船舶原理3.2 Moment新 Balance 1st Moment of Area.pptVIP

Section 3.2 Moment Balance 1st Moment of Area ;There are three conditions that must be met for static equilibrium: SFx = 0 (movement from side to side) SFy = 0 (movement up and down) SM = 0 (rotation, or spinning, about a point); = W =;This is “the moment balance”. Okay, it’s a seesaw… but it’s the same thing.;Ernie has taken his position on the moment balance. As expected, he has thrown the balance out of balance. ;…And now the system is balanced.;w1;Let’s try an example of finding the centroid for the following shape:;y = 6;y = 6;x = 8.75;…the centroid goes by different names. If you’re dealing with the waterplane area, Awp, the centroid value is the Longitudinal Center of Flotation (LCF). The half-breadth of a ship will provide the detailed station values to include in your calculations.;KB;The longitudinal center of buoyancy, LCB, is also a centroid. it’s the distance along the x-axis to the center of buoyancy, B. Since it concerns the center of a volume, the formula involves the distance of the sections, Asect, along the x-axis (and referenced as a distance from amidships).;Finding the locations of LCB and KB, however, will require the use of Simpson’s 1st Equation and the particular ship’s table of offsets to solve because of the complex shape. More on that to follow…!