The most recent tool I put together was a jig for routing out the slots into which fin boxes are installed. I based it on one available in the USA through Greenlight Surf Supply. Theirs is made from sturdy aluminium and stainless steel, but mine, being hand made with a minimal budget, employs MDF as the base material, with a couple of pieces of extruded aluminium for the adjustable width and length limiters.
As you can see, I painstakingly marked out all the relevant dimensions on the jig so that I could set it for my little Ryobi laminate trimmer without having to measure each time. Less than a month after this, I went and bought myself a new Makita plunge router, meaning I had to go back and mark out a whole new set of measurements all over again. It was, however, worth it. The Makita shits all over the Ryobi and I can now do all my fin boxes and plugs with a great deal more assurance than before.
I’ve used the jig on two boards now, including the one below, which was particularly tricky because there were three fin boxes all just millimetres apart. But I have to say, it’s worked out really well. As long as you can clamp it securely in location (it has non-slip pads on the bottom to help with this), the routing is done accurately in seconds, without the need for special form-following router bits with a bearing.
John from Sanded said if I made a batch, he’d sell them through his site. I’ve considered it, but at the moment there just aren’t enough hours in the day. Maybe it’s a job for next year…