The Physics of Wakeboard and Waterski
Soaring across the water’s surface may feel magical, but there’s nothing mystical going on – it’s all about you, your equipment, and the boat that is leading you on.
In other words, it’s a question of science – as with pretty much anything. It’s about finding the perfect stance, getting that tension in the rope the right way, and creating the ideal wave for whoever’s turn it is to ride it.
For that reason, wakeboard and waterski share a lot of similarities. While they look (and feel) very different from one another, they’re underpinned by the same key skills and principles. As two of the most popular tow sports out there, a lot of research has been invested into them from sports engineers and scientists looking to perfect every element, and give watersports enthusiasts and professionals the best time out on the water.
But what do you need to understand about the physics of wakeboarding and waterskiing? As much as you want – but knowing the basics of theory is a great complement to practical learning, so get out your pen and paper and take advantage of our crash course in tow sports…
How come wakeboarders stay on the surface of the water?
The short answer: as the boat gains speed, so does the wakeboarder attached to it. As speed increases, so does downforce – and, correspondingly, thrust. Thrust pushes the board (and the person on it) to the surface and, provided they don’t slow down too much (or tilt the board down), they’ll stay up.
When you begin, you start off in the water. The wakeboard is a very buoyant piece of equipment, so you will feel your feet rising up toward the surface as soon as you get into the water. At this point, you can relax with your head, knees, feet, and board all above the waterline.
Then, when you’re ready, the boat will start to pull off and you’ll feel a growing tension in the rope. It’s important to let the rope do the work here, and not pull back against it in an attempt to heave yourself upright.
Let the boat drag you gradually to your feet – knees bent, arms straight and relaxed. This is where physics really takes over, and the buoyancy of the board combines with Newton’s Third Law to get your feet, your legs, and then the rest of your body up. It doesn’t take a huge amount of upper body strength – just an awareness of what needs to happen in order for you to get started. It’s one of the best watersports for complete beginners.
The story is the same for waterski, although the board is replaced with one or two skis. When the skis are angled up toward the surface, this creates downforce – and, because actions are accompanied by an equal and opposite reaction, upward thrust is also created. The water is pushed down and, accordingly, the skis are pushed up.
How Do Tow Sports Overcome Gravity?
The short answer: when the weight of the water pushing up on the board is higher than the ‘weight’ or force of gravity, wakeboarders and wakerskiers will be able to find their feet on the water’s surface.
It may sound like an obvious point to make, but tow sports don’t work without the boat – or speed – which is why there will always be a big difference between surfing and wakeboarding. While surfers use the momentum of real waves to remain upright on the water, tow sports rely on the wake (the long wave) created by the boat in order to generate those complementary forces of downforce and thrust.
If you were to try to stand still on your wakeboard, you’d wind up back down in the water – even though it’s buoyant. Surfboards have a larger volume, which means the surfer’s weight is balanced by the upwards pressure being exerted by the water beneath it…hence, they can sit on it without sinking it, even when it’s barely moving.
Wakeboards and waterskis have a much lower volume so, if you let go of the rope, you’ll wind up right back where you started – on your back, with your feet up in the air.
This is where the ‘tow’ in tow sports really becomes important. While wakesurfers can let go of the rope and ride the wake in much the same way that surfers ride ocean waves, wakeboarders and waterskiers need to hold onto that rope.
It takes some mental gymnastics and physical strength, but it’s also a lot of fun – one of the reasons why it’s great to get your kids into watersports.
You don’t need to stand in front of a blackboard, drawing complex diagrams and mathematical equations to get good at wakeboarding, but it can help if you understand the basic principles behind a wakeboarder’s ability to stand up – and stay up – as they move through the water. Watersports take a powerful connection between mind and body, so focus more on creating that harmony – not memorizing Newton’s third law…