True Bearing Weather Intelligence
Vessel Performance Report Methodology
- Performance Assessment - Charter Party Agreement:
- The vessel's performance speed during "Good Weather" conditions is used to calculate any gain or loss for time during the voyage. The method used is basis the following English Law precedents:
- The "Didymi" [1988] 2 Lloyd's Rep. 108
- The "Gas Enterprise" [1993] 2 Lloyd's Rep. 352
- In the above English Law precedents, it was determined that the method for calculating any gain or loss for speed was to take the vessel's performance speed during "Good Weather" conditions and apply it to the entire voyage distance.
- The following formulae are used to calculate any time gained or lost for a given voyage: [nm = nautical miles, gw = good weather, allwx = all weather]
- Average Speed knots-gw = Distance nm-gw ÷ Time hours-gw
- Performance Speed knots-gw = Average Speed knots-gw - Current Factor knots-gw
- Charter Party Time Allowed hours = Distance nm-allwx ÷ Charter Party Speed knots
- Performance Time hours = Distance nm-all ÷ Performance Speed knots-gw
- Time hours (gain or loss) = Charter Party Time Allowed hours - Performance Time hours
- Good Weather Definition:
- "Good Weather" conditions for a given voyage are defined according to each individual charter party agreement. In cases where the wave heights are not quantitatively defined and reference to Douglas Sea State is used, the wave heights for Douglas Sea State are as defined by the World Meteorological Organization as follows:
- Douglas Sea State 3: Wind driven sea height of 0.50 to 1.25 meters and swell height of 0 to 2.0 meters.
- Where "No adverse current" is stated in the charter party agreement, days with a net negative influence of currents are to be excluded from the good weather analysis. This exclusion is supported by London Maritime Arbitration award LMLN 723 (2007).
- Consumption Calculation:
- In calculating any loss for bunker consumption where the term "about" applies, a 5% allowance is given to the daily charter party rate. Likewise, to calculate any gain of bunker consumption, a 5% downward allowance is applied to the daily charter party rate. The vessel's consumption during "Good Weather" days as defined by each charter party is used to calculate any gain or loss using the following formulae:
- Performance Consumption tons = Average Daily Consumption tons-gw
- Allowed Consumption tons = (Charter Party Time Allowed hours ÷ 24 hours) × Charter Party Consumption tons per day
- Performance Consumption tons = (Performance Time hours ÷ 24 hours) × Performance Consumption tons
- Consumption tons (gain or loss) = Allowed Consumption tons - Performance Consumption tons
