In addition to the distinctive topside design of the Nordhavn 63, the aspect of her build that is even more important to her sea-keeping abilities is the construction at her very core. By that we mean her scantlings, the dimensions of all of her structural parts, such as her stringers, transverse members, and hull lamination schedule. These are details rarely discussed even by many owners of the boats. Yet, they are the fundamental basis for Nordhavns Yachts' world-ranging abilities and its prominence of the brand as one of the world's leading builders of production expedition vessels.
Building the Nordhavn 63
The Bottom Laminate.
Let's start in the bottom of the boat because that is where her core strength resides. The hull of the Nordhavn 63 is a solid laminate of fiberglass mat, cloth, woven roving and resin. There is no coring material below the waterline. This thick, solid fiberglass hull, in the opinion of Nordhavn's designer, is superior to cored hulls which have two thinner glass laminates separated by a core material such as balsa or foam. One, thick laminate is simply stronger and more puncture resistant. Since the Nordhavn 63 is a displacement boat, weight is not a super-critical factor for its builder and in any case the best place to have weight is in the bottom. We are told by the designers at Nordhavn that they generally follow the American Bureau of Shipping (ABS) standards for hull lamination schedules.
What is ABS?
The American Bureau of Shipping's core service is the provision of classification services through the development of standards called ABS rules. These rules form the basis for assessing the design and construction of new vessels and the integrity of existing vessels and marine structures.
ABS Lamination Schedule.
ABS also has rules that cover recreational vessels that are 78' (24 meters) and larger. While the Nordhavn 63 is obviously smaller so cannot carry an official ABS classification, Nordhavn tells us that it follows the ABS rules in its laminate. Nordhavn says, “The heavier scantlings to which Nordhavns are built not only enhance the overall quality and feel of the boat, they also contribute to its long-term life and resale value."
Places in the hull which will incur added stress, such as where the fin stabilizers attach to the hull are reinforced with added laminates. Nordhavn says the other areas will receive added stress such as the stem and the transom also receive extra laminates.
The Nordhavn 63 has three layers of vinylester resin as a barrier skin coat. Vinylester and epoxy are the only materials used in fiberglass hulls that stop water osmosis, which causes blistering. Because of the hydrostatic pressure of water on the bottom of a hull, if it is made with polyester resin, water will eventually penetrate the hull into core materials.
Stringers for Strength
Stringers in fiberglass yachts are typically made in a "hat section" which can be trapezoidal, rectangular or round. Nordhavn put 12 longitudinal stringers in its new 63. These stringers run the full length of the hull from the bow to the stern.
In the Nordhavn 63 the 12 stringers are 2-1/2" x 5" (6.3 cm x 12.6 cm) and are covered with five layers of woven roving and mat. All of this is in addition to the two huge, beefy stringers for the engine mounts. In addition to these 14 stringers, Nordhavn laminates in an integral lower rub rail just above the waterline which acts as yet another longitudinal stringer, making 16 in all, eight on each side of the boat.
Transverse Hull Supports
Traditionally the main transverse supports for a large fiberglass hull have been the bulkheads and floor timbers. But rugged use of boats over the years -- even those built by the most conscientious builders -- has shown that is not enough. Oil-canning, "wheezing" of the hull in and out, and wracking of the hull in arduous conditions all play havoc on bulkheads and interior structures, sometimes cracking and breaking them. Who hasn't heard creaking and groaning when punching into steep head seas even at displacement speeds?
Nordhavn says that they use as much solid FRP as possible in the bilge and engine room and that any marine grade plywood employed is sheathed in protective fiberglass.
The Deck Adds Strength
Of course, added to all of this is the boat's deck. It is chemically bonded to the hull with 3M 5200 which is now the industry standard for mating decks with hulls. This stuff is so strong the fiberglass will fail before it does we are told by some of the country's best boat builders. Nevertheless, Nordhavn says that ABS would never approve a boat with only the adhesive bonding and so it also glasses the two parts together.
Nordhavn makes sure that the hull and deck flanges to be joined are as thick as are the laminates in those parts, as prescribed by ABS. Then it puts 1/4" bolts through the flange on 6" (15 cm) centers. After that process, the inside of the joint is fiberglassed over with two layers of material.
We like this process because if there is a tiny leak between the 5200, this glass barrier will stop it. (If you have ever had a deck leak that you could not find, then you will appreciate the virtue -- and importance -- of this procedure.) The Nordhavn 63 hull should be one of the stiffest on the water.
Using Internal Structures for Strength
Over the years veteran builders like Nordhavn have gotten savvy about how to use bunks, shelving, cabinets and built-in furniture to add to hull support, by fiberglassing these internal structures to the hull, an egg crate-like internal structure is created which makes hulls much more rugged.The Nordhavn 63 even uses its fiberglass fuel and water tanks to add strength to the vessel. They are fabricated to the shape of the hull and then bonded to the interior surface of the hull with 5200 and fiberglass. They not only provide added rigidity, but also create what amounts to a second bottom where the tanks are located.
How Important is the "Core"?
Scantlings, stringers and transverse members are not particularly glamorous or exciting subjects. You will never see them mentioned in the ads or on the websites for the brands of motoryachts that populate most of the French Riviera. The buyers of these yachts have other objectives, and for the most part they do not include long-distance, owner/operator cruising. For these yacht owners, luxury, styling, status, peer-approval (or envy) and appearance are the primary factors that go into the boat-buying decision.The boaters who would consider a Nordhavn are a different breed and they have far different objectives. At root, they want a boat that can handle the worst of what Mother Nature can dish out that can't be reasonably avoided. They want a boat with a structure that is beyond concern when the going gets rough or when things go wrong. Nordhavn is not the only company building a strong "core" structure into its motoryachts, but it is one of the few brands that is actively seeking buyers who care more about a yacht's build-quality than how many ladies can sun bath on the flying bridge.
Standard and Optional Features
|Washdown: Fresh Water||Standard|
Boats More Than 30 Feet
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