Home . Articles . Boats . Perry on Design . Andrews 72

Andrews 72

1998 February 6

Performace cruiserr

This spectacular design from Alan Andrews was built by Scorpio Yachts in Exeter, Ontario, for an experienced Great Lakes couple who wanted a big, fast boat that could be sailed by a small crew.

All efforts were made to build an ultralight boat, including the use of carbon fiber skins over a Divinycell foam core. Gougeon Pro-Set epoxy was used throughout the whole structure and post cured at an elevated temperature after all the bonding work was completed. The entire interior is composite panels painted white and trimmed with solid mahogany, Herreshoff style. Traditional-looking deck beams are carbon fiber over foam.

It's immediately obvious that this boat is good-looking, from any angle. The ultradelicate sweep to the sheer combines with the low wedge of the cabintrunk to give us a very contemporary-looking yacht in the classic style established by the Swan line. There is not an ugly line on this entire design. The simplicity of the deck lines are as effective as a frugal four-note symphonic theme. Nobody said it had to be complicated to be good.

With 71.5 feet LOA to work with and one couple to make comfy, Alan had no problem designing a great interior layout. The owner's stateroom is almost palatial with a settee opposite the large double berth, a desk and an adjoining head with tub. The saloon features a huge dinette with centerline seat. A pilot berth is outboard of the port settee. The galley has my name all over it: "Braised veal chops for dinner tonight." The nav station opposite the galley is also copiously proportioned and the wet locker has enough room in it to actually allow the wet gear to dry.

Aft, there are two nearly mirror-image stateroom-head combinations. They share a centerline shower stall. If you study the layout carefully, you will note two ladders aft that fold away against the bulkhead to allow access to the deck from the aft cabins. There is certainly no shortage of locker space. This boat could accommodate three couples comfortably and with an unusual amount of privacy. Ventilation comes partially from built-in Dorade boxes that use the corner of the cabintrunk as part of their water trap. Gary Mull was the first designer who I remember using these. Gary called them "sunshine boxes." They save both weight and windage.

The sail plan shows a very tall, multiple-spreader rig (spreaders not shown) on a carbon fiber spar built by Offshore Spars. The total headsail inventory will be one 130-percent furling jib, one asymmetrical chute and a staysail added for heavy weather. Note that the headstay tack is well aft of the bow, allowing the asymmetrical chute to tack to the stem well ahead of the headstay-and not requiring a bowsprit. The SA/D is an aggressive 30.95.

With a D/L of 70.98, I think we can safely call this design a ULDB. A waterline length of 62.6 feet and a 140-horsepower Yanmar give the boat an effortless 10 knots under power and I would think that, with some retuning of the prop's pitch, you would see speeds in excess of 10 knots. We have gone from a time, 20 years ago, when 6.5 knots was a healthy speed under power for any sailboat to today, where we want every tenth of a knot we can get out of our boats under power. The underlining philosophy is that motoring is a drag so let's get it over with as fast as possible.

We are very lucky this month. I called Alan and asked him to provide us with hull design data that most articles are not privy to. "Give us the meat, Alan." The half angle of entry of Attitude is 12.6 degrees. You get this number by measuring the angle between the DWL and the centerline. Twenty-five years ago, when I designed the Valiant 40, I thought I was getting radical for a cruising boat when I used a half angle of entry of 18 degrees. Attitude has a very fine entry and you can be assured that this boat will knife through the water. Look at any of today's fastest boats. Bow waves are well back on the hull and there is no evidence of any vertical flow or "mushing" bow wave. The prismatic coefficient is a textbook .54. The midsection shows an attractive shape with no deadrise (tangent at centerline) and a rather soft turn at the bilge. The BWL is moderate.

The keel is a 9-foot-draft fin with a bulb and wings. Alan relied upon Dave Egan of Egan Tech to optimize the keel design. Dave uses Computational Fluid Dynamic analysis to refine fin, bulb and wing geometries. The bulb is a horizontally squashed shape more radiused on the upper half and more elliptical on the lower half for a lower center of gravity. The wings have an average chord length of 10 inches and are a highly cambered asymmetrical wing section in a slightly nose-down configuration. Total span of both wings is 10.26 feet. The marked dyhedral angle is similar to the wings on the New Zealand America's Cup winner. The target in this exercise was to develop an overall keel configuration that would offer the least amount of drag in the downwind condition while preserving low VCG and upwind lift. The rudder has 16-percent balance area and a near-vertical rudder post to relieve helm pressure at high heeling angles.

Alan Andrews has quietly become one of the most successful race boat designers in the United States. His projects, ranging from Whitbread boats to Transpac record holders, have always been state-of-the-art fast and, more importantly, predictable winners. The dark blue-hulled Attitude shows that Alan has brought both the performance and aesthetic elements together with extraordinary results.