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In-depth | Feature theme

Ship & Boat International September/October 2015

With exponential growth in the complexity of recreational yachts in recent years, naval architects

have been tasked with accommodating an ever-widening range of material handling demands. Where owners might once have required provision for handling a single tender, which could be launched and retrieved from a simple davit on the swim platform, today’s yacht buyer – and especially purchasers of vessels in the 15-40m class – are far more likely to require the capability of launching and retrieving a variety of smaller vehicles, including personal watercraft, tenders and more – sometimes from multiple locations.

The challenge involved with vessels in this size range is twofold. Because the hulls are not large enough to accommodate an internal garage system without sacrificing precious interior space – a prospect that very few owners are willing to entertain – the process of launching and retrieving tenders inevitably requires the use of some sort of deck crane. However, with deck space also at a premium on boats of this style and size, crane selection becomes critical to fulfilling the owner’s objectives.

One reality of contemporary yacht design is that, with the open-concept floor plans and ability to handle the multiple water toys that owners now insist upon, the option of installing the crane in the optimal mounting position may not always be possible. This problem may be further compounded if the owner wishes to use the device to launch and retrieve items stored in different locations, such as a tender mounted on one side of the vessel and a personal watercraft secured to the other.

Arriving at a workable solution requires taking a logical approach to crane selection, with equal respect to functional requirements and installation demands.

Crane selectionWhere commercial vessels with a self-loading/unloading capability may be designed around a specific crane right from the beginning, in the case of recreational yachts the crane is generally added to a pre-approved vessel blueprint long after other design decisions have been made.

This poses unique challenges for the naval architect, since the selection of a specific model crane will be directly impacted by the availability of appropriate installation sites. Because the crane is typically ordered to fit

existing blueprints, by that point in the design process optimal mounting locations may have been previously allocated to other purposes. This is particularly challenging if the crane may be expected to be used for more than simply launching the tender; if, for example, it is also to be tasked with assisting in the loading of ship supplies, lifting pallets of goods to deck level where they can be taken aboard and properly stored.

Installation considerationsWhen determining the specification of a crane, the primary considerations are the weight of the items being lifted and the location where this lifting will take place. More than any other, these two criteria will determine the style of crane to be specified, and the approximate area where it will need to be installed.

Further details will be determined by both shipboard factors, such as the location and availability of solid structural surfaces such as bulkheads, and design specifications of the crane itself, such as weight, reach and mounting configuration. Geometric analysis to ensure the crane can move freely without impacting vessel structures or railings also factors into selecting both the crane and the final installation site.

Employing a logical approach to crane selection can reduce costs and avoid installation challenges. Craig Ritchie reports

Crane selection for recreational yachts

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Owners of yachts, particularly those in the 15-40m range, will benefit from considering crane types and onboard location points at the earliest stage in the design phase (credit: advantec global Innovations)

Control systems

a majority of cranes produced for the recreational yachting market are available with a choice of wired or wireless controls.

the advantage to wired controls is that by being permanently affixed to the crane itself, the control head is not likely to be misplaced or lost. Wireless controls, on the other hand, make it more convenient for an owner to launch and recover the tender by themselves. smaller yachts in the 15-40m range are more likely to be self-crewed by the owner than larger vessels, so, depending on the client’s comfort level, wireless controls may be more desirable.

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35Ship & Boat International September/October 2015

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“We work closely with naval architects to determine mounting considerations using 3D modelling software,” says Dave Marsden, general sales manager for Canada-based yacht crane manufacturer Steelhead Marine. “The naval architect normally provides us with a model of the appropriate section of boat, and we then layer a 3D model of the crane and the tender over top to identify optimal mounting locations, as well as any potential sources of conflict. We introduced this capability six or seven years ago, and it has proven to be a tremendous aid in specifying the right product for different applications.”

Crane reachWhile the weight of the load and location of the lift remain the key elements in crane selection and the identification of the installation site, the crane’s reach must also be considered.

In short-reach applications, as required for launching a small tender or personal watercraft, a fixed boom crane may be the best choice. The simplicity and comparatively

light weight of this design make it attractive in applications where deck space is at a premium or where cost is a significant consideration.

However, in the recreational yacht segment, the majority of cranes installed today utilise a telescopic boom. Although more complex and expensive than a fixed boom unit, a crane with a telescopic boom

offers distinct advantages, the least of which is greater operational flexibility.

Not only does the telescopic boom allow the crew to handle onboard loads from a greater variety of piers that may be varying distances from the vessel, it also enables the operator to better control the distance between the load and the yacht during the actual lift.

as well as launching tenders, owners should consider whether they require their cranes to handle ship supplies and goods (credit: advantec global Innovations)

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Ship & Boat International September/October 2015

Most naval architects would agree that while it is generally desirable to keep the load close to the vessel while being raised or lowered, it is equally desirable to maintain sufficient distance to protect against the possibility of the load swinging on the cable and striking the ship – a common concern when launching or retrieving tenders in rolling seas, for example. Telescopic boom cranes, with their variable reach, allow this additional level of control at the touch of a button.

Telescopic boom cranes offer additional advantages over their fixed boom contemporaries. Being able to retract when not in use, they occupy significantly less overall deck space than a fixed boom crane of the same maximum reach. They also tend to occupy less deck space and weigh less than booms with a knuckle function, while simultaneously offering a less industrial look and better integration with the flowing lines of a recreational vessel – aesthetics remain an important consideration in this sector. Steelhead Marine offers a wide range of telescopic boom cranes, ranging from 0.45tonnes- to 4.5tonnes-lifting capacities.

Location, location, locationRealtors always note that the most important factor impacting the value of a given property is ‘location, location, location’. For naval architects involved with the design of recreational yachts, the same can be said for the specification and installation of cranes. Mounting location has a direct bearing on what sort of crane mounting base is specified – bolt-on, weld-on or standpipe.

“It is generally desirable to position a surface-mount crane over a solid structural surface, such as a bulkhead, whenever possible,” says naval architect Bill Prince, president of Port Washington, Wisconsin-based Bill Prince Yacht Design. “Unfortunately that is simply not always possible. In recreational applications where deck space is at such a premium, we often find the owner wants to locate the tender and the crane that will lift it someplace out of the way, like up on a flybridge deck or over some cantilevered surface.”

When installing a crane, it is helpful to think in terms of total systems integration, rather than treating the crane as a piece of stand-alone equipment, says Andrew Mund, technical director at AdvanTec Global Innovations, parent of Steelhead Marine. Structural integration is just one part – the naval

architect must think in terms of how the crane will integrate with the vessel’s electrical and hydraulic systems as well. “Larger cranes that lift higher loads are exclusively hydraulic,” says Mund. “In some installations you may be able to tap into an existing central hydraulic system, such as that which supplies a bow thruster or stabilising fins. Since you’re not likely to be operating the crane at the same time you’re operating the thruster or the stabilisers out at sea, there is typically HPU capacity available to run the crane. That’s when you need to talk with the crane supplier to understand what they need from a pressure and flow rate standpoint, and when you’re buying your HPU for the thruster and stabiliser, you tell that vendor you need a couple of extra ports in the manifold because you need to send 5gpm at 2,500psi to run the crane.”

If tapping into an existing system is not possible, there may be no alternative but to also install an independent HPU to drive the crane – along with an appropriate hydraulic reservoir, plumbing and electric drive pump, all of which require precious space. The size of specific components, such as the hydraulic reservoir, will be dictated by the crane’s hydraulic demands, including luffing, rotation, extension and the winch.

production vs customLike many other types of marine equipment, cranes are available in both production and custom designs. The attraction of custom designs, of course, is that the crane is perfectly

suited to its specific application. The trade-off is an increased amount of time to design and build it, along with a higher cost.

The advantages of specifying a production crane are many – faster delivery times, greater ease of sourcing replacement parts, lower cost, and the fact that any potential bugs in the design are likely to have been long worked out. “The thing to remember is that even though someone may specify a production model of crane, there is still tremendous variability within that,” says Gary Tyson, production supervisor at Steelhead Marine. “A naval architect can specify a production crane with their choice of boom and one of six variations of bases or standpipes to suit specific applications. We do build custom cranes, but with the different combinations of production booms and bases we offer, the volume of production cranes we produce outnumbers custom orders by a wide margin. They’re less expensive, and generally we can deliver the product more quickly.”

By following a logical approach to crane selection – confirming the loads to be accommodated, the desired installation area, the required reach and mounting details – marine architects can avoid numerous potential pitfalls. Planning for the inclusion of cranes on recreational yachts early in the design process – including provision for hydraulic and electrical feeds along with a suitable mounting surface or provision for a standpipe – can further simplify the final product selection process. SBI

Corrosion resistance

Cranes may be specified with a variety of finishes. In recreational yachting applications, the most commonly used finishes are painting and anodising.

Quality painted surfaces can be expected to last for years, and are easily colour-matched to the boat itself, including metallic finishes. Painting affords the crane builder a far greater colour palette compared to anodising, which, along with the ability to perform in-situ repairs and touch-ups, represents a key advantage to painted surfaces. “steelhead marine uses marine-grade polyurethane paint because it offers superior long-term corrosion protection over powder coating,” notes dave marsden of steelhead marine.

anodised surfaces are harder than painted surfaces, and are typically translucent to transparent in appearance, providing a unique look that is difficult to replicate with paint. Durable and hard-wearing, anodised finishes can be considered very long-lasting and essentially maintenance-free. the disadvantage to anodisation is that in-situ surface repairs to chips or scratches are generally not possible.

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