess Righting Energy

### Slide12:

Angle of Heel Moment Excess Heeling Energy Excess Righting Energy Max Angle of Roll The ship will roll until excess heeling energy equals excess righting energy

### Slide13:

Angle of Heel Moment Excess Heeling Energy Excess Righting Energy Max Angle of Roll Static Angle of Heel If everything stays constant, the ship will settle out to a constant angle of heel

### Slide14:

Angle of Heel Moment Excess Heeling Energy Excess Righting Energy Excess heeling energy greater than excess righting energy Ship will capsize

### CGC JARVIS - November 15, 1972:

CGC JARVIS - November 15, 1972 Prior to damage Added weight only Added weight & Free Surface Effect Dynamic Stability curve

### CGC JARVIS - November 15, 1972:

CGC JARVIS - November 15, 1972 Prior to damage Added weight only Added weight & Free Surface Effect Max roll Dynamic Stability curve Heel

### U.S. Navy Criteria:

U.S. Navy Criteria In 1960’s, U.S. Navy developed dynamic stability design criteria for their ships Compares energy used to heel the ship to energy available to right the ship Applies a safety factor to ensure positive dynamic stability Similar criteria used by shipbuilders worldwide

### U.S. Navy Criteria:

U.S. Navy Criteria Navy criteria addresses specific hazards We’ll briefly look at criteria for: Beam winds with rolling Operating with a weight over the side High speed turns Crowding of Passengers to one side

### Beam Winds With Rolling:

Beam Winds With Rolling DRAFT H - LEVER ARM (feet) - From Center of SAIL AREA to 1/2 DRAFT A - SAIL AREA (square feet) [cross-hatched area] Vw - VELOCITY of WIND in knots H HEELING ARM created by WIND = 0.004 V A H 2 w 2240 ² cos ø 2

### Beam Winds With Rolling:

Beam Winds With Rolling

### Weight Over the Side:

D D Weight Over the Side

### Weight Over the Side:

Weight Over the Side Stability Criteria: 1 (Angle of Heel at Point C)  15 A1 (Excess Righting Energy)  40% A2 (Total Righting Energy) c) Righting Arm at Point C (RA 1)  60% of Maximum Righting Arm (RA 2)

High Speed Turn

### High Speed Turn:

High Speed Turn Stability Criteria: a) 1 (Angle of Heel at Point C)  10 for Newly constructed ships 1 (Angle of Heel at Point C)  15 for Existing ships b) A1 (Excess Righting Energy)  40% A2 (Total Righting Energy) c) Righting Arm at Point C (RA 1)  60% of Maximum Righting Arm (RA 2) A1

### Crowding of Passengers:

Crowding of Passengers D

### Crowding of Passengers:

Crowding of Passengers Stability Criteria: 1 (Angle of Heel at Point C)  15 A1 (Excess Righting Energy)  40% A2 (Total Righting Energy) c) Righting Arm at Point C (RA 1)  60% of Maximum Righting Arm (RA 2)

### 87’ WPB addition:

87’ WPB addition Does this meet Navy Criteria? Not all the time!