When the beams bend on board a yacht, the cause is usually not a mendacious load, but a real one. One that comes from above. Imagine the following scenario: The wind picks up, the tension on the forestay and backstay gradually increases and all of a sudden the doors below deck are reluctant to open. On some sailing boats, "proper zing" is not an unusual litmus test for the height of the loads and the quality of the interior fittings, but on supersailors it is unthinkable. Of course, there is no shortage of forces, but the shipyards' promises of excellence, the astronomically high expectations of customers and the pedantry of the classification societies involved put a stop to them. In addition, comprehensive sensor technology provides information about the rig forces occurring during sailing operations.
On "Sea Eagle", an 81 metre long aluminium hull forms the basis for a huge and very real distorted image. Three masts, up to 61 metres high, guide 3,552 square metres of sailcloth on spacious courses and ensure maximum working loads of 125 tonnes. So far, so feasible. Not only did Royal Huisman set out to build the world's largest aluminium sailing yacht, the customer also wanted a superstructure that spanned almost half the deck - and with its continuous window areas, was far less flexible than the deck below. So how do you bring the rigid and flexible elements together without provoking material fatigue? The solution was found through structural calculations using the finite element method (FEM): an adhesive that aerospace specialists developed together with the class specifically for this project and that compensates for movements of up to two centimetres. The method was only used for the front part of the superstructure; the aft part was conventionally welded to the deck. v groove edge banding router bits
Below the waterline, a flexible hull structure was even desired, as this gives way and prevents a sudden puncture, for example when ramming into large waves. As is usual for aluminium constructions, particular attention was paid to longitudinal stiffening to prevent torsion. This structural puzzle alone took six months of planning, while exoskeletons helped the Huisman employees with the actual welding. In the end, "Sea Eagle" was delivered in 2020 in the shadow of the pandemic, four years after the order was received. The royal Dutch shipyard, which has a 60-year tradition of working with aluminium and is based not far from the IJsselmeer, joined forces with Dykstra Naval Architects from Amsterdam, which had already worked with Huisman on the steel "Athena" (90 metres) and with other shipyards on "Hetairos" (67 metres), "Black Pearl" (106 metres) and "Koru" (127 metres).
The specifications for the super schooner matured in the client's mind while sailing around the world on his 43-metre sloop of the same name and shipyard origin. He was looking for an extremely comfortable and roomy yacht with excellent long-distance qualities to see as much of the world as possible under sail. A true tall ship interpreted in a modern way: practical, powerful and safe, but easy to handle. In the meantime, more than 45,000 nautical miles have been logged; "Sea Eagle" also cruised between the French Polynesian islands of Moorea and Bora Bora and passed the outer reef there at 22 knots.
The reason for the fast progress is the high schooner rig. Dykstra's chief designer Erik Wassen says of the rigging: "There is less impact on the environment when a ship starts quickly in a light breeze. The powerful rig geometry can be quickly adapted to the conditions for safe and effective mileage collection." Dykstra carried out CFD computer simulations and modelled tests, both in the towing tank at TU Delft and in the wind tunnel at the Wolfson Unit in Southampton.
The free passage through the Panama Canal is an ecological advantage. The 61 metre high bottleneck at the western end, the Bridge of the Americas, forces yachts without "Panamax dimensions" and with a high slip rig to lay masts or make a diversion of 8,000 miles. The three carbon palms of "Sea Eagle" increase in height aft and decrease in diameter. Our colleagues from BOOTE EXCLUSIV were able to see the quality of the laminating process for themselves during a visit to Rondal. There, the masts were created in one piece from prepregs, which were cured under vacuum and at 100 degrees Celsius and given two coats of varnish. The angular three 16 metre long booms, in which the battened mainsails are stored, took on a similar shape.
The on-board hydraulics are powerful enough to unfurl the headsail and all three mainsails at the same time without any problems - which should take no longer than with a sloop half the size. Rondal also supplied 34 winches, twelve of which rotate on deck and 22 below deck. The largest drums, for Yankee, staysail and mizzen sails, can handle tensile loads of up to 18 tonnes each. The electrical and hydraulic energy is mainly supplied by two diesel generators. In addition, each of the two 1,081-kilowatt main units from Caterpillar are used for the hydraulics. These move the 1,104-tonner at speeds of up to 22 knots via conventional shaft drives. When motoring at an economical twelve knots, 200 litres of diesel per hour rush through the pipes. Load peaks are absorbed by a powerful battery bank in the engine room amidships, while the main switchboard with power management and parallel connection for synchronising the generators regulates the uninterrupted and efficient power supply.
In its primary use, the "Sea Eagle" is not a motorised glider like the few large formats above it in the Ranking of the longest sailing yachts that push plenty of steel through the sea. At the cross, the crew unfurled over 3,500 square metres of Doyle sails. The sailmakers had to ensure smooth interaction between all three masts under a variety of sail loads - a complex task given the cloth architecture of up to eight different sails. However, running rigging is barely visible on deck: foresail sheets are immediately lowered behind the slides, and the two forward mainsheets are reeved into the superstructure via windward and leeward tackles. Only the mizzen sail runs over two head-sized rollers at the stern.
Safety is a particularly high priority on charter trips, for which guests, some of whom have no sailing experience, have been coming on board since 2023. The flybridge schooner sails Scandinavia, Scotland and the Mediterranean in summer and the Caribbean in winter. The "Sea Eagle" is currently in Stockholm - at Marine Traffic you can follow their journey.
Anyone who pays Burgess 600,000 euros per week will experience an unforgettable charter trip. Although this only covers the use of the yacht, the offer seems tempting. For comparison: motor yachts of a similar length, but with twice the interior volume, are listed for just under one million euros a week. A big difference, not to mention the consumption advantage. This is because the charter rate does not include fuel costs, catering and tips for the crew.
The dimensions of the rig are experienced most directly in the crow's nest. In the mast basket, it extends beyond the third pair of spreaders of the 60 metre high main mast. Guests sail past shrouds and stays made by the Swiss manufacturer Carbo-Link. Only the backstays are made of Kevlar at the customer's request, otherwise carbon fibres form cable diameters of up to 55 millimetres. The maximum specifications of the Dykstra designers: a rigidity of 435 meganewtons and expected working loads of 125 tonnes.
The eyes, fork terminals and the spreader end fittings integrated into the cables are made of titanium. Carbo-Link has projects with working loads of up to 500 tonnes and cable diameters of 100 millimetres in the pipeline on land - meaning that a yacht three times the size of "Sea Eagle" could be equipped with standing rigging.
It is not only the technical marvellous achievements that make up this exceptional construction. The shipyard and designer, Mark Whiteley was also awarded the interior contract, succeeded in actually creating the connection between inside and outside that is often praised in yachting. The saloon and cockpit form a single unit via a bar consisting of two horseshoe elements. The round bar is divided into two halves by a sliding glass door, which transforms the saloon into a film theatre if the weather prevents an outdoor screening on the aft deck. This is also possible in rough seas, with handrails on the sofa backs. Through the lobby and past the galley, day toilet and captain's cabin, you reach the foremost room with a dining area and plenty of lounge furniture. Towards the front, the winches and foremast attract attention, while there is a clear view to the sides. Originally, the forward part of the superstructure was also intended to be suitable for business meetings.
We were able to walk through the 1,150 gross tonnes of interior space for twelve guests and 14 crew members during construction in Vollenhove and walk down the twin staircases amidships to the guest accommodation. The two equally large master suites at the very stern were striking, although at the time they were intended for private use only. The lower deck also has three double cabins and a fitness room to starboard, which can be converted into a cabin for children, the nanny or staff.
Whiteley followed his design maxim of timeless elegance in an almost radical way. The entire interior design relies on three types of wood: Natural oak lies on the floor, ceiling and skirting boards are made of stained wenge and Alpi American Walnut is used as the main veneer - including in the bathrooms, into the front of whose washbasins and cabinets Whiteley integrated beige-coloured leather handrails at the top. In other words, the morning or evening toilet is also used here when sliding the bed, which once again emphasises the consistent multi-sail design. The striking wavy grain of the walnut veneer extends the length of the corridors and living areas horizontally and emphasises the British designer's clever and well thought-out restraint: "This yacht never stops being stylish," he concludes.
Mark Whiteley also worked out the straight-lined exterior alongside Dykstra. In the centre of the open deck areas, the long glass superstructure is complemented by a slender flybridge. Mark Whiteley explains: "The flybridge deck provides a large leisure area for owners and guests; or for those steering from one of the outside helm stations. They are designed to blend in with the surrounding superstructure. The fly is also a platform for viewing the sculptural trees, which visually reflect the rigour of the lines." The crew have been given their own deckhouse on the deck in front of the foremast, which takes them directly to the eight cabins. Aft of this is an oversized mess room and the galley on the port side.
The angular "Sea Eagle" shape contrasts with traditional tall ships with their round gates and clipper prows, such as those that adorn the only slightly longer "Gorch Fock". Erik Wassen from Dykstra categorises the hull shape from a hydrodynamic point of view: "The modern design enables a wide transom and an almost continuous waterline, which promises better sailing characteristics and fast and comfortable crossings. Due to the higher stability, the boat sails with less heel, which significantly improves comfort on board." The width of 12.30 metres, which drastically narrows one hull edge towards the waterline, ensures high dimensional stability. Due to the already large displacement, the fixed keel "only" has to be six metres deep.
The conceptualisation of the 1250-kilogram rudder led to a tendency towards oversizing. As there was no empirical data from comparable yachts, calculation models had to be used. As a result, the carbon coker plunges deep into the five metre long blade, which was subjected to the expected forces on a specially constructed test rig. Rondal also laminated optical sensors into the 220 carbon fibre layers, which provide real-time information about the load situation. This data will also benefit Royal Huisman's next sailing superlative: the Vollenhoven dream factory is working on an 85-metre-long slup, also made of aluminium.
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