The main body of a vessel is called the hull. Regardless of the material used in construction, the layout of the hull is similar in each case. The hull is basically a shell, which keeps the vessel watertight.

The shell is supported, obtains its strength and maintains its shape from internal stiffeners called frames and ribs.

Hulls can be rounded, soft or hard chine and flat bottomed. Some vessels can have more than one hull (catamarans and trimarans).

Hull Shapes

Hull Illustrations

Advantages of Each

Hull Type

Disadvantages of

Each Hull Type

Flat Bottom

Hull

This planing hull has a shallow draught. Good for fishing in small lakes and rivers.

Rides roughly in choppy waters.

Round

Bottom Hull

This typical displacement hull moves easily through the water even at slow speeds.

Has a tendency to roll unless it has a deep keel or stabilizers.

Deep Vee

Hull

This planing hull gives a smoother ride than a flat bottom hull in rough water.

Takes more power to move at the same speed as flat bottom hulls. May roll or bank in sharp turns.

Multi-Hull

Another example of a displacement hull, the multi-hull has greater stability because of its wide beam.

Needs a large area when turning.

Displacement Hull

Whether underway or not moving,it sits in the same position in the water. Hence displacement vessels are deep draught.

Planing Hull

Sits in the water like a displacement hull when not moving, but is designed to 'rise' out of the water when underway so only the bottom is in contact with the sea surface. Hence planing hull vessel are shallow draught.

It is important to ensure your vessel is in good order by inspecting the key features of the vessel before you leave home or the ramp, mooring or wharf. he major causes of breakdowns at sea are engine failure, fuel shortage or contamination, mechanical failure and battery failure.

The Vessel Checklist

On entering the vessel and before operating any switches or engines, check for petrol and or LPG odours; fix any faults before you go out.
Ensure the vessel is well ventilated to prevent carbon monoxide build up from exhaust system.
Inspect the bilges. If there is more bilge water than usual, find and rectify the fault. NOTE: when pumping bilges be aware of the environment. Polluting the waterways is an Offence.
Check fuel, engine oil and coolant levels. Top up if required. Examine Batteries, terminals etc. Do the same for the second engine if carried.
Check the fire extinguisher is in good condition.
Ensure there is sufficient fresh water and food for the length of the voyage with some extra in case of emergency.
Make sure your lights are in working order; it may be a daylight outing, but you could be delayed in returning.
Fuel should be fresh and you should have enough fuel for the full trip plus reserve.
Self-draining holes should be clear.
Ropes and lines should be in good condition and stored ready for use.
Steering cables cables and connections must be in good working order.
Inspect the battery.
Check that appropriate anchors are on board and are properly rigged, stowed and ready for use.
Have one appropriate lifejacket for each person on board and accessible.
Children should have suitably-sized lifejackets and look at means of rigging lifelines in open areas so that children have enough handholds.
If you have a radio, make sure it is on and working. The best way to do this is to report the details for your vessel and voyage to a coast radio station or local base station.
Have up-to-date charts showing ports along your route.
Ensure you have a complete first aid kit.
Essential tools and spare parts should be in good condition.
Keep a sharp knife in a handy place; you may need it to cut ropes etc.
Have a rescue quoit or lifebuoy ready for use.
Have a whistle, mirror, marker dye, flares for emergency signalling.
Do not overload your vessel.
Don't forget the bung!

Keeping your vessel well maintained will extend its life and give you and your family many years of enjoyment.

Examine the interior and exterior of the hull when it is out of the water.
Oxidation, a common problem on aluminum hulls, it appears as white powder spots. Use fine sandpaper on oxidized areas until oxidation has been removed.
To protect the environment, use only environmentally-safe non-phosphate detergents to remove oil and algae from fiberglass hulls.
Check through-hull fittings to make sure they are not cracked or leaking.
Store vessels in a dry area out of the sun. If you must store the vessel for a long period of time, place the trailer on blocks to preserve the tires. Keep it covered, leaving an opening to circulate air.
Clean lines and ropes. Keep them out of the sun when not in use. Replace old lines. Dirt and sand cause deterioration.

Regular maintenance will ensure some of the following parts won't let you down

Water pump: replace regularly especially if you have been operating in the shallows and stirring sand and mud. Water pump impellors also deteriorate if not used for lengthy periods.
Fuel filters and lines: filters become clogged and lines can harden with age and exposure.
Propellers: the bushing of the propeller can fail especially if it has hit sand or rocks. Always carry a spare shear pin.
Spark plugs: plugs can break down unexpectedly. Carry spares.
Gearbox oil: snagged fishing lines on the drive shaft is a common cause of leaking gearbox seals. Water in the gearbox will eventually cause it to fail. Regular oil changes will prevent this. Some of the causes for engine failure are minor, so you should be able to troubleshoot a problem. Take time to learn how to: change the filter and primer bowl; clean and change spark plugs; check for spark; check and replace fuses; change the propeller; clean battery terminals. Don't be a backyard mechanic - have all major servicing done by a qualified mechanic.

All gear in the vessel should be secured firmly to keep it from shifting, and should bee arranged so that the weight is evenly distributed in the vessel.
Properly secure the vessel with several tie-down straps and or safety lines to prevent it from shifting. Never trust the bow winch alone to hold your vessel.
Inpect all lines, tie-downs and the winch. Tighten as necessary. Replace anything that shows signs of wear. Use extra tie-down straps in case one fails.
Tilt and secure the engine to increase road clearance. Use a bracket to support the weight of the outboard. This will help prevent damage if you hit a large bump.
Inspect the hitch and safety chains. Criss-cross the safety chains when attaching them to the towing vehicle to keep the trailer under control if it disconnects. The chains should have a breaking strength of no less than the combined weight of the vessel, motor and trailer.
Grease the bearings in the hubs of the axles to prevent bearings from seizing.
Make sure the traten the wheel nuts on the traileriler lights work properly. Check trailer brakes if fitted.
Make sure you have a spare trailer wheel and check the tire pressures of all the tires.
Tighten the wheel nuts on the trailer wheels to the recommended torque.