Should You Get a Stepped Hull Boat?
S teps in the hull bottoms of boats are nothing new, with the concept dating back to the early designs of planing hull powerboats. Steps are, however, one of the most misunderstood hull design features on the water today.
Inaccurate information, often published in brochures and marketing materials, combined with the fact that different steps can act differently, has led to a sea of misinformation. Let’s set the record straight. Then we’ll take a look at the ups and downs of steps, which you’ll need to think about before you consider purchasing a boat with a stepped hull.
The most common fallacy out there is that steps are designed to suck air in from the hullsides, creating oodles of bubbles that help break the hull’s adhesion to the water as it moves forward. How did this concept become so widespread? Because several manufacturers built stepped-bottom boats (particularly in the early to mid 2000s) that did exactly this.
These steps were little more than poorly thought-out channels running from the hullsides to the center of the boat, in a V-shape (with the point of the V facing forward). Boats built with these steps often enjoyed a very slight speed and efficiency boost. They also fed air—those bubbles running underneath the hull—directly to the outboard engine cooling water intakes, leading to more than a few blown powerheads. In some cases, “breaking the adhesion” made for extremely slippery hulls that were difficult to handle, slid in turns, or even spun out.
These hulls can be dangerous.
Another non-step that’s been sold as a step is what would be better described as a hullside notch. In some cases they may be present only in the boat’s chine, and in others, they may run a foot or two in from the hullsides. These tend to have little effect on a boat’s performance, and seem to have been nothing more than the brainchild of marketers who wanted to claim that their boats were incorporating the latest and greatest in design technology.
There have also been a few rather hare-brained step designs attempted through the years, including curved steps, steps running fore and aft, and steps that are fed by ram vents located abovedecks. Most of these have little to no effect on the boat’s running characteristics and it’s pretty rare to encounter oddballs like this these days, but if you look at a lot of boats occasionally you’ll see one.
Now that we know how a bad step works, let’s look at a good one. A properly designed step is a transition in hull height from one level to a higher level, aft of the step. As the boat moves through the water an area of low pressure naturally forms just aft of the transition. This area of low pressure draws in air from the notches in the hullsides, and creates a pocket of air between the hull bottom and the water. Just how big this pocket is depends on the specific design of the step.
Some builders incorporate multiple steps, to create multiple pockets. And anywhere the bottom of the boat is touching air instead of water, drag gets reduced. Net result? A well-designed step—which is not at all easy to create and requires time, experimentation, and cost to develop—can net a 10 to 15 percent increase in efficiency without creating any negative handling traits.
Might a boat with a stepped hull be right for you? That question depends more on the boat, and less on the step. A savvy boat-buyer won’t choose a boat because it has a step, nor will he avoid one for the same reason.
One caveat: those “bad” steps from a decade or so ago should be avoided. You’ll know if a boat has one when you take it for a sea trial, and it feels like the bottom is constantly in danger of breaking loose or skidding when you make turns. We should also note that most of the worst designs have been culled out by the marketplace through the years, and the vast majority of the boats in production with steps today are well thought-out, thoroughly tested and vetted designs.
Remember that steps are only one variable in a boat’s design. Let’s say, for example, that you’re looking at a well-designed stepped-bottom 26-foot center console that weighs 4,800 pounds, has an 8-foot 6-inch beam, and 24 degrees of transom deadrise. You’re also looking at a 26-foot center console that doesn’t have a step, weighs 4,000 pounds, has an 8-foot beam, and has 16 degrees of deadrise.
Because the boat with the step weighs more, has more beam, and has a steeper transom deadrise angle, it may post identical or even worse efficiency numbers than the boat without a step. In this case, the step’s gains are merely making up for other deficiencies in the design. But these deficiencies also have advantages; the heavy weight helps punch through waves, the wider beam provides more room, and the steeper deadrise has a smoother ride.
The bottom line? All of these different factors need to be taken into account when you’re trying to decide which of these boats will be best for your needs. No single characteristic such as a step should be considered a make-or-break feature.
More than anything else, multiple sea trials on different boats will help you get a feel for how a boat’s “complete package” performs, and whether or not any one specific boat is best for your needs. In any case, the next time you’re looking at a stepped-hull boat you’ll know exactly how that step works—and hopefully, your boat-buying decision will be that much easier to make.
Email Lenny Rudow at
Email Lenny Rudow at ContactUs@fishgame.com