Skeg
The skeg runs from the aft end of the centreboard case to the transom. It can be made from plywood or timber and will be covered in a layer of glass cloth for abrasion resistance.
Use a temporary batten clamped to the transom to position the skeg in the correct place.
Use a block to spile a line marking the underside of the hull.
Cut the bottom edge to the hull profile and mark the line of the transom The skeg should follow the angle of the transom. The dimension of the radius at the lower corner is optional.
Bond the skeg to the hull with a mix of epoxy thickened with silica. The follow with a radius fillet to give the joint strength.
Finally put one layer of glass tape over the joint to give strength. The entire skeg can be covered in glass cloth for impact resistance.