AXE BOW | DAMEN'S SEA AXE
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THE YACHT REPORT AXE BOW | DAMEN’S SEA AXE 46 ISSUE 111
THE YACHT REPORT
AXE BOW | AMELS’ SEA AXE
The Axe Factor
Damen & Amels take a bow
By Tork Buckley
Plumb bows are found in both retro (such as Delphine) and ultra-modern designs (such as
Wally sailing yachts). Plumb-ness of stem purely for style is often confused with a special-purpose
bow that is part of the vessel’s hydrodynamic design. Here we try to dispel the confusion and look
in depth at the Damen axe bow featured on their Sea Axe vessel. We report on how it actually
performed when I sea trialled the first unit to be delivered as an SSV. (SSV is an acronym The
Yacht Report devised for the Superyacht Support Vessel. They are close relatives in many ways to
an Offshore Supply Vessel, and it sounds so much more dignified than a ‘toy carrier’.)
A xes and ‘X’s have become
confused. The X bow was
developed by the ship design
bow. Sabdes Design drew what
looks like an X bow at 50 metres
and also proposes a 72.5-metre for
Damen Shipyards Group so was
not part of the initial Research and
Development consortium. The Sea
division of Ulstein. It was developed Icon Yachts; confusingly these are Axe Fast Yacht Support function is a
in 2005 and had its first use on dubbed “Axebow”. Arguably, unless logical product development from
Bourbon Orca in 2006. There is little following the Ulstein design, they the Sea Axe’s Fast Crew Supply role.
change below the waterline to a are not true X bows, but as will Amels first identified the potential
normal hull, but the bow rises up become clear nor are they axe bows; for sale into superyachting and then
and slopes massively aft from where their form is wholly different and marketed the Sea Axe to superyacht
the forward end of the bow would the draft change is nothing like the clients.
be on a conventional Offshore TU Delft, Marin and Damen axe
Supply Vessel. The aim is similar bow. Amels have been doing pretty well
to that of the Damen axe bow, with in that role. Oberon is the first of two
better efficiency (through lower The Sea Axe was a logical 50-metre SSVs and in September, a
hull resistance), better performance walk-up visitor at the Monaco Yacht
in a head sea, less slamming and
evolution of the work Show resulted in a contract for a
higher maintained speed. Damen did in developing larger 67 metres one at twice the
patrol craft that could displacement of the 50-metre.
Feadship’s Predator has a form
of X bow, of which in issue 94 maintain speed and There have always been a number
Chris van Hooren commented: comfort in bad weather. of approaches to the SSV. I recall
“The keel is raked from 3.5 to 3.6 Peter Jago saying at a previous
forward to 4.2 aft. Aft the hull is The Damen Shipyards Group is Project event (the former Global
pretty conventional but forward a family-owned Dutch company Superyacht Forum) that a support
we arrived at a particular hull with 34 shipyards worldwide, 6,700 vessel should always be faster than
form which is a little bit in the employees and around 1.4 billion the mother ship. This seems very
direction of an X bow.” The X euro annual turnover in 2009. It sound; the toys get put away last
bow was also featured in the de specialises in high-tech vessels and and out first; if there is an interim
Voogt X-Streams’ design study – has become very successful with passage at a higher speed than the
see issue 80. Some other designs its standardisation philosophy. In yacht, then this is a must.
have also been proposed with this 1991 Amels became part of the
ISSUE 111 47
THE YACHT REPORT
AXE BOW | AMELS’ SEA AXE
Not all SSVs, though, have The evaluation of that figure is
R&D ON SEAKEEPING OF HIGH SPEED CRAFT conformed to this logic. A number based on the percentage of chance
1995 – 1999: ENLARGED SHIP CONCEPT
are former Offshore Supply Vessels of exceeding a given vertical
Requirement customer: 35 m
or replications of Offshore Supply acceleration as shown in the graph
Vessels and are relatively slow. scales(third image).
There have been fast designs: the
Final design: 42 m late Björn Johansson proposed a In 2000, Lex Keuning, assistant
very fast 50-metre multihull and professor at Delft University of
BMT Nigel Gee discussed the Technology, started to look at a
economics of both fast and slow different approach for improving
SSV designs in issue 108 on page seeking characteristics of high
48 and in depth in a RINA paper speed craft. The result would be
R&D ON SEAKEEPING OF HIGH SPEED CRAFT
(which was a synfo extra to issue the Sea Axe first built in 2006.
1995 – 1999: ENLARGED SHIP CONCEPT
108). Another well-known yacht In the period of 2003-2006 Delft
owner has a SSV in build in South University, Damen, the Royal
Italy (we hope to report in detail Netherlands Navy, US Coast Guard
on that later); it’s known to be near and Marin Wageningen carried out
1.8
1.6 1.54 1.54
1.67 1.68 completion and in sea trial phase. an extensive research program to
1.4 1.35
1.2
1.27
1.06 Le ngth
determine the merits of the Axe
Index
1 1 1 1 1 1.03
1 0.94 0.93
Building costs
0.8
0.6 Ope ra tiona l costs
0.4
0.2
Tra nsport e fficie ncy
Ope ra bility
The Sea Axe has a top speed of Bow Concept. Three high-speed
0
2600 3300 4000 25 knots and can make a Transat hull forms were tested both at Delft
Design alternative
passage at 18 knots. Oberon is University and Marin Wageningen:
powered by four MTU 12V 400 the enlarged ship (as a base model
M90s driving four fixed propellers. for the research project), a wave
R&D ON SEAKEEPING OF HIGH SPEED CRAFT
1995 – 1999: ENLARGED SHIP CONCEPT This is a special option, though, as piercer (somewhat like the later
Condition 2, peak accelerations
25 CAT 3512 or 3516s are standard developed X-bow) and the Axe Bow
Vertical accellerations (m/s2)
20
Approx 50% lower fit on the 5009 50-metre Sea Axe
peak accelerations
15
due to Enlarged Ship
Concept
vessels. It was a logical evolution of A complex formula (see Synfo
the work Damen did in developing extras) defines the Axe Bow, but in
10
patrol craft that could maintain simple terms it has a higher bow,
5
speed and comfort in bad weather. less change of water line beam,
0
100 10 1 0.1 finer entry, less (actually no) flare
Percentage of exceedance (%)
35 m 42 m
Although in their Offshore Supply and a deeper bow, deeper than any
Vessel role they can and do carry other part of the vessel; it resembles
cargo to a rig they are also crew an axe in profile hence the name.
SEA AXE PROOF
SEA KEEPING CHARACTERISTICS boats designed to bring crew to Also three unusual short chine-like
Com parison: Conventional - Enlarged Ship - Sea Axe
Sea State 5-6 North Sea
and from rigs at high speeds in all parts on the bow (see page 52) are
9
8
Conventional
Enlarged Ship 42m
weathers. The predecessor platform a vital part of the design’s function.
Sea Axe 35m
was the enlarged ship concept (top In addition, the greater the LOA
Approx 50%
7 Sea Axe 50m
Approx 75-80%
6
Vertical Acceleration (g)
5
image) based on the theory that of Sea Axe the more effective all
4
the longer and finer the hull the this is.
3
2
better the comfort, and higher the
1
sustained speed. Why the hull works is well illustrated
0
100 10
Probability of Exceedance (%)
1 0.1
by the difference in sound and pain
The premise was that extending if you slam the flat of your hand
the LOA is relatively cheap and in hard on water or do the same with
fact (second image) it was found the edge. The comparison with
that over four aspects of effective conventional enlarged and Sea Axe
cost were reduced. Extending forms is shown here(bottom image),
from 26 to 33m cost a mere 3% which shows the difference of a
more (6% to 40m), but returned conventional hull enlarged ship at a
transport efficiency of 54% and reduction of 75 to 80% with vertical
67% along with greater comfort. peak accelerations that was achieved
Those extensions were, it seems, in sea state 5 in the North Sea.
a bit extreme for many, but the
modest extension of 35 to 42 metres Clearly this is not a concept; to
produced a reduction of vertical date 20 have been delivered, with
peak accelerations by up to 50%. currently 17 in build. The roles are
48 ISSUE 111
THE YACHT REPORT AXE BOW | AMELS’ SEA AXE 50 ISSUE 111
THE YACHT REPORT
diverse; the majority are Offshore Certainly the lack of slamming and washing down. Victor
Supply Vessel/crew boats. Military endorsed Damen’s claims and Caminada for Amels surveyed
and para military versions are it was quite evident that neither captains and owners about this and
available along with those for SAR, hull nor machinery was taking any interestingly – surprisingly – most
pilot duties etc, plus of course one harm. Speed was reduced only wanted an SSV to full yacht finish.
SSV delivered, one in build and slightly from 25 knots with a solid
one under contract. Damen has 20 knots of forward way easily Yacht finish or not the Sea Axe
the exclusive licence on the Axe maintained. It was a fairly wet ride is an interesting and aggressive
Bow patents, which are owned by but afterall flaring bows are there looking vessel that would be a fine
Delft University of Technology. to keep a yacht dry. This workboat addition to a superyacht owner’s
incurs no harm from taking fleet. Oberon will go fast and stay
So much for the theory and water over and indeed above the fast through horrible conditions;
numbers: does it work? It clearly bridge. In line with its offshore the ideal SSV characteristic –
does; “I do not believe that any other role the bridge offers a full 360 despite a rash of slower designs
ship of this limited size and weight degrees view: a total joy for masters and speed rules.
can come close to this sustained compared with any yacht.
speed for such a long time in these The other visitors on the sea
conditions.” That was the endurance In fact in Offshore Supply Vessel trial were all non-superyacht;
sea trial captain on four hours use there is also an aft facing predominantly from a fairly new
steaming at 29 knots, Beaufort 7 chair for coming stern-to rigs etc, operational sector – offshore wind
with significant wave heights of 2.5 and offloading whatever is on its farm servicing and construction.
metres in very confused seas on a 225m2/250 tons cargo deck. These They were suitably impressed.
35-metre Sea Axe. chairs are part of the overall bridge Windmills usually break when it’s
package that Alphatron affords bad weather so this may be a new
I was invited by Amels to attend a total control from in a seated growth sector for the design.
sea trial just prior to handover of position – a legacy of the need to There has to be a downside as
Oberon – the first of the SSV pair. manoeuvre and unload cargo to there is to all designs. One is the
The yard gleefully wished for really one metre accuracy alongside a narrow beam (9.7 metres on the
bad weather so I would experience rigid structure in massive waves. 50-metre) and the fine bow’s effect
first hand how it performed. The on crew accommodations. This
sea trial started in the Maas River The aft chair has been removed may be easily dealt with by simply
and we zipped off towards the on Oberon and the area will be and cheaply adding length.
Hook of Holland, with a Damen modified after handover to owner
patrol boat on the cargo deck to seating. Unusually Oberon is being For a Helo pad to achieve
give some idea of a typical payload. handed over part finished – or at regulatory compliance, deck
Weather was fair with some wind, least cosmetically so. extensions athwartships would
but as we approached the Hook likely be required. One look at
the vessel could show off its heavy I found Oberon just right for its the Helo deck on an Ulstein X
(weather) mettle. At the entrance purpose. Though I agree the steel bow (below) shows how function
shallow banks, riverine flow and a deck would benefit from decking supersedes form and cosmetics.
sharp depth change conspired to such as Bolidt, yacht quality fairing However, both these are easily
produce really nasty, short, sharp and finish seem both unnecessary engineered and on the 67-metre
waves. These we passed very well and add to the work load on crew Sea Axe SSV a certified Helo pad
with minimal to zero slamming. whose job is carrying, handling is incorporated on the aft ship.
and servicing toys – not polishing This could of course be achieved
Though there was – as might
be expected – large pitching
movement speed, it was effectively
soft at both ends so transition from
pitch down to up and visa versa
was painless, even if the amount of
pitch made keeping on one’s feet a
bit hard. There was no discomfort
expect perhaps for those prone to
seasickness. However, compared
with most yacht hulls or even
conventional ones in the same
conditions, it was very comfortable.
ISSUE 111 51
THE YACHT REPORT
AXE BOW | AMELS’ SEA AXE
in a yacht-look and finish, but with a cargo now carried above these workshop
complexity and price penalty. and maintenance spaces. Extending
that to a yacht design is not impossible.
However, Damen informed me Such a yacht would be ultra specific and
that this is not practical from an limited in resale.
engineering standpoint. All such
variations are anyway changeable Also, for Damen a Sea Axe yacht may not
when specced at the beginning. GA, fit efficiently and economically into their
accommodation and fit out are fully production schedules; I would speculate
customisable to the SSV’s owner’s a yacht version like Oberon be part built
specific role. Oberon, for example, has by Damen then finished elsewhere.
a massive crane (below) – one that Perhaps it would be one Amels yard
would render the deck unusable for a complete or even build entirely. This,
helicopter, while the second Sea Axe has though, is just crystal-ball gazing into Sea
a totally different deck arrangement. So, Axe’s future. For now it’s clearly destined
yes it does work and is the most effective to be seen in significant numbers in all
SSV I have yet seen. its above-mentioned roles while plying
the world’s seas.
I feel the Björn Johansson high-speed
multihull might give the Sea Axe a The final and yet unanswered question
run for its money one day, especially is: how will the Damen, Marin and TU
in usable volume, but that is still a Delft team evolve the Sea Axe design
concept design. Sea Axe is proven and what will supersede it?
in use and through its supply vessel
origins engineered and built to operate Images courtesy of Amels, Tork Buckley
6,000 hours a year for at least 20 years. and Ulstein xbows © Ulstein Group
The obvious penultimate question is; will To comment on this article, email
we see a Sea Axe yacht? It’s hard to say; I issue112@synfo.com with subject:
can see for a very specific client it could The Axe Factor
be both an economical and interesting
platform for a yacht superstructure. The Synfo Extra – read more at www.synfo.
67-metre version, for example, has a com/extras for further information
house along the entire cargo deck with and images on the Sea Axe.
Sea trials in the North Sea in December
52 ISSUE 111
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