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  Topic Review (Newest First)
12-11-2011 08:18 PM
tdw
Quote:
Originally Posted by gaha View Post
river goes up and down,it changes all the time
true, but bridge and overhead wire clearances are based on "Mean High Water Springs" just as charted depths are based on "Mean Low Water Springs".
12-11-2011 08:16 AM
gaha I go under one all the time you call tender on channal 16 or call on phone.Or one long and the one short blast on horn
12-11-2011 08:12 AM
gaha river goes up and down,it changes all the time
11-26-2011 06:17 PM
denverd0n
Quote:
Originally Posted by Undadar View Post
All of the examples I have found have an unlimited raised vertical clearance (ignoring wires and structures other than the bridge).
And those that have wires above them will note on the chart the minimum clearance under the wires.
11-25-2011 11:08 AM
Undadar
Quote:
Originally Posted by Capt~Sam View Post
A bascule bridge is any bridge that can be opened and is not a fixed bridge. The horizontal and verticle clearances is marked on the chart. That is if you have the correct chart for that area.
That's what I thought too and this was the reason for my confusion since the raised vertical clearance is NOT listed on the chart (see the example).

I'm not sure what NOAA's definition is of a bascule bridge (no mention in Chart #1) but every definition that I found is basically "a type of drawbridge consisting of one or two counterweighted leaves which pivot upward on a horizontal axis to allow boat traffic to pass underneath. The counterweights help balance each side of the bridge during the upward swing, which assists in the lifting motion."

All of the examples I have found have an unlimited raised vertical clearance (ignoring wires and structures other than the bridge). For planning purposes, I believe it is appropriate to assume that they have an unlimited raised vertical clearance when not listed otherwise on the chart. Obviously, that will be checked with the bridge operator prior to passing.
11-25-2011 11:04 AM
ebs001 Here's what wiki says A bascule bridge (sometimes referred to as a drawbridge) is a moveable bridge with a counterweight that continuously balances the span, or "leaf," throughout the entire upward swing in providing clearance for boat traffic.

Bascule is a French term for seesaw and balance, and bascule bridges operate along the same principle. They are the most common type of movable bridge in existence because they open quickly and require relatively little energy to operate.

Bascule bridges may be single or double leaf. Both have any truss structure and counterweights below the deck
11-25-2011 10:46 AM
nolatom
Quote:
Originally Posted by Capt~Sam View Post
A bascule bridge is any bridge that can be opened and is not a fixed bridge. The horizontal and verticle clearances is marked on the chart. That is if you have the correct chart for that area.

I thought a bascule had two hinged pieces, a drawbridge one, a lift bridge as OP described above, and a swing bridge rotates on a turntable.
11-25-2011 07:21 AM
Capt~Sam
bascule bridge

A bascule bridge is any bridge that can be opened and is not a fixed bridge. The horizontal and verticle clearances is marked on the chart. That is if you have the correct chart for that area.
11-24-2011 11:20 PM
OlderandWiser 25ft if not opened.
11-24-2011 06:12 PM
sawingknots i have saw bridges that do raise like that especially rail road bridges
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