2000 Miles of notes on the AFS 75cm Skinny UHM Mast.

Intro.

The last few years of mast development in the foil industry seem to have focused on a few variables. Stiffness and thickness being at the top of the list. AFS has, for a while, had this mast quietly listed on their site with essentially no advertising pointing out that the chord depth was a shockingly short 100mm. It's UHM for stiffness and wildly thin. Another AFS rider was the one who actually pointed out the availability of this mast and once I found it I got my order in right away.

I received this mast late summer of 2024 when I was in the midst of a large amount of foil and mast testing. I have ridden it almost exclusively since then with the rare journey back onto the AFS 80cm UHM. Over the last 2000 miles this mast has proven itself time and again becoming not only my favorite mast of all time, but now an irreplaceable and required piece of my kit.

Testing location, conditions, equipment used and riding style.

Wind range and locations tested:

10-60 knots from Rooster Rock to Arlington in the Columbia River Gorge

Data collection:

2000+ miles and counting.

Swell size:

Dead flat to overhead.

Foils used:

Silk 650, 850, 1050

Ultra 750

Enduro 700, 900, 1100 - Standard fuse and short fuse

Tails:

Silk 132, 142, 152

Silk HA38

Ultra Glide 41

Mako Carve 130

Mako Glide 120

Cloud IX fs157

Wings used:

2m Strike v3

2.5m Ocean Rodeo A

2.5m-5m Ocean Rodeo AA

Parawings used:

BRM Ka'a 2.3m

Ozone Pocket Rocket 3m and 2.4m.

Rider Data:

Dedicated to surfing swell with just a sliver of wing freestyle on the flat days. Click here for more details/numbers.

Mast Dims.

If you haven't read my primary mast article yet: 10,000 Miles of notes on mast selection: Searching for perfection. You might want to check that out since I talk a lot more about mast dims in that article then I will here.

My masts actual dims:

Length: 75cm

My preferred mast length. I occasionally consider an 80cm but I can ride any condition on the 75cm so I keep it short for the additional maneuverability. What you see is what you get when measuring an AFS mast. It is 75cm from the board to the end of the mast.

Chord min: 99mm

To my knowledge, this is the shortest chord length of any mast on the market by a healthy margin. I expect it's the primary reason anyone would select this mast and makes for exceptional surfing.

Thickness min: 12.7mm

Thinner is the most definitive way I've found to experience low drag riding and this is the thinnest mast I've ever ridden. All my data shows higher average speeds, lower heart rates, and the longest glides of my life.

Weight: 1.6kg

Hardware: M8 throughout the entire system. Both at the baseplate and fuselage.

Ride Experience and Attributes.

Carving and Maneuverability

This is why you buy this mast. If you were to demo the 75cm skinny UHM and 80cm UHM back to back the differences are shocking. The skinny feels wild, loose, expressive, it amplifies every carving and maneuverability characteristic you can imagine. The Silks, the Ultras, the Enduros, they are all turned up a notch when this mast comes into play.

If we look at the flight elements present in foiling and simplify them a bit we can say that roll is impacted by wingspan, pitch is impacted by fuse length, and yaw is impacted by chord depth. How much so? Well, when I demo'd a 3rd party 120mm chord back to back with the standard 115mm AFS UHM chord I feel a clear difference. Dropping all the way down to the skinny 100mm chord is dramatic. When you start carving turns it is crystal clear that this skinny UHM moves through the water unlike any other mast. Turning radius's are tightened and quick rail to rail turns are effortless. Snappy top turns, one of my favorites in foiling, are made easy with the skinny.

In my experience, the vast majority of these benefits are reaped when your foil is operating in its low end. Riding in the Gorge, even on a HUGE day, is nothing compared to surfing overhead ocean waves. All of my foils see large benefits in maneuverability on the low end when yaw is available. At high speeds when yaw stiffens, this masts benefits are harder for me to notice.

Pumping

More technical than a deep chorded mast but still reasonable. The sensitivity/maneuverability of a short chord is very high and poor technique will be punished here. In my experience deeper chords stabilize the pump onto the pitch axis for more forward drive where a short chorded mast can lose efficiency as it is bled off into the yaw axis if your pump isn't dialed.

Upwind Ability

I haven't found any obvious loss in upwind competency with the skinny mast. My angles remain the same, peaking out at around 90 degrees per reach. The gains are all in the thinner profile which relaxes the drag/fatigue that is transferred to my body and result in better downwind to upwind ratios. Here my tracks show a 44 minute primarily flagged out downwind run reset by a 32 minute upwind.

Stiffness, Stability, Turbulence, Tip Breaches

Stiffness:

This mast is UHM carbon and I have never had any stiffness related symptoms with it on any foil I use. If you compare it to other AFS masts, it is not as stiff as the 80cm UHM standard chord. I think it would be easy for a rider doing a quick demo to mistake the maneuverability (which can also be called instability) as being a stiffness issue, but I really don't think that's the case.

Stability in turbulence and tip breaches:

This is possibly the most maneuverable mast on the market which means that it is also less stable. I feel very strongly that the shortened chord is more sensitive to turbulent water and tip breaches because it is more maneuverable and easier to knock on the yaw axis. This doesn't result in crashes but when you ride this mast back to back with the deeper chorded 80cm UHM with a 115mm chord it's quite obvious that the deeper chord handles those situations better. I've tried even deeper chorded masts which felt like they completely eliminate the feeling of anything in the water. I think this is because the deeper chord tracks and punches through poor conditions better. It doesn't allow you to put yourself in as compromised tight carving situations as the skinny. So, there are pros and cons to be considered when looking at chord depth and stability vs maneuverability. Interestingly, I've been riding the new Ultra Glide 41 (UG41) tail since it came out and the same instability scenarios that I felt from the skinny chorded mast when paired with the insanely stiff Silk tails seem mitigated by this new tail. Could this be due to a change in tail stiffness? The new tail has a very small amount of flex in it that potentially is softening the turbulence? There's probably something to be said about super small tails simply not absorbing as much turbulence. Perhaps a wider span tail (410mm vs 300mm) protects you a bit? I think it's even worth noting that the new UG41 tail is forward swept in design and that could be impacting these scenarios. More time and reflection with that tail is needed.

Speed, Efficiency, Glide

I collect data all year long and usually during the winter I compile all of that data into comparative sets to see if there is anything notable. My best average speeds, top speeds, longest glides, lowest heart rates, and longest sessions are all recorded on this mast. The 12.8mm thickness is an absolute dream to ride and I recommend everyone ride thinner masts. They make a world of difference.

What am I unsure about?

I love this mast. I really do. After riding skinny masts on the market and extensively riding this one I think there's a larger conversation worth having about the complexity of skinny masts in foiling, but I'm going to try to simplify it with AFS only comments here.

Skinny chord vs short fuses and HA foils: Tinkering required.

In my opinion, if you ride the Silk lineup, the skinny masts are legendary. It takes the already stunning Silk foils and gives them that much more. The Ultra and Enduro foils though, are a bit more sensitive due to the relationship of the foils leading edge to the leading and trailing edges of the mast:

It's quite common to see the distance from leading edge of foil to leading edge of mast reduced on modern HA foils. This loosens up the ride and provides better turning. However, the skinny chorded masts are also loosening the ride experience. For my riding style, one or the other is ideal. If you want turns that are enhanced by roll/yaw then the skinny chorded mast is ideal. If you want turns that are enhanced by pitch, then the shorter leading edge to mast length is ideal. When I do both together I am able to create an enormous amount of torque on wide span foils. So much so that the ride becomes uncomfortably twitchy at times. While I can ride the Silks with any tail to tune my experience I find that to be questionable on the Ultra and Enduros. The HA38 tail can throttle back the torque on the Ultra and Enduro 900 to restore a more roll based turn. The UG41 tail is also reasonable on those foils. The smallest Enduro, the 700, with a span between the Silk 850 and 1050, does not seem to suffer from excessive torque. Conversely, if you throw any of those same foils that feel over torqued on the skinny onto the standard 80cm UHM they are all very relaxed again (which may be why I hear so many people preferring the short fuse on that mast).

Long story short, wide span foils with shortened distances from leading edge of foil to leading edge of mast combined with a short chord create an extreme torque based experience that puts incredible demand on the mast. Fortunately, the AFS UHM construction is up to the task and no issues have arisen. However, this requires a more subtle tail selection to keep the system in balance for the average rider. I love that AFS has provided us with the opportunity to tune, select, and learn from the nuanced details of foil setups with their variable fuse length that alters the distance in front of the mast, instead of behind.

Don't be intimidated by the skinny chord. Just realize that if you are using foils with spans greater than the Silk 1050 your tail selection is more critical.

Ventilation, flow separation, and other problems.

I am very pleased to say that after 2000 miles on this mast using the entire Silk range (650, 850, 1050), the Ultra 750, as well as the Enduro 700/900/1100 I haven't experienced ventilation a single time. No flow separation, no unexplained crashes, nothing at all. I've pushed this mast to the limits of my skillset and riding style and it has never failed me. The AFS masts, foils, and tails have always worked flawlessly.

Craftsmanship and Customer Service

Second to none. Every inch of my mast is beautifully made without even the slightest sign of imbalance or imperfection. AFS delivers their gear with a matte finish which sometimes catches people off guard because they are used to a nice gloss finish on their equipment. The reason for this is that matte is more efficient through the water.

Customer service? Well, sometimes, gear breaks. AFS backs their masts with a 3 year warranty (best in the industry?). When something goes wrong with a piece of AFS gear they seem to have perfected the no BS policy with their customer service. Every experience I've had with them or heard of others having with them tells me they'd rather see us happy on the water living our best lives then trying to fight with us over a broken piece of gear. In my opinion, the quality of their designs, craftsmanship in their builds, and customer service policies make them the definitive leader in the industry.

Beginner, Intermediate, or Advanced Riders?

Beginner riders may be intimidated by this mast. Especially if they don't have a quiver of foils and tails to choose from. I've only seen one beginner rider purchase the skinny mast with Enduro 900, standard fuse and ha38 tail. They had to backpedal a bit, use the 80cm HR mast and a large tail to get used to the Enduro 900 for about 10 sessions. Then they switched to the skinny and HA38 tail and have been very successful. So, I'd tell beginner riders that there will be a learning curve on this mast and that the potential tinkering might not be for them.

Intermediate riders will likely be excited about the carving benefits that come from this mast if that is their riding style. It can help with being the next step for these riders who are on medium sized foils and looking for a more playful experience. If you are still developing your swell riding technique and find you need to pump a lot, the 80cm UHM full chord might be a better choice. If your positioning is dialed so you pump less and you are on the verge of breaking into what you would consider the advanced category, this is an excellent choice.

Advanced riders who are dedicated to carving will have a blast on the skinny. The folks in this category who are also comfortable tuning/tinkering with their kits will be able to produce some unique feelings at the edge of comfort with this mast to tune their ride to perfection.

Winging vs Parawinging.

The vast majority of my time with the skinny has been spent winging and it's a phenomenal choice for that. At the moment, I seem to be be rapidly transitioning to parawinging on the Ozone Pocket Rockets. This is the only mast I have used for that and I greatly appreciate the maneuverability of the short chord. I prefer the Silk foils in all riding conditions and the value of being more maneuverable to get into the correct position on swell is more important to me than the more stable pumping platform provided by a full chorded mast.

Final thoughts.

For me, as a person who is in a never ending pursuit of the best carving, I think this is the best mast that the foiling industry has ever seen. I like this mast so much that I don't even consider trying other foil brands. I now know that when I switch the mast out the change will have such a dramatic impact on my riding that the possibility of having a fair comparison between foils is gone. For me, riding this mast with a quiver of Silks and tails has been the pinnacle of my foiling experience.

Thanks for your time.

Thanks for taking the time to read my notes on the AFS 75cm Skinny UHM Mast. I hope you learned something that will enhance your adventures on the water. Feel free to ask any questions in the comments section below (join the site for free) or shoot me an email and I'll do my best to answer your questions!

See you at the river,

Bryan Lee, M.S. Experiential Education.