Matlab Optimization toolbox is a very powerful set of numerical optimization
routines. The output of Miarex calculation was redirected to those optimization
routines, for precise design cases.
Presentation of the problem The problem to be optimized was the following :
An optimal value has to be optimized. At first, only simple condition were set :
Nota : I intend to work on a more general optimization function, as a sum of different operating point over the speed polar. 
Illustration of the degree of freedom 
The optimization process was repeated for two cases, with different Reynolds
numbers and airfoils :
The interest of the optimization is to see which contribution to drag is predominant in directing the solution : Airfoil drag or Induced drag. The influence of the degree of freedom is the following (see the illustration):


Some results Here are displayed some result of the optimization process. 

First the optimal taper location for the 4 cases (model or full size, L/D or
sink optimization) are plotted according to CL.
Some conclusion can be drawn from those plots :

Click ! 
Then the same result about optimal taper location are plotted according
to a nondimensionnal version of the speed polar. This allow to see were on the speed polar
we need a precise value for taper location.
Then the relative importance of each area is quite changed. We can see that the statistical value for taper location found among existing sailplane (between x=0.6 and 0.7) is an optimum for cruising part of the polar. 
Click ! 