Abstract: The present invention relates to a cellular core having, in an expanded state, a bonding surface area suitable for sandwich type construction, wherein the cellular core comprises a plurality of elongate planar rectangular wall elements which define the depth and height of said core and extend in a core plane in a wall element direction, and wherein, in the expanded state of the cellular core, arrays of closed cells are formed between two adjacent wall elements, and wherein a respective cell is formed by wall element sections and bonded wall element sections of the two adjacent wall elements. The bonded wall elements have with this folding facility of the wall elements, the freedom to take a position of being almost or exact rectangular to the skin line which means that with this core we have on almost all positions the best skin support as it is the closest to rectangular support. An advantage is that the core can be formed with a double curvature.