Tech Talk

The profiles are critical to achieve the performance. With a standard profile the fin will be more prone to spin out, and you would have to choose a fin more carefully to suit the conditions due to the narrower performance range. Our profiles have a significantly wider performance “envelope” – they are performing optimally over a much greater range of speed and load, so you don’t need to worry so much about having the fin size perfect. After all, if the conditions change, it’s much better to keep using the same fin than be constantly swapping. Aside from the benefit of the lower surface area (and lower drag), you can get away with the same fin if the conditions change. You can go a size up or down and not worry about losing performance.

The first production fin to reach 50kts was the G10 KA Asy Speed fin from 2008. That is still an amazing fin. The TRIBAL Asy Speed fins were designed to reach 56kts without cavitation. To achieve this, we had to make the fin a bit thinner (in terms of thickness to chord ratio). There is no way around this when it comes to avoiding cavitation. The consequence of this thinner profile is that the low speed performance is reduced – meaning it’s harder to get up to speed, especially if there’s a little bit of chop around. You NEED good lower speed performance to reach high speed unless you have kilometres of perfect conditions (if you’ve found these, PLEASE tell me). So we increased the chord a little bit to increase the surface area to maintain the acceleration capability. This is especially important in the smaller sizes, otherwise they would have impractically low lift to even get past the low-40kt range. Carbon? The needs have determined the shape, and it turns out that this shape in G10 is more than stiff enough! Carbon is certainly useful if you want a fin with lower surface area, choosing poorer acceleration and/or greater susceptibility to spin out. There is nothing stopping the Tribal G10 Asy speed from breaking the record out of the bag, except for a willing & able pilot and exceptional conditions. It’s an advance on the KA series which were the fastest fins in the world year after year since they were released, up until the Luderitz canal opened.

The reason for the different shape is that boards are designed for upright fins. A standard Weed fin with a straight leading edge raked over from the base shifts the centre of pressure too far back to be balanced properly on the board. This is why almost always you need to run the mast track right back. And it gets worse with bigger sizes for this reason. In most places where an upright fin catches weed all the time, you don’t need to run rake all the way to the base to shed the weed. Unless the weed is particularly sticky, the design of the TRIBAL WeedSpeed effectively accelerates the surface weed down the leading edge and over the fully swept tip area. Sub-surface weed is swept away like a normal weed fin, due to the high rake at the middle of the blade. The benefit in having the base area upright is that it keeps the fin centre of pressure more forward so that it’s a lot less out of balance than a traditional weed fin.

For average sailing the best speed fin is the WeedSpeed. It’s very robust and hard to spin out, offers a lot of security in chop and big gusts, and it is very, very fast. Stick it in and GO! The bigger sizes turn your slalom board into a speed board. We’ve had customers pushing past 43kts using the 33cm fin in 68cm boards in chop! The WeedSpeed shape offers huge stability at speed, and doesn’t force the nose down off the wind like conventional fins. The forward centre of pressure allows you to easily build up sail pressure and board speed before the slingshot. The SYM Speed was designed for flatter water, tighter courses where there is an advantage in more surface area – if you are a bigger guy using a speed board with a bigger sail for example. It has less rake than the WeedSpeed so the centre of pressure is a bit further forward. The Asy Speed is designed for flat water conditions, where you have a course on one tack (port or starboard). The fin is much thinner than the symmetric fins and has a bit less lift for its area. It also has lower drag for the area, so if the conditions are for ‘pure speed’ then this is the go-to fin.

This applies to all fins! The most important attribute is that you shouldn’t notice the fin … or have to work around its deficiencies. A great fin just disappears. You don’t notice that it’s great until you get back onto something you thought was great before, and then suddenly you notice all the deficiencies you got used to and developed reflexes to avoid. A good fin works in more than one set of conditions. Conditions always change. A good fin lets you get away with doing something silly without unceremoniously drilling you into the water in front of an audience. A great fin lets you push harder than you thought possible – out of your comfort zone, to new levels!

Ability to provide lift at low speeds so that you can hit the speed course at the highest speed possible. Enter fast, exit faster … The ability to bear away in chop without being scared of spin out or lifting. Here the profile is critical: in these conditions it is subject to high shock loads and a lot of entrained air in the water so it needs to be extremely robust. A good fin lets you go for it even if there’s chop. A mediocre fin has you holding back for fear of spinning out. It might go fast but you won’t be as fast as you could be if you are worrying about crashing. A great fin allows you to sail into anything without fear, without pulling the board around in unexpected ways, and without thinking of the fin at all.

A good slalom fin has free trim for the downwind legs and good top speed, with plenty of bottom end to push upwind in the lulls when you have to, and doesn’t have any sudden instability when you tail walk, hit chop or get nailed by a gust. A great slalom fin is one you can put in and not worry about changing sizes if the conditions change – not thinking at all about the fin when you are sailing. You can just GO where you want, upwind, downwind and always passing your mates.

A good Freeride fin has to be super stable and easy to use. Literally stomp on it and go. No spin out, plenty of bottom end, and it needs to give the board a nice free trim across the wind and off the wind. It has to be super stable in the gybes, no matter how out of balance we might be on the rail. The TRIBAL Powermax does all this in a package that also goes really, really fast. There is no compromise on speed.

The Asymmetric fins from TRIBAL are designed for higher speeds on flat water. They have higher top speed capability and lower drag for the size. You need to choose the tack based on the course. They still work enough on the off tack to get back upwind, but they have to be sailed carefully on this tack since they offer much less lift. The Symmetric fins are best if you want one fin that can go fast on both tacks and where you need good performance to get onto the runs from both tacks. Its easier to get more runs using a symmetric fin since they go upwind better. In a competition this can be important- to increase the chances of getting a good gust. If you are sailing behind a bank, the Asy fin is likely to be the best choice. For open water, shallow areas, or places where both tacks can be sailed in a session, then the Symmetric fins are a better choice.

Controlling fin flex is critical. Raked fins need to be as stiff as possible. Upright fins need to have a little bit of flex, with minimal twist in the tip unless the tip is raked. It is very difficult to achieve this in G10, so the designs are carefully engineered to get the most out of the material.

The centre of pressure of the fins is calculated and the offset in the base is set to keep it lined up with our reference fins between sizes. This means the fins should just work in a wide range of boards.