Simulation of the catenary effect under wind disturbances in anchoring of small boats

It has been conventional knowledge for as long as ships have existed that the catenary effect of an anchor line augments the efficiency of an anchoring system. This is achieved by making the anchor line as heavy as possible thus lowering the effective angle of pull on the anchor. This notion has, however, come under criticism in recent times. Many small boat owners have shifted to lighter tauter lines for anchoring. The argument in favor of this new method is the cost savings associated with lighter anchoring and the tension relief that comes with using lighter and more elastic anchor lines. The purpose of this study is to therefore compare the performance of long slack lines that form catenary shapes with that of shorter taut lines. An analysis is presented that describes the surge motion of a small anchored boat exposed to an input forcing function and various retarding forces and effects. The anchoring system used in the analytical model results in a non-linear but symmetrical restoring force, which resists the force-induced motion of the boat. Two main types of anchor lines are considered: uniform-material and two-material anchor lines. Each anchor line is evaluated both in catenary configuration and taut configuration in terms of its ability to minimize the motions of the boat and tension force in the anchor line due to wind disturbances.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Mechanical Engineering.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2012

Author dc:creator

• Mwarage, Jessy Mbagara

Advisor dc:contributor.advisor

• Douglas Hart.

• Mechanical Engineering.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/75670

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/75670