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43
I Begyndelsen fulgte vi den efter
"Challenger"-Expeditionen givne Anvisning med Hensyn til Manøvren, at
sejle ud clen hele Touglængde i Lie og lade Skraben
trækkes af Skibet, eftersom dette drev for Vinden. Det er
ogsaa rimeligt, at denne Maade maa benyttes, naar
Skrab-ningen skal udføres fra store og fuldkrafts Skibe, som ikke
kan gaa saa langsomt for Maskinen, som Skrabningen
fordrer. Dersom der Intet kommer ivejen, er det forsaavidt
ligegyldigt, hvilken Vej man vælger, men i modsat Fald
taber man meget baade i Tid og Arbejde. Naar man
skraber under Gang mod Vinden, kan man regulere Farten
efter Ønske og standse en Stund, hvis man frygter for at
Farten har løftet Skraben fra Bunden. Driver man i Læ
af Skraben, bestemmes Farten af Vind og Strøm, og tror
man. det gaar for hurtigt, maa man fire ud Toug til
Overflod. hvilket senere atter skal hales ind. Sætter Skraben
sig fast. og man er til Luvart, behøver man ikke at fire
mere end nogle faa Favne, indtil Farten er standset, og
kan derefter strax begynde at Ilive ind, eftersom Skibet
driver ned mod Skraben. Er man derimod i Læ. maa der
fires ud en Mængde Toug. før man kommer paa Kurs og
kan begynde at gaa op mod Skraben.
At faa Skraben løs igjen, naar den har sat sig fast,
kræver ofte en besværlig og langvarig Manøver, der
desuden ikke altid lykkes. Man maa Ilive ind til næsten op og
ned og derefter søge at trække, den løs den modsatte Vej
af den, man skrabede, da den gik sig fast. Da ukjendt
Strøm ofte kan være tilstede, nødes man gjerne til at gjøre
mange Forsøgt Lykkes disse ikke. staar det sidste Middel
tilbage, at kaste Touget til en Pullert, gaa forover i
Maskinen med fuld Kraft og enten rykke Skraben løs eller
sprænge Touget.
Det første Aar forsøgte vi et Par Gange at fæste
Otter-Trawlen efter Skraben, men dette viste sig ikke
videre hensigtsmæssigt. Naar man skraber, er Farten saa
langsom, at Otter-Trawlen slæber langs Bunden som en
Bundt Linegods. og sætter man Fart paa, saa at Otterne
kan skjære ud til Siderne og holde Trawlmundingen aaben,
løfter Skraben sig fra Bunden og gaar med sine- paahængte
Svabere et kort Stykke foran Trawlaabuingen. Den vil
saaledes rimeligvis bortskræmme den Fisk. der muligens
ellers kunde være fangen.
Paa Expeditionens Rejser faldt der naturligvis
adskillige mislykkede Kast med Skrabe og Trawl. Det hændte,
at Apparatet ikke kom i Bund. at det blev iturevet i
Bunden eller satte sig fast. at Skrabetouget sprang under Ind-
a considerable portion of the finest mud had been washed
out. by allowing the trawl-bag to swing backwards and
forwards in the water.
Dredging from the "Vöringen" was carried 011 at
first in the way adopted 011 the "Challenger" Expedition —
viz. by paying out to leward the due amount of rope, the
dredge being then pulled along by the drift of the vessel.
This is perhaps the only feasible method in dredging or trawling
from large ships of full power, which cannot reduce their
speed to the rate required for such operations. True, if
all goes well, it is upon the whole immaterial which way
is selected; but should, on the other hand, a mishap occur,
a serious loss af time and labour will inevitably result.
Dredging head to wind, the speed of a steamer may be
regulated at pleasure, and her way immediately deadened
should there be reason to believe the dredge is oft" the
bottom. When drifting to leeward of the dredge, the
speed will be dependent 011 the wind and the force and
direction of currents, and if too high, an extra amount of
rope has to be veered, which, of course, must afterwards
be hauled in again. Should the dredge foul with the ship
to windward, only a few fathoms will have to be veered
before stopping the engine, after which the heaving in may
be at once commenced, keeping pace with the ship as she
drifts down upon the dredge. ()n the other hand, the ship
being to leeward, a very considerable quantity of rope will
have to be veered before she can be brought head to wind
and steam up to the dredge.
To extricate the dredge when jammed fast at the
bottom, is frequently a very difficult matter, involving hours
of unremitting exertion, not always accompanied by a
successful result. The rope must be hove in till nearly right
up and down, attempt being made to extricate the dredge
by hauling in a direction contrary to that in which it
was moving when the mishap occurred. Moreover, the
action of unknown currents will, by complicating the
expedients adopted, often protract this laborious work. Should
each in turn fail, there is nothing for it but to make fast
the rope to a bollard head, and then, steaming full speed
ahead, either free the dredge by sheer force or break
the rope.
On the first cruise of the Expedition, by way of
experiment. we sometimes made fast the otter-trawl behind
the dredge, and worked both together; but this
arrangement was not found to answer. With amply sufficient
headway for dredging, the otter-trawl will drag along
the bottom like a heap of cordage; and if. on the other
hand, the speed be increased, to make the otters diverge
and keep the mouth of the trawl open, the dredge, with its
hempen tangles, will be lifted ott’ the bottom and move
along a short distance in front of the trawl-bag, scaring
away probably many animals, in particular fishes, that
might otherwise be captured.
Not every cast of the dredge and trawl was. of course,
successful. Sometimes, the apparatus would fail ’to reach
the bottom, or if there get broken, or jammed between
rocks or stones: then again, we had the dredge-rope part.
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