bridge clearance??

unless otherwise stated on a chart or bridge, vertical clearance is always expressed as a minimum not a maximum. this should be construed as the min available vertical height at the lowest point over the navigable water.

as others have noted that dimension does not account for tide at any given moment but I believe it is always expressed based on NGVD.
 
there is more to it than seeing under the bridge, until the cam is really close (within a few ft) you're going to be able to see under the bridge.. the question is whether you can see the underside of the bridge, and that may not be easy to determine with a low res. cam aimed at the bright sunlight behind the bridge...
 
quote:
Originally posted by PascalG

If you re going to play chicken with a bridge using a camera :) the most important thing will be a large readable monitor...may still be hard to read

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I disagree Pascal, the most important thing will be a good recording system to show us what happened later! Good or bad it'll give us a great topic for days.
 
I was docked at Loggerhead for a year, and the channel may be 25' but our 15' beam sure filled the opening.
 
The docks proved to he way to high for boarding at low tides, due too this reason only did we move.
 
quote:
Originally posted by PascalG

there is more to it than seeing under the bridge, until the cam is really close (within a few ft) you're going to be able to see under the bridge.. the question is whether you can see the underside of the bridge, and that may not be easy to determine with a low res. cam aimed at the bright sunlight behind the bridge...

Click to expand...


You can tell with your eyes or a camera if you'll have the clearance to pass under the bridge safely by watching what happens to the horizon you see on the other side of the bridge as you look at it from the height you need to clear it by. If the horizon appears to go up as you get closer you will pass safely. If it stays the same you most likely will not or perhaps just barely clear it. If it goes down you definitely will not clear it.
 
Interesting idea Bill but wont that only work if your eyes are at the level of the highest point? Nav lights and radars are , hopefully, above eye level. :D
 
Low tech solution. Attach a broom handle or brush handle to your bow rail. Extend it to the same height as your tallest point. As you approach the bridge, if the brush handle clears, you're good to go.
 
The camera (or eyes) MUST be at the highest point or it's a total waste of time. But if they are, if you can see under the bridge (and yes see the underside) you can go under it. If you can't, you can't.

If you're STILL in doubt, it's too close; wait for the tide.
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I don't have a "bridge cam" yet. These pics were taken by the Admiral while standing on the ladder to the sundeck. Bridge clearance was MAYBE a foot.
 
quote:
Originally posted by pdecat

Interesting idea Bill but wont that only work if your eyes are at the level of the highest point? Nav lights and radars are , hopefully, above eye level. :D

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Correct. That is why I said: "as you look at it from the height you need to clear it by". :-)

Tough to do in many cases by eye for sure. But you could mount or hold a camera up on a pole at your maximum air draft level.

Of course the low tech solution of a feeler gauge mounted at the bow works too. As long as you have the room to stop and/or back up and the current is not pushing you hard towards the bridge.
 
Problem with a "feeler gauge" is that by the time the gauge says you WON'T clear, you're pretty well committed. You have maybe 15' to stop, reverse, and back out of there. Easier said than done for most of us. I'll take the camera.
 
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