The principles of boats - how do boats work?

Boats are floating. This is achieved by letting the whole boat be much lighter in weight than an amount of water with the same volume as the boat. According to the prinsiple of Archimedes, the lifting power of the water is equal to the weight of water that an immersed object displaces. When a boat is much lighter than the amount of water with the same voluume, it will thus displace an amount of water with a weight that is equal to the weight of the boat before the boat is totally surrounded with water, and the displaced water will hold the boat floating.

In order not to sink the hull of the boat must be theight. Bigger boats are usually also made theight all the way round. Practically this is achieved with doors and windows that are theight for water when they are closed. It is possibler to make a boat totally unsinkable even when it gets great damages, by dividing the boat into a number of compartments with water-theight walls between them. Due to economical concerns, most ships uses this principle so that it can take some damage and penetration of the hull, but not any injury to the hull.

A boat must also hold itself upright, with the upside up and the base of the hull down. In most greater boats this is achieved by making the boat in such a way that most of the weight of the boat is near the bottom below the surface line of the water. The weight of the lower part of the boat will then constantly pull the bottom of the boat downwards, and if wind or movement in the water rotate the boat more or less, this weight will pull the boat back to an upright position again.

If the boat is totallly theight, the hull is heigher than the width of the boat and the upper parts are not too flat, a boat can be pushed totally around, and still go back to an upright position. Due to economical concerns, this possibility is not used fully in most ships. Therefore one still experience that ships go around, then take in water and sink.

Another way to keep a boat upright is to make the bottom of the boat flat and much wider than the height of the hull. Then the force needed to flip the boat around is so great that it is not likely to happen. In smaller boats this principle is often used at the same time as the most of the weight of the boat is held below the water line.

A boat must also be made so that the right side of the boat has the same weight as the left side, and the weight in front of the center is equal to the weight at the back of the center, and that all the weight of the boat is distributed as evenly as possible. In this way the boat will keep itself horisontally and even, and there will be less straining forces along the hull that can cause damage. In order to achive this principle also when a boat is loaded, one generally provides that the load is distributed evenly, or if that is not possible, in either case so that the weight of the load is equal before and after the center and at both sides of the center. The load is also deposited as deep in the boat as possible to keep the weight under the water line as greater as the weight above as possible.

The boat must make as little resitance in the water as possible, to achieve speed and save energy, and it must not easily get out of direction. This is achieved by making the hull narrow and sharp and the boat high and long instead of wide. Then the boat wil blow easily through the water. Ribs along the hull and fins at the backside of the boat are also often used to stabilize the direction.



About safe driving - principles of driving safely

When we learn to drive, we are told about always to drive defensively. People easily think that this is the same as just behaving according to the laws and rules of traffic, and keeping the speed limit. Not to break the rules is of course a basic part of defensive driving, but only the basic part. Defensive driving is the same as behaving intelligently, so that difficult properties of the road and traffic situation do not bring you into trouble. The basic principles of driving intelligently are:

- Look, hear and think before you drive or do any action.

- If the physical condition are difficult, or becoming more difficult, decrease your speed. Things giving difficult road physics can be snow, ice, injured road coating, wet rotten leaves, loose stones or sand, and so on.

- If the sight is difficult, or becoming more difficult, decrease your speed. Things giving difficult sight can be darkness, mist, snowy air, smoke heavy rain and so on.

- Do not get into the path of other traficants. Do not drive in the middle of the road. Do not cross another road at a junction if there are someone driving at that other road towards the junction, and you do not have the legal right to drive first. And even if you have the formal legal right to cross first, wait if someone driving along the other road has a too high speed to be able to stop.

In the winter when the road is icy or covered with snow, or by other slippery conditions, these basic principles are especially important. Ice makes the friction between the tires and the road significantly less, sometimes to only a fraction of the normal friction. The friction at such conditions is also unpredictable. Suddenly the tires can loose the grip.

An especially dangerous combination is smooth ice covered by loose light dry snow or loose wet snow.

Also wet rotten leaves on the road give slippery conditions that can be as dangerous as Ice, especially if it is also raining. Such conditions are very common in the autumn.

Pools of water or broad streams of water on the road caused by rain can also easily make the tires of the car slip their grip on the road. What happens is that the tires are lifted from the ground by the pressure from the water comming under the tires, and the car looses all force that can controle the direction.

- Never do any abrupt action at a slippery road, such as abrupt brakes or abrupt acceleration, suddenly the tires may slip and you loose the steering and controle of the path of your car.

- Always decrease the speed on an icy or slippery road. With a high speed at a slippery road, you can easily loose controle of your car, and it is impossible to brake rapidly. Your car will just slide forwards at the same speed when you push the brakes abruptly.

- Decrease the speed even more in curvatures at a slippery road. When you swing at high speed at an icy road, your car will simply slide forwards in a straight line, and into the opposite path or even out of the road.

Curvatures or swings are formations where several of these basic principles will apply simultaneously.

- Generally one should always decrease the speed in a curvature.

- If you cannot see what is around the swing, or what is coming towards you the opposite way, then decrease the speed. Also make sure you do not drive in the middle of the road. Then you have a better time to react if something unexpected appears. And if you crash, you have a better chance of getting just small injuries if you have a smaller speed.

- If the road is slippery because of ice or other stuff, it is especially important to decrease the speed in a curvature. If you slide in a swing, you easily get into the opposite path or off the road and collide.

A third situation where the basic principles apply especially strong is when you drive in the evening or night at dark, or at misty or smoky conditions. It is difficult to spot people or animals walking along the road in the dark or in a fog. It is also sometimes difficult to be aware of curvatures or irregularities of the road when it is dark or reduced sight through the air.

- When it is dark or misty, always take a good look forward and around before you do any action, and do not engage in any action before you have seen enough and have had time to interpret the things you see.

- And again, reduce the speed.

Reducing the speed at difficult conditions is as seen a basic ingredient of defensive driving. But how much shall you reduce the speed? Unfortunately there is no good answar to this question. Sometimes only a fractional reduction is enough, other times you must reduce the speed to only a fraction of the normal and formally legal speed. If there are many difficulties at the same time, your speed should be reduced significantly. For example in a curvature on an icy road at dark and with snow in the air, it can be necessary to reduce the seed to only on third or lower than normal speed.

With experience you will get better in judging the driving conditions and reducing your speed properly. If you are inexperienced, it is better to be extra careful.

Sometimes you can feel if your speed is too high. If it is difficult or heavy to controle your car, then you should reduce it. Also if you feel you do not see well what is coming towards you, or what is happening around you, you should definitely reduce your speed.