An Axe for defence

It’s into this niche that the business-like Sea Axe slides with a typically fine entry. The story is now quite well known; back in 2000 Lex Keuning of Delft University of Technology started to investigate different hull shapes for high speed craft. After years of research and trials that involved Damen, Delft University, the Royal Netherlands Navy, the US Coast Guard and the Maritime Research Institute, the Axe Bow was born.

With its characteristic high, deep bow, lack of flare and very straight, even beam along the waterline, it looks enough like an axe head to warrant the name. Beyond the efficiency and comfort gained from lowering the wave resistance, it appears just a little scary – all to the good if you are keeping pirates at bay.

Although Damen can’t talk about the ownership (the people buying them have discretion high on the agenda) Jaap Gelling of Damen does say that it’s one of the company’s best-selling lines: “There are now over 150 Sea Axes. We have sold over 30 for offshore patrol functions, the majority of these being the 33m or 50m varieties [though the design reaches up to 85m in length with the Sea Axe 1800].”

But it’s not, as you might expect from a patrol boat, an aluminium hull. “We started looking at aluminium in the beginning. For simple supply operations the speed isn’t too important, but for patrol boats it is critical – and we knew that’s what we would eventually be building. However we were also looking at an extremely high number of operational hours. Around 6,000 hours a year is quite normal for these craft.”

However, there was a clash. “Aluminium has an irritating fatigue characteristic. As you increase the service hours you need to make it thicker and thicker. By the time you get a boat that will fulfil the criteria, it’s unfeasible. Steel, on the other hand, has an almost infinite life below a certain stress level. So it had to be steel, although that was pretty unusual for a new fast supplier design at the time.” Despite being built of ‘unfashionable steel’, Damen sold two Sea Axes to its very first client, who now has 14 of the vessels.

One of the big positives of the Sea Axe design is the clutter-free aft deck which, despite its comparatively slender 10m beam, lends the vessel to easy transformation. It has even found a niche in superyacht support. The lack of high peak accelerations also makes it an extremely stable platform: the highest vertical acceleration ever measured on the bow of a Damen Sea Axe was 1.3G, says Gelling, in very rough seas.

This all plays into its ‘security’ incarnation: the normal accommodation for six is extended to 24 personnel as the main deck has cabins for onboard security specialists. More unusually there are ballistic steel panels protecting both this area and wheelhouse, while the windows are a little smaller than standard with 60mm glass – “making them Kalashnikov proof”, says Gelling. It’s not every day you hear that in support boat specifications.

Despite being called the 5009 (which means 50m long, 9m wide), one of the most popular of the series is actually 53m long. He explains that in 2008 a customer asked Damen to stretch the aft deck by 2.5m for tender requirement reasons. “The result was it went faster, with a bit better seakeeping because it lengthened the vessel at the waterline, meaning even less wave creation and lower resistance. So we kept it.”

The standard propulsion for the 5009 is four Caterpillar 3512 engines, each yielding around 1,100kW, and “A-rated because of the heavy going”. This results in a top speed of 25 knots. Another configuration using 3516s seemed to be popular for a few years, Gelling adds.

Paradoxically, the low oil price has brought the required speed down. “It seems that though there was a trend for 30-plus knots for a while, now that there is a downward pressure on the charter rates, fuel economy has become important again. High speed on big vessels is expensive, so the general demand has settled back to just over 20 knots.” Gelling remains pragmatic about this. “If people ask me what they can do about fuel consumption, I say sail one knot slower,” he says.