Length or Volume? A Paddling Experiment with Zouhair Belkoura

[@ThunderWizard]

Intersting. I am 60 yrs old. I've been surfing short boards for 50 years. The VO2 max info explains a lot. after age 50, I had to start surfing much higher volume boards. The main reason was because I was getting winded much more quickly than when I was younger. I have found that length does factor in a lot, but the main factor for me as a former short boarder has been volume. With a high volume board, I can surf longer and catch more waves and I believe a huge factor is because the increased volume allows me to surf and not get as winded.... Conditions also has a huge impact. Surfing in Florida, I had to have both more length and higher volume. Here in Australia, I can surf much shorter and less volume boards than in Florida. thanks for the great video

[@RobCaseXSWIM]

Wonderful point and you noted the differences in surf spots. The power behind waves does play a role in the board volume you are able to surf as well. As you know, given the same size wave, but with one being 2x the power band than another (e.g. a pipeline wave vs a trestles wave), a surfer can surf lower volume boards with the more powerful band. The way the wave hits an underwater feature like a sandbar or reef can also impact the power the surfer is able to tap into on different kinds of boards. A steeply curved wave, even at 2ft, a small, thin, low volume shortboard can generate speed on. But a mushy, soft, weak 2ft wave would be difficult to generate speed on the same board. My point is to begin to look at the waves you are surfing and determining what board to take based on the way the wave is breaking, rather than which board would be easier to paddle. Paddling technique can be learned so you can paddle any board as effectively and efficiently as the design allows. And it's so nice to have the right board on the right wave, as I'm sure you know. Volume plays a huge role there as higher volume (or designs that plane better in flat spots) holds speed through weak, flat spots on a wave. You wouldn't want that same board design in throaty Kirra or Snapper.

[@waterhound]

This has been somewhat confirmed in racing Stand Up Paddleboards. Testing was not as controlled as we were using GPS watches but our findings mirrored these. In conversations with the board designers more volume is better once the board gets to 17ft 6" (SUP). At that point adding lenght does not increase speeed but volume does as long as it does not impact width.

[@RobCaseXSWIM]

Why am I not surprised you’ve messed around with this David?! :). Epic addition to the conversation. Does it come down to the engine at that point then (i.e. the human power)?

[@timnz009]

I think a longer board paddles faster at sub planing speeds. When catching a wave you transition from a displacement waterline length determined max speed to planing speed. A shortboard transitions to planing a little faster, and has less wetted area drag when planing.

[@RobCaseXSWIM]

Right indeed. Though, we still haven't proven this yet, nor has any university. The best space for this would be in a wavepool and I attempt to get some thoughts going in another podcast episode I did - kzbin.info/www/bejne/aajVg4aabq6glck But it's hardly scientific. Just recorded it to get the minds thinking of how we could test this.

[@GustavoRaiser]

The reason why a shortboard catchs more waves above an longerboard has to do with the hydrodinamics of entering in the wave. In order to catch it, you need to put the nose down. As we know, nosing is much easier in a shortboard, because you can put pressure in the front of the board without moving your body and put the feet in right place for the pumps. Even if you dont accelerate as much in a longboard, you just put the nose down and the wave/ocean will do almost 80% of the job. In a longboard, you need to move to the front of it in order to have some inclination to get down in the wave. But, them you need to get up and move in the board so that you don't bail the board 'cause you can't recover fast enought from the drop. So, a longboard will demand a wave that is fat and won't have the same maneuverability. Your comparisson managed to have 3 boards with the same volume in different sizes, but short-fatties are about getting the best of both worlds. Enought volume to carry you easier into the waves, allowing yet to nose into the abyss and do some tricks.

[@RobCaseXSWIM]

Good points. When it comes to catching waves, it's actually a bit more about how a vessel moves from displacement to planing given where it is during the development of the wave. I wish we had better data on this - our experiment didn't get enough statistically significant data to draw any conclusions. The best way would be to test it in a pool. In this episode I dive a bit more into the catching of waves: kzbin.info/www/bejne/aajVg4aabq6glck

[@mattcorley4622]

I'm trying more long boarding living in Capitola and I feel like I struggle more than any short board I've ridden. It's paradoxical. I realized it's how I position myself during take off. I'm too deep on the long board because I feel like I can't pitch myself like my short board. It's a process that has evolved my paddling.

[@RobCaseXSWIM]

Funny you say that. Once someone is efficient on a shortboard and has balance control - true balance control, longboard paddling ends up being more difficult because there is more mass to control. Our small bodies in relation to the big board doesn’t have as large of an impact (for both paddling and riding). So just remember that. When long boarding - paddling and riding - things take more take to react.

[@rockawaysurfer5619]

This was awesome! I’ve been surfing for two years, and asking myself that question for 23 months. I’d love to see your data for wave catching. To me that’s more important than the speed paddling out.

[@RobCaseXSWIM]

Wave catching certainly is more fun than paddling out too! Thanks for the comment!

[@hrburrell7587]

Great content and conversation, interesting and informative. I will say for me at least ,100 percent that longer/ bigger boards will tire you out. I surf a 12 foot glider, paddles fast and efficient but managing that mass in the water between waves takes a lot out of you. A smaller board though not quite as fast or " efficient" burns way less energy over time.

[@RobCaseXSWIM]

I’m the same way. More mass to move around. That same mass helps with momentum but uses more energy to get started. Thanks for the comment!

[@ToledoH]

I think it is more about the way foam is distributed and the area in contact with the water. If you grab a 1metre brum pole for example, and put in the water horizontally it will sink just a few millimetres but I'd you could keep it vertically it would sink about half metre causing way more drag if you try to move it. So if you know your volume ,yeah, a longer board will paddle better because a narrow and long arrow is the most efficient way to float and cut the water compared thicker or wider board with the same volume. What you reckon?

[@RobCaseXSWIM]

There's definitely to that point. But I do know CSUSM ran a study on three different boards with the same volume, but the volume distributed differently - one with most in the tail, one with most in the middle of the board, and one with most in the nose. The results were not what they/we expected. There was no statistically significant difference in the surfers' oxygen uptake. Meaning, it didn't matter where the volume was placed. That being said, if the difference was more substantial, meaning we spread it over the length, then yes, we should see a difference. The main takeaway from our experiment was that length clearly makes a difference, and the key reason why is that length reduces three forms of drag - wave drag, frontal drag, and form drag. Whereas changing volume only impacts just form drag. Wave and frontal drag increase 8x when speed is doubled while form drag only increases 4x when speed is doubled. So makes sense why reducing frontal and wave drag make such a huge difference.

[@AlleyTrashBoards]

I love how bigger boards paddle, but when I get up I want a smaller board. But at the end of the day, it all depends on the wave I’m surfing. I want something small and nimble for a steep heavy wave, but more girth for those slow fat rolling waves.

[@RobCaseXSWIM]

Agreed. I hate to preach, but paddling technique bridges that gap - being able to paddle any board efficiently with low energy use so you can ride smaller boards when you want to. Or a button on the board that converts a longboard into a shortboard during steep sections and then back into a longboard for fat slow sections! That would be sick.

[@danielbarbieri8199]

Interesting... I think the paddle speed is the key element that makes everything. The determinant factor : depending on the speed you can paddle, will make volume or lenght more efficient.

[@RobCaseXSWIM]

Thanks for the thought. Velocity the surfer moves will be the result of several things - technique, length, volume, design, stroke rate, and fitness. I’m not sure if you mean stroke rate when you say “paddling speed” but if so, yes, that will make an impact. It’s not the only determinant but does indeed impact the resulting velocity.

[@bsmbB]

Less rocker paddles better. A longer board has "less" rocker even if it has the "same" nose and tail rocker as a shorter board because the curve is bigger so it has less rocker at the same length interval as the shorter board.

[@RobCaseXSWIM]

In theory I'm right there with you, but I haven't seen any studies proving that. Maybe that'll be the next experiment we do.

[@Oswood1010]

Very interesting 🙂👌would you say the same applies to catching waves and ride them!?

[@RobCaseXSWIM]

Can't say that yet. Our ocean part of this experiment didn't get enough data. Anecdotally, Zouhair and I caught more waves on the shortboard than the longboard which is not what one might expect. However, the conditions were short period peaky waves, where we could sit inside easier and duck dive while on the longer board, we had to sit out the back and wait for the better ones. So wasn't really a good comparison.

[@chrismaz100]

You can also kick on smaller boards when paddling into waves which isn’t as easy on bigger boards

[@RobCaseXSWIM]

Yes, kicking on shortboards has been proven to increase speed in a small trial experiment. But it was in flatwater only. No studies done on how it reacts when catching waves but I think we all have some strong hypotheses to test.

[@DepthWish]

You guys are considering what the key metrics should be and top speed is interesting to me as is acceleration time to get to that top speed. Secondary would be how much effort it takes to get to that top speed and max acceleration.

[@RobCaseXSWIM]

All great ideas for measuring our activity when we paddle and catch waves.

[@MsLeche86]

Were all the boards the same width? Width would definitely affect planing surface and be a confounding variable.

[@RobCaseXSWIM]

Width all the same. Thickness and length were the only variables.

[@tiagocarvalho983]

good discussion! I'm currently thinking about buying another board for my quiver. I have about 3 boards that are between 5.10 and 6.0 long and 34-36 liters. I caught the waves well and fell a lot in round house cut backs. With a 5.8 33 l I don't miss maneuvers as much but I don't have the same stroke. I'm thinking about keeping the volume above 34 L and buying a 6.6 I think I'll have more stroke and I'll maneuver better and the weight will be better distributed. What do you think! Thank you

[@RobCaseXSWIM]

Thanks for the question. Generally, anything under 7', a surfer would use the same paddling technique stroke, all dependent on their weight to volume ratio and how much of their body sits in the water vs above the water. So from a paddling point of view, the extra length will help according to our experiment. However, I ask that you think about how you would want to surf the waves you are surfing and choose a surfboard that reflects that instead of how it paddles. With good technique, a surfer can paddle any board optimally given the design features of the board. But once they are up and surfing, a surfer would want more volume if the wave has a lot of flat spots, or less volume if the wave is fast and curved ("volume" can be interchanged with "design features" like narrower, or thinner, etc). If you go longer and keep the same volume, yes, your paddling in general will improve, but has the technique changed at all? That is important to consider. Optimize your technique on any surfboard. Then you get the power to choose a board based on the wave shape and conditions rather than the paddle out/wave catching attributes.

[@aussiert]

It’s a balance between length and volume based on the paddlers height and weight

[@RobCaseXSWIM]

Yes, it certainly plays a role because the weight to volume ratio and weight distribution across the board all impact drag amounts.

[@newzealandisno1]

A longer board when catching a wave should lift the back of your body (legs to waist) out of the water as the board floats up, giving you a steeper angle creating more downward speed. A short board will not lift your legs up. They are under the water, creating more drag. So a flatter trajectory down into the wave.

[@RobCaseXSWIM]

Correct, but a longer board doesn't need as much speed to get to planing as a shortboard and therefore can "catch" the wave with a less steep development of the wave (i.e. earlier). What's interesting is when a surfer moves from displacement to planing given where they are in the development of the wave and the board they are riding. Check this episode out for a visual of what I'm trying to explain. kzbin.info/www/bejne/aajVg4aabq6glck Hardly scientific, but gets the mind thinking about how we might test this.

[@GuitarWithBrett]

This is great vid thanks

[@RobCaseXSWIM]

Appreciate the feedback!

[@bluetrain477]

Zouhair I’m interested in seeing what happens if you shape three boards of identical length, width, rocker, and bottom contours, but there different volumes. See you in the water!

[@RobCaseXSWIM]

We'll add it into our list of questions!! Thanks!

[@jksuzuki9350]

what about paddling out through waves?

[@RobCaseXSWIM]

Good question. And one I cover in my Level 2 course. Getting out can add to your energy use or you can save a lot. In terms of board designs, typically a surfer will expend more energy on getting through waves on a bigger board paddling out, and less energy paddling in flatwater on a bigger board.

[@JOEBOWERY]

fascinating

[@beachmaster9042]

Makes sense why people on little boards get angry easy😂

[@RobCaseXSWIM]

LOL! Yeah, that and poor technique. Totally.

[@jonahhex9620]

Interesting

[@joshowen88]

Haha should have waited till the end before I put this comment up; Could you test same length different volume? Feels like a hole in the analysis. You then would see what percentage difference there is between volume. Would be interesting

[@RobCaseXSWIM]

CSU San Marcos did that, and we referenced that. But we used different measurements for efficiency so we drove the boards we used down to them to repeat the experiments with our boards using their efficiency measurement to get a true comparison.

[@hooverbaglegs]

@@RobCaseXSWIM really interesting discussion. What’s your take on Bert Bergen’s theory that thinner boards catch waves more easily than thicker ones (given that all other dim’s are kept the same)?

[@hooverbaglegs]

#Berger

[@RobCaseXSWIM]

Not enough to prove one way or another yet. I think using wavepools can be a great experiment for this. My own anecdotal evidence points to improved surfing performance on the wave when going thinner, since for me paddling isn't an issue. I'll keep my eye out for opportunities to test Bergen's theory.

[@rctrix9063]

Why didn't you just measure drag while the boards were in the pool? If you can sit further outside and catch waves you will always get more waves unless you are just sitting in the wrong place for that boards length/rocker. It's not so much about the crowd but who's on first. Shortboards are often grumpy because of this simple undeniable principle.

[@RobCaseXSWIM]

That is a great idea! If I could measure the drag in isolation between different boards I absolutely would. How might that be done in water is the question. A scientist can analyze and measure drag in computational fluid dynamics but I haven’t seen any instruments available that can measure live drag in water. In terms of wave catching this analysis was for flatwater paddling, not necessarily wave catching. The key to wave catching is how quickly a board and surfer moves from displacement to planing. Length reduces drag in one area, volume in another, and nose rocker would all impact the transition to planing. The question is what makes the biggest impact.