A method for casting a turbine blade body comprises; providing a mold defining the external geometry of the blade body; providing a core defining an internal geometry of the blade body, the core comprising a main body defining an internal chamber of the blade body and having a root end and a tip end and a plurality of pedestals defining an array of cooling channels extending from the internal chamber; casting a molten material between the mold and the core; and removing the core after the molten material has solidified, wherein the pedestals are arranged in a single row starting from the root end to a mid-portion of the main body branching into multiple and divergent rows towards the tip end of the body.