Sunday, February 28, 2010

How to design ship propeller

Last week someone sent me an email requesting help on how to design a ship propeller. He has been writing his final assignment for an undergraduate program for 5 years. He still cannot finish it just because he does not have literature or textbooks about propeller design. Well, propeller design is not a subject that all naval architects studied when they were taking an undergraduate program. Yes, they study resistance and propulsion of ships but going deeper into the subject or the design of marine screw propeller is not always the choice that every naval architect will do. The science of propeller design, actually lies between two fields of co-related engineering which are naval architecture and marine engineering. And  the guy who asked for help is not studying any of them. He studies mechanical engineering. I think that's the reason why he finds that propeller design is very complicated. It is difficult even for naval architects and marine engineers, so it is not surprising to see how difficult it will be for someone who does not study ship propulsion and tries to design a propeller.
A propeller might look like a fan that you use in your house or office. But the complexity of designing a propulsion device that moves or drives a ship in a sea water is huge. Well, I will not blame him for choosing such difficult subject for his final assignment which we in Indonesia like to call Skripsi. What I am going to say now is read the following steps to design a ship's propeller:
Kamome Propeller from Japan
  1. First of all, you need a number of data for the calculation of ship resistance. They are LBP or Length Between Perpendiculars; LWL: Length on Load Waterline; Breadth of Ship; Draft of Ship; Displacement of ship in cubic meters; Position of Center of Buoyancy; Waterplane area coefficient; midship section coefficient, wetted hull area (including the rudder and the appendages; and then the maximum diameter of a propeller. For the calculation of ship resistance, please find an article entitled: An Approximate Power Prediction Method by J. Holtrop and GGJ Mennen, and A Statistical Re-analysis of Resistance and Propulsion Data by J. Holtrop. After performing the calculation, you will get a curve depicting the relationship between effective power and ship speed.
  2. From the EHP or now better known as effective power (PE), find the delivered power, shaft power, and brake power. Perform two calculations which are forward calculation for determining the engine rate of the ship and then the backward calculation for redetermining the delivered power that will be used for calculating the coefficents of Bp and delta.
  3. Most propeller designer will use Troost series propeller which is now known as standard B series propeller from Netherlands Ship Model Basin (NSMB) which is now known as MARIN.
  4. After pitch diameter ratio, the rpm, and the pitch of the propeller the next step in propeller design is calculating the blade area ratios. These ratios can only be obtained after the designer has performed propeller cavitation calculation which is usually based on Burril Method. Then, we get Projected Area Ratio, Developed Blade Area Ratio or Expanded Area Ratio from Burril Cavitation Chart.
  5. Now the principal dimensions of the propellers have been obtained. But we cannot put these numbers on paper in the form of design drawing. We must perform propeller strength calculation to obtain blade thickness diameter ratio. The method that we, as naval architects or marine engineers, use here is Taylor Method.
  6. The last task is drawing. We draw the design or our new propeller based on the standard B-Series propeller using Holst Method. Here, I can say that the design stage is finished.
Still confused about my explanation? Read two reference books that I recommend to you: the first, a very old book, Resistance, Propulsion and Steering of Ships written by Professor Van Lammeren and the second, also an old book The Design of Marine Screw Propeller by T.P.O. Brien.
I hope the one who asked the procedure of designing and calculating the blade thickness of propeller read this post. by Charles Roring 
Whatsapp: +6281332245180

Tuesday, February 23, 2010

Tan and Linda are leaving the Manokwari rainforest for Norway

Two Norwegian students (Linda and Tan) are leaving for Norway tomorrow. They have been doing field research in Manokwari for nearly a month. Their stay in Manokwari has been a unique experience for them. And the data which they have collected, during their visit to Papua, will be used for composing their thesis on the implementation of the UNREDD program for the community based forest protection that is vital in fighting global warming.
Paul Warere (local forest guide) and Tan (an Indian-Norwegian student)
All of us here in Manokwari can only hope that the good and bad experiences which they have faced in Papua will enrich their life so that they will understand how beautiful the rainforest is, how unique the culture of the indigenous Papuan, and how uncomfortable it is for someone to suffer from Malaria Tropica, ha..ha..ha....(laugh).
The Norwegian students, and all of us of course have the same opinion, the view that the whole world community share that the tropical rainforest has to be preserved for the next generations of human being. The indigenous people of Papua have the exclusive rights over their rainforest, but they MUST NOT abuse this important world heritage. It is the responsibility of the whole world community to help the Papuan people and other indigenous tribes in Amazon of Congo in Africa preserve their rainforest.
We pray that their air trip to Norway will be calm so that they will arrive in their country in good condition to meet their loved ones. Happy Traveling - by Charles Roring

Monday, February 22, 2010

Miniature of Arfak House as Souvenir

The traditional wooden house from the Arfak tribe in Manokwari is called Rumah Kaki Seribu or A-Thousand-Feet house. Its form is unique. The house is built on a lot of wooden pillars that protect the people in the house from the high humidity of the ground, and wild boars or snakes. Unfortunately the design of this house does not have enough openings (windows) for air ventilation and natural lighting. The modernization and improvements in the standard of living of the Papuan city dwellers have resulted in the abandonment of the traditional house styles mostly in the Papuan cities. We can only see such houses now in the rural or mountainous areas. To preserve the existence of these houses, the committee for the commemoration of Gospel Preaching Day conducts the annual competition for the construction of the replicas of the Rumah Kaki Seribu throughout the city area. Most Papuan youth groups in Manokwari city participate in the competition.

In addition, some Papuan artists have made miniature of the Papuan traditional houses as souvenirs for domestic and foreign tourists. The souvenirs of Rumah Kaki Seribu are sold in various souvenir shops in the city. The price of the house miniature varies according to size and attention to details. The cheapest is around Rp. 200,000 (20 US dollars) whereas the expensive one can reach up to Rp. 2.5 million rupiahs (or around 250 US dollars).

When tourists buy miniatures of the Kaki Seribu house, they have directly supported the economic livelihood of the Papuan people, especially the artists. I am writing this post to promote this kind of souvenir so that when you come to Manokwari as a tourist, you might be interested in buying one of them. You can go to Ms. Fonataba located in Kompleks Missi Area behind Cathoic Church Santo Agustinus on Jalan Brawijaya who also sell Rumah Kaki Seribu in Manokwari. I hope that the articles about eco-tourism which I upload into this blog will be able to attract more foreign travelers to this town to enjoy the beautiful Papuan natural scenery and the hospitality of Papuan people. by Charles Roring

Saturday, February 20, 2010

Propeller blade thickness ordinates

When a naval architect has finished the design calculation of a propeller, he will continue his work by drawing it. The method of drawing a marine screw propeller is usually based on Holst. Please, read page 204 of the Resistance, Propulsion and Steering of Ships by Prof. W.P.A. Van Lammeren or Marine Propellers and Propulsion for more explanation about it.
Those who want to be a propeller designer must know the basics of propeller geometry. 
Before the developed blade sections can be drawn, the propeller designer must obtain the values of  the  positions of Center Line (CL) of the propellers at each blade section radius (usually from r/R = 0.2 to 0.9 or 1.0) relative to the TE (Trailing Edge) and LC (Leading Edge). In theory, the Developed Area Ratio (AD/A0) is assumed to be similar to the Expanded Area Ratio of the marine screw propeller. By determining the positions of CL, we can place the positions of the maximum blade thickness ordinates for every radius (r/R) based on the standard percentages that are provided by the book.  For the thickness ordinates relative to trailing and leading edge of each blade section radius , the values are derived as percentages of thicknesses compared to the maximum thickness at each radius of the blade. The safe value for blade thickness diameter ratio is obtained from Propeller Strength Calculation usually using Taylor formulas.
Ordinates of Maximum Blade Thickness of B-Series Propeller

Blade Thickness Drawing of B-Series Propeller

Please keep in mind that the percentage of the blade thickness ordinates that I discuss in this post is for the standard  B-Series propeller which is provided by NSMB (the Netherlands Ship Model Basin). The table and the drawing of the newly designed propeller presented in this article is from by undergraduate final assignment: The Propeller Design of Open Hatch Bulk Carrier (OHBC) DWT 45,000 metric tons. by Charles Roring

Friday, February 19, 2010

Eucalyptus Deglupta Boat Building Material in Manokwari of Papua

When I was walking with Russian tourists (Mikhail, Inga and Dima) inside the tropical rainforest of the Table Mountain of Manokwari Papua, we saw a tree whose bark was similar to army uniform. Its extraordinary colored bark will always attract the attention of anybody who passes by the tree. At that time I only knew that its name was eucalyptus. One month later, after reading an article in the, I just knew that it name is eucaplytus deglupta and its wood can be used for boat building. In the Molucan islands the most common wood that is used by boat builders is gofasa or gupasa wood (vitex cofassus). This wood is used for hull skin and hull frames in small passenger and fishing boats. The gufasa wood is more resistant to marine borers compared to eucalyptus. So, eucaplytus may be more suitable for boat interior or furniture. In West Papua the indigenous people are not aware that eucalyptus has high economic values.
The Dutch introduced the plantation of eucalyptus seedlings in the Table Mountain of Manokwari in 1950s. Mature eucalyptus trees absorb a lot of water during dry season.  That's why this kind of tree species is more suitable to be grown along a big river or swampy land.
I have not known the motivation of the Dutch government for planting the eucalyptus in the Table Mountain. Perhaps they want to get their seeds for opening large eucalyptus deglupta's plantation in commercial scale for pulp and paper industry in Papua at that time. Now, the tree is an interesting tourist attraction for foreign travelers who visit the Table Mountain of Manokwari Papua. by Charles Roring

Wednesday, February 17, 2010

Propeller Blades and Ship Vibration

Sometimes when we are sailing on a small motor boat, we feel that the vibration is high. This is probably caused by mistakes done during the selection of propeller. I often see a brochure from the manufacturer of a marine diesel engine which shows that the propeller and the engine is provided as one package. 
As a matter of fact the propeller that is supplied by an engine manufacture might not be suitable for the boat's hull when moving at sea. When a boat owner or builder is ordering an engine, the selection of the propeller has to be given to a propeller designer, a naval architect or a marine engineer who has the knowledge of calculating the ship resistance and effective power and translating it into the engine selection and propeller design for the boat.
Usually to reduce the vibration, a propeller designer will add the number of blades from 2 or 3 to 4 or 5. For passenger ships, the number of blades (Z) for the propeller can be around 5 to 7 blades depending on the size of the ship and the rpm of the engine. The higher the number of blades, the lower will be the propulsion efficiency. The propeller designer will have to compromise such contradicting factors to achieve the best dimensions before the design drawing of this propelling unit could be sent to the propeller manufacturer for production stage.
Watch the following Youtube video to have a closer look of how the rotation of a ship propeller creates vibration.

Also read:
Propeller blade thickness ordinates
Marine Propellers and Propulsion - a book review
Boat Propeller

A Visit to Raimuti island in Manokwari Papua

Last January three Russian tourists visited Raimuti island. It is the smallest island in the Dorey bay of Manokwari Papua. These Russian tourists were Mikhail, Dima and Inga. They spent two weeks hiking around the Table Mountain, the Mansinam island, and then snorkling and fishing in the Raimuti island.
According to their opinion, Raimuti was a small but beautiful place. It is located near Arfai beach, only around two hundred meters from the main Papua land. There are some mangrove trees growing in the island. These vegetations help prevent the island from erosion that can eliminate the whole island from Papua map. Fortunately, not many people visit the island, that's way it still exists until now. Raimuti has been used by fishermen as a resting place or as a place to find fish bait.

A friend of mine, an indigenous Papuan said that there is a sunken warplane wreck around the waters of the Raimuti island. Unfortunately, he did not mention the exact location of the planewreck. The island is also surrounded by coral reef which is an important habitat for fish and other marine creatures.
If you are interested in visiting the island, you can hire a boat that belongs to the fishermen at Arfai beach. Usually its cost is Rp. 100,000 per day. I suggest that you bargain to get the suitable price. Don't forget to bring your own gear if you want to scuba dive around Raimuti, Lemon, and Mansinam islands.

Thursday, February 11, 2010

What you need when traveling inside rainforest

I like going into the tropical rainforest of Papua. I have been doing it since I was in elementary school. Green trees, exotic wild life, sounds of beautiful birds always attract my attention. Since the beginning of this year I began escorting tourists to rainforest of Manokwari. Most often when we are in the middle of the forest, we will need a machete to create pathway when we see that the bush a head of us is impenetrable. We also need it to cut wood for making tents and campfire. I always suggest foreign tourists to set up camps near a village. But it is not always possible. 
Trekking in rainforest of West Papua
For tourists who are in the middle of the jungle, the safest place to build a camp is the river bank. Why? Because when we stay in the forest for several days, we will need water, we need to cook some food and we need to clean our body. When we feel that our staying time in the forest is over, we need water from the river to put out the fire completely to make sure that it will not develop into big fire that can cause dangerous forest fire.
So, based on that explanation, if we stay inside the forest for several days, besides bringing some machetes, we will need a tent, some small rope, and eating and cooking utensils. Most tourists will not go deeper into the jungle but for nature lovers, biologists, or researchers, they will need to go further into the interior region of the Papuan mountains where the forest is still in its pristine condition and no hunters or villagers around. If it is the case then we need GPS equipment, or map, satellite phone, head light, torch, several sleeping bags and enough food.
From my personal experience, I always ask one or two local Papuan as forest guides who can also use their skills in making traps to catch small but edible animals that we can eat when we are running out of food in the forest. But we must always keep in mind that we must minimize any destruction when we travel inside the forest by not cutting bush if it is not necessary, by not throwing plastic garbage and by not killing animals except for food. Actually there are many foods inside the forest such as fruits, edible tubers, vegetables, and fish, so hunting wild animals such as boars, cuscus, soa-soa, tree kangaroo or deer must not be done.
Hiking in Arfak range
Some tourists bring anti malaria pills and first aid kit. Indigenous Papua know a number of plant species for curing malaria, and other tropical diseases, I usually ask them to explain these medicinal herbs to the tourists whom I escort with the Papuan guide when we walk in the forest. The last time when I accompanied an Indian- Norwegian student, my Papuan colleague showed her a tree whose resin has the merit of curing asthma. When he cut its bark, she tastes some of the resin hoping that it can cure the disease that she suffers from.
The last but not the least, we need to bring digital camera or video recorder to make some documentation for our trip. by Charles Roring
Also read:
Traveling to North-east Coast of Waigeo
Adventure tour in Raja Ampat
Hiking and Birdwatching in Sorong of West Papua

Monday, February 8, 2010

Photographing bat in a cave

Yesterday (7 February 2010) I went to the Table Mountain of Manokwari accompanying Tan, a Norwegian student who is doing some field research on the implementation of UNREDD. She looked happy when we finally arrived in a big cave that was the home of bats. She took a lot of pictures of this cave from the front mouth to its interior that is full of stalactites.
The surface of the ground was wet, uneven, and slippy. I fell once and cut my hand. Well, it's the souvenir that I got from exploring this cave. We brought two big lamps to lighten the cave. I used an old digital camera Sony Cyber-shot 6.0 mega pixels to take some pictures of this cave but because its flash light was not strong enough, I had to move closer to the objects to shoot them well.


The bats that live in the cave are from small species. The same as the bigger ones they sleep during the day and look for food at night. The indigenous Papuan told us that they eat insects, sweet fruit (like kersen) and nectar of certain flowers. Also read: Caving in the Table Mountain with Grietje

Saturday, February 6, 2010

Cultural Carnival in Manokwari 6 February 2010

Cultural Carnival in Manokwari in Commemoration of Gospel Landing Day
Delegation from Batak of North Sumatra

Delegation from Manokwari

the cultural festival in Manokwari seen from Pertokoan Kota Cross Road
Yospan dancers
While I am uploading these photos the carnival is still going on

Delegation from Arfak Mountain

Norwegian Student Bought Some Traditional Woven Cloth in Manokwari Papua

Mrs. Marice Fonataba, a master of cloth weaving, was very happy this morning. When most of the town dwellers went to Mansinam island to attend the Gospel Landing Day celebration, she was busy showing her hand-made woven cloth to a tourist. A guest from Norway visited her home. Her name is Tan. She is an Indian-Norwegian who is doing a field research on the possibilities of the implementation of UN-REDD program among forest communities in developing countries. UNREDD is launched by the United Nations to empower villagers and to fight deforestation and global warming.


However, Tan came to Ms. Fonataba's house not for interviewing her on things related to UNREDD but to buy some woven clothes which she has made. Ms. Fonataba was one of the few Papuan women who learned the traditional cloth weaving from Sister Aloysia, a Catholic nun who was originally from South East Maluku islands. There, women weave clothes from natural fibers for their families' clothing.
Tan bought a large sheet of woven cloth which costed her Rp. 500,000. As you can see in the photos of this post, she tried some cloth on her body before deciding to buy one.

The development of tourism industry brings positive impact to the local people if they can get various benefits from it. Handicraft makers, artists who create beautiful carvings and paintings should get government's attention. In other words, creative economy should be the backbone of the tourism industry in Manokwari of West Papua.

If you plan to come to Manokwari, I recommend that you buy souvenirs that are created by Papuan artists as the products of their artistic creativity such as hand made woven cloth, wood carvings, postcards or paintings.. Please, DON'T buy souvenirs that are made of corals, or skins or feather of endangered animals such as birds of paradise, white and goliath cockatoo, kuskus and etc. If you buy them, you have encouraged the destruction of marine environment and the huntings of Papuan animals that are facing extinction .

Friday, February 5, 2010

Manokwari Street Parade Commemorating Gospel Landing Day

This week Manokwari town is busy. There are a lot of religious activities held by Christians community in this town, from boat racing to choir competition, and from art exhibition to street carnival.
Street parade has been an annual agenda for GKI di tanah Papua (the Evangelical Christian Church in Papua Land). It has just been held on 3 and 4 February before the celebration of the Gospel Landing Day on 5 February. Today is the 4 fourth of February and I just returned from Jalan Merdeka to watch the Karnaval Budaya (meaning Cultural Carnival). This carnival was held along the main streets of the town from Sanggeng to GKI Church of Elim in Kwawi area.
During the parade, the participants sang Gospel and traditional songs, performed dances, and wore traditional costumes. Tens of thousands of Christians have come from various towns and villages in Papua and other provinces in Indonesia to Manokwari to participate in this parade creating several kilometers of traffic congestion along the main streets.
Set in the Dorey bay under the Arfak mountain facing the Manokwari town, Mansinam island became the first place where two German missionaries settled to preach Christianity to Papuan people. Otto and Geisler landed on Mansinam island to preach Christianity to, what Alfred Russel Wallace in his book entitled the Malay Archipelago called, "the savage people" 155 years ago  Now majority of the Papuan population are Christians.
Besides being famous for religious tourism, its beautiful scenery and underwater shipwrecks continue to attract foreign tourists from around the world. Just tens of meters away off the Cross monument of the island, lies the Pillbox shipwreck which has usually become the starting point for divers. Another bigger shipwreck, the Shinwa Maru - a Japanese ship and coral reef can be explored at the south east off the Charles Roring

Monday, February 1, 2010

Russian Tourists Saw Kuskus in Manokwari Papua

Last January three Russian tourists came to Manokwari to enjoy the natural beauty of Papuan forest. They walked around the Table Mountain (Gunung Meja) hoping to see Kuskus and other beautiful birds such as White and Goliath Cockatoo and paradise birds (Cendrawasih). Unfortunately, they were not able to see paradise birds and kuskus. They could only see Goliath Cockatoo and Bats in a cave located deep in the jungle of the Table Mountain. These Russian tourists expressed their concerns over the rapidly decreasing number of Kuskus population in Table Mountain's forest where ten years ago, Kuskus could still be seen. Kuskus population in the mountain is in danger of extinction due to huntings. Although this is a protected forest and the hunting activities in the forest have been banned by the government, hunters still kill animals in the forest.
As we could not locate kuskus in its natural habitat, we had to bring these Russian tourists to the house of Mr. Teniwut which was located some two hundred meters from SDN 1 Kota (formerly known as the Dutch Klim en Daal school). There, we saw a cute Kuskus living in a cage. Mr. Teniwut said that the animal was caught in Senopi village in the mountainous region of Manokwari regency. It is an endemic animal of Papua that is rapidly decreasing in number mostly due to huntings. In the past the local Papuan hunted these animals only for their meat. Now they catch Kuskus alive to sell them to wealthy people who will buy them in high prices. When we visited the Table Mountain several days ago, we saw that the local government had built a concrete gate and constructed a wooden house at the entrance of the forest in the Anggori area. Soon, people who want to enter it have to buy tickets. It means that the forest of the Table Mountain in Manokwari will become Hutan Wisata. If this is really their goal, we hope that the local government will be more serious in protecting the forest and in restoring the population of kuskus and other animals which were onced lived in the Table Mountain.
This article was written by Charles Roring (contact email to promote eco-tourism in Papua and to support the local people in getting alternative jobs in tourism related industries so that they will not cut the forest or hunt animals in the Table Mountain of Manokwari of West Papua..