Having Issues with your iSUP's Centre Fin Box?

What is a SUP fin used for?

SUP fins provide stability and traction on the water.  Without fins, a SUP would slip and spin during paddling, making it virtually impossible to paddle in a straight line!

What are the 2 types of SUP fin boxes?

SUP fins typically attach to mounting areas known as fin boxes located on the bottom of paddleboards. There are 2 main types:

1. US fin box which is typically for screw-in fins – This type of fin is secured to the fin box on the board by a small screw (usually a Phillips’s head).  The screw secures a small flange at the front end of the fin’s base, to a hole in the fin box.  

2. Slide in fin box – This type of fin does not utilize screws to secure it to the board; instead, you slide the fin in and secure with safety tab 


We have found 2 common issues with iSUP centre fin boxes:

1.  Trouble with inserting & removing the centre fin

Are you having issues inserting the centre fin? is it getting stuck and not sliding in?

This video will show you how to fix the issue:


The tools we used are a little brush, this can be something like a tooth brush, a rubber mallet, Vaseline and a heat dryer or an ordinary hair dryer. 

1. First clean out the fin box with the brush and remove any sand or debris. 

2. Just with your finger, rube in some Vaseline along the base of the fin box and bottom of the fin.

3. Next we're going to warm up the plastic with the heat dryer. We aren't going crazy or anything, just simply warm it up so it become pliable 

4. Once the plastic is warm and pliable. Place the rounded part of fin into the ridge of the box and lift to reshape the plastic. Make sure to do both sides evenly!

5. With Vaselined fin, slide into the fin box a couple of times. It might be a bit stiff still but should be a lot better than before we started! You can repeat this process if needed. Once you are happy, let it all cool down with the fin in place.


2. Trouble with inserting and removing the safety tab on the centre fin

Which way does the safety tab go in and how do I get it back out again?

Make sure the fin and fin box are aligned properly and then it should slide in/out.
Taking it out, we find a key helps pushing down on the tab.

It can be fiddly but you do just need to push the tab down firmly!


Hope this helps! If you have any further questions then just give us a shout on hello@triwetsuithire.co.uk / 01737 823771

The Tri Wetsuit Hire Team 


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