WHARRAM PAHI 42: A Polynesian Catamaran

The catamaran designs that British multihull pioneer James Wharram first created for amateur boatbuilders in the mid-1960s were influenced by the boats he built and voyaged upon during the 1950s. These “Classic” designs, as Wharram termed them, feature slab-sided, double-ended, V-bottomed plywood hulls with very flat sheerlines and simple triangular sections. The hulls are joined together by solid wood beams and crude slat-planked open bridgedecks.

Wharram’s second-generation “Pahi” designs, which he started developing in the mid-1970s, still feature double-ended V-bottomed hulls, but the sections are slightly rounder and the sheerlines rise at either end in dramatically up-swept prows and sterns. The most successful of these in terms of number of boats built–and also probably the most successful of any of Wharram’s larger designs–is the Pahi 42. It is an excellent example of a no-frills do-it-yourself cruising catamaran with enough space for a family to live aboard long term.

First introduced in 1980, the Pahi 42, a.k.a. the “Captain Cook,” was the first Wharram design to include accommodations space on the bridgedeck in the form of a small low-profile pod containing a berth and/or (in some variations) a nav station. Unlike the Classic designs, which have no underwater foils other than rudders, the Pahis also have daggerboards, though these are quite shallow and are set far forward in each hull. The rudders are inboard, rather than transom-hung, set in V-shaped wells behind the aft cross-beam.

As on the Classic designs, the cross-beams are flexibly mounted to the hulls, but are lashed with rope rather than bolted on with large rubber bushings. Hull construction likewise is very simple, all in plywood, and explicitly conceived to facilitate home-building by amateurs. The frames consist of a series of flat bulkhead panels fastened to a long centerline backbone with longitudinal stringers running down either side to support the plywood skin panels. Through the main central area of each hull the bulkheads all have large cutouts in their midsections to allow room for interior accommodations space. To increase moisture and abrasion resistance the hull exteriors are sheathed in fiberglass cloth and epoxy.

As designed the Pahi 42 has a single mast and flies a loose-footed mainsail with a wishbone boom. There is also a staysail on a wishbone boom and a conventional genoa flying on a bridle over the forward beam. Many owner-builders have substituted other rigs, including Wharram’s unique gaff “wingsail” rig, where the main has a luff sleeve enveloping the mast, but conventional Marconi rigs are probably the most common. The original design also calls for a single outboard engine mounted on the stern deck to serve as auxiliary power, but many owners have engineered other arrangements, including inboard diesel engines and even electric drives.

As its light-ship D/L and SA/D ratios attest, the Pahi 42 has the potential to be a very fast performance cruiser. Wharram claims top speeds in the neighborhood of 18 knots with average cruising speeds of 9 to 12 knots. In reality, however, it probably takes an unusually attentive, disciplined sailor to achieve anything like this. The Pahi seems to be more weight sensitive than most cats and typical owners, who carry lots of stuff on their boats, report average speeds more on the order of 5 to 8 knots.

The boat also does not sail well to windward, as its daggerboards are not large enough and are not positioned properly to generate much lift. Instead they act more like trim boards and help balance the helm while sailing. They also make it difficult to tack. Most owner-builders therefore consider the boards more trouble than they’re worth and don’t install them, preferring instead to retain the extra space below for storage and accommodations. With only its V-shaped hulls to resist leeway the Pahi reportedly sails closehauled at a 60 degree angle to the wind, though performance-oriented owners who keep their boats light claim they can make progress upwind faster than other boats sailing tighter angles. A few builders have also put long fin keels on their boats and these reportedly improve windward performance to some extent.

As for its accommodations plan, the Pahi 42 has much in common with other open-bridgedeck catamarans. Except for the small pod on deck all sheltered living space is contained within the narrow hulls, which have a maximum beam of just 6 feet. The standard layout puts double berths at both ends of each hull, though many may regard the aft “doubles” as wide singles. The central part of the port hull contains a small dinette table and a large galley; the center of the starboard hull is given over to a long chart table or work bench, plus a head.

Naturally, many owner-builders have fiddled the design a bit to suit their own tastes. The most significant changes involve the deck pod. Those who crave more living space tend to enlarge it; in at least one case it has blossomed into something approaching a full-on bridgedeck saloon, which must hurt sailing performance. In other instances, in an effort to save weight and improve performance, builders have omitted the pod entirely.

The great advantage of a Pahi 42, or any Wharram cat for that matter, is its relatively low cost compared to other cats in the same size range. To obtain one new, however, you normally must build it yourself. Wharram estimates this takes between 2,500 to 3,000 hours of effort. The alternative is to buy one used, which now normally costs less than building one.

There is an active brokerage market with boats listed for sale all over the world. The best sources for listings are Wharram himself and another Brit, Scott Brown, who operates mostly online. Because Wharrams are built of plywood, even if sheathed with epoxy and glass, the most important defect to look for is simple rot. This, however, is not hard to detect and, because the boats are structurally so simple, is also not hard to repair.

Specifications

LOA: 42’0”

LWL: 34’0”

Beam: 22’0”

Draft

–Boards up: 2’1”

–Boards down: 3’6”

Displacement

–Light ship: 7,840 lbs.

–Maximum load: 14,560 lbs.

Sail area

–Working sail: 640 sq.ft.

–Maximum sail: 1,000 sq.ft.

Fuel: Variable

Water: Variable

D/L ratio

–Light ship: 89

–Maximum load: 165

SA/D ratio

–Working sail: 25.91 (light ship); 17.14 (max. load)

–Maximum sail: 40.48 (light ship); 26.78 (max. load)

Nominal hull speed

–Light ship: 11.9 knots

–Maximum load: 9.8 knots

Build cost: $70K – $120K

Typical asking prices: $40K – 100K