Increase of draft and DWT on container ships

[Aleksi Lindström]

Hello,

During my research on MSC's fleet, I have noticed a trend which is that they have systematically increased the DWT and max draft on many of their ships.

A couple of examples:
- MSC MICHEL CAPPELLINI, when delivered, the DWT was recorded as 240.854 and draft 17 metres. Now, it has been increased to a whopping 281.456 DWT and draft 18,85 metres.

- MSC FEBE, DWT was 228.149 and draft 16,5 m. Now 254.042 DWT and draft 17,75 m.

- MSC AGRIGENTO, DWT was 110.652 and draft 14,5 m. Now 127.952 DWT and draft 15,85 m.

A couple of questions: a) Why weren't the ships delivered with these larger specs in the first place? b) Are there any structural changes needed when increasing these specs? c) The TEU number can't be increased by these changes, but is this all for the reason that they can now carry heavier containers? d) How does this affect the fuel economy and the service speed of the ship?

Thank you in advance for any insights!

Cheers,
Aleksi

[lappino]

Hello Aleksi,

That's a very interesting subject.

Without going into details, but to answer (some of) your questions: the ships were not delivered with larger specs because they were not designed for larger specs; this is automatically answering the next question, as there are some structural changes that need to be done in order to comply with larger specs. Heavier and "deeper" vessels will also create more drag, and therefore require more power to achieve their specified speed, with all related consequences.

Cheers

Vlad

[MO Roy]

Hi Aleksi (and Vlad),

I'll also try to answer some of your questions.

(Container) ships are, quite frequently, ordered for a certain trade where a certain (expected) capacity is needed (TEU-wise) in conjunction with a certain draft and thus a certain maximum dwt.

Why companies want to increase the draft is because of maximising the capacity (dwt-wise).
This can be because change of trade (ports with deeper draft possibility) or expected higher weight containers.

This needs to be class-approved.
I have sailed on a few ships in the past which had a draft increase.
No real structural changes were made on those ships to allow for a deeper draft.

As you and Vlad already mentioned the higher the draft (for a certain vessel) the higher the fuel consumption will be.
Though sometimes it can be beneficial to have a slight higher draft or trim the vessel forward to get the bulb completely submerged which in general, and especially with higher speeds decreases the fuel-consumption (i.e. optimal trim).

There is however a trend to modify the bulb to a smaller one (during scheduled dockings) to increase flexibility in loading conditions and to have no longer a need to increase and/or trim the vessel forward. And in general trading speeds have come down significantly in the past two decades, decreasing the need for a big bulbous bow.
Nowadays quite a lot of new box-ships are built almost bulb-less.


I hope this answers some of your questions.

Cheers,
Roy

[Aleksi Lindström]

Many thanks to both Vlad & MO Roy, your replies have really helped me in my queries!

[pieter melissen]

Just some remarks here:

The DWT increase of containerships is also related to the number of loaded containers that may/can be carried, (no need to increase TEU capacity, just carry more cargo in the containers,  carrying empties is not a big earning model) In the past when Maersk announced that the Lindo yard was about to produce a new series of contanerships, they were very secretive about the actual DWT capacity, which most of the time not became public until the delivery of the first ship of the new series.