Calculator Inputs
Example Data Table
Sample cases for quick comparison.| # | LOA (m) | Beam (m) | Tugs | Wind (m/s) | Current (m/s) | Margin (%) | Recommended Diameter (m) |
|---|---|---|---|---|---|---|---|
| 1 | 120 | 22 | Yes | 6.0 | 0.5 | 10 | 213.64 |
| 2 | 180 | 30 | Yes | 8.0 | 0.8 | 10 | 328.94 |
| 3 | 220 | 36 | No | 10.0 | 1.2 | 12 | 537.87 |
| 4 | 260 | 42 | No | 14.0 | 1.8 | 15 | 691.69 |
| 5 | 90 | 18 | Yes | 5.0 | 0.3 | 8 | 155.28 |
Formula Used
This calculator provides a transparent planning estimate. It combines a length-based turning factor, a beam allowance, an environment multiplier, and a safety margin.
| Base Diameter | D_base = (k × LOA) + (Beam × A) |
|---|---|
| Environment | M_env = 1 + (0.01 × Wind) + (0.05 × Current) |
| Safety Margin | M_safety = 1 + (Margin% / 100) |
| Recommended | D = D_base × M_env × M_safety |
- k changes with tug assistance and your guideline profile.
- A is the beam allowance fraction (e.g., 50% = 0.50).
- The environment model is intentionally simple and adjustable.
How to Use This Calculator
- Select your input units and enter vessel LOA and beam.
- Choose whether tug assistance is available at the site.
- Pick a guideline profile that matches project conservatism.
- Enter typical wind and current conditions for maneuvering.
- Set beam allowance and safety margin, then calculate.
- Download CSV or PDF for sharing and record keeping.
Baseline geometry from vessel LOA and beam
Sizing begins with the controlling vessel’s LOA and beam. The calculator builds a base diameter by multiplying LOA by a turning factor (k) and adding a configurable beam allowance for sweep and clearance. Beam allowance is entered as a percentage of beam, so planners can reflect fender offsets, bank effects, and pilot preference while testing options in early layouts.
Turning factor and operational support
The turning factor k represents maneuverability and is limited here to 1.1–2.2. Guideline profile and tug availability adjust k, recognizing that tugs can improve pivot control and reduce drift during low-speed turns. Select a conservative profile for exposed entrances or higher consequence operations. Choose the efficient profile for constrained sites where operations are well managed.
Wind and current scenario testing
Wind and current increase required space by adding set and drift that must be corrected mid-turn. This tool applies an environment multiplier: 1 + 0.01×Wind + 0.05×Current, capped at 1.8. Wind is entered from 0–40 m/s and current from 0–5 m/s. Compare calm values to seasonal peaks to verify that the basin still fits dredging and shoreline limits.
Margins, uncertainty, and review notes
After environmental effects, a safety margin of 0–50% is applied to cover uncertainty in loading condition, pilot technique, bathymetry tolerance, and measurement error. Apply higher margins where traffic density is high or contingency maneuvering is limited. Record the chosen inputs in review minutes, then export results so assumptions remain consistent across disciplines and project stages.
Using outputs in construction planning
Outputs include recommended diameter and radius in meters and feet, plus k, environment, and margin multipliers for auditability. Choosing an elliptical basin reports a major axis equal to the recommended diameter and a minor axis at 85%, supporting asymmetric shore constraints. Use the result to coordinate dredge extents, slope toes, revetment alignment, and aid placement, then download CSV or PDF for packages.
FAQs
What does the turning factor k represent?
k scales basin size from vessel LOA to reflect maneuverability, assistance, and operational conservatism. Higher k increases diameter when self-maneuvering or conditions are challenging. It is a planning proxy, not a replacement for navigation simulation.
Why include a beam allowance?
Turning involves lateral sweep of bow and stern, plus clearance to banks, slopes, or fenders. Adding a percentage of beam provides a simple allowance for these effects and helps align early geometry with practical operating envelopes.
How should I choose wind and current values?
Use typical maneuvering conditions, then test a credible worst case for the season. If the recommended diameter changes materially, document both scenarios and coordinate with pilots or operators before freezing the layout.
Is the environment multiplier a standard method?
It is a transparent sensitivity model intended for concept sizing. Final designs should reference local criteria, pilot input, and formal navigation studies, especially for high traffic ports or constrained approaches.
When should I select an elliptical basin?
Choose elliptical when shoreline or existing structures prevent a full circle. The tool reports a major axis and a reduced minor axis to support a feasible footprint while maintaining turning capacity along the longer direction.
Can I use the results for final construction drawings?
Use the output for preliminary planning, estimates, and interdisciplinary coordination. For final drawings, confirm with site bathymetry, geotechnical limits, local authority requirements, and any simulation or ship-handling study results.