How Much Surfboard Do You Really Need?
The answer here is going to end up being surprisingly little, but let's look into the reasons why. The first thing to think about is what we need a surfboard to do -- its most fundamental job is to plane on the surface of the water. Planing means to skim across the surface of the water like a speedboat, a stone being skipped, or, of course, a surfboard. This is a different thing than floating. A container ship floats, but doesn't plane. A skipping stone planes but doesn't float. Many things, like surfboards and speedboats can do both, but it's worth noting what they look like going slow (they sit low in the water) versus what they look like going fast (they skim across the surface of the water). If you're not doing this, you're not surfing. Being able to plane depends on a couple of things. The first is the amount of surface area on your board (or boat, or skipping stone). Bigger boards have more surface area, so they plane more easily. The second is how fast you're going. The faster you go, the more easily you'll plane. Think back to the speedboat at full throttle versus stopped. The final factor in determining how well you plane is your weight. The more you weigh, the more surface area (or more speed) you'll need to keep planing. This means that a bigger surfer either needs to go faster, or he needs to get a board with more surface area.
So, what does it take to get a surfboard planing? Well, if you assume something like a "normal" weight of 180lbs, and a "normal" 6'0" shortboard, we actually have some data on this. This year at the 2011 Quiksilver Pro, they stuck a nifty gadget on some of the competing surfers that measures how fast they're going. I'm not sure this has ever been done before, and it gives us some interesting info. The fastest speed anyone recorded during the whole contest (and remember, these are the world's best pros surfing in good waves) was 41.5kph, or about 26 miles per hour. This speed was just for an instant, and the average speed on that wave was 25 kph (15mph). In fact, the average speed for all of the nine fastest waves of the whole contest was 25kph. The fastest pros in the world at one of the best venues in the world are cruising around at 15mph. Also, if you watch these guys surf, you'll see that the front half of their boards are almost never in the water. This means the amount of surface area they're using to plane is actually a lot smaller than a standard shortboard. (watch Quiksilver's fastest waves. hopefully Quiksilver leaves that link up.)
So if pros are going 15mph, how fast are we, as mere mortals, going? I don't have the same GPS device that Quiksilver was supplying at the contest, but I'd bet that in "decent" waves, most of us are probably going 8-12mph. This is obviously (since we can do it) enough to get a shortboard planing, but like the pros, skilled amateurs are keeping the nose of their boards out of the water even at these slower speeds, indicating that we don't need as much surface area as we've got, either. How little can we get away with? Luckily, we have some good examples from other sports.
Skimboarders ride boards about 4'4" x 20", and they can surf on them without much of a problem. Similarly, bodyboarders are on boards with dimensions around 3'6" x 22" and they can ride waves standing on these boards. These videos show that these average-sized waves still provide enough speed to keep these small boards up and planing. One other sport worth mentioning is wakeboarding. A wakeboard is about 4'6" x 16". Typical wakeboarding speed is about 18-20mph, but I found reference online to someone saying he's done it as slow as 8mph. If you watch wakeboard water starts, you can also see that the rider is up and planing almost immediately, probably at not more than fix or six miles an hour. We've already shown that surfers go faster than this, so it should be possible to surf on a wakeboard if you can somehow catch a wave on it (there are obvious tow-in solutions to this). On the other end of the spectrum, the faster you go, the less surface area you need. At 35-40mph, you can waterski on just the soles of your feet, with almost no planing area at all. I was careful not to include kiteboarders in this list, because their kites pull upwards as well as sideways (instead of straight sideways like a tow rope behind a boat) and make the rider effectively lighter. This is why kiteboarders can pull off crazy airs like jumping over piers. With the wind pushing his kite up, he's nearly weightless, and so he could plane on a lot less surface area that way.
So why are even 'small' surfboards so much bigger than these boards for other sports? Two reasons. One is simply fashion. We've already shown that you can surf on a bodyboard if you want to, but you don't. Why not? Your friends would laugh at you. So you content yourself to buy a 6'0" thruster and fit in with everyone else.
The second reason is a lot more important. It's because it's hard to catch waves on little boards. There are a couple of factors that influence this, but here are the two biggest: The first is position. Since a bigger board paddles faster, you can be sitting farther off the peak when you see a wave approaching, and still get into the right place to catch it before it breaks. Since a smaller board is slower, you have to be sitting closer to the peak to be able to catch the same wave. The second is reason is that bigger boards will plane at slower speeds. This means you can get up and riding on a slower part of the wave, which translates directly into being able to catch it earlier. A smaller board needs to be going faster before you can stand up, so you need to put it on a steeper part of the wave, so you you need to take off later. This second reason compounds the first. If you're sitting outside, and watching a wave roll in under you, not only can you get closer to where the wave is going to break on a bigger board, but you don't have to go as far in the first place, because you can catch the wave farther outside. This all combines to make a lot more waves accessible to you on a bigger board.
The other sports we've talked about largely avoid this problem. A skimboarder gets to literally run to catch a wave. A bodyboarder has swim fins to make up for his smaller board, and a wakeboarder has a speedboat to make his waves for him. A surfer doesn't have any of these advantages, so the best way to catch waves on a smaller board is to get very good at the skill of positioning yourself in the lineup. If you're always sitting in exactly the right spot, it doesn't matter how big or small your board is, you can catch it anyway. You'll also have to get comfortable with later takeoffs than you might be used to on a longer board. These are both problems that anyone who's switched from surfing a longboard to surfing a shortboard has had to deal with. Another alternative is to get a tow rope. There's a video of Bruce Irons being pulled into big barrels in Mexico on a 4'9" kiteboard. The tiny board actually looks like it works fantastic, it's just too small to catch those big waves without the tow ski. Bruce also showed that you could do something similar while paddling though, by surfing a 5'6" at double-overhead Backdoor. You can tell he's going really late on some of these waves, but he proves that the small board is surfable there.
So if you can position yourself correctly in the lineup, you can surf on a lot smaller board than you thought. Even a 3'6" bodyboard. You can even take it one step further than that and go bodysurfing. President Obama can catch waves in Hawaii with no board at all. My next board will be 5'5" x 19.5". I put the bottom layer of glass on it yesterday. It should be ready to ride soon. I'll let you know how it works.