Types of powered craft
There are 2 main classes of powered craft
- Displacement Craft
- Planing Craft
Planing craft can be further broken down into:
- Fully Inflatable - inflatable tubes with solid or inflatable floor
- Rigid Inflatable Boats (RIB's) - rigid hull with inflatable top tubes
- Rigid Hulled - fully rigid plastic, GRP or aluminium hulled craft
Type of craft
|Displacement||These boats are usually fitted with inboard diesel engines and are therefore good for towing and have low running costs. They can carry large loads and have good low speed manoeuvrability.||Due to size and weight, must be kept afloat, for the same reason, they can not be beached. Their Large freeboard makes MOB recovery difficult. They are also prone to damage alongside other craft.|
|Inflatables||Easy to transport, launch and recovery and are inherently extremely buoyant. They can also carry large loads and are suitable for recovery of people from the water.||Their limited draught and displacement means that they are affected by strong winds and certain types of tow can be difficult. The lack of a rigid hull and small freeboard leads to a rough, wet ride.|
|RIB's||Very versatile and particularly suited to costal use. Inflatable tubes give high buoyancy but the rigid hull provides directional stability and seaworthiness.||Requires a trailer for launching and recovery and can be prone to damage. Low initial stability is experienced at rest (except where flooding hulls are used).|
|Rigid Hulled (e.g. Dory)||Stable when at rest, good directional stability and high manoeuvrability at speed. Hulls are often double skinned with buoyancy fitted between the two.||Uncomfortable ride in waves. Requires trailer or launching trolley and hull repairs can be difficult.|
with each type of boat commes the problem of choosing a suitable engine. For more information on this subject, see Barnet Marine Centre's resource pages.
(N.B. only covers outboards)
Choosing a boat
Things to consider when choosing a boat:
|For what role(s) will it be used?||If it intended as a safety boat then a RIB or inflatable is more suitable. A dory makes a good cruising boat or play boat. If a pure work boat is needed then this is best suited to a displacement craft. If you want to water ski then a planing craft is essential.|
|What type of water is it to be used on?||If the boat is only required for inland or inshore use then it need only be of a small size, for example a RIB upto 4m. For costal use, you are looking at a RIB 5m+, or rigid boats around the 4m mark. For offshore cruising, a RIB 5.8m+ is more suited.|
|How many people do you need to carry?||A rigid hulled boat will hold 4 people at 4m. The equivalent size of RIB may only have a single or jockey seating arrangement but an extra person may be able to sit in the bow. Larger craft can hold more like 6 people and can have side facing seats. Inflatables don't tend to have incorporated seating but are usually removable or inflatable. It is more normal to sit on the tubes in which case distribution of weight is important as well as not exceeding the maximum carrying capacity.|
|Who is going to use it?||If a qualified coxwain is to use the boat then there is no problem. If however the boat is to be used by children or youth members then some consideration needs to be given to the handling an performance or different craft. A rib or inflatable are more forgiving to any mistakes made and are less prone to damage compared to a rigid hulled boat. They are probably easier to fall out of though and kill cords should always be worn. For safety, the boat should not be overpowered; a 40hp outboard will suit a RIB at around 4m. A larger engine will be more difficult to control by tiller steering, especially at speed so remote controls are an option. If a rigid hulled craft is to be used by children then adequate fendering will be needed.|
|What type of engine do you want?||The first choice is inboard or outboard although such a choice is usually limited to displacement craft or more expensive RIB's with outdrives. The next choice is petrol or diesel; inboards are nearly always diesel due to the environment in which they are working and the low running costs. Diesel outboards are also available but are heavy and expensive. The main choice for most people, in terms of outboards, is 2 or 4 stroke. 2 strokes are more suited to performance craft due to their high power to weight ratio whilst 4 strokes are used for work boats since they have higher torque. 4 strokes are quiter and cleaner than 2 strokes which are suffering environmental restrictions. In certain conditions, a twin engine setup may be desirable.|
| How are you going to transport it?
||Inflatables can be carried ona car roof or diflated completely and carried in the boot. RIB's and rigid hulled boats up to about 5m need to be towed on a trailer. Boats above 5m may need a slightly more powerful car whilst displacement craft, if they can be recovered from the water easily, normaly require a braked trailer and at least a 4 wheel drive vehicle.|
|What material should it be made of?||RIB's and inflatables tend to be made of PVC or Hypalon, the latter being the preferred choice. Avon and Zodiac tend to make the better boats. Rigid hulled boats can be plastic (woven polyester), GRP or aluminium. Plastic is replacing alot of GRP designs as it is very durable and is lower maintenance. Aluminium tends to be limited to more commercial type craft.|
This is by no means an exhaustive list. There are a great many resources available on the Net regarding the purchase of suitable craft. Many compainies will tailor a craft to your individual needs.
Equipment to carry
The RYA recommends that all boats should carry appropriate safety equipment, according to the areas they are operating in. It is also important that those in the boat know how to use it.
The following list represents the minimum which should be carried whenever the boat is in operation on coastal or major inland open waters:
- Engine ignition switches fitted with a 'kill cord' to be used at all times while under way
- Personal buoyancy aids with minimum of 50N buoyancy
- Alternative propulsion (oars or paddles, spare engine)
- Anchor and warp
- Bucket / bailer, bilge pump
- Mooring lines and spare ropes
- Spare fuel and oil (premixed if appropriate) and funnel
- Engine spares (spark plugs, shear pins, etc) and tools to fit them
- Simple first aid kit
- Distress flares - Inshore Pack
- Vessels with an enclosed cabin should carry a CO2 or powder fire extinguisher
- Inflatable boats - 'Rampatches', bellows
Vessels operating in remote sites or further offshore are advised to carry the following in addition to the above:
- Greater quantity of spare fuel
- More engine spares (propeller, fuel line) and tools to fit them
- Spare small engine
- Steering compass and navigational aids
- More comprehensive first aid kit
- Distress flares - Offshore pack
- Marine VHF radio
Support and recovery roles
Within a Scout group the use of a power boat is usually limited to that of a safety boat or support boat. as such, the crew of the boat will usually find themselves aiding in the righting of capsized craft, recovering MOB's and carrying out simple tows.
Righting a capsized dinghy
A stand-off distance is maintained to allow verbal communication whilst preventing the two craft drifiting together. The normal position to adopt when aiding in the righting of a capsized dinghy is towards the forestay. This position keeps the safety boat clear of sails and ropes and allows the crew to simply 'walk' the boat upright and also prevent total inversion.
Man overboard (MOB) recovery
The final approach should ideally be made from downwind to allow speed to be better controlled. This is dependent on the type of craft since inflatables can drift faster than the casualty due to their being easily affected by wind and tide.
If the MOB is concious then they can be brought aboard facing the boat with the crew aiding them. If unconcious the best way is to have their back to the boat and heave them aboard under the arms. This means that they enter the boat in a more desirable position for resuscitation.
Implementing a tow
Towing alongside is frequently used for recovering an abandoned or waterlogged dinghy. The safety boats engine must be astern of the tow and it's bow needs to be 'toed-in'. If the safety boat has a small draught then manoeuvering will be difficult.