Good questions. Re: the duct tape... It provides a secure method of attaching the thrusters/suction to the PVC pipe on either end without disrupting flow dynamics. Since it is waterproof, I think it will have a long lifetime, but is also easily replaced at $0.
The magnet serves a triple purpose. First, I have 3 50lb. monofilament lines paralleling the tether. The one for the magnet can be released although still attached to the rov with an eye screw (I know, clumsy). By doing this, I can retrieve any ferrous targets without straining the tether, but I can also "mark" interesting bottom finds with the magnet, ensuring that upon retrieving part of a find, I can drop back down to the exact location, currents permitting. On that same magnet line I can attach a 12 inch diameter fishnet, which can lie on the bottom with the magnet, and provide a safe depository for larger collectible items of interest using the capture bucket, which is controlled remotely by the other 2 monofilament lines.
If I find a large ferrous item stuck in the bottom or otherwise too heavy, I can "mark" it with the magnet and retrieve the rov, and develop a plan for more challenging recovery (of a safe, for instance).
The ROV actually has a sightly negative buoyancy to assist in getting to the bottom without wasting energy, but the suction thrusters can assist in vertical motion in addition to clearing out sand and silt. Reversing the thrusters will clear the bottom tube of clogs including those caused by valuable items. In that case, the capture bucket will be closed.
This has been a fun project, and outside of the electronics and associated hardware, the frame and all cost less than $60 plus my assembly time. I'm retired so time is cheap.
I hope in the future to equip a solenoid activator for the clamshell bucket rather than fishing lines and rubber bands, and assign an actuator button to the Logitech joystick controller.
