Simrad PI32 SENSOR - MOUNTING Instructions page 2

Bottom sensor attachment
1.) Locate the middle of the footrope and bend the attachment ring for the stay to the "bottom" and two
strops attached to karabiners on either side to its "top". The strops should create a bridle about 15 to 20
cm in length that will securely hold the bottom sensor in a stable position.
2.) Bend the penetration ring for the detection wire about 30 cm below the footrope as illustrated. Attach
the bottom sensor and check that its detection wire passes through the centre of the penetration ring.
Remove the netting on the inside of the penetration ring.
3.) Attach the rubber strops so that the bottom sensor is held horizontally when towed.
IMPORTANT: Carefully attach the sensor to the inside of the trawl so that it is not subject to damage or
torn off during fishing operations. The sensor's detection wire must always be allowed to pass freely
through the centre of the penetration ring when it is deployed.
Rock hopper, Attachment ring for the
bobbins, etc. stay bent securely to the
"bottom"of the footrope.
Note 1
Penetration ring for
Weight and stay hang
the detection wire.
freely under the trawl.
to both each other and the gear in use (the standard delivery includes a 63 cm stay and 39 cm detection chain
for use with 14 to 16 inch bobbins or rock hoppers).
Configuration - the desired bottom detection distance is relative to the diameter of the rock hoppers,
bobbins or other gear in use. This relationship can be determined and precise stay and detection chain
length adjustments made as described below.
Setup - lay the bottom sensor on an elevated surface and observe detection wire movement while simulating
bottom contact by raising the weight. Adjust the detection chain length as necessary. Tilt the weight
approximately 25°(α is due to drag through the water) opposite the towed direction and adjust the stay
length so that it begins to be taught. Avoid extra links at the weight ends when shorting chains.
IMPORTANT: Weights must be removed from a bottom sensors with a long stays and detection chains
before they transit the drum when hauling to prevent damage.
Karabiners are bent securely to the "top" of the footrope. If the bottom sensor is
attached to the wings, the length of the lashings must be adjusted so that the sensor
points toward the mother vessel when towed.
Lift Off
Note 1
30 cm
Rock hopper
Stay
Bottom
Note 1: The stay can also be attached to the steel spacer between the bobbins/rock
hopper if the footrope is held fairly stable relative to the gear.
Contact - bottom sensors can detect bottom contact with a
precision of just a few centimeters when correct stay and
detection chain lengths are used. Optimal sensor perfor-
mance requires that these lengths are configured with regard
Touch Down
Detection
wire
Detection
chain
End link
Weight
Catch sensor attachment
Sensor attachment - to a net with an approximate mesh size of 140
mm is illustrated below. The distance between the anchor points for
the attachment rings and rubber strops will vary according to mesh
size and sensitivity required.
Karibiner and
Vessel
screw link
Nylon attachment rings,
bent to the netting
Rubber strop Detector wires
Location - attach the sensor at the top of the cod-end, closest to where
the catch is to be monitored. As the cod-end fills the net's mesh will
become taught and activate the catch sensor.
Attachment - the catch sensor's orientation toward the mother vessel is
maintained by the steel/nylon attachment rings, strops and karabiners
bent to the net. The number of mesh squares the sensor is supported
between must be restricted to avaoid unnecessary stress on the gear
when the net is filled to maximum capacity. Note that both steel
attachment rings must be located on the same side of the sensor.
Sensitivity - is determined by the number of mesh squares separating
the two rubber strops (a larger number increases sensitivity, a smaller
reduces it). Simulate sensor activation by stretching the net's mesh to
approximate the load generated by a full catch. Experiment accordingly
to determine the correct attachment points and then permanently
mark their locations for future reference.
Rubber strops - are subject to heavy loading/wear; they should be
changed at regular intervals and checked before shooting. Strops with
cracks or visible signs of damage should be change immediately.
Steel attachment rings,
bent to the netting bent to the netting bent to the netting bent to the netting
Karabiner