Bridge Clearance

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Do you ever need to know the tide heights if you're not crossing a shallow bar? Maybe.

It could be that problems arise above the water. A low bridge can block passage for fly-bridge cruisers and sailboats on high tide, yet let them pass with space to spare on low. Sometimes even runabouts can be blocked by low-hanging roadways.

You obviously need to know your boat's bridge clearance if you navigate anywhere that passage beneath one of these structures is common. The bridge clearance (BC) refers to the height from the waterline (where the surface meets the hull) to the highest point of any structure on the boat, including the mast, tuna tower, or outriggers. (If your radio antennas and riggers fold down, you don't have to measure them in the equation.)

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It's always best to punch around in the backwaters on a rising tide, and to head back for deeper water shortly before the tide peaks and starts to run back out. That way, if you go aground inside, the rising water gives you a good chance to get off anc escape; while if you ground on falling water, you're stuck until the next incoming tide.


Bridge clearance (BC) is the distance from a boat's waterline to the highest point on the topsides. It indicates the height of a bridge under which a boat can pass.

Bridge clearance is listed on marine charts, with the height above mean high water given. So, if you want to pass under a bridge that has 20-foot listed clearance with your sport-fisherman boasting a BC of 19'6'', you aren't going to be able to get through at the peak of a spring tide that's a foot taller than normal high tide (more on spring tides later in this chapter). On the other hand, you can get through that bridge with a 19-foot listed clearance on the bottom of a -1.0 low.

Bet You Didn't Know

In most areas there's a normal progression through four tides, but some days have only three tides. How can this be?

As the 50-minute-per-day regression takes place, the P.M. tide gradually advances past midnight, thus leaving one 24-hour period without four tides, even though the tidal movements maintain their steady procession.

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  • Jarmo Salminen
    What is bridge clearance on a boat?
    2 years ago
  • sebastian
    Where is a boats bridge clearance measured from?
    2 years ago
  • Troy Stevenson
    What does maximum bridge clearance mean for boats?
    2 years ago
  • kenneth
    How to measure Max Bridge Clearance on a boat?
    1 year ago
  • gilly
    Is a boats bridge clearance in the water or on the trailer?
    1 year ago
  • daniela
    What is Pine Island bridge save clearance for boats?
    1 year ago
  • Jukka-Pekk
    How to.measure the height of outriggers to water line plus bridge?
    1 year ago
  • mandy
    How to calculate boat bridge clearence on trailer?
    1 year ago
  • cedivar
    What is the minium bridge clearence for an intrepid boat?
    12 months ago
  • Oona
    What is a bridge clearance aboard a ship?
    12 months ago
  • zahra
    What is the bridge clearance for buccaneer 210 sailboat?
    12 months ago
  • bryn
    What does bridge clearnce at mean high water mean?
    11 months ago
  • mary
    How to calculate bridge clearance?
    10 months ago
  • essi
    What does gridge clearance mean on a boat?
    10 months ago
  • Gianfranco Calabrese
    What is the bridge clearance on cobia boats?
    8 months ago
  • kathleen
    How to measure bridge height of a boat?
    8 months ago
  • maxima brandybuck
    How height of the bridge to let the boat pass under?
    7 months ago
  • jan thalberg
    How is a boays bridge clearance figured?
    5 months ago
  • mungo labingi
    What kinda boat will fit under bridge clearence of 5 feet?
    4 months ago
  • ZANE
    What is hor clearence boating?
    4 months ago
  • karolin
    How to come up with bridge clearance on boat bid calculation?
    2 months ago
  • tomacca
    How to come up with bridge clearance for transport of boat?
    2 months ago
  • jessamine
    How to determine bridge clearance on a yacht?
    1 month ago
  • Sian Forbes
    How do i find the clearance under bridges?
    1 month ago
  • isaias
    What is term for the height of a boat?
    1 month ago
  • martin
    What boat can you buy with heigh clearance of 10 feet?
    18 days ago

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