There are many different types of fin boxes. Some of them are installed before glassing the board and some of them are installed after. I use Futures fin boxes which are installed before glassing. So my last step before glassing the board is to set the fin boxes.
First off, I’ll insert a set of fins into the boxes and insert those into the previously routed slots. This is one final check to ensure that the fins are lined up and there isn’t any final adjusting to do.
During this step is when I noticed my center fin on the Sensei Sebastian was slightly off which allowed me to make some last minute corrections. You can also use an outside angle finder to check the cant of the fins.
Once you’ve convinced yourself that everything is lined up and any adjustments have been made, tape up the base of the fin so you don’t accidentally epoxy your fin into the fin box. You should also cover up the screw hole.
Once everything is taped up, pull them out and set them aside such that you can easily find them and insert them into fin slots once you’d applied the epoxy.
Now it’s time to mix up some epoxy. You really don’t need much when installing fin boxes. Also, if you mix up too little, you can do the fin boxes that you can and mix up some more for the rest.
For the fin boxes I like to thicken the epoxy with cabosil. I feel like I never thicken it quite enough though. Cabosil will add stiffness and strength to the connection. It will also help ensure that the epoxy sticks to the sides of the fin slot.
I used a 1/2″ chip brush to brush the epoxy into the fin slots and made sure to completely coat the sides and the indentation for the flange. There should be some epoxy pooled at the bottom, when you push in the fin boxes you’ll force this up the side and into the grooves around the fin boxes. Futures fin boxes are designed for this. Don’t worry about it spilling over the sides and getting on the board. It’s going to happen. Simply clean it up with a rag or paper towel before it starts to set.
Once you’ve installed the boxes, made sure the grooves are filled with epoxy and cleaned up all the excess, you can then remove the tape you put on earlier.
As you’re working to beat the clock, it’s likely that you may have dabbed a little epoxy on your fins. Take a moment to check and wipe off anything you find.
Once the epoxy has set, you can remove the fins and now you’re ready to glass!
