Floating tether


After several trials and errors, I have a floating tether. I used 200 ft. of Alpha PVC-105/f #4 black tubing and ran 1 pair of 22 AWG wire through it. I started by blowing 30 lb. fish line through the tubing. Then I pulled some strong string through, then the wire. I used a drill with a rod/spool on it to wide up the string. I sealed each end with stuff I bought at BassPro for sealing boats and capped that with 2 layers of heat shrink. I put the whole assembly in my test tank and it floated. I tried in Sat. night on Cayuga lake and it worked. The hardest part is getting the fish line inside the black tubing. I tried a number of things over a couple of days. Like a Q'tip tied to the line, which fit great inside the .25 in tubing but got stuck at maybe 75 ft. The tubing because it was rolled up on a 500 ft. spool is not always round inside and where it was an oval the Q'tip stopped. I ended up using a lure that I cut the hooks off because it could adjust for ID of the tube. I made a pipe fitting that would allow the fish line in while not getting stuck on the air nozzle. Everything is harder then you think...

I have PVC tubes on my OpenROV for ballast and have been adding brass 1 in. by .25 in. washers to adjust for keeping the unit neutral in water. I had adjusted it in my test tank so I thought it was perfect. You would push it under the water and it would drift slowly back to the surface. My test tank water temperature was around 75 degrees F. When I went down to the Cayuga lake the water temperature is in the 50's. The unit sank. I had to remove 5 of the washers. I did not expect to see that!. The washers I added on the sides of the ROV where the threaded rods go through the base. So it is easy to add or remove them at the launch site.

I really need Open Cockpit to be changed on the right side. Remove the keyboard and info, the info could maybe on the diagnostic page, or a help page. Make the camera icon smaller and also the light icon smaller or maybe a number. I need the information that I send back to be visible. Motor information, temperature, heading and depth are really important when you can not see the unit. I found that it is important to able to see the motor numbers when going up or down. What is the chance on getting this updated?

1378-fishlinesetup1.jpg (273 KB) 1379-fishlinesetup2.jpg (211 KB)


Hey John,

It's awesome to see your thoughts RE tether flotation. We've been discussing improved user interface (UI) for cockpit recently as well, however no exact designs have been made. I was thinking of starting a thread some time soon about ideal cockpit layouts for people and was going to ask people to draw examples or show images of themes they like. Perhaps you can sketch a few ideas of what would work best for you in terms of UI and I'll make the thread for us to share our ideas on.

Keep up the awesome work!



...Actually, James Inglas already started a great thread under the User Interface forum topic called "OSD/HUD & GUI" (here's a link) which will be perfect. Perhaps we can post some mock-ups there!



Getting ready to head out on Cayuga Lake with our ROV to look at some previously discovered shipwrecks. I also have been having issues with the non buoyant cable. What I am going to attempt is to put the cable through a poly woven line as a tether and then put pill sized (micro balloon and epoxy mix) into the tether at intervals to neutralize the weight of the line. The micro balloons will hold there buoyancy far beyond the limits of the ROV.


If you buy the correct 1/4 polypropylene rope, it should be sufficient. I don’t know which the correct rope is. I can only say that the one from Uline is NOT the correct one. The short test length I bought from home depot was good, but not long enough, and they had no spools.

Also it is very tedious threading the line.

If you use a clump weight to hold your line in place at the bottom, then you only need the length past the weight to be buoyant. Which will save time. :smiley:


Because of the depths I am working at 60ft to 90 feet, and the multiple locations (ship wrecks, debris fields and cargo) I have implemented the use of an elevator. I send the ROV down in the elevator to a depth 5 to 15 feet above the shipwreck. at this point I back out of the elevator with anywhere between 25 to 100 feet of line. this gives me enough line to do my survey and not waiting for the long assent using up time and power.


I’m currently threading my tether through hollow poly rope and can vouch for how tedious it is. :persevere:

Everbilt brand rope, advertised as floating, is what I have (from Home Depot) and from some testing in the sink it seems to do pretty well and makes the tether at least neutrally buoyant. It’s definitely easier to manage the tether on the parts that I’ve done so far. It’s going to take a while, but for me at least I think it will be worth it.

I plan on diving around floating docks covered in long kelp and I expect little buoys would just be a hindrance.


Hey Craig, would you explain how elevator is made ? Is the same as a clump weight ?