Multiple contact areas? Smaller ship lifted up on impact?FactChecker said:I am curious. There have been two collisions recently between a military ship and a large commercial ship. Both times, the military ship was damaged at the waterline and the other ship was damaged far above the waterline. How does that happen?
In this most recent accident I have seen simulated reenactments where the tanker hits the side of the McCain with the bulbous bow.Dr.D said:It is common for tankers and similar large cargo ships to use what is called "bulbous bow," which is a large, rounded extension of the bow below the waterline. This apparently improves the hydrodynamic performance of the hull, although I do not fully understand why. This means that the absolute front of the tanker is quite aways in front of the visible bow. Warships do not use this bulbous bow. When we look at the photos of the hole in the side of the McCain, it looks almost exactly like a female mold of a bulbous bow.
This would explain why the damage to McCain is at and below the waterline while the damage to the tanker is all much higher.
jim mcnamara said:Unlocked. Please, no speculation.
Dr.D said:It is common for tankers and similar large cargo ships to use what is called "bulbous bow," which is a large, rounded extension of the bow below the waterline. This apparently improves the hydrodynamic performance of the hull, although I do not fully understand why. This means that the absolute front of the tanker is quite aways in front of the visible bow.
Dr.D said:Warships do not use this bulbous bow.
A bulbous bow is a protruding bulb at the bow (or front) of a ship just below the waterline. The bulb modifies the way the water flows around the hull, reducing drag and thus increasing speed, range, fuel efficiency, and stability. Large ships with bulbous bows generally have twelve to fifteen percent better fuel efficiency than similar vessels without them.[1] A bulbous bow also increases the buoyancy of the forward part and hence reduces the pitching of the ship to a small degree.
Bulbous bows have been found to be most effective when used on vessels that meet the following conditions:
Thus, large vessels that cross large bodies of water near their best speed will benefit from a bulbous bow. This would include naval vessels, cargo ships, passenger ships, tankers and supertankers. All of these ships tend to be large and usually operate within a small range of speeds close to their top speed.[3] Bulbous bows are less beneficial in smaller craft and may actually be detrimental to their performance and economy. Thus, they are rarely used on tug boats or recreational craft like powerboats, sailing vessels, and yachts.
- the waterline length is longer than about 15 metres (49.2 ft)
- the vessel will operate most of the time at or near its maximum speed [2]
In fact, the Arleigh Burke (DDG-51) class of which the John S McCain is a member has an upgrade package which includes a bulbous bow. The article referenced here is a bit of a sales pitch, but seems reliable:davenn said:and it isn't a new thing ... warships as far back as 1925 started using a bulging bow
The height of a ship can impact the damage caused in a collision in several ways. First, a taller ship will have a higher center of gravity, making it more likely to tip or capsize upon impact. Second, a taller ship will have more surface area exposed to the impact, increasing the potential for damage. Third, the height of a ship can affect the angle and force of impact, potentially causing more damage to both ships.
Yes, the waterline of a ship can have a significant impact on the damage it sustains in a collision. A ship with a lower waterline will have a smaller area of exposed hull, making it less vulnerable to damage. Additionally, a lower waterline may indicate that the ship has a lower center of gravity, making it less likely to tip or capsize upon impact.
Yes, there are regulations and standards in place for determining the damage height versus waterline in ship collisions. The International Maritime Organization (IMO) has established guidelines for assessing damage to ships in collisions, which include determining the height and waterline of the ships involved.
Yes, there are several other factors that can impact the damage in a ship collision. These include the speed and angle of impact, the design and construction of the ships, and the type of cargo being carried. Additionally, environmental factors such as sea conditions and weather can also play a role in the severity of damage.
While computer simulations can provide valuable insights and predictions, they may not always accurately reflect the actual damage height versus waterline in a ship collision. This is because there are many variables and unpredictable factors involved in a collision, and the accuracy of the simulation will depend on the accuracy of the input data and assumptions made. Actual damage can also vary depending on the specific circumstances of the collision.