Light casings are built around the capstan gear, battery ventilation pipes and other such excrescences outside the hull to provide a streamlined form and so reduce the frictional drag of the hull.
Isigqubuthelo ezilula zakhiwe zujikelza igeyera matshini wokunyuso iankile, ibattery yemibhebho yokukhupha hokufaka umeya nezinye ezinlo ezingenamsebenzi ezingaphandle kwesiqu inika isinie esicu theneyo ukuze ka ngoko inciphise ukuhlikiglanu kwesiqu.