Target Blocks and Cutters

The definition of target blocks and cutters are separate and no check is done on the consistency between them. Nevertheless it is important that the cutters match the target blocks and that the target blocks cover the extension of the selected panels and that they have a sensible overlap between them.

When defining a block it can be given as a nominal box and offsets for the six sides. For special cases also an additional limiting object can be given for any of the sides. The recommendation is to let the sides of the nominal boxes meet between adjacent blocks and then to add an offset on each of the sides. The nominal boxes should also correspond to the cutters used in Block Divide.

The need for target block overlap is determined by the structure surrounding the specific cut. The aim is to create block boxes that will unambiguously collect the resulting panels. The block box overlap should be big enough to allow for example, stiffeners extending outside the panel plate edge and yet small enough to prevent any panel from being totally inside more than one target block.

If for example a cut is made in a frame plane intersecting deck panels the offset must enclose any stiffener extension outside the panel. In the picture below the forward limit of the aft block must enclose the stiffeners (typically a couple of hundred mm) while the aft limit of the forward block can have a smaller offset. The dashed lines show the total block boxes including the offset.

Note: The offsets in both cases must not be smaller than the minimum stiffener length specified in Block Divide.

If the cut is made in the plane of the deck on the other hand and we assume that the deck should end up in the lower block the offsets must be smaller. Below the lower limit of the upper block must not enclose the whole deck but still any panel standing on the deck. Typically it should be bigger than the plate thickness but smaller than the profile height.

The upper limit of the lower block should enclose the deck having an offset bigger than the maximum plate thickness, but not much more than that.

There are cases that are more complicated than these but the general rule is to consider things like minimum plate width, minimum stiffener length and stiffener extensions outside the panel to set appropriate block offsets. If some panels still end up in the wrong block they can be moved to another block for example, by using the Rename function where both panel name and block can be set.