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Rapp. P.-v. Réun. Cons. int. Explor. Mer, 168: 35-38. Janvier 1975.

TONNAGE CERTIFICATE DATA AS FISHING POWER PARAMETERS

F. d e B e e r Netherlands Institute for Fishery Investigations, IJmuiden, Netherlands

INTRODUCTION London, June 1969 — An entirely new system of The international exchange of information about measuring the gross and net fishing vessels and the increasing scientific approach tonnage was set up called the to fisheries in general requires the use of a number of “International Convention on parameters of which there is a great variety especially Tonnage Measurement of in the field of main dimensions, coefficients, propulsion Ships, 1969” .1 data (horse power, propeller, etc.) and other partic­ ulars of fishing vessels. This variety is very often caused Every ship which has been measured and marked by different historical developments in different in accordance with the Convention concluded in Oslo, countries. 1947, is issued with a tonnage certificate called the The tonnage certificate is often used as an easy and “International Tonnage Certificate”. The tonnage of official source for parameters. However, though this a vessel consists of its gross tonnage and net tonnage. certificate is an official one and is based on Inter­ In this paper only the gross tonnage is discussed national Conventions its value for scientific purposes because net tonnage is not often used as a parameter. is questionable. The gross tonnage of a vessel, expressed in cubic meters and register tons (of 2-83 m3), is defined as the sum of all the enclosed spaces.

INTERNATIONAL REGULATIONS ON TONNAGE These are: MEASUREMENT space below tonnage deck trunks International procedures for measuring the tonnage tweendeck space round houses of ships were laid down as follows : enclosed forecastle excess of hatchways bridge spaces spaces above the upper- Geneva, June 1939 - International regulations for break(s) deck included as part of tonnage measurement of ships poop the propelling machinery were issued through the League space. of Nations to obtain a kind of uniform “param eter” (gross However, the following are not included in the gross tonnage and net tonnage) to tonnage: use for harbour dues, dock dues, lock dues, canal dues, etc. double bottom spaces ceiling in holds Oslo, June 1947 - A convention was held to dis­ parts of tanks concrete floors in fish cuss differences in the regula­ space of engine room base holds tions for tonnage measurement casings space of fish processing of ships and in the application machinery of such regulations, the “Con­ vention for a Uniform System All the included spaces are measured from top of of Tonnage Measurement of frames, beams, floors, etc. (Fig. 16). Ships” . It is clear that gross tonnage must be regarded as a Oslo, May 1965 - A revision of the regulations of kind of “administrative parameter” . Great differences the 1947 convention. The ton­ can occur in the gross tonnages of vessels with similar nage mark was introduced. 1 As of September 1974 this was not yet in force.

3* 36 F. de Beer

3. type lb a tonnage certificate for vessels with more than one deck. For this type the second deck is the tonnage deck (open shelter deck ship). A tonnage mark is required.

This system of measuring gross tonnage can create great differences between similar fishing vessels as the following example shows. Two Dutch trawlers built on the same design (body plan, construction plan, etc.) and having the same dimensions given below Figure 16. Tonnage measurement according to 1947 (1965) con­ vention. length overall 50-16 length p.p. 43-25 moulded breadth 8-50 depth upper deck 6-45 depth second deck 4-20 mean draught ± 4.00

have the following tonnage certificates:

vessel SCH 171 SCH 6 type of vessel stern trawler stern trawler year built 1966 1967 identification length 46-35 m 46-30 m type o f certificate I lb Figure 17. Tonnage measurement according to 1969 convention. tonnage deck upper deck second deck gross tonnage 605-81 register tons 362-27 register tons dimensions, displacement, etc. due, for instance, to The main dimensions of a vessel given in the tonnage the positioning of watertight bulkheads in super­ certificate, called identification dimensions, are only structures, differences in type of construction, applica­ set up for the determination of the tonnage. They are tion of excluded spaces, and type of tonnage certifi­ (a) overall length: the distance between the extreme cate. end of the stem and stern. Differences in gross tonnage of 10% to 15% can (b) length : from the fore side of the upper­ occur between similar fishing vessels, measured in ac­ most end of the stem to the aft cordance with the regulations of the convention of side of the upper end of the stern- 1947 but before the revision of 1965. post or, if there is no sternpost, to The upper deck (weather deck) of fishing vessels the point of intersection of the fore with more than one deck was generally regarded as side of the rudderstock and the the tonnage deck. upper deck. The 1965 convention which came into force in the (c) breadth : extreme outside (rubbing pieces Netherlands in April 1967 introduced the tonnage not included). mark. This resulted in three types of tonnage certifi­ (d) depth : the depth is measured in the cates, viz. : middle plane at half length, from the underside of the upper deck 1. type I a tonnage certificate for vessels with one to the upperside of the double deck (upper deck = tonnage deck) ; no bottom plating or top of floors. tonnage mark required. 2. type la a tonnage certificate for vessels with more than one deck and having two gross ton­ THE 1969 LONDON CONVENTION nages. Recognizing that the establishment of a universal upper deck = tonnage deck (closed shelter system of tonnage measurement for ships should con­ deck ship) stitute an important contribution to maritime trans­ second deck = tonnage deck (open shelter port, a conference was held (London, May/June 1969), deck ship) upon the invitation of IMCO, for the purpose of draw­ A tonnage mark is required. ing up a new international convention on tonnage Tonnage certificate data as fishing power parameters 37

Table 15. Stern trawlers

Tonnage Certificate data Bodyplan data

Gross tonnage Length Year Registration no. 1947 1947/1965 o.a. B D built H.P. L s B s D s L pp Lew I m m m m m m m m type I type lb

U K 66 1968 540 104-53 26-08 24-92 6-62 2-59 24-50 6-60 3-10 GO 14 1968 705 120-32 26-25 25-09 6-62 2-77 ---- 24-50 6-60 3-30 KW 141 1966 1200 528-36 48-25 44-92 8-54 3-62 42-00 ---- 8-50 6-45/4-25 SCH 44 1965 500 64-82 25-65 24-06 5-63 2-16 ---- 22-20 5-60 2-60 \ OD 10 1963 720 76-87 25-65 24-71 5-63 2-12 ---- 22-20 5-60 2-60 / senes KW 15 1961 1200 477-56 348-09* 45-62 42-50 8-52 3-79 41-25 ---- 8-50 4-32 KW 41 1963 1200 484-00 345-41* 45-92 42-78 8-52 3-79 41-25 ---- 8-50 4-32 KW 43 1962 1200 480-17 347-72* 45-65 42-53 8-52 3-79 41-25 ---- 8-50 4-32 1 serles KW 123 1964 1200 482-55 335-60* 46-00 42-87 8-52 3-79 41-25 ---- 8-50 4-32 KW 170 1967 1200 375-46 49-15 46-02 8-52 3-48 45-25 ---- 8-50 4-32 \ 4 3 2 i series IJM 57 1966 1320 559-57 49-12 46-06 8-52 3-48 45-25 ---- 8-50 U K 205 1967 660 101-27 26-20 24-07 6-72 2-75 22-85 ---- 6-70 3-40 U K 207 1967 660 101-27 26-20 24-07 6-72 2-75 22-85 ---- 6-70 3-40 > series OD 5 1968 705 104-80 26-20 24-52 6-72 2-75 22-85 ---- 6-70 3-40 KW 81 1967 1600 382-44 49-99 46-13 9-02 5-62 43-50 ---- 900 6-55/4-34 SCH 24/SCH 33 1966 1240 643-74 390-80* 49-84 46-27 8-52 5-30 43-00 ---- 8-50 6-54/4-34 SCH 123 1968 1240 377-00 51-91 48-05 9-02 5-46 45-50 ---- 9-00 6-39/4-24 SCH 110 1967 1200 362-26 49-75 46-18 8-52 5-40 43-00 ---- 8-50 6-39/4-24 G O 9 1967 680 120-19 26-19 25-09 6-03 2-95 ---- 24-70 6-00 3-40 SCH 34 1966 700 91-80 29-50 28-17 5-93 2-48 26-50 ---- 5-90 2-90 U K 64 1967 500 133-01 28-60 26-85 6-42 2-52 25-10 ---- 6-40 3-40 U K 89 1967 450 78-20 26-00 24-54 5-92 2-16 22-60 ---- 5-90 2-90 \ 2 go i series U K 121 1965 435 76-20 25-46 24-14 5-93 2-22 22-60 ---- 5-90

remeasured: vessels with a new tonnage certificate. measurement of ships. It was decided that the con­ tonnage (present) is 98-10 register tons. The total vention should come into force 24 months after the volume of all enclosed spaces V = 329 m3 and hence date on which not less than 25 governments or states, K, = 0-2503. Thus its new gross tonnage would be with a combined merchant fleet not less than 65% of GT = KXV = 82-5. the gross tonnage of the world’s shipping, have signed The dimensions given in the new tonnage certificate, without reservation. called main dimensions, are defined according to the The new convention shall apply to new vessels (with Load Line Convention, 1966. These are a length not less than 24 m (79 ft)) and to existing vessels (with a length not less than 24 m) twelve years (a) length: the length shall be taken as 96% of the after the date on which the convention will come into total length on a waterline at 85% of force. the least moulded depth measured from At the time of writing (1970) this convention is not the top of the keel, or the length from in force. the fore side of the stem to the axis of the According to this convention the gross tonnage of a rudderstock on that waterline, if that be vessel shall be determined by the following formula greater. In ships designed with a rake G T = K 1V where GT = gross tonnage (dimension- of keel, the waterline on which this less), Kx = 0-2 + 0-02 LogI0F, and V = total volume length is measured shall be parallel to (moulded) of all enclosed spaces of the vessel in cubic the designed waterline. meters. For erections there are a number of correc­ (b) breadth: the breadth is the maximum breadth of tions (Fig. 17). the ship, measured amidships to the The factor K\ has been added to prevent great dif­ moulded line of the frame in a ship with ferences between the “present” GT and “new” GT. a metal shell and to the outer surface As an example, consider a side trawler of length p.p. of the hull in a ship with a shell of any 23-35 m, breadth 6-40 m, and depth 3-10 m. Its gross other material. 38 F. de Beer

(c) depth: the moulded depth is the vertical dis­ IMCO DEFINITIONS tance measured from the top of the keel Summary of the tentatively agreed unified definitions to the underside of the upperdeck at the for dimensions and coefficients of fishing vessels. side. (For wood and composite ships, ships having rounded gunwales and Standard waterline : The waterline which is parallel ships with stepped upper deck, see regu­ to the maximum load displacement design waterline lations) . of a vessel, but located at a draught of 0-85 D taken at the midship section. CONCLUSION It is recommended that the waterplane defined by 1. There is very little correlation between the gross this waterline be the horizontal coordinate for the tonnage (convention 1947/1965) and other vessel framework used in integrating hull areas and volumes. parameters such as length, HP, hold capacity, etc. O n vessels where the design waterline is not known, (Table 15). it is recommended that the coordinate system for 2. Due to the introduction of the tonnage mark developing the vessel lines and integrating hull vol­ (1965), comparison of gross tonnage on fishing umes and areas be established with the vertical co­ vessels, especially stern trawlers, will not be pos­ ordinate parallel to the vertical plane of the bulkheads sible without taking into consideration the type of and frames. measurement. (Table 15). Perpendiculars: The forward and after perpendicu­ 3. The convention 1947/1965 permits the gross ton­ lars shall be taken at the forward and after ends of nage of fishing vessels with more than one deck to the standard waterline (L), drawn perpendicularly to be altered at any time, due to the three possible the standard waterline. ways of measurement. (Table 15). 4. The gross tonnge of a fishing vessel measured ac­ Length: (a) Overall (LOA). The distance between cording to the 1969 convention will differ from the lines at the extreme end of the bow and stern perpen­ gross tonnage of the same fishing vessel measured dicular to the standard waterline. according to the present convention. (b) Standard waterline length {L). The 5. If the 1969 convention comes into force, two types length on the standard waterline as defined above of gross tonnage measurement will exist together measured from the inside of the stern shell plating to for about twelve years after the date of its enforce­ the inside of the stem plating of a vessel with a metal ment. shell or from the rabbet aft line of the stern to the 6. The gross tonnage of a fishing vessel according to rabbet front lines of the stem of a vessel with a shell the 1969 convention could be a reasonable “vol­ of any other material. ume parameter”, if the volume of superstructures (with the necessary corrections) is not included. Breadth (B ) : The maximum breadth of a vessel on 7. The dimensions (called identification dimensions) the standard waterline measured to the moulded line given in the present tonnage certificates are ad­ of the frame of a vessel with a metal shell or the outer ministrative dimensions and are questionable as surface of the hull of a vessel with a shell of any other ship’s parameters with the exception of the “length material. overall”. Confusion can be created especially by Depth (D) : The distance from the underside of the the use of depth depending on the height of the freeboard deck at the side to the top of the keel of a double bottom or floor, deck beams and camber. vessel with a metal shell, or to the rabbet lower line of 8. The use of the “main dimensions” (to be given in the keel of a vessel with a shell of any other m aterial future tonnage certificates) as ship parameters is plus the minimum thickness of decking. The distance sensible. However, as these dimensions are defined is to be measured perpendicularly to the standard according to those given in the Load Line Conven­ waterline. The term D gives the depth at any section. tion 1966, they do not take into account the special When used in tabular form the term D must be fol­ features of fishing vessels. The best solution would lowed by a defining term, or sub-index, such as: be to use the definitions tentatively agreed by IMCO1, as summarized below. Dmin — Depth minimum D m - Depth amidships 1 Unified Definition of Main Particulars and Other Properties of Fishing Vessels, PFV X/W.P. 8, July 1970 (Sub-Committee on D f — Depth at forward perpendicular Safety of Fishing Vessels). D a - Depth at after perpendicular.