|

GROUP 15 LOFTING

SHIPYARD NEED A LOFTSMAN

Ships are complex structures. They are the largest structures. Many kinds of workers are employed in the shipbuilding industry. Professional workers such as engineers, designers, and technicians provide the design for a ship's hull. They draw up plans for a safe ship that will move easily and economically through the water. They also plan space for cargo, living quarters, and machinery. A related group of workers, marine engineers, concentrates on designing the machinery that will run a ship. Drafters prepare detailed drawings that give exact measurements and specifications for all the ship's parts. If the plans have been drawn up, they must be translated into the actual parts of the ship.

To continue this job , shipyard will need a lofter worker. In Indonesia and Malaysia lofter usually called as 'Marker'. Loftsman or Marker do this job and make life-sized patterns of each part of the ship to be built. They work in a huge room known as a Mould loft. In most large shipyards, a more modern method called optical marking is used instead of lofting. In optical marking, small-scale drawings of the ship are photographed. How ever, nevertheless the shipyard use the modern method, a loftsman or marker , they will stand for good and always needed. Generally, In shipyard the worker will familiar with a loftsmman or marker. Loftsman or marker have the strategic position in shipyard, because he is the first worker to start make the lines plan as basic of structure of the shipbuilding.

The duty of a loftsman in shipyard is translate the lines plan, to the lofting shop. Body plan is the important part to prepare, because they will use to make the shell plate and template for fairing the shell plate. And continue with the profile and plan view of the line. They will prepare with buttock lines, water lines and spacing of the frame in profile lines. After this job is complete, the Lofter must be translate the mid section of the ship to the body line , profile lines or plan view lines. The lines will developed by the lofter according to the drawing of the ship. All of the lines must be determined from the base line and center of line. This point is important to develop the line.

Loftsman also need to solve some problem in yard, sometimes he make his own mistake, and sometime it come from the fitter, so he must find the way to solve this problem, always need communicate with engineer and supervisor. It's possible for Loftsman or marker to run his own business in shipyard as a sub-con that find a investor who has money to finance his business for a shipyard industry. And until now some of them have made it. But some find the blind way also. However, the lofter always continue his life with lines until his hairs are white.

TYPES OF LOFTING

1. CONVENTIONAL LOFTING2. OPTICAL LOFTING3. COMPUTER LOFTING

NC LOFTING CNC LOFTING

CONVENTIONAL LOFTING

It is the process of transferring information from scaled drawing into full scale templates (normally made of thick paper, plywood or wax paper) before transferring to the work piece. Conventional lofting requires a wide area lofting room with adequate lighting, and level floor. The loftsman need to redraw all lines and curves in the drawing onto the template and full scale fairing also need to be done. Apart from lines and curves, other information such as end position, frame lines, seam or joining locations and checking points need also to be transferred to the templates and hence to the work piece. The information drawn on the templates are then transferred to the work piece by means of lines marking and centre punching.

OPTICAL LOFTING

This lofting process requires special optical chamber. The process involves transferring information from a scale drawing (1: 100) to negative film of smaller scale (1: 500) using camera. The arch from the film will then be projected on to the full-scale work piece inside the optical chamber. The work piece surface must be coated with special kind of dye in order to capture the image correctly. The lines, curves, and other information captured on the surface will be marked permanently on to the work piece using marking process. Optical lofting does not require experience loftsman and uses smaller area. However to ensure accuracy of data, high precision drawing equipment, Vernier Scale and magnifying glass is essential as any small error on the measurement will be magnified many times on the work piece.

COMPUTER LOFTINGThis lofting process does not require any physical transfer of information from drawing to the work piece. Therefore it does not require loftsman and lofting room/chamber as in the previous two methods. On the other hand, it requires computer hardware, special software and experts to carry out this process. Computer lofting can be divided into two categories, i.e. NC and CNC Lofting process.