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<\/figure><\/div>\n\n\n\nThe formula is the same simple one we\nuse in piloting to tell how far off we are when \u201cdipping a light\u201d on a\nlighthouse. The square root of the height of our eye above the water in feet\ntimes 1.17 yields the distance to the horizon in nautical miles. If we use 16\nfeet as the height of eye\u2014about the height of the forecastle head (bow) where we\u2019ll\nhave our lookout\u2014we get a result of approximately four and a half miles (SQRT\n16 = 4 x 1.17 = 4.68). Eric Hiscock\u2019s \u201cBeyond The West Horizon\u201d sounds like a\nromantically distant place, but it\u2019s only as far away as Angel Island. Now, to\nget the distance to the lighthouse, or in our case the mast of the enemy, you\nadd the figure above to the result of the same formula when applied to the estimated\nheight of the sails we see.<\/p>\n\n\n\n
The mast of a full rigged ship will be, say,\n150 feet tall (it could be more\u2014HMS Victory had a mainmast that rose 205 feet\nabove the waterline, for example). Doing the math (SQRT 150 = 12.24 x\n1.17=14.3) and adding the height of eye figure above (4.68) we get around 19\nnautical miles. On a windy day when they\u2019ve doused their royals and\ntopgallants, she\u2019ll be somewhat closer when we first see her, about 16 miles. If\nwe move our lookout up to the fore-top, he\u2019ll be somewhere in the vicinity of 80\nfeet above the water. We\u2019ll see her sooner if we have our man there, at about 23\nmiles. The range on a clear day, then, is between 16 and 23 miles. If we\u2019re\nsailing towards one another the closing speed could be as high as 16-18 knots,\nso we\u2019ll be within an hour or a little more of her. Beat to Quarters! <\/em>On the other hand if she\u2019s chasing us and closing\nat only a knot or less, it could take a day or more to reach us. When the sighted ship is “hull up” it means that the lookout can see the forecastle so she is much closer, so we can do the same calculations as above, but instead of using 150 feet for the top of the mast, we’ll use about 16 as the height of the bow. <\/p>\n\n\n\n There\u2019s a modern use for this\nancient observation technique that we can benefit from, which we\u2019ll get to next\ntime.<\/p>\n","protected":false},"excerpt":{"rendered":" In a recent column we mentioned the phrase, \u201chull down.\u201d In the great days of sail, this was the lookout\u2019s way of communicating the distance to a ship he\u2019s sighted, just coming over the horizon. So how far away is … Continue reading