What is a “Long Tow”?

In the nautical world a “long tow” is a tug boat pulling a barge on a long cable.  When they are towing in the ocean the cable can sometimes be REALLY long.  It is a way of shipping anything that can be loaded on a barge in quantities that are smaller than would justify the use of a full sized containership.  Long tows are used around the world, but here in Hawaii they are a large fraction of the shipping you encounter on the ocean. They are used for almost all inter-island transport, and a large fraction of the goods shipped from the mainland arrives on barges like this.

They can be real trouble if you are not paying attention.  Here’s why:

You are out sailing on the ocean, and you see a tugboat in the distance…


You look around to see if there is anything attached.


I don’t see anything…  do you?  Let’s look a bit further…


Nope.  Still nothing.  Maybe look just a bit further…


Oh!  Look at that!  Yes it is a barge.  And yes, it is attached to that tugboat in front with a very long cable.  When I checked on my radar, this tug and tow combination was over a half mile long.  If you tried to go between them, you would have a VERY bad day.  At night the situation is even worse, although the barges are lit, the lights are typically quite small and non-obvious.

Why are they so far behind?  One reason is the barge does not have any kind of brakes.  If the tugboat’s engine was to stop and the barge was towed close behind, the tug would be run over by something an order of magnitude or two bigger and heavier.  Not a pretty picture.

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6 Responses to What is a “Long Tow”?

  1. Melinda Parke says:

    As a lifetime boat person and a lover of physics I would like to know how a tugboat brings a
    barge to a stop . I see the tugs where I am in Seattle towing barges of sand etc. going really slow. When she gets to the landing area does the tug remove the tow line and push the barge into place?
    Thanks in advance for your reply. Melinda


    • Bill Kinney says:

      Hi Melinda,

      As a lover of physics, you can certainly appreciate that long after the tugboat stops tugging, the barge is still moving. They might not have a lot of velocity, but they can have a huge mass. Even aside from stopping, it is not at all a simple matter for the tug to make the barge take a sharp turn. For any kind of close quarters maneuvers, the tug will stop pulling, and and come back alongside the barge and tie there to keep close control of the barge. This is obviously a maneuver planned well in advance, and not done quickly.

      While there are certainly tugs that push barges, that is usually a special setup. Most tugs do not go from towing to pushing, but many go from towing on a line to a “hip tow” alongside the barge. This is common not just in towing large barges and ships, but even towing small boats. The long tow line is the best set up for moving the “dead” vessel in waves. But you can’t bring anything along side a dock with a long tow line.


  2. Dale says:

    Karen, I’d rather eat dirt than correct you. 🙂


  3. Dale says:

    The “sag” or catenary in the tow cable also provides a shock absorber between the tug and tow. A hard, straight pull can do a lot of damage to the tug, barge, or both. There’s also the risk of parting the towing connection.

    Liked by 1 person

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