1/4" poly rope with tether inside does NOT float


We took our OpenROV for its maiden voyage out on our local pond yesterday ...

We had threaded the tether through the inside of hollow core 1/4 polypropylene rope, which takes some time but it's nice to have something stronger to pull the OpenROV back with instead of its tether.

In the bathtub tests it sort of seemed like it might be floating (wasn't clear), but it the pond, it quite clearly did NOT float.

We'll investigate options, e.g. maybe taping some foam every 10 feet or so, but I just wanted to get this info out there so others could maybe try larger thickness rope.


OK an update here: we attached small foam floats every 10 feet or so for the first 80 feet of tether, and today took the OpenROV back to the local pond and it worked wonderfully. We managed to roll out the entire tether, and, curiously, even the part that did not have floats managed to float today, I suspect because that part of the tether was held at the surface of the water and didn't get water-logged. Before, the OpenROV pulled he front part of the tether under, and that then pulled the rest of it under.

It was amazing how easily the OpenROV could move the tether around once it was floating ... it easily pulled the entire thing out off the spool.


You can also use ping pong balls, I just used hot glue to attach a small cord to the ping pong ball and then tie wrapped it to the Poly rope. If you use this in salt water you will find that it will require less buoyancy compensation. Nice to see the children involved in this project.


Wine corks make pretty good floats... :)


What about weaving neoprene strips in to the hollow core rope at regular intervals (say every 5 feet or so). Neoprene is flexible and buoyant so it could provide some buoyancy and would easily wind up with the tether and not take up much extra space. Neoprene could be ordered on-line or perhaps at your local dive shop (in the form of old wetsuits).


Inserted neoprene sounds like a great idea! Or just try a larger diameter hollow-core rope...

Though, if our experience last time holds up, all you really need is a single float maybe 10-20 feet back from the OpenROV (or however deep you need to go), and then that will serve to hold the entire rest of tether on the water's surface.

At least, on a still pond... if you are in choppy water (ocean waves) I suspect the tether will need added flotation for the whole length you send out...


Very helpful info. Thanks


Perhaps it would float in salt water?


That's true, it may (salt water is denser)... we haven't had a chance to take it to the ocean (yet)...

I also wonder, on the pond, if the tether is still a little wet from last time, if it will still float on the surface from the water's surface tension or not ...