SEILmagasinetvideo
Sailing under a low bridge
March 3, 2023 · 7 min · 3K views · Nesøya bridge, Oslo Fjord
What this video covers
Calculating vertical clearance for a sailboat requires reconciling the vessel's mast height with local tidal data and the bridge's official clearance height. Bridge heights are typically measured from the Highest Astronomical Tide (HAT), meaning low tide can provide significant extra clearance.1:20 Sailors should consult the "Se havnivå" service from Kartverket to determine current water levels relative to the chart datum.2:00 Determining exact mast height often requires consulting ORC measurement certificates, as manufacturer specifications may omit antenna height or modifications made by previous owners.3:33 On an X-362 Sport with a 17-meter mast, the crew calculates clearance for the 15-meter Nesøya bridge in Oslofjorden.5:43 Because current water levels exceed HAT, the mast height exceeds the available clearance.1:56 Using a drone to verify the gap from above, the crew confirms the mast is too tall and aborts the transit to avoid a collision.6:43 Accurate calculations must account for the distance from the deck to the waterline, the mast height, and the height of any masthead equipment.
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