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Vessel Modification

Vessel modification is one of the services that Naval Architecture and Marine Solutions can provide to clients’.

Vessel owners often need to respond to market demands by upgrading and modifying their vessels. A large component of our work relates to modifying and converting existing vessels; including structural design; reviewing stability and powering requirements; and retrofitting of new equipment. Whether it is a minor or major vessel modification, NMS’ naval architects are well qualified for the task.

Talking to Naval Architecture and Marine Solutions (NMS) before making alterations or vessel modifications can ensure that you receive the correct advice before making such an investment, and can also ensure that your vessel remains safe, operable and meets your expectations.

Undertaking vessel modifications without the correct advice can lead to a vessel;

o Being made unsafe or inoperable
o Failing to meet it’s operation requirements
o Failing to meet the requisite stability requirements
o Failing to meet its approval or statutory authority’s requirements.

One of the most critical aspects of any vessel modification is the impact on vessel stability. Modifying a vessel or its equipment can affect the stability. The magnitude of the impact is a function of both the weight of the vessel modification, and where the alteration takes place.

Weight changes can have differing effects on your vessel:

o Adding significant amounts of weight high up reduces stability.
o Weight added below the deck generally improves the vessel’s ability to right itself, but added weight reduces freeboard. As freeboard reduces, a vessels range of stability reduces. Not all
stability issues can be resolved with ballast.
o Just as adding weight high reduces stability, so does removing weight down low.
o Adding individual pieces of gear and equipment to a vessel may not have much of an effect in isolation, but when the combined weight of all of the changes is considered, the effect can be
significant both on stability and fuel consumption.

Vessel lengthening is one of the larger scale vessel modifications that we regularly become involved with.

Midship lengthening is a popular way of maximising the load carrying capacity and deck area. Stern extensions can improve deck space and capacity. Often stern extensions are in addition to repowers which may include changing propulsors (jets for props), or shaft realignments. Bow modifications are typically aimed at improving performance and/or seakeeping.

Irrespective of how it is achieved, lengthening will generally improve the efficiency of a vessel.

If you are looking at lengthening a vessel, we can assist you by providing a range of options to allow the cost versus benefit analysis to be made for the vessel modification.

Advice can include:

o Where the extension would be most compatible with the existing structural arrangement of the hull and super structure
o The difference various extension lengths would have on speed, carrying capacity, and transport efficiency
o We will evaluate what additional vessel modification may be needed in order to make the boat as safe and economic to operate as possible.

Our collective operations experience allows us to develop cost-effective and timely solutions for vessel modification that respond to our clients’ needs.

Throughout the vessel modification process, NMS can work closely with the owner and boatyard / shipyard in order to ensure you receive a quality product.

We also liaise and manage the requisite approval or regulatory authority submission to Department of Transport, Department of Mines and Petroleum, or any other statutory agency.

Recent examples of our vessel modification work includes:

o NMS prepared the construction drawings for the installation of a Shark Jaw to an existing vessel, completed structural calculations and prepared an addendum to the stability book to reflect the
alterations. The stability addendum and structural drawings were submitted to Lloyds.

o NMS reviewed the suitability of a proposed site for the navigation and berthing facilities for a large yacht. The variables considered when assessing the suitability of the site included wind,
waves, current, depth, squat, waterway width and approach channels.

o NMS reviewed the connection details used to join modular barges together, to form a larger floating platform. Different configurations were considered, taking into account the existing connection
pins and lugs, applied loads, and allowable stresses. We specified modified lugs for the vessel, which we have designed to significantly enhance the load carrying capacity of the barges in
the various configurations.

o NMS looked at the feasibility of extending and repowering an existing 25 metre ferry. The owner wanted to increase the seating capacity whilst still maintaining the required service speed. We
presented the client with various lengthening options, allowing them to look at the cost versus benefits for each proposed vessel modification. On confirmation of the clients preferred
configuration, NMS prepared the construction and engineering drawings so the works can be carried out. Through our contacts in the local boat building industry, we have been able to recommend
builders who can supervise the works on the clients’ behalf. On the completion of the vessel modification, NMS will attend sea trials, undertake the inclining, and prepare the new stability booklet
and liaise with the clients’ statutory authority.

By Shaun Ritson
Naval Architect
Naval Architecture and Marine Solutions