Fuel saving from running a ship at its CFD- or model-tested optimum trim.
Formula
$$ \Delta F = \text{ME}\text{ref} \cdot p\text{trim} \cdot f_\text{cov} \cdot \frac{h}{24} $$
Symbol legend
| Symbol | Meaning | Unit | Source |
|---|---|---|---|
| $\Delta F$ | Fuel saved over the period | t | result |
| $\text{ME}_\text{ref}$ | Main-engine daily fuel rate at even-keel reference | t / day | voyage log |
| $p_\text{trim}$ | Resistance reduction at optimum trim | fraction | CFD / model test |
| $f_\text{cov}$ | Share of voyage hours where optimum trim is practical | fraction | operations policy |
| $h$ | Hours at sea | h | voyage log |
Typical optimum-trim savings:
- Tanker, design draft: 1–2 %
- Container, part-draft: 2–4 %
- Ro-Pax: 1–2 %
- Bulker, part-laden: 1–3 %
Sources
- NAPA - Trim Assistant / Loading Computer.
- Kongsberg - K-Trim.
- IMO Resolution MEPC.282(70) - SEEMP guidance on trim optimisation.