COLLAR DE EJE PERFIL NACA Ø 31,8 mm (ZN)

Function and technical context

The shaft collar with Ø 31.8 mm NACA profile is a component of the transmission system of shaft-driven vessels, made of zinc (ZN) to act simultaneously as a fastening element and as an integrated sacrificial anode. Its NACA hydrodynamic profile significantly reduces turbulence and drag in the tail axis area, improving propulsive efficiency compared to conventional circular section collars. Being made of zinc, it cathodically protects the shaft, propeller and other submerged metal components against galvanic corrosion, which is one of the main causes of premature deterioration in the shell of any boat. A worn collar or one with depleted cathodic protection exposes the shaft and propeller to accelerated corrosion that can compromise the structural integrity of the transmission and lead to serious breakdowns in navigation.

When to replace this part?

Zinc anodes must be replaced when they have lost approximately 50% of their mass, an unequivocal sign that the cathodic protection is close to being exhausted; Visually, a very reduced, irregular or deeply cracked anode indicates that it no longer performs its sacrificial function effectively. For boats in regular use, it is recommended to inspect the collar at each seasonal docking and replace it at least once a year, although in areas with high conductivity water or greater galvanic activity the interval may be shorter. Replacing the shaft collar preventively each season is a basic maintenance practice that prevents costly shaft or propeller repairs due to galvanic corrosion and ensures the hydrodynamic efficiency of the transmission.

Compatibility