need some help regarding elevation of rudder (gap)

I need some help regarding the elevation of the rudder. The rudder top end is generally very close to the stern of the ship (vertically) but in my present project it has a big gap. The present project is at design stage only and I cannot post the photograph. I posted another photograph of my previous project.

 

Ya.. on a sailing yacht the rudder wants to be close to the hull. Generally you first fit the rudder with a good size gap, measure, drop, then with epxoy bog and fairing compound, close the gap.

 

Sry .. but i think u dint get it .. regrets i wasnt clear enough ..

There is no gap on the rudder .. i wanted to mean the gap between the stern shell of the ship and the top of rudder. What I feel is if there is more gap, due to flow separation there will be more resistance for ship movement.

 

That is correct.

I think you could also take a look at this comment: http://www.boatdesign.net/forums/boat-design/need-help-rudder-designs-29416.html#post302458