Mary, Let me attempt to clear up the confusion I have caused.

First thing to remember is a moment is a force times a distance.

The righting moment (RM) is the total weight of the boat and crew multiplied by the distance between the centre of buoyancy (CoB) and centre of gravity (CoG) in the horizontal direction.

The heeling moment (HM) is the Force of the wind on the boat (mainly in the sail though) multiplied by the distance between the CoB and the centre of effort (CoE) of the wind in the vertical direction.

As with most things in engineering these two forces have to be opposite and equal otherwise the boat falls over.

With the HM the distance is more or less constant but as the wind changes the force increases and so the HM increases.

With the RM the weight is more or less constant but the distance increases as the crew moves to windward (CoG changes) and/or the boat heels (as the boat heels the CoB moves toward the leeward side).

One thing to remember here is that these two things change constantly but what we are interested in is the maximum HM or RM. With the HM there is no maximum, the wind can blow very hard, but there is a maximum RM the crew can only move so far to windward! That may be why most people talk about RM not HM.

So when there is no wind the HM force is 0 and so the crew sits on top of the boats CoB so the RM distance is also 0. As the wind starts to blow the HM force increases and so the boat heels and/or the crew move to windward just enough so that the HM and RM are again equal.

Lets say the Heeling moment distance is 4 and the RM weight is 200.
HM RM
Force x distance Force x distance
Stationary boat 0 x 4 = 200 x 0
Windy boat 100 x 4 = 200 x 2

Everything nice and equal.

This is a dynamic thing and both are constantly changing with the crew moving and reacting to each change in the wind, but over any period of time the two have to be equal and opposite and cannot exceed a maximum governed by the weight and width of the boat.

Some people think that by moving the mast to windward you are lengthening the HM distance as you are moving the CofE further away from the CofB.

And that is what I thought Mary thought and that was dumb dumb dumb as I have no Idea what Mary thought.

However moving the mast does not alter the HM because the heeling moment only takes into account distance in the vertical direction.

I think Wouter and others are saying it does increase RM because among other things it moves the CofG slightly further to windward.

I did not understand Wouters statement because I knew that HM and RM have to be equal and opposite and Wouter was implying they could be different. I don’t think that is what he really meant. What he meant to say was that maximum RM does increase. It’s a bit of a chicken and egg thing because then the HM also has to increase to be equal and opposite.

It’s a case of both of us not being clear enough. And that is partly why engineers argue all the time!

Is that Clear enough?