I assume that they were designed without a keel and with their long shallow hull and extended mast how did they prevent them from capsizing. I am particularly interested in how they crossed oceans such as the north sea.
Longships did not have a fin keel like modern yachts, but they did have a keel as can be seen in those that we still have. This was a long keel running the entire length of the ship. This will not provide as much righting moment as a fin keel (the length of the fin keel acts as a lever) but does give a much shallower draft.