Stepped bottoms have added many benefits to a boat's performance, mostly increased speed and fuel economy. But rarely have you heard that they benefit a boat's handling. Why? Steps force air beneath the boat's hull, which can disrupt the hull's adhesion to the water. Less adhesion equals less maneuverability.
Or so they say. While developing its new 38 ZR for a return to offshore racing, Donzi consulted Jim Caldwell, who was instrumental in designing the first stepped hulls for Fountain. Donzi claims that Caldwell's new design, called Fluid Diversion, improves a stepped-hull boat's handling by diverting water away from certain sections, or pressure points, on its running surface. As you initiate a turn, water is pushed away from the bottom of the inboard side of the hull, resulting in more stability.
The 38 ZR's two steps are approximately 1" tall and run aft from the chine to the keel. The deadrise varies in each of the boat's three running surfaces-ahead of the front step, between the steps, and abaft the second step-to aid in water diversion. The majority of the displacement is on the third running surface. At 85 mph, 14 square inches of the forward bottom section contact the water. Amidships, the area grows to about 33 square inches, and in the aft bottom, the contact area is 60 square inches. For lateral stability, the 38 ZR's bottom has a V-pad about 1'3" wide with varying side heights depending on the location in the bottom.
The Highs: Lower profile and low center of gravity give the driver a better feel for the boat. F-16 canopies, bucket seats, and a power footrest provide exceptional comfort. Aft deck boxes provide needed stowage capacity.
The Lows: All that engine hatch space and no upholstery for bikini-clad babes to lay on. Needs gas struts on locker hatches abaft bench seat. Too pricey for stock 500s. No portable head.
Does it work? During my test, I made rapid-fire slalom passes at 40, 50, and 60 mph. Quick directional changes often upend a stepped hull, but the 38 ZR tracked through cleanly and never bobbled. At 70 mph, I mimicked a three-buoy turn that you would take in an offshore race and the boat held its line perfectly. As I completed the maneuver, I hit the gas and imagined myself heading for the checkered flag.
What few waves I encountered were dismissed without so much as a flinch and when we cranked up the 470-hp Mercury Racing HP500EFI Bravo XZs, we hit 85.8 mph at 5200 rpm. In subsequent runs at Mercury's Lake X test facility, after some drive-height adjustments, Donzi said it kicked up the top speed to 88 mph.
The only other sit-down offshore go-fast this size is the Cigarette 36 Gladiator ($240,250 with twin HP500EFI Bravo XZs), which runs in the low 90-mph range. The 38 ZR is 1' longer, 2" wider, 900 pounds heavier, and has 5" more freeboard so passengers sit deeper in the boat, which makes them feel more secure in rough water.
Low Rider. The 38 ZR has a low center of gravity, which contributes to how well it handles. Not only are the fuel tanks in the belly of the boat, but Donzi runs all the wire harnesses and cables, which can weigh hundreds of pounds, under the cockpit decking in PVC tubes. Access them all in the engine compartment simply by lifting out removable sections of decking. Although I liked the racy style of the lightweight manual engine hatch that rises on twin gas struts and latches when closed, for a pleasureboat, I'd prefer a power hatch.
Because Donzi also offers the 38 ZR with staggered engine installations, the boat has an enormous engine compartment. The engines in our test boat were mounted tight against the transom on aluminum L-angles bolted through the stringers with backing plates. This left at least 5' of space forward. The only accessories mounted forward in the engine compartment are the battery switch panels and the automatic fire suppression system on the bulkhead. Trim pumps are mounted on the outboard stringers on each side. For easy cleanups and a squeaky clean look, the bilge is finished in Awlgrip.
Beneath the Awlgrip, the 38 ZR is built with 10 perimeter bulkheads and stringers formed out of ATC closed-cell foam and then sandwiched in Kevlar. For added strength, the bulkheads are installed crash style, which means they form a point at the keel and taper aft out to the hullsides. If the boat stuffs into a wave, the shape of the bulkheads helps support the hull at the point of impact.
Lamination on the 38 ZR consists of alternating layers of Kevlar and S-glass with vinylester resin. Donzi uses Kevlar instead of coring in the bottom to keep the hull strong, light, and more durable. To ensure proper curing, the hull and deck sit in the mold for two weeks, then are attached in a shoebox-style joint that's bonded on the outside with Dexter chemical sealant, on the inside with three layers of Kevlar and one layer of S-glass, and then through-bolted. The rubrail is also through-bolted. Cigarette attaches its hull and deck in a butt-fit joint that is glassed over inside and out. It looks cool, but without a rubrail to protect it, the gel coat will get damaged during hard docking.
Safe and Sound. When I used to race offshore, I preferred to sit behind the wheel rather than stand. I was reminded of this as I climbed behind the wheel of the 38 ZR. The high-backed bucket seats that recline five degrees and power footrests felt comfortable and secure, and the quarter F-16 canopies blocked the wind.
In the race layout, the 38 ZR has two buckets up front with a starboard helm and port throttleman's position with controls in the center. The pleasureboat version I tested is set up for one person to drive and throttle, or for two people to operate. What's smart is that the steering wheel is to port, so when I ran solo, I could work the Latham controls with my right hand. Even when a throttleman takes control of the sticks from the starboard seat, he's throttling with his right hand. The optional second set of levers ($1,657) is tucked into a cleanly finished coaming box in the starboard inwale.
Behind the quarter canopies, the dash is finished in matte black to kill glare, and ahead of each bucket seat is a compass. The helm to port has a full complement of Gaffrig Monster Series gauges, including a 120-mph speedometer. The gauges are separated by engine in columns on each side of the steering wheel. To starboard, the throttleman's dash also has a duplicate set of instruments.
The Cigarette has an open bench across the back, but the 38 ZR has individual buckets for three. Pay the extra $1,871 for the powder-coated aluminum footrests, pistol-grip style grabhandles in the armrests between the seats, and grabrails on the inwales-your backseat passengers will thank you. In addition to the lockers beneath the aft seat cushions, a pair between the bench seat and the engine hatch provide needed space for fenders and other gear. Gunwale trays forward of the back seats are ideal for docklines. Cigarette's only stowage is in the bench seat base and in a glovebox in the port dash.
Cigarette outdoes the 38 ZR with its upholstered engine hatch. The 38 ZR's hatch provides exceptional ventilation, but I prefer a padded top to stretch out on.
On the 38 ZR's deck, a pair of hatches that are finished on the underside provide access to check on the hull or to inspect dash wiring, which was squeaky clean.
Last Word. Stepping up to the plate brings maneuverability and speed.
LOA..............38'1" ** **
Draft (max.)..3' ** **
Displacement (lbs., approx.)........8,700
Transom deadrise........22° ** **
Bridge clearance.......4'6" ** **
Minimum cockpit depth...........3'2"
Fuel capacity (gal.)............256 ** **
Price (w/standard power).....$329,929
Price (w/test power).....$329,929
Standard power Twin 470-hp Mercury Racing HP500EFI Bravo XZ V-8 gasoline stern drives.
Optional power Twin gasoline stern drives to 2,000 hp total.
Test boat power Twin 470-hp Mercury Racing HP500EFI Bravo XZ ITS V-8 gasoline stern drives with 502 cid, 4.47" bore x 4.0" stroke, swinging 15 ¼ " x 31" four-bladed ss props through 1.5:1 reductions.
Standard equipment (major items) Integrated navigation lights w/flush lenses; recessed ss deck rail; twin F-16 quarter canopies; Gaffrig Platinum Series Monster gauges; Latham Marine controls with trim on throttles; hydraulic steering.