Massive towing job

billyboy
16th September 2008, 23:35
A while ago now i saw on a TV program Five tugs towing a huge towering structure. the tugs were neatly fanned out ahead of the tow. The middle tug was slightly ahead of the other four and his hawser was straight in line with the tow. My question is. How do the wing tugs manage to hold station, in perfect formation like that for so long. bearing in mind the two outside tugs have their hawsers at a fair angle maybe 45o. Whats the secret of these skilled skippers?
Anyone know how they do it?

JimC
17th September 2008, 16:56
Yes, but I'm not telling you!

Mr-Tomcat
17th September 2008, 18:50
Go on please, having never been to see it would still be nice to know.

Andy.

non descript
17th September 2008, 19:08
A very fair question Andy, and hopefully someone will be able to tell us without undue problem.

ddraigmor
17th September 2008, 22:15
I only ever did tandem tows with barges and semi subs so not quite the same - but I was at Loch Kishorn when they floated the Ninian Central out and that was impressive to watch.

Oh and I don't know!

Jonty

Dougster
17th September 2008, 23:19
Do they not have some sort of bridle fitted to stop them capsizing at angle?

michaelF
17th September 2008, 23:39
Billyboy ,
having been a skipper of AHTS boats i will try to give some insight to your question . Firstly i have only ever towed with three tugs maximum and all of these were semi subs or jack up rigs nothing really large like i think you are describing.

When you are a "wing" tug the secret is to keep as tight as possible to the lead tug , also if as you describe the tow wire is leading out at a large angle
if you do not use as much power as the lead tug effectively letting him do more work , your steerage capability improves , the same effect can also be achieved by slacking out your tow line a little .
Also with some vessels i sailed on i could just by turning a dial when using unilever control change the " effective " centre of floatation or in other words the point about which the ship would turn .

Hope this helps .


mike

billyboy
18th September 2008, 02:33
Billyboy ,
having been a skipper of AHTS boats i will try to give some insight to your question . Firstly i have only ever towed with three tugs maximum and all of these were semi subs or jack up rigs nothing really large like i think you are describing.

When you are a "wing" tug the secret is to keep as tight as possible to the lead tug , also if as you describe the tow wire is leading out at a large angle
if you do not use as much power as the lead tug effectively letting him do more work , your steerage capability improves , the same effect can also be achieved by slacking out your tow line a little .
Also with some vessels i sailed on i could just by turning a dial when using unilever control change the " effective " centre of floatation or in other words the point about which the ship would turn .

Hope this helps .


mike
Ah so its all down to hi tech gadgets then. I had visions of the outer wing tugs being swung in towards the lead tug due to the angle they were pulling at. I can understand that a bit of biased wheel could keep one away from the lead tug but at what angle.
Had a look on the net yesterday but could not find the picture. There is one about somewhere with seven large tugs neatly fanned out ahead of the tow. Now that must take a fair bit of co-ordination to maintain the formation (Thumb)

spongebob
18th September 2008, 05:40
It might be a dumb question but do the wing tugs use some form of paravane or similar device fixed midway on the tow line.
I have only been involved in one long sea haul and we ended up sinking the tow

Bob

billyboy
18th September 2008, 10:09
Ooh, tell us all about that sinking Bob

jimmys
18th September 2008, 10:23
There was a big tow from Hunterston to Kishorn and then out to the field, I think it was the Maureen platform with large tanks fitted. I saw it at Hunterston. You could not miss it. Lots of tugs all fanned out.

regards
jimmy

michaelF
18th September 2008, 12:24
Ah so its all down to hi tech gadgets then

I would not go as far as to say that Billyboy , much better to keep station manually , adjusting your power and course as required .

Not having seen the picture of the tugs and structure being towed , it could be that the outermost wing tugs were only there to aid in changes of course of the structure and not actually for towing . They could also be used as a brake .

mike

JimC
18th September 2008, 17:28
I think the picture you saw was probably one of the large concrete structures built for the Valhalla field in the Norwegian Sector. It may even have been the Ekofisk main structure. Was it circular or did it have several 'pepper-pot' support tower?

Jim C.

JimC
18th September 2008, 17:34
Actually, the wing tugs don't need to have an angle on the tow-line. If all the vessels pull at constant, equal power with straight tow-lines, the overall resultant pull will be forward in the direction of the centre line of the lead tug. This is best explained by considering the wing tug line as the ends of a bow -string and the platform being towed as an arrow. OK?

Jim C.

timeout
18th September 2008, 19:44
There was a big tow from Hunterston to Kishorn and then out to the field, I think it was the Maureen platform with large tanks fitted. I saw it at Hunterston. You could not miss it. Lots of tugs all fanned out.

regards
jimmy

Please see links below

Regards Timeout


http://www.shipsnostalgia.com/gallery/showphoto.php?photo=92315

http://www.shipsnostalgia.com/gallery/showphoto.php?photo=92316

spongebob
18th September 2008, 21:51
JimC, thats a good description, let me draw a diagram of resultant forces in my mind. Still confusing though and we need a tug master to put our minds to rest.
Billyboy, that was my long winded thread "The Devonport ferries and the long haul" dec 07

Bob

billyboy
19th September 2008, 00:02
Ah...the Maureen platform picture looks like the one. All those tugs having to maintain formation and distance from each other. Over a long voyage too!
If ever one got too close to another the water between the would draw them together. Like ships refueling at sea must remain a certain distance apart.

jimmys
20th September 2008, 14:45
Thanks Timeout thats the ones.

I have been involved in two substantial long deep sea tows. One of the problems you have is there is a natural movement of the tow to the side. You go to bed the tow is dead in line and wake up four hours later and the cable is at twenty degrees. The tug needs to manoeuvre to get in line and it wastes time.
With the fan formation the two outside tugs can adjust to correct this problem. I would assume on the Maureen the outer tugs were constantly doing this.

regards
jimmy

BillH
20th September 2008, 14:54
Ah...the Maureen platform picture looks like the one. All those tugs having to maintain formation and distance from each other. Over a long voyage too!
If ever one got too close to another the water between the would draw them together. Like ships refueling at sea must remain a certain distance apart.
Interaction I think is the word used to describe the drawing together effect when steaming parallel and getting too close.

AndyJohannessen
27th September 2008, 22:22
Billy Boy,
I think what you saw was "Super Structures" on Discovery channel.They where towing a large supply platform out of Stavanger.I have that on video it's a great programme.If you can watch it agailn the Master in charge I think it was Maersk challenger, did explain how things where done.I still have this programme in my collection,but I must admit it surprises me that ddraigmor doesn't know he seems to be expert at every thing else.

Andy.

ddraigmor
28th September 2008, 00:05
Andy,

Never did any floating structures, mate. Rigs, ships, barges, tandem tows and once three barges - but nothing of that size or complication.

I was a good observer Andy. Not an expert. Are there experts on here? I doubt that anyone would call themselves that. Professionals, maybe but experts? Not a word I would use.

Jonty

billyboy
28th September 2008, 00:17
Must agree that the Expert dig was a little out of order Andy.
Mr Ddraigmore has gaine a vast amount of experience of the towing game all over the world. That,as he quite rightly says, does not make him an expert any more than the Captains he sailed under.
The towing game can be very complex business to a rock dodger like me with very little experience.
Still a mystery to me how so many tugs pulling hard can hold position in perfect formation like that for so long without a coming together of hull's.
Imagine connecting up all them bridles, hawsers and penants. No mean feat in itself

ddraigmor
28th September 2008, 01:14
No worries Billyboy! Andy was - hopefully - not being sarcastic?

I tried to look up some info and what I can see has already been said by Masters and those with command experience - the tugs were attached to points on the structure (like a bow I think someone likened it to).

As for the interaction effect, they work that out to make sure it has no chance of happening.

I'll keep looking and if I can come up with anything I'll post the link.

Jonty

Don Matheson
28th September 2008, 08:20
Billyboy can you remember the date of this very large tow. We were finished a drilling contract in Israel in April 95 and a Maersk AHTS coming from Singapore to Stavanger was diverted to us to bring us from Ashdod to Invergordon. Maersk not being one to miss out on work changed their plan and found another tug. That in itself was quite a long tow using only one tug but we were 'self propelled' and our propulsion motors were used all the way home. I am sure at one point we were pushing the tug.
On the towing side I have only been involved in using two tugs for single tow.
IIRC the tow from Stavanger was shown on discovery channel so no doubt will be coming to a tv station near you soon or again as so often happens.
Don

billyboy
29th September 2008, 00:43
really cant remember the date. Sure there were 7 tugs on it though

K urgess
29th September 2008, 13:26
Are you thinking of the Troll A tow out, Billy?
Half way down this page -
http://dvice.com/archives/2008/02/troll_a_gas_pla.php
Very difficult to find the actual photographs
Cheers
Kris

billyboy
30th September 2008, 07:35
That looks something like it Fubar. the picture i saw was taken from a different angle (a helicopter shot i would think).
Some co ordination required to keep all them tugs in formation eh. And a LOT of horsepower from 8 tugs too.
Thanks for posting that link Fubar

BillH
30th September 2008, 09:45
That looks something like it Fubar. the picture i saw was taken from a different angle (a helicopter shot i would think).
Some co ordination required to keep all them tugs in formation eh. And a LOT of horsepower from 8 tugs too.
Thanks for posting that link Fubar
There was a documentary on TV recently showing the process of getting one of these structures out through the fjords etc.

There were numerous defined points that had surveyors with theodolites and rangefinders monitoring the position of the structure against a pre-defined route so maintaining the depth below it.

They continually monitored and fed the info to a towmaster who controlled the tugs. He then had them adjust their power as necessary to maintain the set course.

Very interesting process

K urgess
30th September 2008, 10:18
I remember the photograph you're thinking of Billy.
Taken from height ahead of the tugs and the tow.
I'm sure it's on site somewhere but I'm b.....ed if I can find it.

Cheers
Kris

billyboy
30th September 2008, 11:12
I thought that too Fubar. Damned if i can find it either

timo
30th September 2008, 13:32
Billyboy, are you thinking of the statfjord B tow out, that was a well photo'd event with numerous tugs on the tow, several United Towing tugs on that job if I remember right.

billyboy
30th September 2008, 23:18
quite possible. The old brain cells are not what they used to be these days Timo

B.Nicholson
11th May 2009, 22:18
A while ago now i saw on a TV program Five tugs towing a huge towering structure. the tugs were neatly fanned out ahead of the tow. The middle tug was slightly ahead of the other four and his hawser was straight in line with the tow. My question is. How do the wing tugs manage to hold station, in perfect formation like that for so long. bearing in mind the two outside tugs have their hawsers at a fair angle maybe 45o. Whats the secret of these skilled skippers?
Anyone know how they do it?

Dont know what JimC is hiding. But. The outer tugs (What you call wing )have to keep altering course frequently . I did a few of these multible tows. They are no problem but you have to be alert. you are being pulled all the time into the lead tug.
Bob N

exsailor
12th May 2009, 11:04
Billyboy,

A couple of pictures for you. The first shows steamed direction vs direction actually made good by the wing tugs, as mentioned in Post #14. www.oilrig-photos.com/picture/number175.asp

Second picture shows the ultimate - 9 vessels pulling and 2 pushing. http://en.wikipedia.org/wiki/Offshore_concrete_structure
Scroll down to and click on photo of Statfjord A Platform.

Regards,
Dennis.

billyboy
12th May 2009, 11:15
ex Sailor. Many thanks for the two informative links. heck of a co ordination for the tow master.

gdynia
12th May 2009, 19:36
Billy put a photo that might interest you of one tow job we did in Sakalin Island on my gallery

B.Nicholson
30th May 2009, 03:14
Actually, the wing tugs don't need to have an angle on the tow-line. If all the vessels pull at constant, equal power with straight tow-lines, the overall resultant pull will be forward in the direction of the centre line of the lead tug. This is best explained by considering the wing tug line as the ends of a bow -string and the platform being towed as an arrow. OK?

Jim C.

Jim C just reading your post again. You are so wrong my friend. the lead tug holds the main course & speed .The wings (as you call them) they are counter-acting to maintain the main course all of the time. just Imagine the lead tug is steaming north, then the wings getting dragged close to the lead tug, depending on on the speed of the tow. the wing tugs can be making 45/50/ 60 degrees of leeway to counteract elements.Tide , Wind , etc.whatever, You could have wing tug 1 on the port side steering 340 Degs and wing tug 2 on stbd side steering 050 degs all to make a heading of north. Therefore speed for the wing tugs is changing all the time .
Bob N

billyboy
30th May 2009, 04:03
Billy put a photo that might interest you of one tow job we did in Sakalin Island on my gallery

Nice one Nev. Brilliant navigational achevements from all tugs. I know that they have sat nav and ECDIS these but it is still some task for the towmaster.

RayJordandpo
30th May 2009, 12:46
I've done a few of those tow outs in the past, utilising up to six tugs. In my experience the "wing" or outer tugs were constantly having to adjust their heading and speed to keep station on the the lead tug. I'm even seen a tug run over anothers towline and I can assure you it is not a nice experience. I know 'cos it was me that did it.

roddy
30th May 2009, 19:35
Dunlin Alpha tow-out is in the gallery, with the 6 tugs all alongside each other, that was not part of plan A. When we started the tow out, on relatively short gear and built up the horses, the tugs all came together despite our best efforts. We were all matched in size and still well up the fjord so we just let it happen, once we lengthened the gear we all came apart. We were on the starboard wing, I don't remember it being too difficult keeping station (but time is a great healer and the sail away party in Stord was still the main topic of conversation!). I have had more difficulty as second tug on rig moves, however it is all a long time ago and now relegated to "lamp swinging sessions" in the pub.

Roddy

RayJordandpo
31st May 2009, 07:49
Roddy
I still have bad dreams about us going backwards in a full gale for what seemed like weeks! Slacking that bar tight wire bridle off was no fun either but like you say time is a great healer.

roddy
31st May 2009, 09:43
Ray

It was weeks, and I still have scars

Roddy