Life and Work of aNAVAL ARCHITECT

ASME BC and ASME UBC Technical Panel Presentation

Callum Campbell, P.Eng. Senior Naval Architect

3 March 2013

naval architects

As kids,

might dream of designing …

Something this beautiful

Or this grand

Or this big

Or this challenging

designing a hard-working harbour tug

But in reality, a Naval Architect is just as happy

Or a local ferry

Or even one of the ever-present deck barges.

Big and small, the common thread is …

A naval architect works in projects of all scope and scale

professionals in

Naval architects are

things that float

professionals in

professionals in

• SHIP STRUCTURES• STABILITY• RESISTANCE AND POWERING• SEAKEEPING• DESIGN

This is a ferry under construction at a shipyard in Alaska

SHIP STRUCTURES

•Follow the shape of the hull•Adhere to rules for scantlings•Provide access for construction and inspection•Compatible with production methods of shipyard•Minimize space for casks of wine

SHIP STRUCTURES

casks of wine?Yup, it’s true.

• Historically, the usefulness of a ship is measured in a unit called “gross tons”.

• A gross ton is not a measure of weight, but actually a measure of internal volume where the volume unit is that of a wine cask.

• There are prescriptive regulations about the way to measure gross tonnage, but it turns out that by filling the ship with steel structure, the tonnage (or wine carrying capacity) can be decreased substantially.

• Why would you want to do this? By reducing tonnage, an owner or operator can usually pay fewer taxes, employ fewer crew, etc.

SHIP STRUCTURES

SHIP STRUCTURES

Here’s the internal framework of that ferry

SHIP STRUCTURES

The ends of the ship are filled with structure which …

SHIP STRUCTURES

renders these areas useless for carriage of wine …

SHIP STRUCTURES

and therefore reduces tonnage …

SHIP STRUCTURES

and benefits the ship owner.

STABILITY

This is a crane barge. It is used for waterfront construction.

STABILITY

A naval architect calculates the lift capacity of the crane

• Two Problems:– Problem 1:

• The lift capacity of the crane is dependent on the side to side list of the boom.• A crane might pick up a lift over the end of the barge, and then rotate over the side • In doing so, the incline of the boom will change, and so will the lift capacity• The naval architect must answer: How much boom list?

– Problem 2:• Secondly, the stability of the system must be investigated • Stability typically involves drawing a conclusion about the centre of gravity relative

to the centre of buoyancy.• The naval architect must make sure that the deck stays well above the water, and

that the barge always has lots of reserve stability, or righting energy, to ensure it will always stay upright

STABILITY

• To assess the situation, a naval architect calculates the exact centre of gravity

for any given lift loadat any radius

and at any angle of rotation• Once calculated, a naval architect uses specialized hydrostatic

software to calculate the crane capacity, and the stability performance of the crane/ barge.

STABILITY

Resistance and PoweringRESISTANCE AND POWERING

This is a picture of the ferry in drydock

• The twin screw vessel was originally configured for each propeller to be driven by two main engines through a gearbox, making for four main engines in total.

• Since the relatively high speeds that the vessel was originally designed for were no longer required, the owner wished to operate only a single main engine per propeller, and wanted to investigate propeller modifications that could be required to accommodate the change in shaft power.

• Using specialized software, a naval architect computes the resistance of the hull, the power prediction, and the characteristics of the propulsors (i.e. shaft speed, propeller diameter, propeller shape).

RESISTANCE AND POWERING

SEAKEEPING

This is a typical coastal container barge.

SEAKEEPING

This type of barge is towed by a tug along the coast.

• Seakeeping, is an investigation into a ship’s response to ocean waves.

• The question is – in what sort of seaways will be dangerous for this type of transport – when do the waves become “too big” to continue operations?

• This type of analysis is undertaken by modelling the hull, and using specialized software to predict the Response Amplitude Operators which, when coupled to the spectrum of a seaway, help to predict the motions.

• Using the results, we can present operating instructions for the master of the tug boat to help provide guidance on what to do.

SEAKEEPING

DESIGN

Design is a synthesis of the techniques previously described

DESIGN

This is the design spiral.

DESIGN

It shows the process of design …

DESIGN

An idea converges to a final product through iterations

• A naval architect spends a few weeks preparing a concept design, where the structure, the stability, and the resistance and powering are loosely calculated.

• If the concept proves valid, the design moves onto a preliminary design phase. This work might take a few months, and involves a more detailed investigation into weights, centers, stability, powering, and equipment selection.

• From there, the design moves onto details design where the design is fully, and clearly defined, and lastly production design, which is the way to convey all the information of the design to the shipyard.

DESIGN

So if as a kid you had dreams like this …

you’ll start worrying about nightmares like this

Once a naval architect,