From what I’ve seen in surf foil and downwing videos, the better the riders, the smaller the stabs.
And that made me wonder, are stabs really just making your setup more pitch stable in the expense of performance? And if so, shouldn’t we all use the smallest stabs we are comfortable riding?
Pitch stability is something that is also trained, so being able to have more stability this way might unlock better performance. I’d love to hear your opinions on this, as someone that’s starting to ride a smaller stab and finding that it’s harder but could be more fun
Yes, in a standard plane a stab provides downforce and a significant amount of drag. The smaller the stab, the more pitch sensitive, but also more lift and less drag everything else staying the same.
For me the the sweet spot is to reduce span as much as possible without making it too high aspect as that is less fun for surf. Best is to find a nice stab and just downsize it, never a bad outcome.
I played with the Axis skinny stabs and they were all the same span but as you lost chord they got really funky and unpleasant. Nice experiment but not nice stab range other than for going straight
I agree completely. Reducing span is the main gain.
The other thought is winglets. I don’t like winglets on a stab. When coming up to the top of a wave after a bottom turn, I like to be able to unweight and rotate the foil. Winglets and span play a part in resistance to that.
Some theories disagree. James Casey for example goes to a smaller front foil and larger stab when towing. He wants the extra drag of a larger stab in the system. So it just depends what you are trying to solve for and the system needs to work together.
I think maybe the larger stab is used to create more drag to prevent a smaller, faster, front foil from out running the wave and help keep you in the pocket.
This could be useful when towing big fast surf.
The stab angle and length of the fuse are also really important.
A greater stab angle creates more front foot pressure and drag and low end. A flatter stab does the opposite.
Longer fuses increase the leverage the stab has over the front wing leading to more front foot pressure without stab related drag increasing.
A long fuse can give the same pitch stability with smaller stabs than a short fuse.
The fuse shape makes a difference, Code’s chunky fuse probably calms the pitch compared to brands with thinner fuses.
Found it easier to go fast with a longer fuse and a larger, flatter stab compared to setups with a shorter fuse and stock stab angle. I can get used to riding a tiny stab and short fuse, but no way to push it as fast.
Early on in your riding and progression they are like training wheels.
Once you reach the low end of tail sizes it’s not just about finding something smaller. It’s about matching your tail to the experience you want or need on the water that day based on your foil and conditions.
Just like the smallest front foil isn’t always the goal, neither is the smallest tail.
I ride a 113² UHA tail for glide days.
125² Surf tail when it’s good.
157² Surf tail to slow fast foils in swell.
Next purchase is a 115² Surf tail for hero days.
Really interesting topic, I think the training wheels analogy doesn’t really apply as some folks have pointed out since different size stabs are useful for different purposes. That being said, as generic advice if you are going to have the “wrong size” stab (read producing downforce that is not well synchronized to the pitching moment of the foil system to be specific) then it is easier from a rider perspective to to have too much downforce at high speed than too little. More performance can be gleaned from from “too little” as has been pointed out since the front wing needs to produce less lift, the tail wing is producing less drag, low end is slightly improved, turning is slightly improved, but ultimately if you are holding back in your riding as your stability increases when you accelerate to higher speeds your actual experience will surely go down if you push this too far. How far you can push it is of course a matter of skill so in that respect I suppose the analogy does have some merit
Further complicating the matter though is the angle of attack of a stab has a huge bearing on the downforce created so a sub-question arises being what is “better” a larger stab at a lower angle of attack or smaller stab at higher angle of attack?
Furthermore, stabs have wildly different cross sections which generate significantly more or less downforce at the same speed and angle of attack - so this needs to be taken into account alongside the lift distribution which can make a higher span stab “feel” lower span or vice versa. Aspect ratio also plays a huge role not only in the efficiency of a stab but also how it’s lift responds to changes in speed since it’s angle of attack is “set” by the front wing since it seeks the angle required to produce the necessary lift to keep on foil at speed.
Despite going super deep on stabs it’s very tough to have a cursory glance at another brand’s stab selection and recommend one to another rider, but , fairly easy to suggest a different shim depending on the specific complaint they have on their current setup (or similarly suggest the sizing up/down a stab in the same range).
I’ve found myself preferring a bit larger stab set at a lower angle of attack for my riding which is reflected in our new Agent foils. We also use a very different section than our front wings since the stab does not need to produce a lot of lift at a high angle of attack like the front wing rather is optimized for max efficiency at the narrower range of angles of attack stabs operate in. Along with the larger size we also use quite a bit of aerodynamic and geometric twist across the span which centralizes the lift at cruising speeds making them more “turny” while recruiting more of the span at really high speed to provide downforce and stability. This also has the minor benefit of giving the tail more “positive lift” when the front wing is near stall so provides a touch more low end to the setup.
Thank you, sounds really interesting. It’s such a shame that Gong V2 stabs are fixed and therefore cannot have their AOA changed, i’d love to try to shim them.
Also keep in mind that a tail isn’t something to think about on it’s own like you might think about a front wing.
A tail is more of a part of the system and what kind of effect it has on the entire system will change drastically with the rest of the setup.
For example I am very comfortable pumping my 1950 front with with my 50 stab but my 700 front wing would be near impossible and I even had to size all the way up to 130 to have a chance with it.
yeah, great point Slappy. For sure great cross compatibility is possible between different setups but requires active testing and adjustments to dial in.
