Hello i have been trying to deploy in deeper water where there is a current up to 1knt in the water column, near the bottom not an issue
By deeper water i mean 80 to 100m
I try anchoring the boat upcurrent and deploying the rov to descend as quickly as possible but the location that i end up is then variable and in addition the problem of having the tether being pulled by the current causes issues with moving around at depth.
Can any members share their experiences? Rope with a weight and gripper released at bottom? TMS would be great but then deployment etc, cost, weight. I toyed with the idea of a cage but issues of tether drag and entangelment.
Solutions we use 1-2 knot current, 50-100 meter depth:
Moving boat following ROV (using UW positioning)
This way the tether is manually handled, ie depth + max 30 meters out.
ROV movs free and ship follows.
Clump weight with separate rope permanent attached to ROV tether at about 30 meters from ROV
This way the ship has to lead and the ROV to follow.
Mainly used at stronger currents > 1knot +
Locate the objective with the depth sounder, drop a tracking weight (weight + rope + buoy) and finally anchor (or Minn Kota electric anchor or a good captain but be careful of the tether with the boat’s propeller !!) in the direction of the wind /current.
We follow with the camera the spotting line up to the target. Be careful not to turn around the rope otherwise it will get tangled !!
In the Mediterranean, with a heavy BR2 and 200 slim tether (less drag) I often dive around 150m, 189m my record !!
The power of heavy manages to hold its course with a reasonable current.
Of course, it’s complicated not to get tangled up but as long as it’s not on a wreck or a rock, you can put everything up and get tangled up in the port !!
For my needs, a heavy cage with built-in TMS, batteries and lights made the most sense. Lower the cage to depth, release the ROV, ROV is heavy enough neither the tether nor the current jerk it around.
Thanks Bo, that sounds practical, any particular method you use for attaching the clump weight, and how heavy? would expect a few kilos of lead sufficient?
Just strap tehther to the line.
Weight have been 25 to 50 kg.
Use some wing on the weight to prevent spininng,
one way is a foldable anchor with only one wing out.
but then deployment etc, cost, weight. I toyed with the idea of a cage but issues of tether drag and entangelment.