The job that requires the most modification to an existing boat is the installation of the brackets to hold the centreboard in place. I thought it would be good to provide a step by step guide for how I made mine.
The design
The internet is full of foiling moth photo’s these days to get ideas on how to build things. The idea with the block is to ensure that it will bond to the existing centre case and spread the load over quite a large area. To decide the width, I measured my orbital sander and made sure it would fit inside the mould to round off the corners. If you would like to make one yourself I have included the drawings for the mould here, and the template for cutting out the cloth here.
The Mould
As the brackets are essentially flat, I decided to start with a female mould made from MDF. I purchased 2 sheets from my local hardware, one 7mm (the thinnest that they had) and another 10mm for the backing board. I then proceeded to make a three piece mould as shown in these photos.
Making The brackets
To layup the brackets, the cloth of choice was uni-directional carbon with the fibres oriented vertically. With the 300gsm uni, that I used this equates to a around 14 layers of uni, 7 of each shape in the cloth cut template. For aesthetics and to provide some lateral strength as well, I also threw a couple of layers of carbon cloth for good measure and on any surface that someone will actually see. I also used the off-cuts to fill out the curve where the cloth bends 90 degrees.
Despite several layers of release wax and PVA, getting the finished brackets from the mould wes a bit of a challenge, and I had to actually split and then repair the mould at one point.
Installing the brackets
Ok this is where you start to cry… take one trusty angle grinder with a diamond blade, and cut an access hole in your cockpit. Then cut the holes for the brackets to fit through.
In this shot, you can clearly see where we left some of my boat’s previous deck in place to support the centreboard case when we re-decked the boat, after the 91 nationals in Tasmania. In addition to the old deck, we have used timber reinforcing on the back of the case and the rudder pintles, as shown below. You can also see the kevlar that we have running from the top of the case to the hull floor. I must have subconsciously known that we were going to be trying to hydrofoil at some point. If I was building this boat today, I would probably use carbon tubes instead, in a race car roll cage like structure, attached to the back, front and sides of the case.
The fun step is next, covering the brackets in a resin and micro-baloon based glue, and then install them into the boat. Take care to ensure that the brackets are installed correctly and the holding pin is square to the case. Another key concern is to ensure that the 1/4″ pin can slide in freely. To do this, used a 1/4″ bolt, with three nuts on it to force the top of the plates apart, and keep the whole thing square. I then tied this bolt to some tube that I laid across the deck, to ensure that the brackets didn’t fall down. Once that was finished, I layered a heap of carbon strips over the bracket to spread the loads and strengthen the bond to the case. For additional security I also added some carbon where the case joins with the floor.
With hindsight being 20-20, the one thing that I would change about the design would be to have the angle better match the curve of the cockpit floor, instead of 90 degrees. This would require less filler when the bracket is installed, which means less glue and less weight.