If you are going to blend a CLARK Y into a symmetrical airfoil I suggest you put the more cambered airfoil (CLARK-Y) at the tip and give the wing a couple of degrees of wash-out. In this way you will get a wing with very nice stalling qualities. The washout is needed because the cambered airfoil has a zero-lift angle of attack that is below zero whereas the symmetrical airfoil has zero lift at 0 degrees.

/Red B.