Aux 2 Unit 16 Q3

Panting and pounding – they often occur together in heavy seas, especially when a vessel is driven hard. Here’s why:  

Understanding Pounding and Panting

• Pounding: As a ship moves head-on into large waves, the bow repeatedly rises and falls, slamming into the water with significant force. This creates heavy impact loads on the hull, particularly in the forward sections.
• Panting: Panting refers to the in-and-out movement of the hull plating in the forward sections of the ship, caused by the fluctuating water pressure as the bow plunges through waves.

Why They Occur Together:

1. Common Cause: Both pounding and panting are primarily caused by the vessel’s motion and the forces exerted by waves, especially in head seas or when the vessel is driven hard into rough weather.
2. Bow Area Affected: Both phenomena predominantly affect the forward sections of the hull, particularly the bow and the area just aft of the forepeak bulkhead.
3. Pressure Fluctuations: As the vessel pitches in heavy seas, the bow experiences alternating high and low pressures as it slams into waves (pounding) and then emerges (panting). These rapid pressure changes create the conditions for both panting and pounding to occur.
4. Structural Stress: Both pounding and panting induce significant stresses on the hull structure. Pounding causes impact loads, while panting causes repeated flexing and deformation of the plating. The combination of these stresses can be particularly damaging.

How Panting is Exacerbated by Pounding:

• Weakened Structure: Pounding can weaken the hull structure in the forward sections, making it more susceptible to panting stresses.
• Increased Flexibility: The impact loads from pounding can increase the flexibility of the plating, making it more prone to panting movements.
• Stress Concentration: Pounding can create stress concentrations in the hull, which can then be further amplified by the panting action.

Mitigation Measures:

• Reduce Speed: Slowing down is the most effective way to reduce both pounding and panting.
• Alter Course: Changing course to avoid heading directly into the waves can also help.
• Strengthened Structure: Reinforcing the hull in the forward sections with stronger framing and thicker plating can improve its resistance to both pounding and panting.

In conclusion, panting and pounding often occur together in heavy seas because they share a common cause (wave action) and affect the same area of the hull (the bow). The impact loads from pounding can exacerbate panting stresses, leading to a combined effect that can be particularly damaging to the vessel’s structure. Taking appropriate mitigation measures, such as reducing speed or altering course, can help minimize both pounding and panting and ensure the safety and integrity of the vessel.

Both panting and pounding put tremendous stress on a ship’s hull, particularly in the forward sections (bow area). To withstand these forces, shipbuilders employ various strengthening measures during the design and construction phases.

Strengthening against Panting:

• Increased Plating Thickness: The shell plating in the forward region, especially near the bow, is made thicker than in other areas. This provides greater resistance to the in-and-out flexing caused by panting.
• Panting Stringers and Beams: These are additional longitudinal stiffeners fitted to the inside of the hull plating. They run parallel to the ship’s centerline and provide extra support to the plating, preventing excessive flexing and buckling.
• Solid Floors in Forepeak Tank: The forepeak tank, located at the very front of the ship, is often fitted with solid floors (plating) instead of the usual open floors. This creates a more rigid structure to resist panting stresses.
• Bracket Floors: These are extra strong floors fitted in the forward region, typically extending from the centerline to the turn of the bilge. They provide additional support to the shell plating and help distribute panting stresses.
• Breast Hooks: These are triangular-shaped plates fitted internally at the bow, connecting the port and starboard stringers. They reinforce the stem and provide additional support against panting.

Strengthening against Pounding:

• Increased Bottom Plating Thickness: The bottom plating in the forward region, particularly near the keel, is increased in thickness to withstand the impact loads from pounding.
• Closer Frame Spacing: The spacing between frames in the forward section is reduced, providing more support to the plating and reducing the size of unsupported panels.
• Stronger Frames and Beams: The frames and beams in the forward region are made stronger and deeper to withstand the impact loads and distribute them more effectively.
• Solid Floors: Similar to panting, solid floors in the forward tanks help create a more rigid structure to resist pounding.

Combined Measures:

• Panting Stringers and Pounding: Panting stringers also contribute to resisting pounding by providing longitudinal strength and distributing the impact loads.
• Overall Structural Continuity: The entire forward structure, including the collision bulkhead, framing, and plating, is designed to work together to resist both panting and pounding stresses.

Additional Considerations:

• Hull Form: The shape of the bow can influence the severity of panting and pounding. A finer bow with a sharper entry angle can reduce the impact loads and pressure fluctuations.
• Operational Practices: Avoiding heavy weather or adjusting speed and course can also help minimize panting and pounding stresses.

By incorporating these strengthening measures and considering the vessel’s operational profile, ship designers can create robust and resilient hulls capable of withstanding the combined effects of panting and pounding, ensuring the safety and longevity of the vessel.