Submarine Cable Design Calculator

The catenary parameter a equals horizontal tension divided by submerged weight per unit length, so it's the ratio between the force holding the cable taut horizontally and the force pulling it down. A large a means horizontal tension dominates relative to weight, which stretches the curve out and flattens it — this is why increasing horizontal tension in the calculator increases layback distance and reduces the departure angle at the vessel, while a heavier cable per meter produces a tighter, more steeply hanging curve for the same tension.

The catenary equations this calculator solves — h = a(cosh(x/a) − 1) and the related tension and length relations — are only valid for a cable hanging in a single vertical plane under gravity alone. Adding lateral current drag would pull the cable sideways out of that plane, turning it into a genuinely three-dimensional shape that the closed-form catenary equations can't represent, so the drag force is computed as a separate reference estimate rather than being fed back into the layback, length, or tension calculations.

No — top tension and departure angle come purely from the static catenary geometry and tension balance, with no check against the cable's minimum bend radius. A cable can produce mathematically valid catenary results here while actually exceeding its allowable curvature near the hang-off point or touchdown, so bend radius must be verified separately against the manufacturer's minimum bend radius specification before finalizing an installation plan.

This model assumes a static hang with no lateral current and no vessel motion, which represents standard installation planning but not real operating conditions. In strong cross-currents, during dynamic vessel heave and surge, or near the touchdown point where seabed friction and lay tension dynamics matter, the real cable configuration departs from this idealized shape and needs iterative numerical or finite-element analysis rather than the closed-form equations used here.