This Excel sheet calculates the required Bollard Pull to tow a conventional ship shaped vessel.
It rigorously calculates all the forces on the vessel, viz.
1. Calm Water Resistance: It is calculated using the established Holtrop and Mennen formula
2. Wind resistance: Based on Wind Height and Shape coefficients from ABS MODU rules, and corrected for wind direction.
3. Wave Resistance: From DNV Rules for Marine Operations, and corrected for forward vessel speed using Faltinsen, 1990
4. Propeller resistance and Hawser resistance: From US Navy Towing Manual
Useful in Marine Operations. It can be used to predict the bollard pull to tow a vessel. The tug can be accordingly selected.
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Q. Does it calculate Bollard Pull for the stall condition or for tow condition?
A. The spreadsheet can calculate for both ‘Stall’ and ‘Tow’ condition. For ‘Stall’ condition, the vessel speed has to be input as zero. However, user should note to provide the appropriate environmental condition for the ‘Stall’ and ‘Tow’ cases.
Q. Some of the inputs (like wetted surface area) are not available. How do I get them?
A. Default values are provided in the spreadsheet. You can use them.
Q. Does this work for any ship type?
A. This product is valid only for conventional ship shaped vessel with a bulbous bow. It should not be used for high speed vessels or barges or any non-conventional vessel shape.
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