# Where is the Fulcrum for a Boat Hit by a Wave?

• Ilan
In summary, the conversation discusses the behavior of a boat when hit by a wave and the resulting righting moment. The question is raised about which point the boat rotates around and there is a discussion about the center of buoyancy and center of gravity. An animation is shared, and it is concluded that the center of buoyancy typically remains stationary, but some hull shapes may cause it to move. The concept of metacentric height is also mentioned.
Ilan
Hi,

I'm making an animation of how a boat behaves when hit by a wave. This is how it looks like after the wave:

(see attachment)

At this point there should be a righting moment that tries to balance the boat by turning it clockwise.

Which point does the boat rotate around?

I'm not sure because the forces act on the C of B and the C of G and so I was thinking it would be the black dot, but shouldn't the C of B not move since it is a circular bottom?

What do you guys think?

Thanks!

------------------
EDIT:

Ok so I tried to animate it:

If this motion is correct, then does that mean that the fulcrum moves? Why?

#### Attachments

• boat.jpg
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Yeah, the centre of buoyancy remains stationary. (its, basically just the centre of geometry of the part inside the liquid, and hence as shown in the animation remains unaffected as boat moves).

So the motion of the boat can be considered as pure rotation about its C of B. (like rotation about a pivot)

Some hull shapes are designed so that the CoB moves outboard when the boat heels over. Consider a catamaran. With the mast vertical the CoB is mid way between the two hulls. With one hull "flying" the CoB has moved to the hull still in the water.

Most boats, including this one, will have a center of buoyancy that moves. The circular hull would only enable a stationary center of buoyancy if it was at the center of the circle. The wiki link explains it well.

## 1. Where is the fulcrum located on a boat hit by a wave?

The fulcrum on a boat hit by a wave is typically located at the center of mass of the boat. This is the point where the boat's weight is evenly distributed and there is no net force acting on the boat.

## 2. How does the location of the fulcrum affect the boat's stability when hit by a wave?

The location of the fulcrum is crucial in determining the boat's stability when hit by a wave. If the fulcrum is located at the center of mass, the boat will remain stable as the wave passes. However, if the fulcrum is located off-center, the boat may tip or capsize due to the imbalance of forces.

## 3. Can the fulcrum be moved to improve the boat's stability when hit by a wave?

Yes, the fulcrum can be moved by redistributing the weight of the boat. This can be done by shifting cargo or passengers to different locations on the boat, or by adding ballast to one side of the boat to counterbalance the force of the wave.

## 4. How does the size and strength of the wave affect the position of the fulcrum?

The size and strength of the wave can greatly impact the position of the fulcrum. Larger and stronger waves will exert more force on the boat, causing the fulcrum to shift and potentially destabilizing the boat. It is important for the boat's crew to adjust the position of the fulcrum accordingly to maintain stability.

## 5. Is the fulcrum always located at the same point on a boat hit by a wave?

No, the location of the fulcrum may vary depending on the size and shape of the boat, the distribution of weight, and the force of the wave. It is important for boat operators to understand the concept of the fulcrum and be able to adjust its position as needed to maintain stability in different wave conditions.

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