Tài liệu Lesson 7-Workmanship for Hull Building(1) pptx

Lesson 7-Workmanship for Hull Building(1)

It is really fascinating to gaze at a colossal ship standing high on a slipway or sailing

fast at the blue sea, and you will be still more excited if you are offered a chance to pay a

visit to the wonderful labyrinth inside a ship. Indeed, a ship, to the mind of a naval

architect, is a true work of art.

But few of the ordinary people have any idea about the workmanship for hull building.

One might be surprised to learn that, the construction of "a floating little town" with such

complicated . hull form and such complex hull structures, should start with the very paper

work.

To give you some brief introduction on the primary workmanship for hull building,

we would like to relate as follows:

1. Lofting

Lofting is the first workmanship for hull building, and will therefore influence the

quality of the following workmanship. And that's why high accuracy has to be obtained

during lofting.

Usually, lofting is conducted on a mould loft. There are two steps here. First, we must

work out a projection plane in the light of geometrical principles in proportions as 1 : 1, 1 :

5 or 1 : 10 in accordance with the given sizes indicated on drawings. Then, different sorts

of model plates, model rods and model cases as well as sketches are to be prepared as the

reference to material marking, processing and fabrication.

Besides, lofting can be made use of to make up the shortcomings of drawings, for it is

impossible to mark all the shapes of members on the drawings. Furthermore, no matter how

careful you are when drawing a lines plan, errors are inevitable in respect to hull cleanness

when the plan is magnified. In this case improvement will be made upon the plan by means

of lofting.

With regard to the methods of lines lofting, the advanced mathematical lofting is widely

used nowadays, which calibrates and provides lines offsets for a clean hull with the help of

an electronic computer.

2. Material Marking

The exact meaning of material marking is to draw an expansion of a certain hull

member after the lofting workmanship, and mark the member expansion on steel plate or

fashioned steel with the aid of model plates, model rods or sketches, with the symbols for

processing and fabrication marked out on it as well.

Various methods of material marking are available, but the most common ones for

material marking are those respectively by model plates, by sketches or by optics.

3. Processing of Hull Members

The workmanship for the processing of hull members may be classified into cold

processing and hot processing, and might as well be divided into edge processing and shape

processing according to the processing methods of members.

3.1 Calibration and Rust Removal for Steel Plates