Indirect Tow Mode

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[Cloud]

The release of the new Editor has totally opened the potential of SS08. Now finally people can put together the situation they've been wanting to try out.

I wanted to see if I could make an indirect tow mode work in SS08; So I put together a mission coming into RTM with the VLCC and 4 harbor tugs. One of the 4 tugs I used aft in an escort position and used an indirect tow mode to help the Latitude in a tight turn to Port. I'm happy to report that it was reasonably effective.

Now while admitedly these tugs probably don't have a skeg for escort towing and VSTEP isn't going to the extreme of modelling hydrodynamic effects like that, there's more than enough here to have fun with. 

Here's some pics to illustrate. Now go run download the editor if you haven't already!!! 

Also a link to some more discussion about this mission.; http://www.shipsim.com/ShipSimForum/index.php/topic,1421.msg23429.html#msg23429 (http://www.shipsim.com/ShipSimForum/index.php/topic,1421.msg23429.html#msg23429)

Cheers,

Cloud

[seegurke]

Hehe, that look quite nice. Didn't know, that you can moore the tug with the bow towards another ship like you did. Well, I'll try immediately

[Cloud]

I used the mooring line function and not the towline function for this one. There is really a lot of flexibility to do whatever you want!  Have fun with tug! 

[marcstrat]

Greetings,Cloud
It's a nice mission to bring in that vessel in a harbour.
However,all your tugs are on one side of that vessel,it gives you less possibility's to move.
Try next time (2)at the bow,and (2) at the stern,than you are able to move that vessel,with more freedom.
This is just an idea,i realy like this action.
Regards
Marc

[Cloud]

Hi Marc,

Yes indeed, I understand the configuration you are mentioning, and you certainly make a good point. 

In fact you are touching upon a very interesting debate here regarding how harbor tugs are handled for vessel assist. Not surprisingly the US and Europe have a very different approach to this subject. 
I attached two photos as examples; the top is typical for two tug assist in the US, the bottom in Rotterdam as you can tell with long hawsers out the panama chocks is typical in European ports.

The really great thing is we can try it all.. 

Cheers!

[ACM van Oudheusden Jr.]

hallo cloud ,

nice mission

did you know that vessel with a draft larger dan 17.40m are escorted by a vessel of the port authority te last part of the euro channel (the entrance to rotterdam)

maybe you can also add this to the mission ?

kind regards
marco

[seegurke]

Didn't know this and would be a very cool idea for a mission with the Latitude. But that won't work until you can set the speed of AI traffic in the editor.

[Cloud]

HI Marco,

Didn't know that either but certainly sounds like a good measure for a draft restricted vessel in a busy Port. 

I haven't had much time to mess around with SS08 these last few days, so sorry for that, but here's the mission file I've been using to set up my scenarios for Latitude in RTM. There's already some bollards at the oil terminal in  Maasvlakte (sorry If I butchered it  ) and directly across at the Europort side. Have fun.

Cheers and thanks for that great picture! 

[tuggman]

love the mission. i was doing indirect with 2006 worked really well i found three tugs did the job (VLCC)
even on that tight turn to port. with one boat on each bow and center lead aft. hard to port as you make the
turn port tug backing full aft indirect full to starboard.and the starboard bow standing by to push or steady the the ship.   

                                  Thanks, Tuggamn

[Stuart2007]

Not surprisingly the US and Europe have a very different approach to this subject. 

And even less of a surprise is that while America does it X way, Europe does it Y way, we British have to be akward and do it Z way.

Joking aside, last winter coming into Portsmouth (I suspect our ship was under command of the bloke who pranged HMS St Albans) we had 2 tugs- one was at the starboard bow and was just pushing the ship with the tug, whilst the stern tug was tied to the starboard rear quarter.

The starboard was in the lee of the wind and I suspect that this was in order to avoid the wind catching the ship on its final turn (90 degree starboard) and smacking into one of Her Majestys destroyers. From the marine accident report, PO Portsmouth started the turn, got caught by the wind and kept turning... which was unfortunate for HMS St Albans.

The why and where of the tug positioning, I couldn't tell you. But I assume that you mean indirect when they are on a rope and direct when they just push it with contact between the two vessels?

Stu

[Cloud]

Hey Guys,

love the mission. i was doing indirect with 2006 worked really well i found three tugs did the job (VLCC)

Tuggman, glad to hear you're enjoying it, sounds like you're getting right into it 


Hey Stu, how's it going? Sounds like a pretty hairy situation you're describing there in Portsmouth. Did the Destroyer get pretty crunched up?

But I assume that you mean indirect when they are on a rope and direct when they just push it with contact between the two vessels?]But I assume that you mean indirect when they are on a rope and direct when they just push it with contact between the two vessels?

Regarding indirect towing, and granted there's probably some variation in terminology worldwide, but generally refers to a very effective maneuver used by escort tugs to increase their bollard pull beyond what is theoretically possible with main engine power alone.

Basically the tug uses it's power to come off the heading of the tow working against the line at an angle. The towing force comes from the hydrodynamic lift created by the tug's hull form and generates bollard pull well in excess of what could be achieved by pulling the line directly. Here's a link with some pictures that gives a more complete explanation.....

http://www.towingsolutionsinc.com/technology-escort_tugs.html (http://www.towingsolutionsinc.com/technology-escort_tugs.html)

I also attached an example of an ASD (Azimuthing Stern Drive) escort tug design. Note the skeg piece appendage on the hull to generate the hydrodynamic lift i'm mentioning.

Cheers 

[Stuart2007]

Hi Cloud

The time I was on at Portsmouth was about a year after the accident- I wasn't on the ship during the accident. I just suspect it was the same skipper (there were other reasons for suspecting this, but thats long drawn out).

To be honest, that time the wind wasn't TOO bad but there were rumours of the bow thruster not working properly (so say the crew). IF I remember rightly, on the outward trip, the tug was just stationed between us and the destroyer quay it was only on the way back that both assisted. IIRC the tug didn't appear to be doing much, but merely 'at the ready' (although I can't say as I'm not an expert).

Re-reading your towing link...
Stu

[Cloud]

Hey Stu,

Interesting that you say the bow thruster may not have been working properly....

Just a thought; Some ports (i'm thinking San Juan, Puerto Rico just off the top of my head) can require a standby tug/tugs if you don't have a fully operational bow thruster and are over a certain length even if you don't need it or intend to us it. Just a local requirement.

[Eemspoort]

Just be coinsedence i run in to this movie. It's from a tug-company in the States, Moran, assisting the Ever Round from Evergreen. Here you can see, and is explained, indirect towing.

http://www.morantug.com/movie.asp (http://www.morantug.com/movie.asp)

[Cloud]

Great movie Eemspoort!!   Excellent find!