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Getting Up to Speed

Everything you need to know about going really fast on a surfboard

| posted on August 26, 2013
As surfboards move through water, air bubbles collect around the fins, creating drag. Photo: Glaser

As surfboards move through water, air bubbles collect around the fins creating drag. Photo: Glaser

Aaron Perry is a San Francisco-based surfer who makes boats. Not the kind of boats that T-Pain and friends used to so thoroughly enjoy, but the kind that use cutting edge research and technology to move at incredible speeds through water. As the Design Engineer for the ORACLE boat racing team as well as an avid Ocean Beach surfer, Perry knows a thing or two about going fast. While working on our September issue’s cover story, “Unlimited Speed”, about searching for the uppermost limits of surfboard speed, I decided to ask Perry for a crash course in hydrodynamics. Here are the CliffsNotes:

Fins Give Control, But Create Drag
“When it comes to the drag of fins, or any body moving through water, there are different categories. First you’ve got form drag, which is the shape of the foil itself. Some shapes create more drag than others, but there is a generic set of foils developed by NASA called NACA airfoil, which have been shown to produce minimum drag. Right now I doubt that surfboard fins are matching NACA airfoil shapes, so drag could probably be reduced there. On the other hand, with surfboard fins the goal isn’t always maximum speed in a straight line. The most drag resistant foil might allow more speed, but could negatively impact maneuverability. Another factor for surfboard fins is fin friction, which comes from how polished the surface is, but the biggest factor on a surfboard fin is ventilation. That’s when you see underwater shots of guys doing big turns and they have a huge bubble of air that’s trailing on a fin, which is creating drag.”

Finless Is Faster
“If you took the fins completely out of the equation on a surfboard, you would get less drag for sure. I’ve seen some videos of guys like Derek Hynd on those boards moving very fast, but you give up so much in terms of maneuverability. Many kite boards are finless but have a side cut [symmetrical indentations in the plan line] much like those surfboards, and with that you can get a lot of grip on the water even without fins. Your ability to do abrupt turns will obviously be compromised though.”

What Works for Golf Balls Does Not Apply to Surfboards
“I’ve heard people talk about how textured surfaces could increase speed through water, much like the surface of a golf ball through air, but there isn’t any hard evidence to suggest that is true. I was involved with a program where we placed plates of steel sanded to varying degrees into a towing tank to see the differences in drag, but we didn’t see any change. I’ve heard many conflicting views on surface texture, but we’ve never seen any evidence of it working better. In boat racing, we polish everything until it’s pretty much a mirror.”

If You Go Really, Really, Ridiculously Fast, Cavitation May Occur
“Cavitation happens at really high speeds when the pressure is low enough in the fluid around a foil for it to vaporize, which in surfing would mean the water vaporizing around the fins. In the sailing world, it’s pretty rare until you get up to 50 miles per hour. When this happens, it causes vibration that slows you down, but it would be very difficult for a surfer to reach speeds that would actually cause cavitation in the fins. Perhaps if you are a big-wave surfer, you might find a wave that would allow you to reach those speeds.”

There Is a Speed Ceiling
“You can minimize drag but you can’t escape it. Think of a skydiver in free fall: at a certain point, the air resistance is going to cause them to reach terminal velocity, and further acceleration is not possible. In sailing, or surfing, when you calculate the drag of any surfaces above the water, plus any surfaces below the water, that dictates your maximum speed. You can try to reduce the dragging components above and below the water to push that threshold higher by getting rid of the leash, changing the fins, manipulating the bottom surface of the board, but there will always be some drag working against you.”

We’re Probably a Lot Slower Than We Think
“I was talking to someone who did speed sailing with wind surfboards. He said he was in an event and reached the fastest he’d ever gone, but when he got out of the water and looked at the charts he actually came in last place going thirty miles per hour. In surfing or sailing it ends up feeling like you are going much faster than you are because you’re exposed to the wind and water. When our guys are going 50 miles per hour in a racing boat, it always looks much faster than that if you are comparing it to something moving on land.”

  • TheOtherBrettSimpson

    In regards to the ‘We’re Probably a Lost Slower Than We Think’ section: How does the physics of how a wave breaks affect a surfers speed?

    Some friends and I google earthed the distance of our rides at a long left point recently and the distance travelled was .25 of a mile and the rides were 25 seconds long. Thus we calculated that we were traveling a mean speed of 36mph. Obviously at times we were going slower than 36mph (stalling/cutting back) and also faster than 36mph (driving/racing down the line), but what we really wondered was how the physics of the wave breaking (ie. water drawing off the reef, water moving up the face of the wave) influenced the speed in which our surfboards were moving across the wave.

    Is a surfers speed not as easily calculated using distance traveled and duration of ride? Would the equation be a combination of distance traveled and duration of ride plus the variable of how fast the water is moving under the board? Think in terms of the difference of a wake boarders speed compared to the speed a standing wave surfer is “traveling”.

    • .,

      Theres no way you were going 36 mph on a surfboard unless it was jaws or something

    • GP

      While surfing, you have to distinguish speed relative to land vs speed relative to the wave

    • Mark

      “some friends” yahooooooo!

  • Woody

    OtherBrett,… your math is seriously in question. Here are the world record speed holders in surfing by the way:

    In Snapper Rocks, Mick Fanning is currently the fastest surfer. The
    Australian champion recorded a maximum speed of 39,1 km/h. In second
    place, Joel Parkinson stands with 34,6 km/h. Bede Durbidge is third
    (33,6 km/h) and 10-time world champion Kelly Slater places in fourth (32
    km/h).

    Note: 39.1 km/h = 25 MPH.

    I seriously doubt you are surfing faster than these guys.

    • Roy Stuart

      What nonsense, one attempt by the asp people in relatively small waves somehow magically becomes the standard? Other people have been measuring speed too… and going faster than that but they don’t count because they are not part of the ASP hierarchy with its faultless scrutineering? I’ve reached 60kph peak speeds in weaker waves than were ridden at Snapper during that event, using the same measurement methods. Your argument is circular i.e. the ASP guys are the fastest because they must be the fastest because they are the best.

      • .,

        I’d love to see that superman. BULLSHIT

      • swearengen

        How, exactly, did you reach 60 kph (37mph) in waves with less power than that Snapper Event someone mentioned earlier?

        Mick Fanning (25mph) is still widely considered one of the fastest surfers on the planet, and you’re saying you went a good 12 miles an hour faster than he did–and in shittier surf?

        What I gather from your statment is either a) the ASP’s GPS speedometers weren’t properly calibrated, b) you’re riding some truly fucking revolutionary equipment, or c) you’re full of shit.

        Which is it?

        • Roy Stuart

          Yeah I’m riding revolutionary equipment and ‘widely considered’ is not relevant.

      • Max

        Roy to see how fast this speed looks on the water this video is a windsurf world record in 2012 and hes doing about 100kph and he’s totally flying. This is with a fully overpowered rig, flat water and the whole kit is built for max speed in blazing 80-100kph winds. Your speed at 60kph is then 60% of this guys world windsurf speed record at http://www.youtube.com/watch?v=t15LZ1Er-a8

    • Roy Stuart

      By the way Woody the maths used by OtherBrett is elementary and is correct… in reality you are just using the phrase “your math is seriously in question not because of a mathematical error but because you can’t comprehend the possibility that anyone could go faster than Mick Fanning did on one random small day at Snapper.

    • E-Z-E

      Comparing us gooks to the likes of Mick and Parko? lmfao

  • larkstan

    Woody and Roy, the math is elementary, but measuring distance traveled on a wave with google earth is likely to have significant error. And world records are determined by measuring under controlled conditions; many claim to have gone faster, and may well have, but the “record” will always be held by the person who documented and qualified his or her effort.

    • Common Sense

      Next time put a Cycling or Jogging GPS tracker in a waterproof pouch and retry?
      that will yield concrete results?
      just an idea.

      • larkstan

        Worth a try.

      • Roy Stuart

        already done.

    • Roy Stuart

      I used gps.

  • Guy

    His math might be correct but his measurements are simply not accurate enough. Using google maps to estimate .25 miles as a wave length is up for much variability. It’s a decent thought but when you get a result of 36mph you need to step back and judge wether that’s reasonable. Has anyone ever been towed behind a boat going around those speeds? I know I’ve been towed at 20 mph on a wake board and with the slightest bit of chop things a very difficult. I’ve never been near that feeling on a surfboardMost people are surfing well below 20mph on waves under 10ft.

  • Max

    With all the air moves the top speeds may be during a big air when there is no water drag.. Big down the line waves should prove really fast like J-Bay, Ulu, Cloudbreak and Chopes – be good to track the WCT at these events. The huge Cloudbreak paddle session surfing on guns looked closs to max speed..

  • TheOtherBretSimpson

    My question was more along the lines of: Does it feel like we are going faster than we are because water is actually moving in the opposite direction than we are traveling? Example: If you are surfing a standing wave, you are not traveling any distance so your speed is 0mph, but since the water is moving under the board their is a perceived speed.

  • CFD Engineer

    Someone should just ask one of the CFD engineers at Mclaren to design a board and fins and be done with it.

  • Lee Hale

    Yeah, I agree with this article. There’s been much progress in finless surfing; however, with the, etc. by CatchSurf. I’ve been riding a finless One board for some time, and I love it so much my shaper on Maui has agreed to shape it with a little different rails just past the Y Point towards the bottom of the board. Having a rail that provides cohesion when riding in the pocket is what I’m looking for. As an example, I’m changing the degrees of the rail from 35-40 up to a 45 angle in degree, because if you look at a wave in the barrel it’s a full circle, or almond shape. If you ride a board with L shaped rails, it’s probably not going to work very well. That’s why nobody does…But, if you use a nice 45 degree rail towards the tail and a performance rail towards the nose you get speed and a board that maneuvers at only 54″ in length..Please help me mine funded. http://www.gofundme.com/surfboard

  • Billy

    Anyone wakeboard, it feels like you are traveling much faster than I have ever surfed, and the boat will usually travel at approximently 25mph. Traveling over water feels muchhh faster than on land.

  • Jamii Hamlin

    I frequently use a garmin for surfski paddling and gauge my speed, distance travelled, time etc with a good degree of accuracy…….that includes catching wind waves and surfing waves themselves.
    On average downwind paddling where the white capping wind is generating the the early formation of waves, I may travel at 15-17 km/h and have short spikes of 20 -25 km/h when linking with a swell for maybe a 50-100m ride. Sometimes we play in the waves, although naturally I can’t really ride a breaking wave as easily on a surfski as a surfboard but occasionally manage to ride similarly in angle at the speed of the wave, but hardly think my speeds have every reach these claimed speed 36 mph / 57 km/h in my local beach/reefs breaks …..but have on one occasion in extremely maxed conditions of 45 knots wind and 4-6m swell had a few spikes at 40 km/h plus and a top speed of 58 km/h…I was hanging on for life and had no steering control of my 7.5 m surfski even having push the pedal flat made no difference.

    Those speeds that where recorded at Snapper where movement speeds….not entirely a true reflection of the waves traveling speed.

    It very possible to reach high speeds at Pipe, JBay Teahupoo and during big wave or tow surfing but only for short periods and doing turns at 25 km/h plus is going to take some serious leg and fins strength…and skill!

  • Mr Waha

    Wanna go fast? Ride a TOMO designs. Period.

  • Al Goodwin

    he could be going 36mph,all up. Remember the wave itself is going a good 10mph or more so that should be considered as well? A tail wind would help too

  • Jan

    or support these guys and you’ll know for sure in a few months..

    http://www.kickstarter.com/projects/activereplay/trace-the-most-advanced-activity-monitor-for-actio