Towed depth vs. cable length

[erikgreen]

Hi all -

I'm currently working on a couple of projects for towed sensors, and I'm wondering if anyone has a set of calculations or rule of thumb for length of cable/umbilical vs. depth of fish. Basically, I am planning on towing for example a camera sled on X ft of cable, and I'm wondering how deep I can expect to get it to run - how much cable can I expect to need for a given depth?

I'm thinking the angle of the cable and therefore the length needed will be determined by the water drag of the tow, and I'm expecting to run off a vessel traveling <5 knots. I'm hoping to get the camera 100 feet down on about 200 feet of cable assuming it's fairly streamlined, is this reasonable thinking?

Thanks for any info,

Erik

[erikgreen]

I'll reply to myself

Checking on specs for deep sea towed sonars, it looks like the rule of thumb is 3x the desired depth, IE for me 300 feet if I want 100 depth.

So I'll try that, plus I'll use a heavy cable and streamlined hulls on my projects to get 'em down deep.

Erik

[Kerno]

Your 3 to 1 rule of thumb is pretty close. You're going to find that the vessel speed plays a major role in the depth. That can be used to your advantage, because if you have a depth finder watching the depth under the hull, you can speed up or slow down to "fly" the towed object higher or lower. If you're towing a camera, you will probably want to put a simple depth transducer on the sled so you know where it is in the water column.