How to make sure the stern shaft length and diameter?

This is definitely a good question. You may understand by Sinooutput briefly introducing the design process of the ship.
 
1. Firstly, refer to similar ship types according to the requirements by the shipowner. That is to find the same purpose, larger and smaller boats for reference, then design job.
2. Make ship model and drag model, and calculate the power required by the main engine according to the speed requirements.
3. Add main engine, sub-cabin, add cargo...finally calculate the weight of the ship.
4. The calculated weight must be different from the original estimate.
Then increase or decrease the size of the hull and repeat the above steps.
Repeat the calculation many times until the error is less than the allowable range.
Take a general cargo ship as an example: the engine room needs space. The VLCC is wide enough to fit tightly to the bottom of the boat, and the tail shaft is relatively short. Small boats have to be arranged toward the midpoint of the boat, and the tail shaft is relatively long.
To be honest, the length of the tail shaft was really not taken seriously during the whole process, but it is very necessary to calculate the exact datas in order for ships better performance.
Sinooutput usually supply the stern shaft with tube completely, it will include what? Please leave your email address and list your requirements, we will reply you as soon as possible.
 
Ships travel based on the propulsion system. Modern propulsion systems basically use a method in which the main engine uses a drive shaft/stern shaft to drive the propeller. Since the main engine is in the engine room(inside the ship), and the propeller is in the water(outside the ship), the drive shaft must pass through the hull.

So we should better know:
It is not an easy job to let the stern shaft through the hull. It is directly related to the stern shaft structure. In order to better support the weight of the stern shaft and the propeller,meanwhile to deal with the vibration force of the propeller and the impact of water after the propeller is started, a stern post needs to be added to let the stern part of the ship gradually close to the stern post, so as to strengthen the stern shaft structure.

In addition to this component, since it is impossible to install the stern shaft bearing and sealing device, in order to realize the lubrication and cooling of the bearing, another important component--the stern tube. Of course, there are also the ribs of the stern tip cabin. Each rib extends to a certain height from the position of the stern shaft to further ensure the strength.

The stern shaft tube, also called stern tube, usually the stern tube rear end fixed on the stern post at the stern, and the front end fixed on the watertight bulkhead. The tail pipe comes out of the stern tube. There are front and rear bearings in the stern tube to support the stern tube, so the overall weight of the propeller and the power of rotation are transmitted to the ship in the form of bearings to the stern tube and then to the stern post, and it will never damage the hull. In this case, the bearing must be easy to use. How should the bearing be lubricated and cooled?

This problem can be solved by sealing the head and tail ends of the stern tube, filling the tube with lubricating oil, or sealing only the head end and letting seawater enter from the tail end for water lubrication.
 
As a result, a new problem comes out. The tail shaft has to rotate and prevent sea water from entering. It cannot be sealed. How can it be sealed? The sealing of engine pistons in motion provides designers with ideas.

When the engine is running, the cylinder, cylinder head and piston form a closed space. The ring groove of the piston is larger than the piston ring, and the diameter of the piston is smaller than the inner diameter of the cylinder, so high-pressure gas will enter the ring groove and piston ring. In the gap, the downward pressure of the gas directly presses the piston ring against the lower wall of the ring groove, and the radial force also presses the piston ring against the cylinder wall.

When the piston moves up and down, the piston ring and the cylinder wall rub against each other. Even if the surfaces of the cylinder wall and the piston ring are relatively smooth, they will still fit closely under the action of various forces to form a sealing surface. To put it simply, the tightly fitting friction surface can play a sealing role. Based on this principle, some more practical sealing methods have been produced, such as packing sealing, end sealing, cup sealing etc. Here maybe no space for more details. So please subscribe Sinooutput you will receive more information from us even every day.

So, since the tail shaft can be designed to penetrate the hull, there must be a clear way to deal with a series of problems that may occur. Just like the truth for scientific and technological inventions in other fields. Problems arise, solve problems, and create convenience for people. This is the power of science and technology.
This is just like Sinooutput all members always believe ways, ideas, methods, tools and skills are more important than hard work, so also just like our enterprise another value message, that is: live seriously and work happily, not just work harder and play harder. Harder is very good spirit for we each generation, but do direction hard work really will wasted so much time and went around so many UN-necessary roads. So please always keep in mind: Methods/direction is important than work hard. But please remember I did not mean to to forget hard, i mean we could work smart, once you use some skills or with some methods, just to keep it and use it in your job contentiously.