The Dufour Nautitech 435
Blue Water Cruising January 1999
Long a pacesetter in monohull prduction, this French builder now boasts five multihulls in its line of voyaging boats, including the lightweight and sensible 435.
by Quentin Warren
The cruising multihull revolution that changed the profile of so many major sailboat shows at the outset of this decade resulted in a new and seemingly endless generation of production-fabricated catamarans and trimarans. Plywood homebuilt one-offs the multihull staple in most harbors 20 years ago, now languish in the tall grass at the edges of boatyards and backyards, replaced by legions of fiberglass twin and triple-hulled fare.
Established manufacturers - Performance Cruising in the States, for example, builder of the popular Gemini line of inshore cruising cats, and U. K. based Prout Catamarans, builder of a long line of ocean-cruising cats up to 50 feet in length - certainly had their feet in the door from the start. But leading the charge most conspicuously in recent years have been the French Lagoon, Privilege, Fontaine Pajot, and now a revitalized Dufour enjoy a commanding market presence.
Dufour, long a monohull pacesetter in Europe, stepped up to the production cruising cat plate relatively recently and now offers five models in their Nautitech line ranging from 39 to 98 ( not a typo! ) feet. Perhaps the most sensible of the group in the context of Blue Water Sailing and the magazine's readership is the Nautitech 435, launched in 1996.
Will she go fast ?
The French obsession with speed and performance offshore has infiltrated this vessel and breaks it apart from comparable cruising cats, especially those non-French, whose directives are aimed more at amenity and payload. This is not to say that the 435 is spartan - anything but. It is to say that the Mortain & Mavrikios design achieves a workable blend of hull configuration, buoyancy, wetted surface and horsepower, without reneging on a healthy measure of creature comfort.
The 435 bows sport very fine, razorlike entries, with enough waterline beam and volume in each hull as you work your way aft to float the boat effectively. The mistake made in many cruising cat designs is the follow the lead of displacement monohulls and include way too much hull volume, purely to carry a lot of people and a lot of stuff.
This works fine when you're plugged in at the dock, and it works fine in big, heavy-ballasted monohulls, but it wrecks performance in a planing cat. No matter how you cut it, you can't load these machines up and expect them to sail in the way that multihulls are advertised to sail. Submersion kills speed.
In the same breath, you can't turn a cruising cat's hulls into a pair of meager rails and enjoy instant performance. You do that on a racing cat. You need form and volume to keep the boat on its lines, to let it accept a month's worth of provisioning without sinking three inches. With fine bows and judicious volume, Alain Mortain and Yiannis Mavikios have provided solutions - as much for the boat through the water as for the crew in the saloon.
Bride-deck clearance is a generous 2'7", more than average for this type of vessel, which keeps waves slapping and boat pounding to a minimum. Longish fin keels abet tracking without contributing to excessive draft; these are fixed under the hulls but remain separate and sacrificial, able to come away without destroying the integrity of the boat should the water go thin and the vessel nudge the planet inadvertently. Spade rudders well aft are supported on stainless stocks run through self-aligning bearings.
Dufour addresses the weight-saving issue at the construction stage Hulls and deck are entirely vacuum-bagged, built as GRP sandwiches using closed-cell PVC foam core and a calculated assortment of bidirectional and tridirectional fiberglass cloths. Watertight compartments at the bows and sterns are foam-filled and act as practical crash boxes. Main structural bulkheads are epoxy-strengthened marine plywood, bonded to hulls and deck.
Conservative jets
Powering the 435 is a medium-tall fractional sloop rig with an enormously roachy mainsail and a fairly benign jib. Without a permanent backstay to bollix up the stern, catamaran mains can afford to be so configured, and with full battens and a traveler that takes advantage of the boat's 20-foot beam, it becomes a very effective foil. The SA/D number tips in at around 23.9 - conservative for a performance-oriented cruising multihull. Likewise, a Bruce Number of 1.18 points to a catamaran with fairly average power. However, with a D/L mark of 113 and with the advantages gained by clean hulls as discussed above, it would be erroneous to call this Nautitech underspec'd, especially in the context of blue water sailing.
Many would argue that horsepower is secondary to seakindliness in the big scheme of things offshore. The 435 with its fine bows should be adept et piercing through waves. The high bride-deck should clear all but the most insistent seas. With deepest sections amidship and ample underwater foils, steering and tracking are enhanced. Overall beam at nearly 50 percent of LOA should keep the vessel firmly on her feet. Indeed, the development of a moderate sailplan only serves to control further the heeling forces encountered in windy conditions.
Accommodation
As accommodations go, the 435 offers no real surprises. As is typical for this genre of cat, the bridgedeck carries a moderate-size lounging cockpit just aft of a generous main saloon. Dual steering stations inhabit the sterns, outboard. Integrated into the saloon area are the galley and nav-station, which leaves room in the hulls for private quarters. You can order the boat with up to four sleeping compartments and four heads. The fewer the better, however, as far as we're concerned. Less weight, fewer systems, fewer headaches (literally and figuratively). In fact, perhaps the most sensible layout available is what Dufour calls the " Prestige " version - an owner's hull to starboard with a big stateroom aft and dressing area plus head forward, and a secondary hull to port with another stateroom, a smaller head, a "technical room" and crew's quarters forward.
Blue Water thoughts
As noted, one of the biggest problems facing cruising catamarans - especially those forced to submit to the common denominator dictated by mass production - is weight. Where offshore racing mutilhullers can forgo amenity and payload, offshore voyagers must relent and carry along reasonable equipment and stores. The conundrum has frustrated the cruising multihull sector for ages.
The Nautitech 435 is not immune to this caveat, but the design gives the boat a noteworthy chance at good performance in a voyaging scenario. We have been aboard the 435 in coastal conditions and can attest to its featherlike response at the helm, eager acceleration, and good turn of speed. The design aims at this; Dufour's construction backs it up.
Nonetheless, you can't take it all with you aboard a multi. Those who attempt to bury one of these boats with gear will pay the price in sluggish performance. The compromise is simply a matter of hydrodynamics. The Nautitech is worth looking at because it appears to reduce the penalty to a minimum.
This article was written by Quentin Warren and published in the January 1999 edition of Blue Water Cruising. Pictures from the article have not been reproduced in the reading room
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