Question for tug folks

Steve Hodges
11th May 2009, 22:22
Could one of you tug experts please enlighten an old deep sea engineer?
I was down at Tilbury today when three of the Svitzer tugs left their moorings over on the Gravesend side and set off upriver, ( maybe to drag a big box boat off Northfleet Hope terminal?) HT BLADE was proceeding normally, but SVITZER REDBRIDGE and SVITZER ANGLIA were both going backwards, at much the same speed, and continued like that until out of my sight. Why would they choose to do this? I appreciate that they are water tractors and can go equally as fast astern, but to get from A to B why not go with the "sharp end" first?
I await enlightenment!

Santos
11th May 2009, 22:53
Perhaps they were trying to wind back the mileage prior to sale (Jester)

Chris

billyboy
11th May 2009, 23:13
It saved the skipper from swiveling his seat round i expect ...LOL

tridentport
12th May 2009, 00:25
I once asked the same question and was told - "Easier to steer a straight course when going astern."
Perhaps its something to do with the position of the propulsion units.
See http://www.shipsnostalgia.com/gallery/showphoto.php?photo=110380
Regards, Alan.

Derek Roger
12th May 2009, 01:55
Why not ??

BillH
12th May 2009, 05:46
Could one of you tug experts please enlighten an old deep sea engineer?
I was down at Tilbury today when three of the Svitzer tugs left their moorings over on the Gravesend side and set off upriver, ( maybe to drag a big box boat off Northfleet Hope terminal?) HT BLADE was proceeding normally, but SVITZER REDBRIDGE and SVITZER ANGLIA were both going backwards, at much the same speed, and continued like that until out of my sight. Why would they choose to do this? I appreciate that they are water tractors and can go equally as fast astern, but to get from A to B why not go with the "sharp end" first?
I await enlightenment!
The vessels are propelled by Voith Schneider cycloidal steerable propulsion units which are below the hull about 2/3rds forward. Aft of them is a large keel fin. With this arrangement some masters find it preferrable to travel stern first.
Simplistic answer but in reality probably more complex.

Steve Hodges
12th May 2009, 22:02
Thanks for your replies, gentlemen. I suppose these Voith Schneider jobs must have different steering characteristics when "running light" as opposed to towing or pushing. But I do like the idea of winding the "clock" back!

cryan
20th May 2009, 19:54
Voiths suffer from similar effect to helicopters when going straight so the skeg aft keeps them on course. this works better when going ahead, however it is beter to work astern to keep the voiths forward of the towing point for manouvering. Mibbe the skipper just likes going backwards.