The RNLI Severn class lifeboat is made up from various materials, each one is specially chosen for its suitability for a particular area of the boat. In this activity there are 6 different areas of the boat to build. They are:
- Propeller
- Hull
- Superstructure
There are 9 different materials to choose from to help in building the lifeboat and some are more suitable than others for each area.
Wood - A lightweight material but not the strongest. If worked in layers wood can be made into complex shapes but can be time consuming and expensive to upkeep. Wood has average impact resistance
Rubber deforms very easily and hasn’t got the necessary strength to hold its shape under huge loads. It is a very flexible and easily worked material.
Glass is brittle and shatters under load. You can see through it, but it is not as tough as some plastics. It is also difficult to make awkward shapes out of glass.
Fibreglass is very strong but it is also very expensive. It can be easily shaped and doesn’t need much looking after, so although it’s expensive to make the costs over time are less.
Plastic - A lightweight material, some plastics are transparent. It is lighter than glass and can be tougher and less likely to crack. Plastic is easy to mould into shapes but needs help from reinforcing materials to have great strength. Some plastics are very flexible.
Bronze - Very heavy and expensive, it is too pliable to support large loads. It is strong however and when mixed with other metals is very resistant to fatigue and corrosion in seawater. Bronze can be cast and machined to shape.
Aluminium - Not as strong as steel and can be expensive to make. It also suffers from fatigue and corrosion problems through life. Lightweight and medium strength, if mixed with another material like bronze it can be made resistant to fatigue and corrosion in sea water.
Concrete - Although strong in compression it is weak in tension and heavy. To get the right strength it is often reinforced with steel and is then even heavier. Concrete is also brittle which means it can crack easily. It is difficult to make a complicated shape out of concrete and thin sections would not be able to take high loads.
Steel is strong and can be formed into appropriate shapes at an acceptable cost and weight. Steel is heavy and also rusts, it can therefore cost a lot to maintain.
Choosing the correct material for each of the 6 areas will complete the build and the lifeboat will be ready to sail.
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The ideal solution for the Severn class lifeboat is:
Propeller – which is made from bronze
Hull - which is made from fibre glass
Superstructure - which is also made from fibre glass
Windows - which are made from plastic
Crane - which is made from steel
Inflatable - which is made from rubber
Please note:
The RNLI neither warrants nor guarantees these facts. All the information has been simplified to suit the wide age group using this website. This building game is meant to illustrate the types of considerations that engineers bear in mind when selecting materials for their suitability, life costs and average material properties etc.
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