Underwater cable for towing a camera

I think most marine applications use Spectra cables now. Spectra is a high molecular weight polyethylene. Searching on Alli, the first thing I found was 6mm cable 40 feet long with a minimum breaking strength of 7000 lbs. Cost $19.50 with free shipping. Lots of other spectra cables which are long er and stronger ( also more expensive ).

Dan

For tethering, you need woven rather than twisted line. When you start adding additional lines (optical and power cables) to this support, they'll need slack, which has to form a regular shape, with a predictable drag. The camera itself must also be physically shaped for stability in the flow.

If it's just a few feet, you might consider a rigid oval or tubular conduit as the physical interface, carrying any optical or power lines. This could even carry forced air pressure.

RL

I planned to have only optical link to the tower, because having electric in seawater(cable) is not, lets say, easy. But with fibre I could at least have video out and steering in.

We will probably have 100 feet or more of cable. I fear to think how much it weights and what kind of equipment is needed to reel it back without crushing anything.

I tried Googling Spectra cables but found nothing relevant, I think but what is Alli?

Leif M

Probably aliexpress.com. They sell both fantasy and real stuff there, but you have to be Prince Ivan to figure it out.

Cheers

Phil Hobbs

Short for

I did a ouick look. A 30 meter ( about 100 feet ) of 6mm ( about 1-4 inch ) braided winch cable weighs .6 kg ( about a lb ) and has a breaking strength of 8000 lbs ( why that is not in metric , I do not know. ) and costs $52 with shipping.

I looked on Ebay and did not have much luck. It did help to add ' winch " to the search term.

On Alli you can search on Kevlar and get spectra cable. You really do not want kevlar as sunlight degrades it.

Dan

One of the reasons to use Spectra. Very little stretch.

Dan

Well, that's more than a few feet. A tether may stretch. I'm not sure that fibre optic cable can. Would need to be reinforced. You might need to separate the functions. On the same reel one could crush the other, under tension.

Might be quicker just to see how commercial towed units handle the issue.

Mind you, people deal with 100ft garden hoses all the time, with varying success. I think they are made of various grades of cosmetic garbage.

RL

More like a Chinese Amazon. if you buy stuff there when it arrives check that its genuine, I've had a few fakes or otherwise "not as described" products arrive, never had a problem getting a refund though.

Amazon Marketplace, maybe. They're all random 3rd party vendors. Alibaba is just a middleman for the suppliers (and there are more than

Getting a refund is only easy if the amount is trivially small. If it's a serious order size, you're probably not dealing through Alixpress at all.

In the middle, you have to return the goods with tracking and asymmetrical shipping costs (maybe $100+ to return goods) come into play.

--sp

If it's "not as described" that's grounds for a full refund. Enabling counterfeitors is not in Aliexpress' interest. they will take action.

It you just don't like it then yeah, you'll be asked to ship it back.

If you open a dispute the vendor has 4 days to negotiate a solution, if you can't agree the website says it will be resolved in your favour,

I can't see any reason why Aliexpress would side with the vendor, unless the customer is a known troblemaker.

Well, that's my experience. Have you (or anyone else here) ever gotten a **full** refund for something over $200 USD without shipping the bad product back (or shipping it back at the vendor's expense)?

People complain about eBay and Paypal too. I think Amazon is a lot more strict with their vendors.

--sp

Good to hear.

Yes, even on ebay they would be banned after a few such incidents.

--sp