Towing Bridles

[Dunderbird2]

Looking to make up a towing bridle for my 6ton 34 ft yacht. I'm making it so I can fit it forward from mid ship cleats to be towed, and aft from mid ship cleats via winches and rear cleats so I can tow someone else, or my seabrake drogue.
Question is what to make it out of. Some say not 3strand nylon as the stretch is bad, others say use 3strand nylon the stretch is good. I'm starting to get confused as both camps are reputable.

[Snowpetrel]

Interesting idea, using the one bridle both ways. I think both approaches are reasonable, and both have advantages and disadvantages. Id probably be inclined to go spectra, as its light weight, high strength and lack of chafe would make deploying the bridle much easier. You can get the stretch from the towrope itself. But heavy nylon with substantial antichafe would work as well.

Most modern harbour tugs use dyneema for towlines these days. Sometimes with a short elastic nylon tail to cope with shock.

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[StuM]

You don't need a lot of stretch in a towing bridle. It's the main tow line attached to the bridle that should be absorbing shock loads. It's not uncommon these days to use HMPE lines for bridles because you can get away with a smaller diameter line which makes attaching to the strong points available on your average yacht a lot easier and it's also easier to use anti-chafe gear.

Even for tow lines (SAR situations, not commercial), nylon is not recommended. The stretch is excessive and it is dangerous because of recoil. Even if the tow rope doesn't fail, a failed cleat coming at you at high speed is not nice

Generally polyester or polypropylene are used for SAR tow situations. I prefer polyester for a number of reasons.

[Dunderbird2]

It works out pretty good lengthwise to use it both ways. I plan to make two lengths around 12m with eye splices at end so when I'm towing seabrake I can pull it over one quarter if required for steering etc. I think some people worry that if the nylon breaks it could ping back and injure someone. But that is what a lot of people use ?

[Dunderbird2]

Sorry StuM got your reply as I was typing mine. Yep that does make sense.

[Snowpetrel]

If you are using it with a seabrake type drogue you absolutely don't want or need stretch.

A little is ok but nylon is the wrong material to use for a speed limiting drogue like a seabrake.

Even a series drogue doesnt need the stretch as the cones have enough give through the water to absorb the shock.

I had a bad night once running with a drogue set on stretchy climbing rope.

So for that use definitely I'd far prefer dyneema.

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[Hydra]

Whatever the material, I would avoid using 3-strand line for towing because it twists and untwists when the tension changes. Then, both arms of the bridle would be twisted together, resulting in chafe.

FYI, the emergency towing rig of French warships is made of a short chain painter to eliminate chafe in the stern fairlead of the towing ship, then approx 200m of Nylon squareline connected to a few shackles of anchoring chain of the towed ship. The length of this chain is adjusted to keep part of the rig in the water.

Alain

[Dunderbird2]

This is all good stuff. I was think of using spare anchor rode for this but sounds like dyneema is the go.