Beam trawling - A study on the resistance of a beam trawl and measurement of the forces acting upon the rigging

BEAM TRAWLING

a study on the resistance

of a beam trawl and

measurement of the forces

acting upon the rigging

ir.

e.j.de boer

afdeling technisch onderzoek

directie van de visserijen

ARCHIEF

Lab.

y. Scheepsbouwkunde

Technische Hogeschool

Deift

Benaming Proj.

Atcurtecht ocrbchoudcn oigens de wet

BEAN TRAtLING, a study on the resistance of a beam travi and measurement of the forces

acting upon the rigging by

ir. E.J. de 3oer

: Measurement of forces acting on different parts of the beam trawl gear when fishing.

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Contents

Purpose of the study Reason

Procedure

?leasurement and Recording Description of the veSsel The Beam Gear

The rigging

The resistance of' a beam gear

Difference in resistance towing intide or tideward page 11

Forces acting on rigging when shooting the gear page 11

Forces acting ort rigging when hauling the gear The influence of the condition of the seabed on

the forces acting on the riggthg

Beam trawling description of gear handling

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Rangschimerk page 1 page 1 page 2 page 2 page page 5 page 6 page 8 page 13 page 13 page 15

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List of figures

figure 1: rigging beam trawler 13M 44 figure 2: gantry beam trawler IJ)I 44 figure 3: beamgear

figure

4:

beam for beam trawl

figure

5:

trawlhead foi- beam trawl figure

6:

beam net IJN 44

figure 7: torces acting on rigging figure 8: resi8tance beamgear

figure 9: influence direction of tide at resistance figure 10: shooting of beamgear - friction withdrawn

figure 11: shooting of beamgear engaged friction

figure 12: hauling of beamgear

figure 13: fishing at muddy and sandy grounds

fishing at rough ground forces on rigging

beam trawling departure homeport

beam trawling heading for fishing grounds

beam trawling shooting of gear

beam trawling fishing

beam trawling hauling codend

beam trawlirig lifting codend

beam trawling emptying codend

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figure 14: figure 15: figure 16: figure 17: figure 18: figure 19: figure 20: figure 21:

BEAN TRAWLING, a study on the resistance of a beam trawl and measurement of the forces acting upon the rigging.

PURPOSE: The purpose of this study is to get information about the resistance of' a beam gear and about the torces acting upon various parts of the rigging under several working conditions. This information is of importance in order to calculate the

dimensions of booms, parts of the gear and winch. Furthermore this study will give a brief revev of the factors influencing the resistance and/or forces.

REASON: Since

₁₉₅₈

the importance of beam trawling for flat fish

increased continuously. The species moat valuable are soles. At the start this type of fishery was executed with gears having a

horizontal netopening of about 6 meter. This dimension was given

by the available propulsive power. This propulsive power varied

at that moment between

₁₅₀

and 240 h.p. The fisherman soon

realized that the catch increased with the horizontal netopening and the weight of the tickler-chains, The former gives an increase of fished seabed per unit of time (constant speed); the latter is of influence upon the catch per square meter seabed.

To tow a big and heavy gear one needs more power than for a small one. So we have seen in this type of fishery a steady increase of propulsive power. At this moment the beam length is about 9-10 meters. A longer beam will be unmanageable and has to be of a stronger construction because of the bending momenta and buckling forces. At the same time the. boom has to be longer and of a heavier construction. The development of gear dimensions has come to an end, but the increase of towed weight of tickler-chaina is still continuing. Nowadays vesSels with a propulsie

power of

₇₅₀

h.p. tow 1.200 kg of tickler-chains in front of each

groundi-ope. The increase of propulsive power during the last years

has been startling. E.g. in

₁₉₆₇

the average propulsive power of

vessels beam trawlingfor flat fish vas 320 h.p. The average

pro-pulsive power of the 37 vessels, built in

_1967,

was

540

h.p.

(max.

700

h.p. - min.

405 h.p.).

This figure for the ₄₄ vessels,

built in

1968, was 650 h.p. (max. 750

_{h.p. - min.}

360 h.p.).

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At present, March 1969, vessels are under consideration with a

propulsive power of up to

₉₆₀

h.p.

Because of the increase in dimensions and weight of the beam gear, the forces acting upon warps, stays, topping-lifts, boom., etc. were increasing too. The fact that damage at winches, riggin and gear occurred frequently led to the iessity of this study. PROCEDURE: To get information about the resistance of the gear and the forces acting upon the rigging, the following parameters have to be measured:

the speed of the vessels through the water, the speed of the vessel over ground,

the pull in the warp, the pull in the forestay, e, the pull in the topping-lift,

the position of the boom, the warplength,

the waterdepth, and the angle of roll.

To get a Sound Judgment of the factors influencing the resistance and forces the. gear has to be towed. under various conditions. NEASUREftNT and UECORDIG apparatus:

The. speed of the vessel through the water was measured by

means of a CHETKEEFF ELECTRONIC LOG. This log is of the

impeller type and has two ranges: .0-5 knots for fishing speeds and O-10 knots for free-running speeds. At the lower range the accuracy is within 0.1 knot.

The log was mounted in a special outrigger at portside of _the

vessel (picture i). The distance between the log and the _hull

ofthe vessel is 0.5 meter. At this distance there is _no

in-fluence of t-he boundery layer. During the trials the vessel's course was kept tideward or intide to avoid influences by

transverse currents. The speed

Indicator-unit

_{was mounted iii}

the

wheelhouse.

The speed of the vessel over the bottom was measured by _the

DECCA NAVIGATOR UNIT, wMch is generally used by this _{type of}

fishery, mostly In combinationwith a TRACK PLOTTER. Every day the Decca was calibrated.

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c. d. and e. The pulla in the warp, forestay and topping-lift

were measured by BROSA loadcell transducers. For measurement of the pulls in the warp and forestay two loadcella type EHM 2138 (0-20 ton) were used. The pull in the topping-lift was measured by a loadcell type EHM 2137 (0-10 ton).

The accuracy of the loadcella is better than 0,25% f.s. The measuring system consists of a resistance wire; half bridge 2 x 1.50012. The loadcells can resist a waterpreasure of 30 kgf/cm2 and are suitable for use in seawater.

Figire (i) and (2) show the position of the loadcells in the. rigging. Picture (2) ahowa the loadcell for measurement of the pull in the warp. The angle over which the warp loadcell measures is kept constant by towing with the boom in a fixed position.

The pulls were recorded on a RIKADENKI 3-pen recorder, type B-34SS. This is a.compensation recorder with the following

measuring rangea: 10-20-50-100-500 mV, 1-5-lO-50-1OÖ y.

The paper width is 250 mm; pen speed 0.5 sec, f.d. The input resistance is lo k.Q. The accuracy is + 0.5% f.s.

The position of the boom was measured by an angle meter of own

design. During ail trials the boom-angle with _{the horizon was}

+ 2 degrees.

During the trials the warplength between fishblock and the bridle was 75 meters. ihIs length was measured and marked at the warp.

The waterdepth was measured by the _{Vessels echosounders FTJRUNO}

type 850-A and 861-A.

The angle of roll was measured by a portable ROLL RECORDER

MUIRHEAD type D-993-8, The roll angle bearing _{scale of the}

recorder is 16 degrees per inch deflection. _{The accuracy la}

better than 1% f.s.

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DisCflIPÇlft OF 'rIlE

fhe vesei9 registrationnumber IJIl is a idetrawJ.er with

the foil )t'iIL dimensions

Jen:Lh o.a0 26,...5 meier

I enLh P. p. 23,

35 m?ter

benm

_6,4o

meter

depI 3, U) meter

dratt forward (c.w.1.) _{1,95 meter}

draFt aft (c.t:,1.)

_2,63

_meter

mean (c.,L.)

_2,29

meter

1'9,5 tons (metric)

waterpiane coefficient C

_{= O771}

block coefficient _{Cb =}

primatic coefficient C1) =

0,645

max. section coefficient C =

0,744

max. sect.

The vessel has a four stroke main engine, _{developing 5/a) 1.h.p.}

at 750

r.p.m. This engine dz-lares a propeller lth fixed pitch:

diameter 2.000 mm

pitch _{1.290 nvn}

56%

number of blades 4

The gearbox has a reduction gearing 2,91i : 1.

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The winch has tour drums, two for the warps and two for the topping-lifts, and two whipping drums. The winch is driven by

a high pressure hydromotor MANNESMANN, type MAN

36,

which is

of the axial piston type with fixed flow, The hydromotor drives

by a gearbox with reduction gearing 64 : i the main shaft of

the winch. The maximum speed of the hyd.romotor is 1.500 r.p.m..; the flow capacity.i.s 301,9 cm3/r.pm.

The hydropunip is a MANNESMANN axial piston pump with variable

flow, type MAP

36.

The hydropump is driven by a DA? auxiliary

engine developing 90 h.p. at 1.500 r.p.m. This engine is remote-ly controlled from the wheelhouse.

The frictions and brakes of the

winch are pneumatically

con-trolled from the wheelhouse. The air is taken from the air bottles,

which are

kept under pressure by an electrical driven compressor.

TIFE BEAM GEAR: The beam gear consists of three main componente (picture ): a. the beam and the trawiheads,

the net, and

the tickler-chains.

ad a. The beam has three parts (figure

4).

The middle section

is stronger than the outer sections due to the greater bending moments. When bent after a fastener it is only necessary to replace the damaged part of the beam. The trawiheads (figure 5) are situated at the ends of

the beam. The parts of the beam and the trawiheads _are

kept together by the headline and the component of the tension in the bridles in the direction of the beam. The bridle, running to the middle section of the beam,

is idle under normal fishing conditions. This bridle picks up a pulling force when the beam starts bending.

The function of the beam with trawiheads is to give _the

net under all working conditions a fixed horiZontal and

vertical netopening.

These

_{parameters are not depending}

on the speed of the gear as i the case with an

otter-trawl. Furthermore the trawihead. ac.t as connecting points the chains. So the amount of tickler-chains does not influence the netopening.

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Pigure 3 shows a beam gear when towed on the seabed.

ad b. Figure 6 is a drawing of the net. The net is a two seam

net, the belly of which is cut away deeply. The mesh

length is 72 (75) stretched. To resist the wear caused

by the seabed the part of the belly which contacts the seabed is doubledo The groundrope has a length of 22 meter.

To the groundrope a 16 chain is attàched to keep the

groundrope in good contact with the seabed, preventing the escape of fish underneath. Attached to this chain are five 12 n tickler-chains (length resp. 2,5

_3,5

_'&,5

5,3 6,5 meter). These lighter tickler-chains cover the

area between the heavy tickler-chains and the groundrope. ad c. The function of the tickler-chains is to chase the flat

fish out of the seabed and bring them within reach of the netopening. Thit gear had six heavy tickler-chains with

various diameter. The chain lengths were resp. 15,7 14&,9

13,3 13,1 11,7 10,0 meters. The total weight was

G6o kg.

Figure 3 "Trawihead for beam trawl" shows that it is posai-ble to connect as much as 10 chains to the trawiheads. The chain wear depends on the seabed conditions0 After 6-12 weeks of fishing the chains have to be rénewed. Due to the wear the chains are lengthened which can cause fouling of the chains.

THE RIGGING: For years the normal arrangement was the boom fitted to the main mast, with the warp running along the boom. Figure 7-A gives the drawing of this arrangement and.shows that the pull at the forestay and the buckling forces acting upon the boom are heavy. In general the forestay is fixed, which makes

it impossible to bring the booms on deck, _{e.g. in bad weather.}

Nowadays a f ew vessels have a diaconnectable forestay; by means of a tackle the forestay can be paid out to make lowering of the booms on deck possible. However in practise this system gives difficulties. The warps running along the boom give the

follo-wing disadvntage when a fastener occurs: using this arrangement

the fishing block situated at the top of the boom has to be con-nected by means of a wire to a sliphook.

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In case of danger when hauling, the capsizing moment can be reduced by lowering the fishing block. By doing this the warp will run over the bulwark. When hauling with the warp in this position he will be damaged heavily or even break. So in prac-tice the skipper mostly tries to get free from the fastener by hauling with the fishing block attached to the end of the boom. To overcome these difficulties the next step was the erection of a gallois as forward a possible. As figure 7-B shows the pull at the forestay and the buckling forces at the boom reduce considerable. The difficulty. of lowering the boom on deck is not solved,

The following step in the development of the rigging was the erection of a gantry in front of the wheelhouse, as shown in figure 7-C. Using this arrangement the pull at the forestay and the buckling forces acting upon the boom decrease consider-ably. Furthermore it is important that the boom length can be reduced by,some 2 meters, what has a great influence upon the resistance against buckling. When a fastener occurs the

cap-sizing moment can be reduced by paying out the backetay, As _a

result the boom will swing forward to the position of the gal.. low.0 The position of the gallow as forward as possible reduces

not only the forces actin _{upon boom and forestay, but al3o}

prevents the vessel from coming perpendicular to wind, and/or

current 'during a fastener. T3y situatinc' the gallois' _{s forward}

as possible the vessel wi].l aLways come intide, decreasing the danger.

The values as given in figure 7 apply only to the supposition

thf t the boom, backstay and forestay lie in the _{same plane.}

The force P is the horizontal component of the warp pull, For

a better understanding the vertical

_{component of}

_{the warp pull}

is neglected. Because of the ratio between warp length and

waterdepth this vertical component is small compared to the

horizontal componsat.

when using a gantry in front of the wheelhouse, _{the influence}

of the vessel's pitching upon the warp pull variations _{is less}

than in the other two arrangements. A dieadvantage of _having

the gantry in front of the wheelhouse is the fact _{the skipper}

cannot

see

the two gears simultaniously,

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THE RÉSISTANCE 0F

A BEAN GEAR: The resistance of a beam gear

consists of two main componente. Bach of these components can be subdivided. The main components are:

1. the hydrodynaisic resistance, which

can be

divided in the resistance of the beam and the traviheade, the resistance of the tickler-chains, and

the resistance of the net.

2. the bottom friction resistance, which can be divided in the resistance of the trawiheads,

the resistance of the tickler-chains, and

the resistance of the parts of the net, which _{are in}

contact with the seabed, e.g. the groundrope, the

chain groundrope, the lighter tickler-chains and a

part of the belly.

In general the resistance R of an object towed through a liquid

is:

R=Cd.

.v.A (kgf)

C. _{= the drag coefficient of the towed object}

ft

= the mass density of the liquid (kgfaac m )

y the speed of the towed object through

the

_liqmid

A _{= the projected area of the object on a plane}

perpendicular to the direction of movement. The drag coefficient Cd is, if the object dola not deform due

to

the

towing motion, dependent on the

_*hape

_{and dimensiOns of}

the object. However a net

vili

_{deform in relation to the tswing}

speed. It the net is towed at a very slow speed the setting of

the net will not be correct. When increasing _{the speed, the}

pressure generation inside the nat will give the net _{such a}

shape that the meshes open correctly with a top angle of about

60 degrees. At high speeds the meshes will stretchs which causes

reduction of the draining area. Due to this the webbing doesn't

permit to pasa all the water entering _{the netopening. The net}

throws back part of the water. The drag coefficient Cd will increase.

A beam gear has the property that _{the projected area A in all}

working conditions is fixed..

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Summari&ing it can be stated

that under

normal fishing

conditiOns

the hydtodynainic resistance of a bearn gear vili be proportional to the square of the speed. In formula z

R=c.v2

(kgf)

Cd .

1/y.

A (kgfsec2m2)

The bottom friction resistance depends on:

the condition of the seabed; on a hard9 sandy seabed the resistance will be lese than on a muddy bottom.

the weight of the parts of the gear which are in contact

with the seabed in general the reaiátanoe of an object

that is moved over a plane is given by the formula z

Rf.N (kgf)

f coefficient of friction; this coefficient depends

on the materials which are in COntact.

N the reaction force between object and piane.

the shape and the construction of the belly Of the net. During the trials three resistance curves of the gear were determined.

a. The hydxodynamic resistance of the complete gear as a function of the vesel's speed.

This was done by towing the complete gear at a distance of about 2 meters below the surface at several speeds. Therefore the gear was rigged in such a way that at all

speeds the undersidea or the trawlheada were in a

hori-zontal position, At each speed sufficient warp was paid out that a mark at the warp iras just above the

water-surface. This dietance together with the known distance

between fish blCk and wateraurface, makes it possible to calculate the angle between the warp and the horizon-tal Plane. The loadceil gives the pull in the warps; the boom was kept in e rixed position.

Graph A of figure 8 gives the results. Aa was expected

the hydrodynamic resiitance proved to be proportional to the square of the speed. This was true up to a speed of

4 knots,

The maximum attainable speed was

_4,45

knots; the

resis-tance at this speed was

2.680 kf.

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The total resistance of the complete gear as a function of the vessel's speed.

The method was the same as under a.; the angle between warp and the horizontal plane was calCulated from the measured waterdepth and the length of warp paid out.

Graph 13 of figure 8 gives the results. The maximum

attainable speed vas

_3.7

knots; the resistance at this

speed was 3.000 k.

As the graph shows, the bottom resistance has a great

influence on the total resistance,. At a speed of

_3.7

_knot4

the hydrodynamic resistance of the gear is l.660kgf,

while the bottom friction resistance is

_1.340

kgf.

Summarizing: Under this working condition the total resistance can be divided in 56% hydrodynamic

resis-tance and

4%

bottom friction resistance.

The graph showi that the bottom friction resistance is

almost independent of the towing speed. Due _{to the}

bottom contact the resistance of the gear at speed

zero is about

1.260

kgf.

The resistance of the gear without _{tickler-chains:}

Graph C of figure 8 shows the resistance of the _gear

without tickler-chains as a function of the vessel's

speed. The weight of.the removed tickler-chains _was

660 kg. The maximum attainable speed was 4.15 knots;

the resistance at this speed was 2.830 _kgf.

Comparing graphs C and B ehow that at a speed of

37

knots the resistance of the gear without

tickler-chains is

_2.380

_{kgf. In order to tow 660 kg}

tickler-chains at a speed of

_3.7

_{knots under this working}

condition a propulsive power of 620 kgf, _{or 20% of}

the total resistance, is needed.

Summarizing: 1 kg tickler-chain gives an increase of the resistance of about i kgf.

Working condition: The above mentioned values apply only to the working conditions at the moment of the trials. The depth

of the seas where the trials were made, is _{9 fathoms. The}

sea-bed is a hard, sandy but smooth bottom, Factors influencing _the

measurements are catch, bottom foul, _etc.

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The seabed at the place of the trials was very clean and the

catch wasneglectable.

During the trials the tide current was 0.7 Içnots; windforce Beaufort 39 direction E.N.E.

DIFFERENCE IN RESISTANCE FOR TOWING INTIDE OR TIDEWARD:

Due to the tidal currents in the North Sea there are consider-able differences between the speed of the vessel (and gear) through the water and the speed of the gear over the ground.

Generally speaking: y y + y coeo(

ground vessel - tide

+ = tideward - = intide

o(= angle between direction of tide and the vessel's course.

From this formulae it follows that at a given speed of the vessel the speed of the gear over ground depends on the

direc-tion and the velocity of the tidal current.

Graph Din figure 9 gives the resistance of the gear towing tideward; graph E under the same working conditions towing in-tide. The velocity of the tidal current amounted to 0.7 knóts,

Towing intide, the maximum attainable speed of the vessel was

4.4

_{knots; the measured reaistance of the complete gear amounted}

to 2.780 kgf. The engine speed was 750 r.p.m.

Towing tideward9 the maximum attainable speed of the vessel was 3.7 knots; the measured resistance amounted to 3.000 kgf. The revs, of the engine decreased to 720 r.p.m.

Towing tideward, the speed over ground will be higher than when

towing intide, resp.

4.4

and 3.7 knots.

FORCES ACTING ON RIGGING WHEN SHOOTING THE GEAR:

Until two years ago the winch was generally driven by the main engine by means of a flat belt, a one-way drive tor hauling

only. Shooting the gears was accomplised with the drums _free

running; the weight and the resistance of the gears in the

water pulled off the warps from the drums, Warp speed was

con-trolled by the brAkes. To decrease the shooting time, it is common to speed up the revs, of the main engine to full ahead.

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Just before the brakes are put on, the skipper reduces revs, in

order to overcome heavy loada on warps and winch.

Figure lo gives a recording of the above mentionéd method for shooting a gear at. two different revs, of the main engine, resp.

600 and

₄₅₀

r.p.m. The influence of the revs, upon the loads is

shown Clearly.

When the codend is emptied the skipper has to execute two actions, n order to bring the gears in fishing position. At

first to bring the boom in his fishing position and secondly to pay out warp. In Order to safe time these actions are execu-ted simultaneously.

The reàordinga show the above mentioned actions clearly. The parts A-B, reap. D-E, show the shooting of the warp and the lowering of the boom, which takes place with geared winch drive. At the moment, upon which the booms have r ached their position, the frictions are withdrawn, and the brakes on the topping-lift drum are engaged. From this moment the warps pay out unchecked at a higher speed. The pull at the warps decreases. The function of the forestay Is shown clearly.

The application of hydraulic and electric driven winches during the last two years made it possible to shoot the gears with

frictions engaged. When the amount ot warp paid out is sufficient the winch drive is stopped, after which the brakes are put on. fly doing this the wear of the brake-linings and the loads at parts of the rigging is less compared to the formerly mentioned method. Furthermore the chance of fouling the gear8, when

shoot-ing tideward, decreases considerably. The latter can be explain-ed as follows: When shooting the gear.s with frictions engagexplain-ed the difference between speed of the vessel and speed of the gears will be less, than when shooting with disengaged frictions. 1ze

to this, the chance that the relative speed of the gear with regard to the velocity of the tidal current becomes negative, can be neglected. As a result of this thé nét (nylon) cannot be pushed over the beam, because this would cause damage to the net when starting to tow. The disadvantage of shooting the gears with engaged frictions is the longer shooting-time compared to

the former method.

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Ra ngsc h ik me r k

ING WHEN HAULING THE GEAR:

r thinks it necessary to haul, he engages ing the revs, to euch a value that the able. The pull at the warps when hauling The gear (weight, dimensions, mesh-size and yarn, cut of the net, etc.)

The catch (amount and species, bottom dirt, etc.) The speed of the gear through the water and over the ground; these are dependent of the speed of the vessel through the water and over ground, the warp speed and the momentary ratio between waterdepth and warplength. The condition of the seabed,

Figure 12 shows a recording of hauling the gear (no catch). The gear is hauled #Lththe main engine running at 500 r.p.m.;

the hydromotor running at full speed.

The recording shows that, due to the change of the encountering speed between waves and vessel, the movement of the vessel variea The gear stays at the seabed till the warp is almost vertical under the fish biok (dependent on the vessels's speed). I:n

figure 12 the moment the gear leaves the seabed is marked with x-x, The increase of warp pull at the end of the haul is caused

boom,

with the r suit that the angle over asures varies.

the pull at the topping-lift increases everage. Due to the greater inclination d of the haul the pull at the forestay e backstay is keeping the boom in its

CONDITION 0F THE SEABED ON THE FORCES ACTING seabed will be of great influence on the

and topping-lift. Figure 13 shows the

p pull when fishing on muddy,

resp,

sandy

arlatioù in warp pull is mainly caused by f the gear. The gear shows the tendency

mud0

Rangsch i k me rk

Benaming

FORCES ACTING ON RIGG The moment, the íkippe the winch while dropp

vessel stays manoevr

depends on:

by the topping of the whICh the loadcell me When topping the boom due to the changing i of the warp at the en decreases to zero.; th Position.

THE INFLUENCE OF THE ON THE RIGGING:

The condition of the pull in warp, forestay differences in the war grounds.

On muddy

grounds

the y

the irregular motion o to dig itself into the

rechnisch Visserijonderzoek

A.tesre(ht oorbchoden 'øIgens de wet

Schaal Gecontroleerd

Fòrmaat

A4

page 13

The attainable speed of the vessel was 2.15 knots.

On a hard, sandy bottom the warp pull variations were

signifi-cantly leas; the attainable vessel's speed was

3.7

knots.

Figure 11& shows the variation of warp pull when fishing on

rough grounds; simultaneously the pull at forestay

and

topping-lift are recorded. The maximum pulla are caused by the uneven seabed. As a result of these variations the revolutions of the

main engine vary between

680

740 r.p.m.;

the vessel's speed

varies between

3.5

4.3 knots.

In general, fishermen keep the warps steeper when fishing on rough grounds in order to get more lift.

Figure 14 shows the forestay performing its function mainly at the occurence of héavy warp pulls, e.g. at the'moment the vessel has a fastener.

As discussed before, the forestay pull is influenced by the ratio between warplength and waterdepth.

Benamirtg

Technisch Yisserijonderzoek

Atcrs,ht DO bchøt.den ogens de wet Getekend Gezien

Formaat

Rangschikmcrk

page l4

Beam trawlin description of gear handling

The following description for handling of the gear on board

beamtrawlers, apply to a

side

trawler with the booms fitted

to a gantry in front of the wheelhouse. The, handling of the gear on board stern trawlers and side trawlers with another rigging diff ers slightly from the given description.

The side trawler with i gantry in front of the wheelhouse is chosen because. this type is quite common (see page 7). departure homeport (fig. 15)

The booms are in a vertical position, in order not to hamper the movement of the vessel In the harbour. The gears are

stowed on deck. To overcome damage to the deck the trawiheads are placed on p].ates of

plywood.

The tickler-chains are lying on deck; the net is draped over the beam. Movement of the booms is prevented by the backatay.

headln,g for fishing grounds (fig. 16)

As soon as possible after leaving port the booms are lowered so far that in general the booms are not touching the water-surface due to the rolling of the vessel. To overcome slamming of the booms there is pull at the warp.

shooting of gear (fig. 17)

For bringing the beamgear outboard the booms are brought in such a position that they make an angle of about 60 degrees

with the horizon. fly pulling the beamgears over the bulwark

they are brought outboard. The aftpart of the net stays on

board. This is done to avoid the possibility of the net coining in the propeller, e.g. when turning. The booms are lowered to their fishing position and the revolutions of the propeller are increased. The codend and lazy decky are thrown overboard.

The shooting

of the

_{gears can start. Shooting is done in}

general with almost fuji speed. Just before theshooting

opera-tion is stopped the revs, of the propeller are slowed down tó diminish the jerk at. the warp when engaging the brakes.

fishing (fig. i.fl)

The only action taken when fishing is paying _{out or hauling}

warp. This depends on the depthvariation of the seabed and on the condition of the seabed. The warps are hauled with the engine at half ahead.

Benaming Form aat Rangschikmerk

A4

page 15 Technisch Visserijonderzoek Schaal

j

Benam Ing

Formaat

The moment the gear is almost vertical under the fishing block the boom is topped, to auch a position that the deckhand can reach for the lazy decky. At the end of the haul the engine is

stopped.

hauling codend (fig. 19)

The lazy decky is brought to thc whipping drum and the codend is hauled. The moment the splitting strop reaches the bulwark

the hauling of the codend by means of the whipping

drum is

stopped. The hook of the fish tackle is attached to the split-ting

strop.

lifting codend (fig. 20)

The fish tackle is running to

a block

at the top of the main

mast. 1y means of the whipping drum the codend is brought to

the

fore part of the vessel arid hoisted over

the buiwark.

Due

to the movement of the coderid the beam will turn till a fore and art direction.

emptying codend (fig. 21 )

To prevent the beam from

turTLiri;

too far, the lazy decky is

fastened to the bulwark. After emptyirL

of th

codend the

engine is put at slow ahead and due to this the beam turn back to the norma] position. The codend and the lazy decky

are throw overboard and the procedure of shootin the gear

starts again.

Rngschik mcrk

A

page 16

Schaal Gecontroleerd

Technisch Visrijonderzoe

TFe//N'f'/ F/J/«9Dh''fI2ZôC Au;quireckI oorbeheuden oIgens de act

Schaal /. fO Gatekend

44

7. Foriaat

A4

Rangchikmerk 96.cJ'-.'l- ' Gecontroleerd Gezien Benaming

rFe,¼reN'

fF1

4eec-Auteu?eedlt oorbehoudcn volgens de w.

U OI'9

L

Benaming

GANTRY BEAMTRAWLER 1JM44

SeMai

,:ç0

Getekendy E

o

o

-o

L.

o

u

o

Gecontroleerd Gezien

Figure 2

o. L. Formaat

A4

j

u

a

o

Rangachiknierk /ao-,J./o. L

split*i'ng strop

cross section

underside view

chain grouncirope

BEAMGEAR

Benaming

frawihead

BEAMG EAR

7FC'/M&e'// Ani.. hi oo,bsho.deA eigsns da w.i IGeiekend

Figuré 3

Schaal Gecóntroleerd

warp

Formaat 3

f

Benarn ng i T i'

Figure 4

i i I I I I t t i , I t i I I £

BLOM aV8R IDû,WOR

jg,y PR IM JZQL'L

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Figure 5

¿,D D«XiQI'EfS Fyf P02 64''U//O 20ft5 or rna3t

4-R3ngsc hkmerk 69.06.0

1.10-r,e,/h,ed y/SI(4/'h'ßeDe

Getekend Gcz,cri Schaal

///

Gecontrolcerd

o o

>1

E

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_-

w E

995

75 29

75 30

72 72

5o

- di E _-o E C 210/96 DOUBLE 210/9 6 DOUBLE 2.1.0; 210 DO!.

length groundrope 22 met

er

length chain groundrope 22.6 meter

20

.30

50

60

-n C m 150 2 10/120 72 130 210/120 72 100 120 72

o

cv,

50

96

splitting

72

strop

B LE

50

back

8.5 METER 210

250

E E: C 120

t'

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w.' E.. di

_-

W. E o

i.

w E C

100

belly

8.5 METER

65

65

Ben.ming

Figure 7

FORCES ACTING on RIGGING

Formaat

technisch visserijonderz

1: 200

Getekend Gezien Rangschik merk

o

o

o

w

u

u' w

t

i

1

4

-r-1

H

V Benaming

Resistance beamgear

Gecontroleerd Gezien

Figure 8

56% formait

A4

44%

Rangschlkmark 1

2

3

4

5

Vshp(knof)

A

-

full gear without botfomcontacf

B

_{gear without tickler chains}

C ---full

gear

&

20%

t

Schaal Getekend AFD TCKN ISCHONDERZOEX

2

i

Benaming

Influence direction of f ¡de at resistance

AFD TECRN ISCHONDERZOEK

AUUr?MCht oorbehoud.n VOIg!flSde w.t I

Formaat

A4

Rangschikmerk E

intide

MqOR : 72

r-.rj.m.

j

f

- -

fideward

Figure 9

----r

5

(knot)

'p-1 2

3

4

-s StaaI Gecontroleerd Getekend

a8

Gezien

Benaming

600 R.P.M.

160 SSC.

29 SEC.2I SEC.

in. lift

-4-

-forestay

o,

I0

9 2 F

shooting of beamgear.. friction withdrawn

Figure 10

ko RoP.M

i.

it

Formaat

A4

-t kA 3100 !R.IP.M. Rarigschikmerk áeP.O/.ô/.f 38 SEC. 22.5EC

_t.

I

AFD TECIIN ISCH0NDERZ0.K Gecontroleerd

Auteo.echt -0, behouden nLgens de wet [Gecekenci Geziert

75

otung of

8

o

o

o

-:7

720 R.P.M.

Figure

600 R.P.M.

11 750 R.P.MI 4

t*

60 SEC.I 4

t

a f

T_T+

I

.Lg

I

o re s ay

topping

f ishing

shooting

(75m.)

34.5 rn/rn in

gear

lowering

boon

mean warpspeed:

Benarn Ing

shoohng of beamgear.. engaged friction

AA

4u

-AFD. TECHNISCHONDERZOEX Aturiecht ''bcho.dcn leni d et

Schaal Gecontrolcerd

Genen

hauling of gear

Figure 12

fishing

I__

____

warp

11

IIAiIII11!1Í1

já:'

_jI

'!IJj!JtIJ'' 'II

_{!+__}

'

6Osec

IuiÍ

1111111

topping

y

of boom

500 r.p.m.

28.5 meter/min

80 kgf/cm2

75 meier

8 fathom

revs main engine (hauling)

mean warpspeed

mean working pressure hydromotor

warp length

waterdepfh

Benamung

Hauling of beamgear

- _Formaat

-4-25

AFD. TECHNISCHONDERZOEK Ateurret bnod -Schaal Gecontrok'erd AA Gecekend Geven

MUDDY GROUND

revs, engine

waferdepth

warplength

winddirection

windforce

course

speed

2.1.5 3.70

knot

io

date 18.7.1968

date .15.7.1968

Benaming

Fishing at muddy and sandy grounds

Form ait

A4

HARD, SANDY GROUND

Rangschlkmerk

720

-

720

8

8

75

-

75

NW _W 3 3

iø

1900

o. k L.4 6OAsec

..

i----4---1 r.p.m.

Figure 13

fathom

meter

Bf

AFD. TECHNISCHONDERZOEK [chaat Geconcrolccrct

H..

revs, ranging between 680.720 r.p.m.

speed variation

4.3.3.5 knot

waterdepfh 12 fathom

warp length 75 meter

_I

i

6Oec

II

I

II

I

wap

111

IIIItII

I

IlL

I

L Ê g ¡

_III

IIII!i1

i!UiPiII I1!g

'

__Ii

I

iii!iiíui

k .1k

JITII1

JI

topj

li t

Figure 14

Benvnlng

Fishing at rough ground_forces on rigging

Formaat

AID TECBNISCEONDERZOEK Gecontroleerd

A4

technisch visserijonderz,

Aiji,ut$iech( vooebthoudt

,uIflns de set

Figure 15

Formaat

A3

Ranschi It merk

Getekend I Schaal

i

: 2001

8naming

departure

Figure 16

Benamìng

BEAM TRAWLING

heading for

fshinggrounds

technisch visserijonderz

Aui

lic

eo.b.heuds

Ølg.ns di

.t

Formazi

A3

Rangschk merk

Schaal i Getekend

200

Benamung

BEAM TRAWLING shooting of gear

technisch visserijoriderz

Schaal i

: 200

Figure 17

Gecontroleerd

Formaat Rangschik merk

Gezuen

Aut.0

ii

oo,b.houdsn .eluni d. wsi

I Benaming

BEAM TRAWLING,

fishing

Gezien

Figure 1.8

Gecontroleerd

Formaat Rangschik merk

Aijt.grirehi voorb.hOUdSfl vOIg.flS de wet

technisch vsseriJonderz5

1

: 200

Figre 19

Benarning

BEAM TRAWLING

hauling, codend

Formaat

A3

Rangchik merk

Schaal

i : 200

Gecekend

technisch vIsserIjonderz

hi veorb.houd.n vclgsnl d. wei A Gecontroleerci Gezien

!_____

__,_

:t:±::;:;-_I

I J

:::

I

!:-.HL2

_.:::: ---__ij

I .

Benaming

technisch visserijonderz

1 : 200

Figure 20

BEAM TRAWLING

lifting codend

Gecontroleerd Geaien

Formaat Rangschik merk

Aujeuç;r.hi veovbthoudfl voig.n, d. wn

Beriaming

BEAM TRAWLING

technisch visserijonderz.

Schaal i

: 200

e mptyi ng

codend

Figure 21

Gecontroleerø

Formaat Rangschik merk

Gezien Aiji hi oob.houd. oi1sni de wet Getekend

Overall view of beamgear; one of the parts of the beam is beaded; clearly the position of the tickler-chains is shown. - - --

-r

---S S-- S;' ', J

L-

_SS - --,-- .S__ j -S. t - S'--SS S

---'--

;--

:--'

-S 5,t -

-S---ii

-Gantry with boom In fishing position.

Loadcells for measurement of warp- and topping-lift pull; vessel fishing with steep warp; forestay almost slack.

,...,.: .,,

-- ---

-_y

-

----

::-f

Ships log mounted in outrigger; backstay running to top of boom in background.

Loadcell for measurement of warptension; boom in position as necessary at end of haul, when