Improvements in or connected with Trawl-nets.
Year: 1897

page_text: Date of Application, 16th Sept., 1897-Accepted, 4th Dec.,
1897
COMPLETE SPECIFICATION.
Improvements in or connected with Trawl-nets.
I, JOHANN COHRS, of 24 Grosse Elbstrasse, Altona-on-the-Elbe in the German
Empire, Fish Auctioneer, do hereby declare the nature of this invention, and in
what manner the same is to be performed, to be particularly described and
ascertained in and by the following statement :-
This invention relates to improvements in or connected with trawl-nets by means
of which the opening of the ground trawl-net can be maintained with the smallest
possible expenditure of power on the part of the trawling vessel.
The accompanying Drawings illustrate one method of carrying out my invention.
Figure 1 is a plan of a trawl-net with an improved "otter-board" applied thereto.
Figure 2 is a section, Figure 3 a side view, Figure 4 a front view, and Figure 5 a
back view of the said otter-board.
The improved otter-boards hereinafter described avoid all the inconveniences of
the otter-boards heretofore employed.
Each of the two otter-boards A consists of upper and lower horizontal connecting
boards a and b, between which are arranged any convenient number of vertical
obliquely disposed boards ce placed at the most suitable angle after the manner of
louvre-boards. These louvre-boards have a sharp knife-like front edge d in order
to offer the least possible resistance to the water. The louvre-boards may be
covered with sheet iron for the purpose of increasing their strength and to reduce
their friction in the water. The outer louvre-boards c are rigidly connected to the
upper and lower horizontal connecting boards a and b in order to make the entire
otter-board frame firm and stiff, but the inner louvre boards c¹ are either made fast
to the boards a and b or are so arranged that they can turn on pins e in such boards;
in the latter case the boards c¹ can be adjusted to any suitable angle by means of
the bar f to which the boards c¹ may be adjustably attached, as at e¹ for example,
and clamped into the desired position by the clamping screws g which pass through
slotted holes in the bar f; or any other suitable device may be employed for increas-
ing or decreasing the obliquity of such louvre-boards as may be required. To the
under side of the connecting board b are fastened metal plates h, which act as weights
in order to maintain the entire frame A constantly in an upright position. In
place of or in addition to these metal plates correspondingly heavy rollers r may.
be employed, as shown in Figures 3 and 5, for the purpose of facilitating the
passage of the otter-boards over the ground. At the four corners of the front
side of the otter-board are connected bridle-chains or ropes which by means of the
attachment connect the otter-board to the tow-warp B. By adjusting the bridle-
chains or ropes k in relation to the attachment l, the point of connection with the
tow-warp B can be varied according to circumstances. At the back of the otter-
board A iron rods m are attached to the upper and lower connecting boards a and b
on which rods rings n are adapted to slide, the float line o, and the ground line p of
the net C being fastened to the said rings n as shown. Or the said float line and
ground line may be attached direct to the back of the upper and lower boards a b
The action of the apparatus is as follows:-
When the net is lowered into the water the otter-boards A always come to rest
CD027

page_text: on the ground in a vertical position under the action of the weights h. When
drawn forward the two otter-boards move obliquely away from one another until the
net is completely open, when the rings n have a tendency. to move inwards on the
rods m and the louvre-boards c c¹ are thereby brought into such a position that as
the net is drawn along they offer the least possible resistance to the action of the
water consistent with their necessarily oblique action thereon.
The above described otter-boards have the advantage over others now in use that
the draft is uniform at all points of the otter-board, and consequently all tendency
for the board to lift or to dig into the ground is avoided. Moreover the pressure of
the water streaming through between the louvre boards is more effective than in
the otter-board as ordinarily constructed, consequently the size and weight of the
boards can be reduced.
Having now particularly described and ascertained the nature of the said invention,
and in what manner the same is to be performed, I declare that what I
claim is :-
First. The improvements in or connected with trawl-nets which consist of the
employment of any suitable number of vertical obliquely disposed louvre-boards
mounted in frames and fastened beside one another between two horizontal connect-
ing boards the lower of which is weighted by means of metal plates, weights or
rollers, and an adjustable point of attachment of such otter-boards to the tow-warp,
substantially as described.
Second. In apparatus of the kind herein described the device for adjusting the
vertical obliquely disposed louvre-boards to any required angle to the direction of
draft, substantially as described.
Dated this 16th day of September 1897.
J. COHRS,
Per W. H. Beck,
115 Cannon Street, London, E.C., Agent.