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Vertical clearance ??
Since I'm the one what caused most of the confusion and gave the most
bad info, let me try an example to hopefully clear up the mess. Your tide datum is MLLW (also called Zero tide) On your chart you have a box showing tidal data. In this box, MHW is listed as +6.0'; MHHW is listed at +7.0'. You are on a sailboat approaching a bridge. The height at your present draft to the tip of an antenna at the masthead, is 50'. The clearance of the bridge shown on the chart, is 50' at MHW. AT Zero tide (MLLW), you will have 6' clearance between your antenna and the bridge. At +6.0' tide (MHW), you will hear a slight "Ping" as the tip of your antenna touches the bridge. At any stage of the tide which your tables show to be greater than this (+7.0,8.0,9.0, etc.) your next stop will be the nearest boatyard for repairs. At any stage of the tide where the numbers show a minus reading (below MLLW) you will gain additional clearance. All warnings about accuracy of tables and predictions based on possible weather, etc. conditions, still apply. BG otn PS got my hands on a light list .....no tidal info in there for particular lights, that I could see. |
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