Enter the minimum thickness of the long-side plate used to build the vessel, or the minimum thickness measured for an existing vessel. The short-side thickness value is a required entry for all vessel types.
According to Appendix 13, vessels A3 and C1 (Figure 20C and 20K, respectively) are
assumed to have equivalent long and short-side thicknesses. Thus, the long-side thickness
is not a required entry for these two vessel types.