Mast thickness doesn't matter.

It’s 2026, which means I’ve been designing foil masts for 10 years now, and foiling for 13. But I've been skiing for 40, and riding mountain bikes for 30; we're still in the infancy stage of this sport. The industry has changed a lot in these last 10 years, with new forms and foiling brands, and much improved equipment. But the one thing that hasn’t changed, and needs to, is a completely unjustified fixation on mast thickness and continued belief that it is an effective predictor of mast performance.

I was at a Christmas party recently talking to a Naval Architect who’s sailed around the world, designed and built a sailboat in his backyard, and is part of an esteemed team of engineers working on foiling ferries for the Puget Sound region. When I told him about the biggest challenge in my industry-effective marketing in a sea of misinformation and ill-informed design theory, he laughed. “Well, I guess if you have no idea where else to start when designing a foil section, you could start with thickness,” he said.

The truth is, when designing a mast foil section, there are so many other and more effective places to start. Desired speed range, packaging constraints like board mounts or fuselage interfaces, desired and effective mast lengths, rider weight and skill level, even salinity and temperature of the water. Starting with thickness and assuming that it alone and in some way affects performance of the mast is about the same as characterizing ski performance by waist width and ignoring camber, rocker, turning radius, stiffness, and weight. It’s the equivalent of characterizing a mountain bike by wheel diameter, and ignoring suspension kinematics, geometry (reach, head tube angle), tires, and frame stiffness. Not into either of those sports? It’s like comparing cars by engine displacement, and ignoring power, torque, chassis design, drag coefficient, and curb weight. Why does our industry continue to fixate on thickness, and try to dumb down what is truly a very complex multidisciplinary optimization challenge? The marketing in our industry doesn't help, and comparing foil design to sticking your hand out of a car window will most certainly lead to some false conclusions. But I get it, this stuff is complex and complicated. I went to school for 6 years to study engineering, and have been a practicing for over 20; I am still learning. I don’t expect someone on a forum with limited technical experience to understand the detailed fluid dynamics of how foils work, but I do expect them to open their minds and listen to experts who do.

I’ve been wanting to write this blog post for 10 years, basically ever since we launched our first mast in 2017 which made anyone riding a wet noodle realize what they had been missing. As the industry scrambled to acknowledge that mast stiffness actually mattered, they used simple marketing tactics to convince potential customers of the drawbacks of switching to a non-OEM mast: Cedrus was accused of being slow, due to thickness, but mainly by the people who hadn’t actually ridden it. Customers riding the mast felt any added drag was well worth the benefits of stiffness (and universality). Many of these masts are still being ripped today, and you can find videos of them pumping fine in the surf by skilled athletes. But with the launch of our Evolution lineup in late 2023, we’ve quelled any concerns about the drag of our masts with industry leading glide and by proving the importance of chord length (wetted area) with Surf, and ventilation resistance with Wind. I actually got a message last night from someone who asked for my “thoughts on the new trend of thin reduced chord and thickness masts for even less drag for downwind racing.” I’ll give you my thoughts: Cedrus started it, over 2 years ago. We believe that reducing chord length and thickness does reduce drag, but not without drawbacks. This is why we have chosen to focus our entire business on the mast, and offer a fleet of discipline-specific designs catering to the needs of each rider, just like foils do.

But I’m here to present data and facts, not just rant. I’m going to start with a list of common myths, and then get into more detailed analysis in an effort to prove how little mast thickness actually matters.

Myth 1: Minimum thickness (typically down low on the mast) is most important, because that portion of the mast is always submerged. Truth is, the material that is always submerged contributes least to mast drag because it doesn’t pierce the water and create spray drag. Spray drag is not captured by traditional closed loop CFD tools like Xfoil, and often overlooked by foil designers. It’s the resulting force from deflecting water up and out of the way of the mast, and occurs only at the air/water boundary. The difference in drag between a mast foot (bottom 10cm) of 16mm and 20mm is 0.07N. The difference in spray drag between 16 and 20mm piercing region is 0.43N, an order of magnitude higher. This is the primary reason tapered masts feel so much more sensitive to ride height than one that is constant profile, like Cedrus. Many Cedrus owners report that they feel the glide of Surf (and even our new Forged masts) is better than any mast the’ve ridden. This is because the piercing region is constant thickness and not causing drastic changes in drag as you move up and down on the mast. We took a lot of flack early on when we launched the first constant-section (non-tapered) carbon mast, but our designs offer a more progressive and forgiving ride than those that taper, and average speeds can be faster. Spray drag accounts for about 25% of mast drag when an 80cm mast is ridden at half-height, and even more when riding higher on the mast. The thickness of the mast at the foot near the fuselage is the least important variable in all of mast design. The mast foot should be optimized for structural performance, ensuring a stiff and strong connection to the foil. Do not listen to anyone tell you that the benefits of a 12mm thick mast are worth the risks of M6 screws, because they're not.

Myth 2: I’ve ridden thin masts, and they felt faster. Well, the mast you rode was also a different profile/shape, different chord length, probably a different length, and most importantly mounted to a different foil. There are so many variables that affect the feel and performance of the mast, let alone the complete system, that you cannot isolate thickness as the variable that made the mast feel faster. It is simply impossible to extrapolate mast thickness as the variable that made a setup feel faster.

Myth 3: Mast shape (Cd, or coefficient of drag) doesn’t matter because it’s the smallest term in the drag equation. The profile shape of the mast has a bigger impact than thickness, and is actually the most important variable of the whole equation. For example, a NACA 0016 foil with 19mm thickness and 120mm chord length has 30% higher drag than the original Cedrus profile with the same 19x120mm dimensions at 10kts. Analysis below shows that reducing thickness from 19mm to 16mm only cuts drag 11%. Characterizing mast performance by thickness, or even thickness and chord, completely ignores the profile shape, which can be optimized for specific Reynolds numbers (speeds) and have a far greater impact on performance than those other variables. The above image is a bit of an exaggeration of the point we’re trying to make, but valid nonetheless: the fat foil has the same drag as the skinny wire.

Myth 4: A 13mm thick mast can be just as stiff as a 16mm thick mast through the use of UHM material. False, no amount of material modulus can make up for the loss in stiffness of super thin masts. For example, a 16 mm thick mast will have almost twice the bending stiffness of a 13mm thick mast assuming same chord length, material, and layup. This is due to the simple relationship of moment of inertia (I) = 1/12(chord)(thickness)^3. Even if the 16mm thick mast uses intermediate modulus fibers, as is the case of some of our masts, it can still be stiffer than the UHM 13mm. By nature of our products, universal masts with no rider weight limit and compatible with any foil on the market, Cedrus will never sacrifice stiffness and/or strength in pursuit of unnecessarily thin masts. We have customers who’ve tried OEM 13mm thick masts and prefer their Evolution Surf primarily due to increased pumping efficiency and foil control. Really thin masts are good in a straight line only.

Myth 5: Thick foils are slow because they are pushing more water out of the way due to more frontal area. No, when analyzing the fluid dynamics of streamlined bodies, the area term in the drag equation is typically wetted area, not frontal area. Thicker foils can actually be faster by improving laminarity of flow and by providing a more forgiving, wider speed range. Thin foils are less forgiving and more prone to flow separation (ventilation and stalling), and the effects can be felt when breaching tips in a transition for example. I've personally experienced full mast ventilation in botched transitions due to breaching tips with short chord/skinny masts, while the flow separation is unable to propagate up the length of Evolution Wind thanks to longer chord. Thickness does play a role in this. Furthermore, and as discussed previously, thick foils enable increased stiffness and strength which can yield benefits through pumping efficiency and stability, offsetting potential losses in speed alone. Falling is really slow, and a broken mast is a quick way to kill a good session.

Now, for some numbers to put this all into perspective. Looking at the ranges of thickness and chord length in our mast lineup, you will find thickness between 16 and 20mm, and chord lengths 80-120mm. The drag associated with each of these profiles with 40cm of submerged length was calculated at a range of speeds (10 and 20kts), and spray drag was included. I didn’t originally explore sections less than 16mm thick, because stiffness falls off a cliff. But to illustrate the points of this blog post, I have interpolated the configurations highlighted in yellow. POR refers to point of reference, the 16x120mm profile of our forged mast.

First off, big picture: typical lifting foils in our industry have a lift/drag ratio of 20. There’s actually a range, from about 18 for low aspect foils to 22 for the higher aspect, but let’s just assume 20 for simplicity. To keep numbers round let’s say the rider (suited up, wet, with a board) weighs 100kg wet (or 220lbs). For a foil to generate enough lift (9.8N/kg) to support this mass (~1000N), 50N of drag will be created. There is no way around that, the foil always has to generate enough lift to support the rider. This means that at low speed (10kts), the Cedrus Forged profile (16x120mm) will account for less than 10% of the total system (mast + foil) drag (4.73N/54.73N). This is even ignoring the rear stabilizer, which applies additional downwards lift, resulting in additional drag. So if you were to drop mast thickness from 16 to 14, which lowers stiffness by 33%, you will see a total drag reduction of your setup of less than 1%. You won’t feel that, but you will most certainly feel your mast flex as you pump out to the next set or try a tight bottom turn in the pocket. Improve the efficiency (L/D ratio) of your foil from 20 to 22 (10%), and you will save about the total drag of your mast (5N).

At 20kts, the mast starts to play a bigger role, and contributes almost 18N, or 23% of total drag. That’s not insignificant, and we begin to see why kite racers and wing foilers and maybe downwind racers start to care more about mast drag and sanding 0.1mm of material off their mast before the start. But even cutting mast thickness by 2mm (13%) only lowers the drag contribution to 16.8N, or a 2% reduction in total system drag. Again, you probably won’t feel this, but you will certainly wish you had a stiffer mast at 20kts. Riding a little higher on your mast, just 10cm in fact, will cut drag to 14.25N, which results in more than 4x the savings of that 2mm thickness reduction. Improving your ability to control mast ride height is the best way to reduce drag, and only until this is mastered should you care about mast thickness.

If mast thickness doesn’t matter, then why does chord length? Well, the truth is both thickness and chord length impact drag. We’re not denying that, and this is reflected in our products. But reducing chord length and thickness too much for optimum drag will obviously yield a mast that begins to lack adequate stiffness, or cause other problems like flow separation and ventilation. So if we’re trying to meet a minimum stiffness requirement for our customers, which we are, we’ve found that adjusting chord length allows us to reduce drag at high speed with the lowest impact on stiffness. For example, dropping 20mm chord length off the 16x120mm section at 20kts lowers drag by 11%, but only reduces stiffness by 17%. You’d have to drop thickness to less than 14mm in order to even approach the same drag reduction, and you’re already looking at 33% reduction in stiffness; we’re not going to make that sacrifice. At lower speeds, both chord length and thickness can both be used to effectively lower drag with similar impacts to stiffness, which is what we did when we launched Evolution Surf in 2023.

But we didn’t want to stop at this simple, back of the envelope Xfoil analysis. We ran full CFD model with a high aspect 800cm^2 foil to show just how little the mast drag matters. This analysis even had a conservatively small fuselage without any detailed structure required for the foil interface. At 5m/s (10kts), the foil requires an angle of attack (alpha) of about 10 degrees to lift the 200lb rider. The forged aluminum mast ridden at half height (40cm), generates about 6.9N of drag. While this is higher than our mast-only Xfoil analysis discussed previously, the total drag of the system is also higher at 66N due to the inclusion of the tail and interaction of all components. The analysis confirms that at 10kts, the mast accounts for 10% of total system drag (6.9/66).

At high speed, the simulation confirmed that the mast begins to play a bigger role. The higher speeds allow the front foil to generate more lift at a lower alpha, although total drag numbers still increase.

At 20kts, the front foil can nose down from 10 to 2 degrees (kind of amazing that our brain can do this real-time), and still generate the necessary ~1000N of lift. Total drag of the system increases to around 110N, with the mast contributing about 27N, or 25%. Again, this full-scale multi-thousand dollar CFD package agrees nicely with the back-of-the envelope and free Xfoil analysis.

Thinking back to our original Xfoil mast drag analysis, where we looked at independent effects of chord length and thickness, you can see about 1N of variation in drag at 10kts, and 4N at 20N when modifying thickness between 14 and 20mm. With CFD, we can get a little bit more detailed, so as a final exercise we looked compared the drag of three different foil mast assemblies: Forged, Tapered, and Tiny. The tapered mast reduces from 16x120mm at waterline down to 14x110mm at the fuselage, while the tiny mast is a constant 14x110mm the entire wetted length. The below charts show total drag and mast drag of these three configuration at different speeds (alphas).

As you can see, total drag dramatically increases with speed, but the foil becomes so much more efficient at 15kts (reduced alpha) that you don't see much of an increase in drag until then. The mast drag component of the 3 different models is basically in the noise, and doesn't really diverge until 20kts. 20kts is really fast, and I personally have yet to hit that regularly even while wing foiling. Above 20kts, there is about 4-5N of drag difference between the 3 masts when looking at just mast drag, and a little more noise when looking at total drag. So overall, the CFD analysis confirms that you can really only save a few % points of drag (5N out of 150N total) with your mast once you're riding a fairly optimized model like Cedrus, and at speeds approaching and above 20kts only. Remember, both alternative configurations cut thickness and chord length, meaning the gains on thickness alone are even that much slimmer, pun intended.

Don’t get me wrong, I’m a foiler too and I think I “feel” mast drag. I can feel the difference between Surf, Wind, and Forged, but it's a lot more than thickness alone that's changing the feel of those masts. To me it’s most obvious right when I begin to descend a wave, and alpha decreases to nearly zero as I accelerate down the face towards the trough. But all good things come to an end, and when I truly need help reducing drag it’s typically when trying to pump to the next wave or at high alphas when I’m asking the front foil to do a lot of work, and the mast is actually contributing the least amount of drag to the system. I obviously believe in low drag masts, as evidenced by Evolution Surf, which arguably started the “skinny mast” trend. But there are certainly drawbacks, like stability and forgiveness, which is why we offer a range of masts including ventilation-proof Evolution Wind. And despite being a gear designer, I’m the first to admit that rider skill has the biggest impact on performance. But that doesn’t help me sell product, right?

In closing, the only truth in all of this is that it’s still way more complicated than even this blog article makes it out to be, and there is no single parameter that can adequately characterize mast performance. Mast design is an exercise in multi-disciplinary optimization, and the right mast for you will depend on a number of things. What I ultimately care about as a rider is how a mast feels, not chord length or thickness. If you race in a straight line, and you are looking for the absolute lowest drag setup, and have foils to match, then maybe a super thin/skinny mast is the right setup for you. But if you like to turn, ride bigger foils, jump, ride across a range of speeds, or simply not worry about breaking equipment, then a little mast thickness has far more benefits than the potential increase in drag. Regardless, for those of you interested in optimizing your setup based on all possible variables, I give you the following list in order of impact on total drag:

1. Rider weight
2. Foil size
3. Foil design
4. Tail
5. Rider ability to control mast height
6. Mast design
   1. Section profile
   2. Taper design
   3. Chord length
   4. Mast thickness