Tether modification



I have read several threads about improving the tether, but because some of them are quite old, I am wondering how well certain modifications work…

To put the tether into a woven polypropylene rope, diameter ca 6 mm, is mentioned several times…
How is The long term experience with this option…?

I want to use a float ca 3 m from the rov to keep it away from the bottom, and try to get the rest neutral …

All in freshwater!!

Thank you!



I am still very happy with it. You should make sure the rope you buy is dense enough though. The rope I tested with (to determine positive buoyancy) was a better rope that the spool I bought. It did not occur to me that there might be a difference. :D.

To be clear, my tether is not actually positively buoyant, so if you use the correct rope yours will be even better than mine!
The rope also protects the tether scratches etc.


Thanks Darcy,

I found a company who makes a rope with the two wire tether inside, they weave it around it… For little money… (Polypropylene)
Difficult to calculate the weights , but it will improve the buoyancy … And protects the wires.

I will update h
When things get ready… We have minus 15 C so no diving the next weeks anyway.



I can’t wait to see what you come up with!

I just wanted to make you aware (if you were not already) that we sell neutrally buoyant tether in our store. I know it is expensive compared to the ROV and assume you are trying to make a lower cost version, just wanted to throw out the link.

Good luck and can’t wait to hear more!



thks Brian… I know, but my budget is limited and I like challenges to find an alternative solution for tighter budgets.

still under development…
Polypropylenehas ca. 0.91 Gr cm3
So a rope with a diameter of ca. 6mm will have 25.71 Gr /m, freshwater ca. 28.26 so a positive 2.55 Gr.
Wire is ca. 2,7 Gr under water…
Combined with a little trapped air it should help the tether under water.

The ideal solution would be to integrate a thin rope inside with a even smaller relative weight, but I can not think of a flexible material… any suggestions…?
Especially if the rope is woven around the centre wires, it is easily achieved adding another material inside.

another Solution I found is used in the Fishing off shore… Cork-lines with integrated Corks…
ca. 600 Gr on 100 m… worth trying…


p.s. the woven Poly Rope will be below 0,5€/m


Hi There.
I have used cheap polypropylene rope, bought on eBay, taken the core out and threaded over the twisted pair of wires. It was a nightmare job to do, it took a whole day. I found the most I could do was 30 metres at a time, in the garden, so I used 3x 30 metres, of different colours, which may one day be useful, if we’re ever brave enough to go that deep.
It has ended up just under 5mm. I would say it is very slightly negative buoyancy in seawater and, I may be imagining it, but seems to have quite a drag.
I’m still struggling to steer and position accurately, mainly the drag on the tether stops you turning right or left, unless you make sure there’s loads of slack, or reverse a bit.
I would love to try it out in a clear pool, but I don’t have access to one, just the open sea!
The reel works well though. and you can see the waterproof connector.
Good luck.

Finding Acrylic Cement Outside the USA

Negative buoyancy means it sinks, I presume? Am I right?


You’re right e4andy. Negative means that it is more dense than the water and therefore sinks.

I like the idea of the shackle connection for security. That is just what I need for my connection.

Good luck.


How are your experience with the rather cheap connectors…?
( I think these are the ones from specs in another thread : Ebay like for LED outdoor ?
I want to go beyond 30 m depth…

I found another way of pulling the wires though the poly… ( weaving was at the far end not possible for little money)
Just going out of the weaved shell every 5-6 m, and going in through the same hole… works fast!
I will post this this weekend…



Thanks Martin. If you notice, I’ve actually got 2 connections. The shackle goes on to the hole in the central acrylic plate, but I was worried if that snapped off I’d be lost, so I use a second little toy carabiner to attach that string loop as well.


Hi Roel,
The connector seems fine, although I haven’t gone deep yet. It has an o ring which I put some lubricant on and I can’t see anywhere that it would fail easily.
Regarding the poly, I ended up doing the same, I couldn’t do the whole 30m in one go but, as you say, out and in works well.


That is a great idea! I imagine the work would go much faster!


Hi Darcy,

i dien´t manage to work on the tether this weekend… but it is very fast and due to the flexibility of the the 2 wire tether it´s easy to re-insert them through the same hole of the Poly.
I did 2 x 6 m within 10-15 minutes… :blush:

Now I am sourcing a connector… Probably go for the Seacon to be sure at 40-50 m depth.

I will write a Build report with some more tweeks.



Thanks for sharing your experiences. Did you use a device that allows unrolling the tether during a dive, something like a slip ring connector. I want to upgrade my system with such a device but I have not found a good connector yet.

The connector you are referring to allows disconnecting the ROV from the tether, correct?


Yes, I want to disconnect the Rov, so it will fit within a Pelican Suitcase ( 79,-€ @ Conrad)
And the cheap ones look ok… I can’t think of where they would leak but to be sure I want to buy some Seacons.
More expensive, but better be sure as 3 times cheap.

I am also looking for a slipring , ADAfruit type… not available in Germany but I found some in Austria…

It is still too cold for diving so I have still some time…

I covered the Camera around with foam to avoid LED reflections, and the best is…that this works like a window sweeper when the tube is foggy ( condensed Water) still experimenting …but it should work…



Okay, that is a good idea!

Please keep me updated about the slipring adapter. That is exactly what i need too. Maybe we can even place an order together (pm?) if that reduces shipment costs. We were diving in ice yesterday (pretty cold).

Yes, I did the foam application too and the wiping mechanism is a very nice side effect. I have also placed a anti fog bag.(example product, any thing similar will work). It works quite good!


I’m using the Adafruit slip ring and it works really well. The ROV just unreels under its own power. Only slight issue is that if you have many meters to reel in, you can run it through a cloth but it is difficult to dry out the damp rope when it is coiled on the reel.


Thanks for the fog bags… look good…already ordered!
and good news… the slipping is on stock again in Germany:

And if diving with ice-cold water causes no issues with the foggy tube, like you yesterday… I am maybe worried too much about this.



The connector I use is the super cheap one (I got it on dx.com) and I have used it as deep as 208 meters. I put a drop off mineral oil in it before closing it.



after trying to use the polypropylene rope, ø 6mm, and investing hrs and hrs , I was rather unhappy with the result.
So stripping down the rope took another evening…

Especially the rope soaking so much water and being wet for the next couple of days was quite annoying, also the buoyancy was not that good… w.a.w. it sinks…

So after a couple of drinks and brainstorming, I found another solution, which after a couple of trails works very nice, and is adjustable.

I have used ø 15 mm cork balls, available in Architecture Model Shops ( they use them for trees)
Please find some that are NOT made of pressed cork…
A small hole in the centre an they are easily put onto the tether.
The great advantage is, that you can move them up and down , and adjust the buoyancy as you like…

I have them at a distance of approx. 60 cm and the tether hovers nicely underwater…
They take no water, and I hope they withstand some depth.
The drag is also very minimal…due the minimal size and round shape.

Costing 10€ for 100 pcs… Time a couple of hours…

Have fun!