A new Raymarine autopilot is being installed on Second Star, using a Type II linear drive to drive the rudder quadrant below the decks. A strong mounting bracket was needed to bolt to a strong bulkhead to sustain the 1,000 lb plus loads expected under extreme operation. A custom carbon fibre mounting bracket was designed for this purpose. The bracket was made by laminating several layers of carbon cloth over and under a center core of fibreglass cloth. A corner gusset was added after the initial layup and set in place with a fillet of thickened epoxy. Here the part is ready for tabbing lamination of carbon cloth to securely bond the gusset to the part. The flat flanges will be drilled for through bolting to the bulkhead and the linear actuator’s cast bast will bolt to the left angle surface. This custom bracket allows for easy access for future service and keeps the unit out of the way of other items in the rudder compartment located under the aft berth.
The gusset reinforcement patches are ready for epoxy to bond to the bracket. Resin, acetone and alcohol for cleanup, scale, mixing cup, etc are ready. I am using a two part epoxy in a 2:1 mix ration, 2 parts resin to 1 part hardener. The rudder reference mounting bracket will be laminated at this time over a portion of the same form that was used to make the larger actuator mounting bracket. The form was easily made from plywood and covered with waxed sheet plastic taped to the form. A small glass mirror is helpful for laying up small pieces when a smooth flat surface is required in the finished part. Later I will laminate a 3′ square panel with a white gel coat surface using polyester gel coat and vinyl-ester resin, but for the carbon brackets, epoxy will be used.
This picture shows the carbon reinforcement to the gusset in place, ready for final trimming of the edges. Carbon fibre is very sharp so the edges must be trimmed and sanded to prevent cuts to hands and fingers.
The process of making carbon parts can be very simple, as the case of the carbon rudder reference mounting bracket. Four layers of carbon cloth are simply laid upon the simple form and saturated with wet epoxy, one layer at at time working out the air bubbles with a hard roller. It may look a little messy, but after the epoxy cures, the part is cut and trimmed to its final size with a professional look and feel. A small piece of peel ply was placed over the future bonding area (left side in picture), obviating the need to sand the part again before bonding to the rudder post gusset in the boat.
After cure, the peel ply is pulled from the surface exposing a surface ready for bonding.