An Introduction to STR Hull Concept

The idea for the Submerge Trimaran hull concept (STR) presented on this paper it’s originated from the Nautilus System (NTLS) stabilizers for motions and currents, which is based on a 2 sides linear approximation using Keulegan-Carpenter number (KC) to obtain the roll motion damping coefficients from  the roll decay test of  high block coefficient vessels with bilge keels and from which it´s possible to understand that, the damping that’s  rules the roll motion of high block coefficient vessels with appendages is more significant at lower oscillations amplitudes (roll decay test latest cycles), it´s mean at lower KC numbers   (KC <) were the steady state flow regime is predominant and the GM_T has a linear variation  in the stability curve, which however didn’t occur for larger oscillation amplitudes (roll decay test initial cycles) were highest KC numbers (KC >) are relevant (drag forces) meaning that, the action of appendages such as bilge keels is less effective in reducing roll amplitudes as results of the turbulence derived from the back and forth oscillating  flow, being the main  source for the energy dissipation the vessel hull form capability to generate waves. Therefore, the Submerge Trimaran hull (STR) is a NTLS variation to be applied in conventional vessels with advance velocity to obtain a reduction to the roll amplitudes by increasing the potential damping while restricting the transversal oscillation flow by doing a hull modification from a perspective that considers as a base a hull immerse in a steady state flow regime (lower KC numbers) that´s has the effect of varying the natural roll period, extending the GM_T (STR) linear variation in the transverse stability envelope for a broader range of sea state, as more external excitation energy it´s require to obtain the same conventional hull roll amplitude, as part of the main motivation for the STR hull concept development idea, which is to achieve an overall improvement to a vessel sea keeping performance to cross ocean routes efficiently with energy savings and decabornization.