This is our latest D.I.Y. CNC boat project and a "dusty one" - the goal is to fill the "empty" space inside the new rudder bearing bucket system on board the performance sailing catamaran with lightweight foam blocks. This will cause additional lift and buoyancy at the aft of the boat. We are custom making foam blocks that snug the shape of the rudder buckets. As the foam prevents water to fill up the space, this is improve the performance under sail as it will reduce drag induced by the transom.
The rudder bucket assembly has been designed by an external naval architect and our part consisted in preparing the 3D file on the computer. We calculated that we needed about 20 layers of 25mm foam to fill the volume properly. Cleaning up the 3D file took quiet a while as the original file was not ready for utilization in the CNC software right away. Have a look at the rudder bearings and you will understand better why we want to fill the gaps.
Our little CNC machine was working non-stop to cut out the four different sections of foam that we stacked together to have the best shape possible filling the gaps. We used "purple" lightweight close-cell foam. Our router likes to cut the foam, almost like butter compared to other harder materials.
The rudder is not straight inside the compartment therefore the positioning of the foam parts was very important. We machines positioning holes and pvc tubing for gluing the parts together.
The result of our effort are four shaped foam blocks that fit nicely in the rudder bucket assembly. With the purple foam, they almost look like enormous pieces of cake.
Next step is to cover the foam parts with some carbon tissue to make it watertight and floating.
Pictures and results to follow...
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