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Author Topic: Asian vs Western Tug Designs.  (Read 1043 times)
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Judgie
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« on: April 30, 2018, 10:19:39 am »

Good evening all,

Over time i've been noticing distinct differences between, let's call them "Asian" and "Western (European/US)" tug designs.

I.e. what I call the "Japanese style ASD Tug" and the modern Robert Allan/Damen ASD designs, please see the attached pictures.

The Asian Vessel Design: Comparably high length to beam ratio for a tug, shallower draft, very flared bow with wheelhouse set quite far back. Relatively lower bollard pull and power compared to the euro designs, for a tug that is often longer than the comparable euro design. Doesn't appear to have a skeg to assist in conducting indirect and powered indirect towage. Somewhat shallower draft than Western Design. Rather "rounded" hull construction.

Western Design: ASD tug design philosophy most of us are familiar with. Smallest possible size with highest possible bollard pull and power, usually considerably more than the asian design. Capable of Indirect and Powered indirect towing. Somewhat deeper draft than Asian design but often not by much. Often simple single or double chine construction and slab sided.

So what I am getting at here, is what advantages does the Asian design still have compared to the Western Design? it's still popular in many Asian Countries, especially in Japan where they are still building them, including a new LNG Hybrid variant. They usually have lower bollard pull, are larger and don't seem to be capable of indirect towing?

I'm tossing up the two designs for my next tug build using a pair of Blue Robotics T200's, and while I find the look of the Asian design very appealing, I'm not certain which to go with.

Many thanks for your time,

Judgie
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em777
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« Reply #1 on: April 30, 2018, 12:15:47 pm »

Hi Judgie,

As a skipper of both designs I will give you a few of my thoughts.

Firstly, the contract that the vessels are built for is important.  For example, think of the Svitzer tugs in Milford Haven.  They were built as terminal tugs to escort and work in push pull mode.  Therefore they have very rounded bows.  This was designed this way as calculations of pressure and heat distribution per square inch were calculated when pushing up on the LNG vessels.  The skeg as you rightly noted allows the escort mode of operation which in an oil and gas port they are required to do. 

The Japanese hull form however makes them a much much better sea boat.  There is probably a disadvantage to pushing with such a narrow bow, but the flare makes the tug cut through a sea much more comfortably than a round bow. A tug built to service one port wont need the same coastal steaming qualities as one that may have to travel.

Next point to consider is who is living there.  Take a Damen 2411 for instance. Fantastic tugs but really a "day boat".  Crews go home after a relatively small stay.  Other tugs have accomodation for up to 6 persons 24/7 and this then determines size.  Tugs that work in harbour systems will always be smaller than tugs designed for terminal work as they need to fit around tight corners etc.

Some tugs are a mixture of both.  My current vessel is a Robert Allan design but has Niigata controls, engines, gearboxes, clutches and units.  This makes her a fantastic vessel to handle, but where my company needed a higher bollard pull they had to look at different engine manufacturers for other tugs of the same class.

If you look at what tugs the UK were building in the 1970's and then look at what Japan were building they were miles ahead.  We had twin screw and they had ASD.  That ASD design has evolved into modern day standards but the overall tug is much the same.  A ship owner wont go spending money on a tug which is equipped both structurally and stability wise for escorting if its not needed.  The japanese tug seems favourable but if he can have it built in Europe more cheaply then that will overrule the Japanese design.  If the Japanese tug cant provide the required bollard pull then again the shipowner will look elsewhere.

Cheers,

John
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