Such a ship is in the same class as the Terra Nova, Bear, Thetis, and Neptune of existing whalers, the Proteus (lost), and the exploring ship Discovery.
Length and beam having been determined, the form of hull was next to be considered. In the navigation of the particular regions contemplated by the Expedition, a light draft is preferable to a heavier one, as enabling the ship to go closer to the shore, and thus get round a barrier, or retreat close in shore from advancing heavy ice, and let it ground outside of the ship.
The element of light draft also enters into the consideration of the lifting of the ship under heavy pressure from ice-floes. The deeper a ship is in the water, the more difficult will it be for her to rise and save herself.
It has been well said that while a form of hull that would allow a ship to rise easily and readily under ice pressure is desirable, and this desirability has been recognised, no ship previous to the Fram had been built to meet that requirement.
In the Fram almost everything else was sacrificed to this requirement. Seaworthiness was sacrificed, and as the Fram’s experience in her two voyages shows, ability to make her way through ice was sacrificed.
For the purpose for which she was designed, i. e., to enter the ice and then drift with it, evading destruction from ice pressure, she was well adapted, but as the designers of the German Antarctic ship Gauss said in discussing the Fram model, she would have been even better adapted for this had she been bowl-shaped.
Contrary to popular ideas, the work which an Arctic ship has to do is not principally that of breaking up one season’s ice, as is done by harbour and river icebreakers, in Canadian and Russian waters for instance. Such conditions of level, unbroken ice of uniform thickness are found only in Melville Bay on the upward voyage, where the one season ice is encountered, and late in the season when the new ice is beginning to form. The main work of the Arctic ship is that of threading and pushing and wedging and prying her way among and between and around fragments and cakes and large floes of ice, the latter of such thickness (twenty to fifty or seventy feet) that nothing could break a passage through them. Of course, nothing can be done but squeeze a way around these. It is for this reason that the powerful Russian Ermack is not available for a Polar voyage, and why she is not treated of in this discussion. Fifty Ermacks merged in one could not break through these floes, and in squeezing around them the Ermack could not carry enough coal to take her half-way to the Pole.
To return to the hull model. In the Fram everything was sacrificed to secure certainty of lifting under pressure. In the Gauss, which is a modified Fram, while the broad beam of the Fram (thirty-six feet) was retained, greater length was given the ship to render her a better sea boat for the long voyage from Germany to the Antarctic Circle. Her ratio is 1 to 4.25 as compared with the Fram’s 1 to 3.25. The Gauss’s draft, however, is excessive (nineteen feet).
As already noted, great draft is a disadvantage in the region under consideration, and every increase in beam makes impassable leads which otherwise would be available, and greatly increases the power required and the difficulties of pushing a way through loose ice.
The English Discovery was built, as was to be expected, on the lines of the Scotch whalers, with a little broader beam. Her ratio is 1 to 5.27. Her draft is a little less than that of the whalers. She was not specially modelled to rise under pressure, but was specially constructed (as the Fram and Gauss were not) for ramming a way through opposing ice.