Problems with bonding the Fanthom tether

Hi guys, im struggeling with potting the teather to the penetrator. I have tried with a flexible marine grade epoxy (West systems G-flex 650) that works well with the thrusters and Scotchcast resin 40, but none seem to stick. I read that the jacket is PE, and that explains alot, as PE is really hard to bond well. Do you just rely on the potting between the individual strands? Using a propane torch on the PE jacket may help (Flame treatment).

I made a 3D printed mold that I thought would work well, but when I flex the cable, the Scotchcast lets go.

Anyone who is trying to bond to PE or other low surface energy substrates should look at the products that RelTek LLC has. Their link is:

I have used their products in the submarine community and they have done development / testing for me in the past.

The price tag is more than likely going to gag you, but you get what you pay for and I know their primers etc. work. Price seems to be the major delimiter between the hobby world and commercial / military.

We chemically etched the umbilical before bonding. We purchased a pint of Acton Technologies FluoroEtch product.

We spliced a SubConn undersea electrical connector onto the umbilical which is indeed jacketed with a polyethylene cover. We etched both the umbilical and the pigtail on the SubConn 8 pin connector.

We used a 3M 82-F1 splice kit. Worked like a charm.

Magnus, what was the surface preparation before you tried the G-flex? I would expect G-flex to stick better if the tether had been sanded and/or flame treated first.

You might experiment with the contents of this kit:

It’s available at Home Depot in the U.S. It’s on my to-do list to try various methods for bonding the tether, one of which includes using that Loctite product to bond O-rings to the tether before potting with the Scotchcast rubber.

Has anyone found any more tricks here in the last few years? The yellow tether that I have is almost impossible to get anything to bond to it. I am doing experiments now and will feedback results, but any help would be appreciated.

Hi, Iv always just used brillo pads like the ones in the link. Rub the cable really hard and scuff it up. Iv never had any problems.

Thanks @Tangaroa. Will add this to the list of tests. I have been scraping the jacket with a stanley blade to get a rough scuff on it or sanding with 180 grit so far.

Hi. Using abrasive pads is really a band aid fix, by using a mechanical solution to a chemical compatibility issue. The old tether is polyethylene, a polymer known to be really difficult to bond.

A trick that can help with both this polymer and others is to do a flame treatment, where you use an open propane / butane torch to gently sweep over the plastic. You dont want to melt the plastic, but the flame must touch the plastic right before you add the resin. This allows for a better chemical bond to the polymer, and will also help when gluing other polymers. I have done multiple test with Scotchcast 2131 which I used for these things, and flame treatment has helped in all the different cables / umbillicals I have tried. The general bond strength and peel resistance were multiplied by many times in my non-scientific tests.