Anyone know the max weight the Fathom tether can handle for lowering and pulling the BR2 in and out of water?
I have BR2 +heavy conf. + gripper with the Fathom tether attached with thimble to the rear panel (as per assembly guidelines). I plan to also mount a stereo-camera housing frame at the bottom of the frame(see photo) that weighs 6kg. My fieldwork will take place from a vessel where I will need to lower the ROV into the water, and was planning to do this by the tether? will it be ok with the extra 6kg of weight?
Thanks in advance for any info and tips.
According to BR specs, the working strength of the Fathom tether is 80 lbs. What is the weight of your BR2 with all accessories attached? Because your support vessel may be accelerating up and down with wave motion, the actual pull on the tether could be significantly more than just the dead weight of the BR2. You can calculate how much by researching the vertical acceleration of your support vessel with wave motion. I’m sure Elliot can give incite on this.
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One of the ways we do it, is attaching stress relief on the tether far enough so you can reach it while the ROV is still in water. With soft chuckle to secure it to the ROV it provides an excellent option for retrieving your ROV.
Thanks Richard for your thoughts on this. BR2 and all gadgets (heavy config + gripper + stereo-housing+ cameras) weighs 18.5kg , which is 40.1 lbs.
@EliotBR Any thoughts of lowering and pulling up the BR2 with a dead weight of 40.1 lbs from a speed boat into the ocean when there is a swell? Any tips and tricks to lower risk of tether management in the case of vertical acceleration?
Hi Scott, thanks for your input, but I am afraid I can’t see the photo (not sure if its my internet or if it did not fully load, so I am not entirely sure what your "stress relief " is made of or looks like…could you try to share again?
A pole with a hook on the end may also work. The freeboard on a speedboat can’t be much. A poll with a hook on the end should work. At 40lbs I would definitely not use the tether.
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Hi @Salome,
The working and breaking strengths of our tethers are available in the Technical Details on the product page. Our current tether options are both rated to a working strength of 35kgf (80 lbs as @model14 mentioned) 
In our Operation Manual we specify that it’s ok to deploy and retrieve our ROVs by the tether as long as you’re careful to avoid dropping or jerking on it (dynamic loads are much larger than static ones), and avoid dragging it over sharp edges / coral.
Strong swells and/or waves could also cause dynamic loading, but that may not be relevant depending on your operating conditions.
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