p becomes, for example, p square is l square plus d square; then you can say that p into cos of this angle is l p into sin of this angle - in terms of this angle, this angle, this angle… we can make all the sort of - we can resolve all of them; this is alpha, this is actually… this part is alpha; I will just write down this expression - that is very simple; because, I am not… the problem of this course is that the space is a problem; p becomes l square plus d square and n becomes (No audio from 17:13 to 17:44) this is very simple, I will just may be go through this with this; this way, I think it can come here now.
n is obviously l cos alpha, because if you look at this n is l cos alpha plus d into sin alpha; this n is l cos alpha plus d sin alpha, because this is my angle alpha; similarly, t is going to be… t … now, t is this side; t is going to be…this is alpha again; d cos alpha minus l sin alpha and, of course, in terms of coefficient it becomes like that.
One more thing is important - there are…probably, I should say; supposing you call this distance to be a, this distance to be - this is my centre, actually this point is my center of pressure where all this you know forces are… having done everything is a center of pressure from where the entire force get to acting.
Let us say, that this is equal to e; what is my… another…. one important point is what is the moment coming on this stock? Remember, this is my stock here on which this force comes here and I want to find out moment coming on that stock; that will n into this distance - the moment coming will be n into e minus a.
E minus a.
So, the moment here I can write - moment of that equal to n into… in fact, moment on the stock - let me call it rudder stock - into e minus a; this is important sometimes because this moment that comes is the moment…. you have got a rudder and you have got a steering gear machine that you have to turn; it has to turn against that kind of moment; you are turning this rudder about this point like this and the moment that you need - if you have turned so much, the moment that is coming on that is so much; therefore, you need to… that moment… because that much of moment you have to apply; this is necessary for your steering gear design - that is why you need that.
Why I am saying that is because in the rudder design we will find out that essentially if you can estimate this l etcetera from every section you can integrate and then get the