Feature 1 | Yacht Design anD construction
Lead shot installed
levels of confidence in the weights increase.
in double bottom
The process of assigning weight qualities can
structure (credit:
assist greatly in assessing the overall levels
Burness corlett
of confidence. This process should continue
three Quays
right up to delivery of the yacht, but the first
(southampton)
inclination test once it is afloat will of course
Ltd).
prove if the weight management system has
functioned well (or not!).
The project manager at the shipyard will
of course want to know if there is a worrying
trend in the weight, but in any event a
weight report should be prepared internally
on a regular basis up until delivery. Many
shipbuilding contracts also require the
shipyard to provide the owner with a weight
report, usually on a quarterly basis, but
more frequently if weight is a particularly
critical feature of the design, for example in
a high-speed yacht. These reports should
be accompanied by the corresponding key
loading conditions demonstrating compliance
with trim and stability requirements. Weight
reporting should process upwards from
the originator to section leaders through to
a weight coordinator, who in turn should
report directly to the project manager. The
weight coordinator has the responsibility of
combining all the data from the various input
through plan approval, witnessing model centre of gravity value of each component. sources into a manageable document, from
testing, on site supervision and test and trials As a minimum this would be ‘estimated’, which the regular reports can be prepared.
attendance. The designer will continue to ‘calculated’ or ‘weighed’, and whether the Contract variations are an inevitable part
develop the interior design after contract data has been provided by the shipyard or of shipbuilding, and the way in which they
award until an interior design and build subcontractor / supplier. These qualifications are to be handled should be described in
subcontract can be let by the shipyard, so he/ will then allow the trend in weight quality detail in the contract. This should include
she and the shipyard will need to agree on to be tracked on a continuous basis, and to a statement of the effect of any proposed
space and weight limitations to enable the highlight any areas which have not improved changes on the vessel performance including
design of the remainder of the yacht to be in line with expected design development. weight before agreement is reached on the
progressed. Control of weight data can be more difficult variation. An efficient and functioning
Once the shipbuilding contract has been let when provided by subcontractors, so it is weight management system will be able to
the shipyard should, among many other key beneficial for the shipyard to agree weight provide important data in this respect.
tasks, set up a weight management system. limits within the subcontract. The weight management system should
This should enable active control of all weight Suitable margins are always included form an integral part of the shipyard’s quality
aspects of the design and build. It is sound for both weight and centre of gravity at management system (whether formal or
shipyard practice to have a project work the design stage, and these can reduce in not), and should therefore be subjected to
breakdown structure for the whole vessel magnitude as the design progresses and regular auditing to ensure all concerned in
on which all activities from design through the process are carrying out their required
procurement to construction is based. By responsibilities. BCTQ have carried out
basing the weight management system several external audits of different shipyard
on this structure a reliable and complete weight management processes, and with
weight database can be maintained which their experience have been able to assist in
will ensure its ability to provide a credible improving the systems as well as helping the
prediction of the final lightship weight and shipyard and owner find solutions to weight
centre of gravity. As the design is developed, problems in the design. SBI
information on the various components of
the yacht will become better defined, and
it is therefore very advantageous to assign Lead shot ballast (credit: Burness corlett
a ‘quality’ description to the weight and three Quays (southampton) Ltd).
24 Ship & Boat International March/April 2010
SBI_MarApr10_p23-24.indd 24 26/02/2010 12:21:48
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