The science behind how wake boats create surfable waves.
Never underestimate a boater's desire for fun on the water — and boat designers' ingenuity to deliver waves of fun. Wakeboats are only growing in popularity, but watching some hotshot surfing a flat calm lake behind a boat moving 10 to 11 mph seems to defy physics — and logic. How do they make those giant waves?
There are actually four factors working together to create a wake, even if you can't see them above the waterline. Here's how it works.
Tip: Ballast systems can harbor invasive species. Particularly if you use a wakeboat in freshwater, practice “Clean, Drain, Dry” every time you pull your boat. Read “Coping With Aquatic Invasives” or visit BoatUS.org/Invasives to learn more.
The wake behind the boat is mostly attributed from water the boat has displaced. The heavier the boat, the more water displaced, the bigger the wake. A wakeboat fills its ballast tanks to increase the boat's displacement. Depending on the size of its tank, an extra 1,000 to 3,000 (a few models boast 5,000) pounds of water ballast is taken into the boat to increase the wake. Some boats have hard ballast tanks for the water (the most common), some use soft bags, others have built-in floodable cavities in the stringer system. These boats are designed to fill up or empty ballast in less than three minutes, using designated pumps for each tank — one to take in, one to pump out.
The Flow Of Water
There are now more than a dozen manufacturers building wakeboats, each with their own proprietary systems to shape wakes. Some are similar to large trim tabs that deflect water downward, but at an extreme angle to optimize downward pressure on the water. Others are a blade, wedge, or contoured plate that is designed to redirect the flow of water on one side of the boat in order to create a clean and perfectly shaped wave on the opposite side. Before these systems came about, surfers were listing their boats to one side by putting additional weight or people to the preferred surf side. Now, surfboats can be evenly weighted without the need to shift weight to change the surf side. Malibu's Surf Gate and Nautique's Surf System can both change the wave on the fly, depending on what the surfer desires. A lot of manufacturers have systems that control the size of the wave, and some even put control right into the surfer's hands with remotes or other devices that can make adjustments while they're surfing.
The boat's hull shape also plays a role in the wake shape, and each manufacturer has its own proprietary design. As a general rule, the hulls are deep-V designs with a hard keel forward that narrows at the aft corners. The angled running surface helps shape long, powerful waves. These hulls are flatter than those of typical runabouts. While a traditional flat bottom delivers rough riding at speed, naval architects and engineers find a balance to provide a smooth ride while not towing a rider. The ultimate goal is for hull designers to create bigger and crisper waves.
Moving all that displaced water takes a lot of power. Wakeboats incorporate three options for propulsion: V-drive, Volvo Penta's relatively new forward drive, and jet drive, all designed to keep a propeller away from the rider. V-drive has been around the longest and is most common, but all have their pros and cons when it comes to maneuverability at slow speeds, the quality of wake, and fuel efficiency. Regardless, to carry that extra water ballast, horsepower on a 20-foot surfboat is generally substantially higher than a typical runabout. Start at 250-hp and go up from there.
Surf systems are a recent development for wakeboats, so the owners of early wakeboat designs or traditional runabouts can boost their wakes with aftermarket products installed on their hulls. These retrofitted products work on nearly every inboard boat, and most emulate wake systems on designated wakeboats. Wakemakers.com, a marine parts distributor, is a good starting point for learning what's available for modifying your runabout, including wake creators, ballast containers, and other accessories. Mussel Mast'R from Wake-Worx is an aftermarket passive inline filtration system that helps prevent invasives from entering the tanks. For less than $200, the system can be retrofitted to any boat.