Sicaflex should be used between the rudder stock and the top of the rudder blade (see fig 1 for reference). Current Jefa rudder blades already have sicaflex applied on this edge, but in time it could be necessary to reapply more as needed. Due to temperature changes and forces, there could be small movements between the glass fiber of the blade and the rudder stock material. Without this sealant water could run into the rudder blade.
Before any anti-fouling can be applied to the new rudder blade it should first be treated with a non-water penetrable epoxy coating. This will prevent water from entering in the gel coat and underlying GRP structure. Old rudders should be cleaned from anti-fouling residues, dirt and marine growth and thoroughly degreased.
Prior to the initial stages of the anti-fouling process all metal surfaces have to be prepared with an epoxy primer. You should follow the same procedure as instructed for aluminum propeller sail drives. This primer will give the surfaces a much better protection in the hostile seawater environment. Please be careful to not primer to far inside the bearing as it could run into the roller bearings.
Special non-metallic anti-fouling should be used before applying anti-fouling to the hull and rudder blades. Products designed for sail drives and propellers are the best to use in this situation. When metal consisting anti-fouling is in contact with the rudder shaft and bearings severe electrolysis could occur. Take a look at this Electrolysis article from Jefa. Keep any metal parts 3-5cm away from the hull anti-fouling.
You can now proceed with the anti-fouling of the hull and rudder blade. Be very careful to not cover any previously anti-fouled metals and make sure there is absolutely no contact between the anti-fouling of the hull and rudder blade. Remember 3-5cm of space between any metal parts from the anti-fouling!!!