|MadSci Network: Engineering|
Good question Phil, and it's interesting that it got forwarded to me, as I'm in the merchant marine. Anyhow, It really depends most of all on where the tug is... In the wider parts of the Mississippi, they'll tow them alongside the tug. At sea, where the barges are much larger, they tow them behind the tugboat at the end of a fairly long cable. However, the main reason that they are pushed is because of control. When you see a tug and barge, you really have to think of it as a single unit like any ocean-going vessel or even a small boat. A ship is controlled in much the same way as an airplane, in that the movement is in direct response to a medium acting on the control surfaces (water flowing past the rudder). Actually, the rudder does not give that much control without the help of the water that has just pushed against it by the propellers, hence the reason why most ships are difficult (at best) to control in reverse. Another control factor is that the rudder is as far aft (the back of the vessel) as possible to provide leverage (not the most technical of descriptions, but it works). In fact, if you watch a boat or ship turn, you will notice that it turns around a point about 1/4 of the ships length forward of the stern. If the tug was rigidly attached to a barge being towed, it basically could only slide right or left and not actually turn. The oceangoing tugs get around this by using that long cable to their advantage and dragging the front of the barge in the direction they want to go (at the expense of fine control). Obviously that wouldn't work though in a river or the Inter-Coastal Waterway. Hopefully, I've answered your question well enough for you, Fair winds, and following seas, John Metcalfe 3rd Mate, Unlimited Tonnage (Ocean)
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