Testing Tether Ballast

Since the ROV body won't be ready any time soon, I'm working on the ballast for the tether. The plan is to make lots of beads that will be strung evenly along the full length of the wire. The first step is to figure how much ballast I actually need to make the tether neutrally buoyant.




My spool of wire weighs about three pounds and the ballast has a density of about 30lbs/cubic foot, so I cut a block a little bit  larger than what I needed and wrapped all the wire around it. Winding 500' of wire takes a while.



So I built this winder out of legos. I never cease to be amazed at how useful legos are. This probably saved me an hour of tedious winding.



As expected, the block just barely floats. So the next thing to do is to cut off a little bit at a time and retest to find out exactly how much I need. I don't have any pictures of this part, but it turned out that I need ~104.4 cubic inches of foam to make the tether almost perfectly neutral. That means I need 1000 beads with a volume of 0.104 cubic inches each. Easy enough.

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