Originally Posted by Adelie
Changing the lead point didn’t change the overturning moment on the jack stands only the specific load path to the chain plates. Also it increased the load in the halyards.
In technical terms the jack stands are the fulcrum.
The over turning moment is the product of horizontal distance between the fulcrum and a vertical up through the centre of gravity of the motor
and the weight of the motor.
Resisting the overturning moment is the moment being generated by the weight of the boat multiplied by the horizontal distance between the fulcrum ie. the jack stand, and a vertical line through the centre of gravity of the boat. We'll call this the static moment.
If the static moment exceeds the overturning moment the boat won't tip over. This assumes that the jacks are standing vertical if they are at an angle, which is more usual, it gets a little more complicated.
In technical terms the load on the halyards is a vector problem.
The vertical load of the engine constitutes the y axis. The length of the boom the x axis. The resultant, after applying a little maths or trigonometry, is the halyard or hypotenuse. Since the length of the boom and the weight of the engine are constant, decreasing both the y axis, and consequent to this the hypotenuse, increases both the compressive loading on the boom and the tensile loading on the halyard.
This stuff is all junior high school
stuff if one can remember and apply it.
If one assumes the mast vertical and the boom horizontal