The unique patterns of iron-clads in the form of scale-plating on thick planking appeared at wall gates built in the early periods of Yi dynasty are photographically represented, and also a competency of such an iron-clad item to match the attack capability of firing weapons of the same periods is extensively discussed. Referring to these realistic patterns of iron-clads at Yi dynasty, together with careful evaluations of selected records and the iron-clad turtle-boat tradition, a simplified model conception of the iron-clad for the combat turtle-boats of Admiral Yi Sun-sin is schematically introduced. With regard to the amount of iron needed for the roofdeck plating with an average plated-thickness of 3mm and the iron spikes with an average unit weight of 250gm, a range of 4-7 tons as a primary estimate per ship is figured out. It thus appears that 5-9 tons iron may be needed per ship due to an additional iron to shield the gunport areas in bulwarks as well. The underlying logic of the present approach on the turtle-boats was shortly represented in the previous English work "A Short-Note on the Iron-clad Turtle-boats of Admiral Yi Sun-sin", Korea Journal Vol. 17, No. 1, 1977.