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南太平洋海域調査研究報告
OCCASIONAL PAPERS

No.58（2017 年 3 月）
No.58（March 2017）

Design and Application of Unsinkable Tuna Longboatfor Local Fishermen
HETHARIA Wolter R. and METEKOHY Obed
Faculty of Engineering, Pattimura University

Abstract
The activities of fishermen in archipelago regions (Eastern Indonesia and Pacific) mostly relate to theefforts in catching fishes and other marine resources. One of the most valuable fish is Tuna which is caught
by simple up to modern big vessels and fishing gears. Most Moluccas fishermen are using small “tunalongboats” for this purpose. Those small boats operate in open seas where most of the time the sea
conditions are rough. In many cases, those small boats could not resist in such conditions which will end-up
with flooding, capsizing or sinking. Some records showed the fishermen and boats are lost at sea. A study
was executed to solve this problem. Three new tuna long boats, with the size of 1.5 GT each, were designed.
Those boats were provided with solid boxes inside to provide reserve buoyancy. The boats wereconstructed with the material of composite (Fibre Glass Reinforced Plastic). Then, the boats were tested atsea. The results of test showed that for a maximum flooding of boats, they still float (unsinkable) with aminimum trim level. In addition, for a capsize condition, they were still afloat and easily were returned toupright position. The results of boat design and evaluating were recommended to be applied to the users. Atraining program was conducted for the local boat builders during the study. Nowadays, the local boat
builders have developed this unsinkable concept to their new boats into the market.
Keywords: Fibre Glass Reinforced Plastic (FRP), reserve buoyancy, solid boxes, training program

Introduction
Eastern Indonesian waters as well as some Pacific regions have great potential of marine
products, particularly tuna fish. This kind of fish has a valuable selling price in theinternational markets. Tuna fishes are caugth in some fishing grounds in Eastern Indonesianand Pacific waters. They are caugth by using some simple up to modern vessels with fishinggears. Local fishermen, especially in Moluccas, are using small boat, called “tuna longboat”
with the capacity of 1.5 GT. The boat is operated by two fishermen where they use the fishinggears of hand or trolling lines. The fishing grounds are in open waters with some rough sea
conditions. At certain periods, there are strong winds with big waves. The operation of thosesmall boats in such rough waters is not possible. Some accidents occurred where the boats
were flooded, capsized and sinked. The fishermen lost their life at sea. The boats were

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HETHARIA Wolter R. and METEKOHY Obeddesigned and constructed by local boat builders without paying any attentions of boat designconcept. The design process were only based on traditional experiences where this issue lasts
for long time. Such small boats were constructed with the material of wood or Fibre Glass
Reinforced Plastic (FRP).
A study was conducted to find the solutions. New boat configuration was introduced inthis study. A team of design and construction of small fishing boat, Faculty of Engineering,
Pattimura University was responsible for this work. Three boats (hull material of FRP), withthe size of 1.5 GT each, were designed and constructed based on proper ship design concept.
Those boats were provided with some solid boxes inside. The configuration and dimensionsof solid boxes were calculated and distributed properly along the boats. Furthermore, theboats were tested at sea for floating purpose. At the test, the boats were filled with sea water
into all compartments inside. It was found that the boats were still afloat at certain draft. Inaddition, the boats were capsized at an upside-down position. It was found also that the boats
were still afloat at certain condition and easily to be turned into their initial upright position.

Boat Design and Construction
Design of a boat should be based on some requirements, design considerations andfollowing the whole design process (TAGGART 1983). In this case, design consideration is theboat ability to afloat on upright or even in capcized positions. In addition, a consideration ofboat operation and environmental conditions would end up with a boat configuration. Other
considerations are based on the requirements of small fishing boat with a certain cathingtarget. The boat was also designed to fulfill the requirements as a fishing boat (FYSON 1985).
Some input design parameters should be determined to be included in the design process.
Fishing gears were choosen properly to be fixed in this small fishing boat (HETHARIA et al.
2001, HETHARIA et al. 2003). The design process ended up with boat dimensions, geometricalhull forms, structures, general arrangements and other design parameters. In addition, blue
prints are included for construction phase.
To keep a boat afloats on its upright position at designed waterline, a certain reservebuoyancy is required. A relationship of total boat weight should be the same as boat weightdisplacement and is presented as (LEWIS 1988, RAWSON and TUPPER 1984):
Total weight = ∆, (t)and∆=Vxγ(1)Total weight = lightweight (LWT) + deadweight (DWT)(2)
where: ∆ = weight displacement (t)V = volume displacement (m3)γ = specific weight of sea water (t/m3)
LWT = lightweight = boat hull+engine+ equipments.
DWT = deadweight = cargo (fish and ice) + crews + fuel + lugages + fishinggears + live bait fishes.

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Design and Application of Unsinkable Tuna Longboat for Local Fishermen

For a critical condition, cargo is considered as water that fills all compartments in boat.
(3)

Cargo = Wtotal water

In this study, some solid-closed boxes (with foam inside) were provided inside the boat
in order to reduce total water weight or to keep the boat still afloat. On the other hand, theinside solid boxes provide the buoyancy forces when the boat is in the capsized condition.
This will make the boat afloat at capsized condition.
In addition, a distribution of closed boxes along the boat were arranged in order to obtaina proper longintudinal centre of gravity (LCG) which aproaches the position of longintudinal
centre of buoyancy (LCB).
LCG =LCB(4)

When the boat is in capsized condition, the relationship of volume below should be met:
Vboat = Vhull sheel + structures + Vsolid boxes(5)

In the case where the boat still afloat at the upright or capziced positions then thequantity of inside solid boxes should be provided to meet Archimedes’ principle of floating
subject. Besides, the location of LCG should be as close as LCB to ensure the boat would not
be in excessive trim condition.
The hull material of FRP was applied for the boats. The construction of boats were basedon the procedure of using FRP (reffered to “Marine Design Manual for Fiberglass ReinforcedPlastic”). The boats were constructed at the Faculty of Engineering, Pattimura University,Ambon, Moluccas. The boats were constructed as prototype for evaluating their performanceat sea (HETHARIA 2008). Three boats (similar configurations) were constructed based on theparameters of output design. All boats have the same size which was 1.5 GT. They were Fatek08, Barracuda and Yellow Fin, as seen in Fig. 1. The boat dimensions and output design
parameters are presented in Table 1.

Fig. 1. Tuna longboats 1.5 GT.

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HETHARIA Wolter R. and METEKOHY Obed

Table 1. Dimensions of tuna longboat.
No Items

SymbolDim

Unit

No Items

1 Length Overall

LOA

8.050

M

Condition: Full Load at Designed Waterline

Dim

2 Length of Waterline

LWL

7.600

M

Flooding to Upper Line, Upright Position

Unit

3 Length Bet. Perpend.

LBP

7.600

M

19 Reserve weight

0.509

Ton

4 BeamB

1.076

M

20 Reserve volume0.497

M

5 Maximum Beam

Bmax

1.165

M

21 Reserve freeboard

0.067

M

6 Draft

D0.390M

22 After draft

0.518

M

7 HeightH0.640

M

23 Fore draft

0.713

M

8 Block Coef.

CB

0.641

24 Reserve freeboard aft to U.L

0.224

M

9 Midship Coef.

CM

0.795

25 Reserve freeboard fore toU.L

0.037

M

10 Prismatic Coef.

CP

0.807

Condition: Capsized, Upside Down

11 Waterplane Coef.

CW

0.773

26 Volume displacement

0.807

M

12 Gross Tonnage

GT1.500

Tons

27 Weight displacement

0.827

Ton

13 Vol. displacement

V2.045M

28 Long. Centre of Buoyancy-1.360M

14 Wt. displacement,

∆

2.096

Ton

29 Total boat weight

0.548

Ton

15 Length C. Buoyancy

LCB-0.200

M

30 Long. Centre of Gravity-4.540M

16 Total boat weight

W

2.088

Ton

31 Trim: by stern

17 Length C. Gravity

LCG-0.202

M

32 Reserve weight

0.279

Ton

33 Reserve volume0.272

M

18 Trim : even keel

3333

Other output design parameters are:

Payload: 0.7 t fish and 0.35 t ice
Ratio ice/fish: 0.5
Volume of solid boxes: 0.623 m3 (14.3 %)Total volume: 4.37 m3
Prime mover: outboard engine 25 or 40 HP
Crew: 2 persons
Fishing gears: hand line and trolling line
Autonomy: 50 nautical milles
Fishing grounds: Banda Sea, Seram Sea and other Moluccas waters

Sea Trial
The boats sea trial tests were excecuted in order to confirm the output design. The tests
included speed and floating conditions. The test of speed was executed based on a procedureof speed testing. The tests were executed in Ambon bay for three boats (Fig. 2). The results ofthe tests met the design requirements. At the floating test, all components such as engine andequipments were still attached on boats (Fig. 3, 4). The boats reached the speed of 12 or 15
knots for the engine power of 25 HP or 40 HP, respectively.
The tests for floating purpose were executed in three conditions, which are:

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Design and Application of Unsinkable Tuna Longboat for Local Fishermen

1. Loading condition up to designed waterline to check full capacity of cargo loads.
2. Loading condition up to upper line to check the ability to afloat in flooding
condition.
3. Capsized condition to check the ability of boat to afloat in such condition.
The test of full cargo load was set-up for boat draft up to the designed waterline. Thiswas adjusted for a payload of 0.70 t and bulk ice of 0.35 t. It was found that the boats were ineven keel position. The test of flooding condition was executed by filling sea water to allcompartments inside the boat. All compartments were filled with water meanwhile some boat
equipments were fixed. From theoretical computation, the total weight of displacement was
4.08 t and total boat weight was 3.576 t.

Fig. 2. A sea trial test for the speed.

Fig. 3. A floating test for upright position.

Fig. 4. A foating test for capsized condition.

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HETHARIA Wolter R. and METEKOHY Obed

This means that there was still a reserve weight of 0.50 t or reserve volume of 0.50 m3
was provided. It was found also from the test measurement that the boats were trim by bow. A
reserve freeboard was measured for three boats as follows:
After freeboard to upper line:
Fatek 08: 0.20 m
Barracuda: 0.22 m

Yellow Fin: 0.215 m

Fore freeboard to upper line:Fatek 08: 0.041 m
Barracuda: 0.045 m

Yellow Fin: 0.042 m

The tests of capcized were executed by turning the boats to upside-down position. From
theoretical computation, total weight displacement was 0.827 t and total boat weight was0.548 t. This means that reserve weight of 0.279 t or reserve volume of 0.272 m3 wereprovided for the boats. It was found also from the test that the boats were trim by stern.
Vertical dimensions of freeboard height were found from measuring floating conditions. Theyare:
After freeboard measured from DWL (immersed):
Fatek 08: -0.010 m
Barracuda: -0.011 m

Yellow Fin: -0.010 m

Fore freeboard measured from DWL (emerged):
Fatek 08: 0.018 m
Barracuda: 0.019 m

Yellow Fin: 0.017 m

It was seen from the results of sea trial tests that the designed boats were afloat to their
upright as well as capziced positions. Those results were closed to the theoreticalcomputations. For a loading condition to designed waterline, it was found that the boats werein even keel condition. A cargo capacity of fish 1.0 t and ice 0.50 t was designed in this work.
A critical conditon where the boats were fully flooded was obtained by filling water into allboats’ compartments. The results were all three boats still afloat with a little trim by bow.
According to theoretical computations, a reserve of after and fore free board to upper line
were 0.224 m and 0.037 m, respectively. Where from the results of sea trial tests, they were0.21 m and 0.043 m. The differences were came from the difference of LCG position in thisloading condition.
When the boats were capcized, they were still aflot as seen from the results of the tests.
The boats were trimmed by stern. An indication of measurement for this condition was
freeboard measured from designed waterline. On the average, after freeboard measured fromDWL for the three boats are -0.11 m. The negative sign means that the boats were immersed
at after perpendicular. Meanwhile, fore freeboard measured from DWL for the three boats are+0.018 m. The positive sign means that the boats were emmerged at fore perpendicular.

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Design and Application of Unsinkable Tuna Longboat for Local FishermenTraining Program for Local Boat Builders
During the project of boats construction in 2008, the local boat builders were participated.
The training project was organized by Department of Naval Architecture, Faculty ofEngineering, Pattimura University, Ambon, Moluccas. The total of 55 participants fromprivate and government sectors in Moluccas are involved. They were trained for theoreticaland practical approaches of boat design and construction (Fig. 5). By the knowledge achieved
during the training period, they continue to develop this concept to their new product of boats.

Conclusion and Future Work
From the results of theoretical computation and sea trial tests, it was concluded thatwhen a boat is provided with some solid boxes inside it is still afloat even in full of water orcapsized conditions. Those solid boxes reduce the quantity of water coming into the boat.
Besides, the solid boxes create the buoyancy of the boat in the capziced position. A proper
distribution of solid boxes give a condition where the boats were not trimmed excesivelly.
This condition makes easy operation of turning back the boat from the capsized condition toits initial upright condition.
The boats were designed, constructed and tested for their capability to afloat. It wasrecommended to be applied to the users. The local boat builders have developed this concept
for their new products and this help the local fishermen for preventing the sink of boat in therough seas. This concept of boat design is recommended to be used for the fishermen in
Eastern Indonesia as well as the users in the Pacific regions.
The application of this concept for the larger fishing boats is still in the question markbut it will be some solutions for the future. However, this concept will be applied soon for thesmall fast passenger boats operated in the archipelago regions.

Fig. 5. A training session for local boat builders.

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HETHARIA Wolter R. and METEKOHY ObedAcknowledgements
Special thanks are dedicated to the Directorate General of Higher Education, Departmentof National Education, for their financial support to The Maritime Project Faculty ofEngineering Pattimura University, 2008.
Special thanks are dedicated also to the Team of Design and Construction Small Fishing
Boat, Department of Naval Architecture, Faculty of Engineering, Pattimura University. Your
hard works are greatly apreciated.

References
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McGraw-Hill Book Company Inc., New York, USA.
FYSON, J. 1985. Design of Small Fishing Vessels, 319 pp., the Food and Agriculture
Organization of the United Nations, Fishing News Books, Farnham, UK.
LEWIS, E. V. 1988. Principles of Naval Architecture, Vol. I, Stability and Strength, 310 pp.,
SNAME, Jersey City, New Jersey, USA.
HETHARIA, W. R., DE FRETES, E. R. and MATATULA, L. A. T. 2001. Desain dan Operasi Alat
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