I built a CF rudder and bracket for my RBA. For the vertical part of the bracket I just carved a block of blue foam insulation covered it with packing tape and butcher's wax. I added a slight arch to the vertical member to increase it's stiffness. The horizontal part lays on the rear deck which was covered in contact paper and wax. You then just lay bias strips of cloth on the right angle formed by the mold and the deck.

When it cures you can cut out the shape and a V-groove to accept the rudder. Wet sanding up to 400 grit will give you a professional finish. Remember to varnish for UV protection. I will post a picture later today.

Regards,

Jack