NOTE: the 656zp has been redesigned as the 220LX
In HOT BOAT'S Annual Awards Issue this past April, Stingray's 656zp was named
Compact Boat of the Year for 1994. The fact that Stingray won the award was not
particularly surprising since the South Carolina-based boatbuilder has been winning
accolades for its various models for quite some time. What was surprising, however,
was the margin of its victory. Normally, Boat of the Year competitions are close.
This time, however, it was a cakewalk for the Stingray entry as the 656zp far
outdistanced its rivals and was the clear-cut winner in its class.
According to our test-team drivers, the 656zp was the sleeper of the year.."
a well-mannered family bowrider sportboat that simply didn't have any faults and did
nothing wrong, especially when it came to performance."
So how did Stingray do it? They use the same MerCruiser packages everyone else
does, and their boats are priced so reasonably that it often makes their competition
wince. So what's the secret?
Actually, it's no secret at all. In fact, the Stingray difference even has a
number - . This is how Stingray's
exclusive Z-plane hull design is registered with the U.S. Patent Office, protecting it
But let's back up for a minute and review some of the basics about vee-bottom hull
design. First of all, Stingray can't take any credit for coming up with the original
concept of the modern-day vee-bottom. That was done nearly 40 years ago by naval
architect C. Raymond Hunt, who is considered the father of the classic roe-hull. Until
Hunt came along, planing hulls of that era had a relatively shallow vee-entry at the bow
and a long, hard chine forward. Hunt changed that trend by significantly deepening the
forward sections of the hull and maintaining a constant amount of deadrise (vee) all the
way back to the transom. The result was a smoother-riding, more manageable boat in
Essentially, the typical vee-bottom is a variation of the standard-planing mono-hull.
Unlike a displacement-type hull that simply pushes water out of its way, the planing hull
achieves greater speed and more efficiency by "lifting" out of the water as it
gains speed. What happens at a certain speed is that hydrodynamic forces overcome the
static buoyant forces and the hull reacts by moving forward and up, out of the water. We
commonly refer to this condition as planing.
Once the boat is on plane, drag (friction caused by the remaining wetted hull surface)
becomes the determining factor (along with available horsepower/thrust) in how fast a boat
Most vee-bottom hulls are measured by the amount of deadrise. Deadrise is calculated
by measuring the angle on each side of the hull bottom at the transom. Imagine, if you
will, looking at your boat's transom from directly behind the boat while it is out of the
water. Next, picture a horizontal line at the lowest point of your keel running out to
each chine. The gap or angle formed by this imaginary line is measured in degrees. If the
angle is small, such as eight to ten degrees, the hull would be regarded as a shallow-vee.
If it's ten to 16 degrees, it's a full-vee. And when you begin to exceed 18 degrees up to
24, you are now talking about a hull that qualifies as a deep-vee.
As you have probably noticed, the vast majority of vee-bottoms have angular strakes
that protrude from the otherwise smooth running surface. These strakes run longitudinally,
from bow to stem, and are placed in a variety of locations depending upon the make and size
At planing speeds, strakes serve several purposes. Primarily, they are there to provide
additional lift, acting somewhat like an extra chine and helping to get more hull out of the
water, thus reducing drag and increasing overall performance. Strakes also tend to break up
the flow of water beneath the hull to eliminate some of the surface tension that develops
between the water and the bottom. Furthermore, strakes can generate tiny air pockets and
bubbles, sometimes referred to as vortices, to assist in this process.
About five years ago, Stingray was designing and building its line of family sportboats,
using this same vee-bottom technology. The boats performed well, but Stingray President Al
Fink was not completely satisfied. "We've always taken a lot of pride in the way our
boats perform," said Fink. "But to us, performance means more than just top speed.
I was looking for a way to improve the turning characteristics of our boats. Like most
vee-bottoms, there was a tendency to occasionally catch a chine in a fast corner, which can
surprise a novice driver. Our testing also indicated that it was possible to induce propeller
ventilation [slip] if too much power was applied or too sharp a turn was attempted. In both
cases, I wanted to develop a better hull design to eliminate those shortcomings."
After many months of computer-assisted engineering, the Stingray design team came up with
what they thought would be a reasonable solution in terms of a new vee-bottom hull
In a nutshell, the Z-plane hull design essentially incorporates the hull strakes into the
bottom, rather than having them appear as external appendages that have been added on after
the hull surface was completed. If you study the accompanying diagrams, you will see that the
Z-plane has only two angles instead of the conventional three found in a typical roe-bottom
with nonintegrated strakes.
Initially, it was thought that the new Z-plane design would probably sacrifice a little
top speed in order to achieve the better overall handling, especially in the turns. "We
assumed that because we were reducing the amount of lifting potential that the boat might run
a little slower," said Fink. "We never really intended that the Z-plane bottom would
give us extra miles an hour on the top end too."
As the testing phase began, it became immediately evident that Stingray was on to something
big. Not only did the boat turn better and lose the tendency to ventilate the prop, but it also
ran faster with the same amount of horsepower.
When the Stingray design team started to analyze the data, they found that the integral
Z-plane strakes were delivering an undisturbed flow of water beneath the hull and to the
propeller. What was happening was that the minuscule air bubbles and tiny vortices created by
conventional vee-bottom strakes had disappeared. And, although some hull designers feel that
aeration under the hull is an advantage in optimizing top-speed potential, Stingray was finding
that cleaner, less disturbed water flow was actually more of a benefit.
"It didn't take long for us to realize that the lack of air entrapped beneath the hull
provided a much more positive feel for the driver, both in cornering and while running at full
throttle," commented Fink. "Consequently, we got the best of everything. Our boats still
ride beautifully in the water without the need for excessive trim, and the propeller has optimum
bite to deliver maximum thrust and efficiency."
But Stingray didn't stop there. "We also recognized the fact that a notched transom design
would also enhance our performance," said Fink. "It's been proven in all types of racing
that a notch, or cavity, in front of the lower-unit gearcase will allow you to mount the drive unit
higher [more vertically out of the water] thus reducing gearcase drag and generating more
performance. And as expected, because the Z-plane design was not disturbing the water flow to the
prop, the advantage of raising the drive unit to a higher X dimension worked perfectly. Our time to
plane off was quicker and so were our full-throttle speeds."
So how does all of this relate directly to how Stingray performance compares to similar family
sportboats? The numbers don't lie. Over the past five years, Stingray has kept copious records
regarding published boat performances of all major boat brands. With almost no exception, Stingray
models have achieved the fastest top speeds with given stock engine packages in virtually every
For example, Stingray's 606 (20' bowrider) has been radar-tested at 55 mph with a stock 4.3LX
(V-6) MerCruiser. The next two closest 20-foot bowriders hit the list at 51.4 and 50.3 mph
respectively. In the 21-foot category, Stingray's 656 (21' 5"), powered by a MerCruiser 5.7L
small-block V-8, was caught at 59.3 mph by a Mercury Boat House Bulletin report. The next nearest
21-footer on the list came in at 57.6 mph, while the average performance with that particular power
plant is in the low-50-mph range. And If you want to see if the z-plane works in even larger hulls,
Stingray's 719 (23' 6") family cuddy cabin cruiser with a little 4.3LX (V-6) MerCruiser tells
the story. With that package, the 4,000 pound Stingray still makes a top speed of 44.1 mph. A check
of the official record won't show another 23-plus-foot cruiser with a 4.3LX over 40 mph.
Although mile-per-hour numbers are usually how boats are judged, Stingray has taken the time and
energy to convert some of these speed figures into actual dollar savings at the gas pump. Depending
on the models/brands used for comparison purposes, Stingray claims to save boaters with standard
5.7L stern-drive power as much as $650-$900 per year (based on 100 hours of annual operation) just
in fuel costs. The numbers become pretty significant if you boat a lot.
Maybe the Z-plane isn't quite the hull-design breakthrough that the original modern-day
vee-bottom was but it certainly has had a positive impact for Stingray owners around the world. The
next time you decide to pick on that "unassuming-looking" family boat, you better make
sure it doesn't carry the Stingray Logo. If it does, you could be in for the chase of your life.
Hot Boat Magazine