Smith Board Co was started because our whole founding team are all pretty big guys, and we couldn’t find a board that was made for people our size. Originally we just wanted to make boards for bigger riders like us, but when we tried to figure out how to do that, we found there weren’t really answers to any of the questions we had. How big should we go if we’re 6 ft? 6 and a half feet? What will the trade-offs be with a bigger board? How do we know if a board is too big? 

When we couldn’t find good answers to any of these questions, we changed our goal from just building boards for bigger people, to trying to deeply understand everything that was going on when you ride. We’re engineers, so we love to put numbers and equations behind all of this, but we also want to spread the understanding behind the numbers to the whole community so there’s somewhere to go if you have questions like we did. In fact that’s the inspiration behind these articles. 

Wakesurf Board Size

The first and most obvious one, the one we started with, is board size. If you’ve ever ridden a board that’s too small for you, you probably noticed that you’re riding a bit lower and it’s harder to generate speed. In essence the board feels slower. That’s because the main effect of board size is keeping you above and on top of the water. It does so in two ways, by increasing buoyancy and increasing lift.

Buoyancy: the big player keeping you afloat

Buoyancy is the force that pushes straight up out of the water on an object that is displacing water. Think about putting a rock in a bucket of water. The rock sinks and the water rises. The displaced water wants to go somewhere, but it’s lighter than the rock so it can only go up. If the object is lighter than water, then the water that would have been displaced essentially sinks instead of the object which ‘pushes’ the object up. So if you have a bigger board, it’s displacing more water. The more water that’s displaced, the more water there is trying to sink and ‘pushing’ up against the board. That’s the buoyancy. 

Lift: Buoyancy's little cousin keeping you afloat

For the lift, a bigger board has a bigger surface area which means there is more water flowing underneath it. When flowing water comes in contact with a surface, it slows down which increases the pressure at that point of contact. That pressure ‘pushes’ up against the board generating lift. The same lift on wings that lets airplanes fly. The more surface area you have in contact with flowing water, the more points of contact there are each ‘pushing’ up against the board. So if you have more surface area, then you have more lift. 

These two things, buoyancy and lift, help keep you on top of the water. This decreases the drag that ‘pushes’ you back and in the end decreases your speed. 

So why don't we create huge boards?

So what’s the tradeoff? Why doesn’t everyone just get the biggest board they can so they can get more lift and more buoyancy? Well at some point the board get’s big enough that you have a whole lot of forces that are pushing up against that board which makes turning harder and harder. Think about when you turn into the wave. You weight your toes and dip that side farther into the water. If you put more pressure on the back of the board than the front, then the board turns at an angle and you move in the direction of that angle. It’s more complicated, but for the most part that’s it. You dig one side of the board in and turn that way. 

But if you’re riding a board that’s too big, then you have to push much harder against all that lift and buoyancy to get the same amount of the board in the water. If you’re big enough for the board, then that’s not a big issue because you have more weight to push around. If a heavier person leans over their toes the same amount as a lighter person, the heavier person will be pushing down with more force. Even for the exact same movement. They just have more weight. 

Finding the sweet spot in board size

The big takeaway here is that there’s a sweet spot when it comes to finding the right size board for your body. If you go too small, you’re going to sink too far into the water, and you’ll find it hard to build up speed. But if you go too big, you’ll have to work much harder to maneuver the board in any way. Currently there’s no definitive guide on what size board you should get based on your weight, height or any other factors. There's no where to find that if you’re 180 pounds you should get a 50” board, if you’re 150 pounds you should get a 48” board. That doesn’t exist yet, and it’s not quite as simple as that anyway, but here at SBC we’re working to build and pass along an understanding of these things so that everyone can choose the best board for them. Hopefully by reading this article and understanding the physics behind these choices, you can get an idea of what to consider and why it’s important.