In short, we do a lot of inspections on long/line objects, cables, pipelines etc. Inspections are done with BlueROV and surface boat, by following each other along the inspected object, passing with the ROV close and above of the object (pipeline for example) from its beginning to its end.
The question for the discussion is: has anyone tried to tow a BlueROV with a boat, so the main thrust forward is coming from the vessel engine, not the BlueROV thrusters? BlueROV thrusters are then in charge of keeping the desired depth and staying on course with the inspected object (inputing these changes via remote controller). The goal would be to conserve electric battery energy of the ROV while going faster. Simple, isnât it?
Similar to the towing side scans, we are just thinking of towing the BlueROV. The tether mounting point should be moved from back side to center and forward, so the rotation wouldnât be caused by boat tow.
The topic is not so straight forward so I was hoping for community thoughts and experiences with this idea.
This isnât something Iâve personally tried, but the idea seems reasonably straightforward. My main concerns would be
avoiding cutting the tether with the boat propeller
may need to route the tether via the side or bottom of the boat
likely need to avoid sharp turns
need to be careful of excess tether slack when first starting to move the boat
avoiding high tether strain
may need an additional cord to take the load
ROV pitch angle
the boat is above, so the mounting/pulling point would need to be from somewhere on the top of the ROV, to avoid undesired pitching
video stability
depending on how smoothly and fast the boat is moving, and whether any oscillations are induced in the ROV, there may be problems with capturing usable images/footage
may help to add elements that improve the hydrodynamic flow, to reduce drag and oscillations
Weâve done that before checkout how to use a clump weight for observation class ROVâs, the clump weight should work as a âTMSâ but only as a dead weight. Leave like 10m of tether for the ROV to move freely.
Done hundreds of hours of this type of survey with both BR2 down to 100m depth and a larger inspection class ROV down to 300m. As Luis has said unless you are operating very shallow you will need a depressor weight to keep the cable down ahead of the ROV. How much weight you need depends very much on your tow speed, length of cable and depth youâre running at. Be aware that you will need to be on high alert for underwater obstructions as its hard to instantly stop the boat and unless you have very good viz its easy too run into things such as rocks, unknown wrecks and discarded fishing nets and lines. We always used to run a forward looking sonar on the inspection class ROV for this very reasonâŚ
