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Calcimator

Submarine Cable Design Calculator

Model the catenary profile of submarine cables and umbilicals — compute layback distance, cable length, top tension, and departure angle for installation engineering.

Inputs

Results

Layback distance (m)

290.24

Suspended cable length (m)

316.39

Top tension (N)

25,500

Catenary parameter a (m)400
Departure angle (°)38.34
Suspended weight (N)15,819.3
Lateral current drag (N)5,837.3
How to Use This Calculator
  1. Enter water depth (m), cable submerged weight (N/m), and horizontal tension (N) at the touchdown point.
  2. Enter hang-off height above waterline (m) and cable outer diameter (m).
  3. Read catenary shape parameters: top tension (N), lay-back distance (m), and touchdown angle (degrees).
  4. Verify maximum curvature against minimum bend radius — violation causes cable damage.
  5. Use lay-back distance and water depth to plan vessel positioning during installation.

How the result changes with Submerged weight (N/m)

Submerged weight (N/m)Layback distance (m)Suspended cable length (m)Top tension (N)
50079.87144.5775,000
1,75034.9120.89212,500
3,25022.34115.99377,500
4,50017.52114.36515,000

What each input means

Water depth (m)
Depth from mean water level to seabed at installation location.
Submerged weight (N/m)
Cable weight per meter in seawater (dry weight minus buoyancy).
Horizontal tension (N)
Horizontal component of bottom tension at the touchdown point.
Hang-off height above WL (m)
Height of cable hang-off point above the waterline.
Cable outer diameter (m)
Overall outer diameter of the cable or umbilical.
Cross-current velocity (m/s)
Lateral current velocity for drag load estimation.
Cable drag coefficient
Normal drag coefficient for the cable cross-section.

What each result means

Catenary parameter a (m)
a = T_H / w — defines the catenary shape. Larger a = flatter curve.
Layback distance (m)
Horizontal distance from vessel to seabed touchdown point.
Suspended cable length (m)
Length of cable along the catenary from touchdown to hang-off.
Top tension (N)
Tension at the hang-off point (vessel end). T_top = T_H + w*h.
Departure angle (°)
Angle of the cable at the hang-off point from horizontal.
Suspended weight (N)
Total submerged weight of the suspended cable span.
Lateral current drag (N)
Estimated total lateral drag from cross-current on suspended cable.

How this is calculated

Worked example, using the default values

  1. Identify Input Parameters
    4 parameters
    Water depth (m) = 100, Submerged weight (N/m) = 50, Horizontal tension (N) = 20000, Hang-off height above WL (m) = 10 = 7 input(s) provided
  2. Calculate Layback distance
    290.24 = 290.24
  3. Calculate Suspended cable length
    316.39 = 316.39
  4. Calculate Top tension
    Top tension = horizontalTension + submergedWeight * h
    25500 = 25500
  5. Calculate Catenary parameter a
    Catenary parameter a = horizontalTension / submergedWeight
    400 = 400
  6. Calculate Departure angle
    Departure angle = (departureAngleRad * 180) / π
    38.34 = 38.34

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