We put together a blog article last year to demystify paddleboard fins.  We tried to turn all of the jargon into a short, simple article that anyone can understand, even if you don't have a degree in fluid mechanics.

Since then we've been contacted by lots of people asking for more advice about fins.  So maybe we didn't do as a job as demystifying as we thought. But those searching for advice are often asking about river fins.  This isn't really surprising. It's the fastest growing component of paddleboarding, and one of the most neglected by surf and windsurf focused brands.

So we went away and thought long and hard about the type of SUP fins that our inflatable SUP customers need for river SUP. And we spoke to our customers, our partners and friends, to make sure we really understood what people really needed. And then we went away and found a supplier for exactly the type of fins that most iSUP customers are looking for.

But first a reminder about why fins are needed (apologies if we’re teaching grannies to suck eggs, but don’t forget, there are newcomers to SUP every day who might not have heard this before!

Fins have two main purposes:

To help you stay in a straight line.  If you’ve ever paddled a SUP without fins (yes, we’ve done it as well, arrived at the put in, pumped the board up, and realised we have no fins! [1]) you’ll know how difficult it is to track in a straight line. With a fin in place, the fin counteracts the drive of the paddle, stopping the tail of the board swinging around. The larger the surface area of a fin, the easier it is to paddle your SUP in a straight line, and the more difficult it is to turn. It’s not quite as simple as this, with other factors such as length and shape coming into pay. If you want to find out about the factors, then you want to check out our earlier article.

To slow the board down.  This might seem counter intuitive if you’re not a surfer. But the side fins (also known as 'bites' serve to ‘bite’ the wave and provide a focus to pivot on. Surfing with a central single fin is preferred by surfers who prefer gentle and graceful carving. But if you want to slash and hack, then you need a different fin arrangement. With three fins in a thruster arrangement being the most common.

If you keep these two key purposes in mind for the rest of this article, it should all come together by the time you've finished.

In addition to satisfying these two purposes, there are a few other key requirements for river SUP:

The most important requirement was that fins should be interchangeable between all sorts of boards, not just between McConks boards [2].

All of our centre fins are compatible with all universal centre fin boxes (often called US fin box).  Every decent brand in the world uses these on their premium range of boards – Red Paddle, Starboard, Naish, Fanatic. And this applies to the quality UK brands as well – Fatstick, Loco, Freshwater bay.  If you’re not sure if your board has a universal box, take a photo of the box, or a fin that fits the box and send it to andy@mcconks.com, and we will let you know if your box is compatible.   

Our 2” side bites are compatible with all FCS fin boxes, and also with the Kumano and Suru surf click fit system. 

In general, the stiffer a fin is,  the better the performance. This is true for both centre fins and side fins, as any surfer will tell you.  This is great if you’re paddling your SUP in deep water on the sea. If you’re in shallow water, fins have an annoying knack hitting submerged rocks. Or catching on the river bed.  The best outcome is the rider is catapulted off the front of the board as it comes to an abrupt and unexpected halt. And narrowly avoids knocking themselves out on a rock. Stepping up the damage scale, if you’re using stiff fins, you’re very like to snap a fin.  Stepping it up further, you could crack a fin box, or a rip the fin box off the board, causing expensive or irreversible damage.   And right at the top of the damage scale, you could be catapulted off the board walloping your helmet or a flailing limb against a very hard rock. And the possible outcomes there are pretty sobering. Especially if you're in serious whitewater.

So for whitewater paddling, or shallow river paddling, you should always use soft flexible fins. These take much of the impact of rock strikes, and they flex as the bump along river beds. This gives you a flying chance of staying on the board, and reduces the risk damage to the fins, your SUP board, or you.  

And even endurance river races such as the #Trent100 start off in shallow river sections that would benefit from flexible fins. Several competitors this year said they wished they’d started the event with a range of fins, including some flex fins.

The other requirements were more fin/discpline specific….

After speaking to competitors in some of the endurance river events, it became clear that there was a desire for a flexible, indestructible SUP fin that:

-         Has a large surface area and race foil for effective straight line tracking

-         Has a strong rake on the leading edge that clears weeds and other detritus effectively

-         Is robust enough to take knocks and bumps from rocks and shopping trolleys, but strong enough to maintain its shape in normal conditions

These fins are 10” long, so provide great tracking.  And digging so deep provide significant stability and directional benefits in cross wind / cross surface chop conditions.

And for the fashion conscious, we even do them in two colours (going against our normal rule of keeping it simple!)

In river races not in shallow water, the benefits of a stiffer fin come into their own, and there's little need to compromise with flexible fins. 

This 8" carbon fin has a strong rake for weed clearance, and the cutout allows for swift pivot turns if needed, whilst still allowing for excellent tracking.

This is the first of our superflexible short river centre fins.  This SUP fin is only 5 inches long, which gives you 3 or four inches more clearance than the fins that come as standard with most decent SUP boards with removable fins.  These are an awesome compromise between tracking, weed clearance, and speed.

The second is a shorter 3” fin, but with almost the same surface area as the 5” fin. We do this by having a very long fin base (takes up the whole length of a standard US fin box), and by extending trailing edge of the fin well behind the fin box.

These fins fit all FCS box or Sauru surf / Kumano surf click boxes.

Extending behind the box, these have a surprising amount of surface area for the fin depth.  Use with the 3" or 5" centre fins for a perfect whitewater SUP setup.

River fins haven't had the same amount of R&D that surf and open ocean fins have received.  So this is a relatively new and exciting playground.

Get out there with different fins, and see what works for you.

Tell the world via SUP hacks if you have experience or comments on what works for you.

If you've got ideas on what would work for you, but doesn't exist yet, speak to us. We like prototyping new products for our customers!

[1]      This is the ONLY good thing about fixed SUP fins. You can’t lose them or turn up to paddleboard without them. In every other way they are inferior to removable fins and detract from your objective of having fun on the water!

[2]      Our 2” river fins will fit the click fin boxes on Badfish SUP and McConks SUP, and any SUP board with FCS fin boxes. So if the mood takes you, you can even shove three 2” fins in your FCS thruster set up on your surf board. By extension this flexibility applies in reverse to our inflatable SUP boards.  There  are a massive number of SUP fins out there that fit our boards.  And this is the real benefit of having a universal centre fin box – the huge amount of choice.  Any universal fin (including FCS connect) can be used in the centre box.  So you can check out fins from Black Fin Project,  or FCS or Futures fins.  Or from any of the very many aftermarket fin resellers out there.