On my Garcia Exploration 45, a boat that I helped to design to my exact specifications, the two aluminium rudders are supported by skegs. As an added protection, the upper section of the rudder blades is made of light composite material that will crumple and compress without causing any damage to the hull itself. This is exactly what happened in a collision with a large lump of ice in the Arctic and the rudder continued to function normally for several thousand miles until repairs could be made. As in the case of displacement, unless hull material is put at the top of the list of priorities, or you order a one-off, this is another decision that may be taken out of your hands. In most cases boats are built in the most suitable material the architect and builder have agreed upon. For a long voyage the builder might be persuaded to put some additional strength in critical areas, so it is worth discussing this as early as possible in the process so that such modifications can be done during the initial building stages.
Metal hulls, whether steel or aluminium, are attractive for their intrinsic strength, but there are disadvantages to both materials as well. Steel hulls and decks need good initial preparation for painting, and then careful maintenance throughout the boat’s lifetime. In the case of aluminium hulls, some people may be concerned about the risk of electrolytic reaction. This is quite unjustified: modern alloys as well as building methods have taken care of that.
For high latitudes, aluminium or steel hulls are the best choice