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

  • Context: Undergrad 
  • Thread starter Thread starter Ilan
  • Start date Start date
  • Tags Tags
    Fulcrum
Click For Summary

Discussion Overview

The discussion revolves around the dynamics of a boat when it is hit by a wave, specifically focusing on the concept of the fulcrum point around which the boat rotates. Participants explore the relationship between the center of buoyancy (C of B) and the center of gravity (C of G) in the context of boat motion and stability.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant suggests that the righting moment after a wave impacts the boat causes it to rotate clockwise, questioning the point of rotation.
  • Another participant asserts that the center of buoyancy remains stationary, indicating that the boat's motion can be treated as pure rotation about this point.
  • A different viewpoint notes that some hull designs, like catamarans, have a center of buoyancy that shifts outboard when the boat heels, complicating the notion of a fixed fulcrum.
  • One participant references an article on metacentric height, implying that such calculations are standard in maritime contexts, particularly for cargo ships.
  • Another participant argues that most boats have a center of buoyancy that moves, challenging the idea that a circular hull would keep the center of buoyancy stationary unless it is at the center of the circle.

Areas of Agreement / Disagreement

Participants express differing views on whether the center of buoyancy remains stationary or moves during the boat's motion, indicating that multiple competing perspectives exist without a clear consensus.

Contextual Notes

Participants discuss the implications of hull shape on the center of buoyancy and the conditions under which it may shift, highlighting the complexity of the topic without resolving the debate.

Who May Find This Useful

This discussion may be of interest to individuals studying naval architecture, marine engineering, or those involved in animation and simulation of fluid dynamics related to boats.

Ilan
Messages
2
Reaction score
0
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:

http://www.ironwhisk.com/wordpress/wp-content/uploads/2012/12/test.swf

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

Attachments

  • boat.jpg
    boat.jpg
    13.9 KB · Views: 493
Last edited:
Physics news on Phys.org
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.
 

Similar threads

Graduate Can a gyroscope lift a fulcrum (and itself), hinged to the floor?
  • · Replies 8 ·
Replies
8
Views
3K
High School Need help explaining river-boat problems
  • · Replies 26 ·
Replies
26
Views
7K
Undergrad Is it possible to "violate" momentum at the expense of more energy?
  • · Replies 2 ·
Replies
2
Views
1K
High School Why the energy that waves transfer is only dependent on amplitude
  • · Replies 10 ·
Replies
10
Views
4K
Calculating Composite Center of Gravity -- Boat Rack for my Truck
  • · Replies 5 ·
Replies
5
Views
5K
Misc. Digitizing a Boat Hull: Mac26 Modeling Data
  • · Replies 33 ·
2
Replies
33
Views
4K
Undergrad Lagrangian coordinate transformation (Noether)
  • · Replies 11 ·
Replies
11
Views
2K
Undergrad What happens if two moving shock waves collide?
  • · Replies 3 ·
Replies
3
Views
3K
Graduate This invention should work ELSE the conservation laws are wrong.
  • · Replies 1 ·
Replies
1
Views
2K
Torque with "complex" object (static/equilibrium)
  • · Replies 1 ·
Replies
1
Views
2K