Saturday, August 29, 2009
Tuesday, August 25, 2009
Modern passenger ships have been integrated into Indonesian maritime industry since they were first introduced into Indonesian waters in 1980s. After the ro-pax ferry KMPTampomas accident in late January 1981, PELNI - the largest passenger lines in Indonesia began to modernize its fleet of passenger ships to prevent such disaster from occurring again.
In the middle of 1980s, PELNI received new passenger ships from Meyer Werft (shipyard) of Germany into its fleet to serve major ports in Indonesian islands. Some of them are KM Kambuna, KM Kerinci, KM Umsini, and KM Rinjani. KM stands for Kapal Motor or Motor Ship. These ships each could carry around 3,000 people but during the high seasons they double the capacity to between 4,000 and 5,000 passengers given that the summer load waterline did not exceed the minimum freeboard stipulated by IMO or Classification Rules.
All the additional passengers were deck ones. This is still practiced by PELNI lines at the moment. Although it is a dangerous practice during bad weather, as long as it still adheres to the stipulated freeboard, PELNI considers that the additional number of passengers will not bring the ship into the risk of sinking.
It is not clear whether PELNI also increases the number of life jackets, boats and rafts to protect the passengers at sea. In addition, the additional passengers that PELNI ships have to carry during school holiday, Idul Fitri, Christmas and New Year seasons make the sea voyages are not comfortable.
More passengers mean more rooms, water, and food the ships should provide. In fact, passengers often complain that they run out of water to shower. The gangways and decks look dirty too during high season voyages.
Although waste streams produced by passenger ships are smaller compared to the whole amount produced by the whole world shipping industry, when not properly treated and discharged into the sea, they really threaten the marine environment.
The provisioning of modern passenger ships has restored passengers' confidence over PELNI's service. Feeling that such investment in high cost European made ships was worthy due to the profits and better safety standards the ships gave to the company, PELNI ordered more ships in 1990s.
Today there are nearly 30 passenger ships PELNI has in its fleet. It is a state owned shipping company that is intended not only to transport people but also to connect the whole territory of Indonesian islands as one undivided country. So, it is the government's policy to provide ships that support the development of national integrity of Indonesia and also to serve passengers from moving from one island to another.
When transatlantic passenger ship-liners have long been replaced by airplanes, it is amazing to see that PELNI is the only company that runs true passenger liners in fast schedules transporting a lot of people every year. Also read: Boat building and Living tradition of the Mentawai Tribe; Sailing Across the North Pole with Boat to the New World
Saturday, August 22, 2009
In today's post, I am going to tell a story about boat building tradition maintained by one of the tribes in Mentawai. Mentawai is a group of islands located west of Sumatra, Indonesia. Boat or canoe is made from log in the middle of the jungle. The boat will be used for transporting people and food. There are not calculations of displacement or stability involved in this boat building. The builders only used their intuition and tradition..
The boat is not constructed from pieces of wood but it is dug out from large log. The length of the boat can be up to seven or eight meters. One thing that is interesting here is that the Mentawai tribe performs unique ritual in every step of boat or canoe building. After making the boat, they will have to push it to the river which is quite far from the place where they built the boat. The inauguration of the boat was carried out with simple ritual and prayers.
Although the boat is very simple in design, its draft is well predicted if I should not say well calculated. Even experienced naval architects will admire their way of making boat from the log. Last week, TV5 Monde Asie, a global satellite French TV aired a program about the daily life of the Mentawai tribe. This indigenous people are still living in traditional ways - no electricity or even basic health care facilities provided by the government. They still have to go out for hunting boars using bow and arrows and machetes. I forgot the name of the producers of this documentary film. I highly respect and appreciate their works in making this film.
What I like the most from the TV program is the rituals the tribe performed to heal sick person. A shaman and some men killed a boar and used it in the healing ritual. They performed a dance until they were trance. I wish I could understand the whole story of the natural dance unfortunately the program was in French.
The rapid deforestation or the conversion of tropical rainforest in Mentawai islands into massive mono-culture palm plantation is a major threat to the survivability of this indigenous people. They had to face investors who are only greedy of making money from the lucrative CPO or bio-fuel commodity.
The concern of this indigenous Mentawai people should be ours too. As more and more trees are cut to make way for palm plantation, questions should be raised whether the bio-fuel industry is legitimate if large areas of forest should be jeopardized. Also read: Sailing Across the North Pole with Boat to the New World;
Friday, August 21, 2009
On this article, I am not going to talk about ship but a little about a legendary boat. There was a legend in Ireland which says that the Irish monks were the first European to land on the New World. Around one thousand years ago, an Irish boat sailed across the north-pole waters to find a new land. They used a boat whose hull was not made of wood but animal skin. I read the story about this expedition on an article of National Geographic Magazine. I forgot the year of its publication. I wonder how a small boat crossed the Atlantic. It was too dangerous to sail from Ireland to the New World with a boat that was not seaworthy. All naval architects would agree with this.
There were some Irishmen who re-built similar boat and used it to cross the icy ocean and landed on Canadian territory. They proved that the Irish monks could have been the first Europeans to find the New World. I saw that the cover picture about the story was very interesting and I drew it on a small paper. The boat had sails decorated with red-cross. I used Derwent watercolor pencils to make the drawing. It took three days to finish the drawing of the boat.
Wednesday, August 19, 2009
After performing the calculation for estimating the ship's displacement, deadweight, as well as the lightweight of a new design, the next step a naval architect will usually calculate is the length. There are many books about ship design that deal with the estimation of ship's length. I recommend Merchant Ship Design by Munro-Smith, Ship Design and Construction published by SNAME, or two other books that I will mention below.
If the new ship is going to operate on international shipping, it might pass through Panama Canal which only allows the maximum length to be 289.56 m. Length of the ship can be estimated using Sneekluth's formula. Please, see page 2 of Ship Design for Efficiency and Economy, written by H. Sneekluth and V. Bertram.
LPP = Length Between Perpendiculars (meters)
Δ = ship's displacement (ton)
V = speed (knots)
Fn = Froude number
The length of the new ship can also be calculated using cube root format which is presented on page 5 of Ship Design and Performance for Masters and Mates as follows:
Cube root format
L = LBP
p= density of sea water = 1.025 metric tons/ m3
CB = block coefficient
CD = deadweight coefficient
Although I only present two formulas here, actually, there are still other formulas for estimating the length of a new ship. If you are now designing a new ship, I suggest that you design its lines plan using delftship. Also read: How to calculate displacement of newly designed ship and Ship rudder
Tuesday, August 18, 2009
Displacement of a ship is the volume of water that it displaces when floating at sea or river. The volume is calculated in cubic meter. If it is multiplied with the sea water density (1.025 metric ton/cubic meter) then we can get the displacement which equals to the ship weight.
On page 4 of Ship Design and Performance for Masters and Mates, Dr. C.B. Barrass gave a simple formula for calculating the displacement of newly designed ships. The formula is called deadweight coefficient.
CD = dwt/W
The following table is the typical deadweight coefficient for various types of merchant ships
|DWT Coefficients of Merchant Ships|
The deadweight coefficient varies from one ship to another depending on its type and is calculated up to SLWL or Summer Load Water Line. It is the condition where a ship is fully loaded.
Lwt = displacement - deadweight
= W - dwt
= 20,000 - 12,000 = 8,000 metric tons This is only for preliminary design calculation.
If we see on the table above, the ship is a container ship.
When the lines-plan of a ship is available, the calculation of her displacement can be done by integrating the areas of waterlines usually from WL 0 to Summer Load Waterline. Similar calculation of ship displacement can also be carried out by integrating the areas of stations from the stern to the forward end of the ship. Hydrostatic and Bonjean curves provide a lot of information which sailors or ship designers can use to analyze the hydrostatic and hydrodinamic properties of the ship.
There is a good book for naval architects or anybody who is interested in learning about this topic. Its title is Ship Design: Methodologies of Preliminary Design, written by Apostolos Papanikolaou.
You could order this book to learn more about the determination of hull form, the main dimensions and the basic characteristics of different types of ships. I highly recommend this book for you to read it.
Ship's Displacement Calculation Using Simpson's Rules
Thursday, August 13, 2009
Many times when we go to the beach, we can see parents accompany their children swimming. But among the crowded swimmers, there are some who are more interested in playing with boat toys. The passion of the sea and the ship in little boy's mind bring his imagination tens of years in the future where he dreams of building a ship or being the captain of a ship sailing across the ocean.
I made a painting about such scene using watercolour pencil depicting how a father accompanies his son playing a toy of a sailing boat. Right behind them a few miles away, there is a cruise ship moving.
The message from this painting is that we must not ignore the passion of a little boy playing with his boat. We have to encourage him, if necessary, by taking him to a sea voyage aboard a real cruise ship or passenger ship where he can see the real ship.
Perhaps, the boy has another dream. Being somebody who can build a ship or boat. He might not know the name of such profession as being a naval architect is not a common job anybody sees in every day life. There are not many schools that provide such study program. So, what we must do is to guide the boy in pursuing his passion on the sea and the ship through a positive way. by Charles Roring also read: Is traveling with cruise ship still an attractive adventure? and The Speed of Ship and Propeller Pitch
Saturday, August 8, 2009
1. To keep the ship on a straight line, from Port 'A' to Port 'B.' In other words, to have good course keeping properties.
Usually the height of a rudder is 1.75 its length. Please, see the following illustration as a guidance for naval architects when designing ship's rudder.