Air Draft and Bridge Openings

Spit Bridge,Sydney`s only currently opening bridge, opens at scheduled times only. It carries a large volume of road traffic to northern harbour and northern beaches areas. Maximum closed clearance is 6 metres, Doriana is fine, I know a GB52 with mast modified for hydraulic operation to fit under. Several complimentary moorings are provided either side of the bridge for boats arriving out of sync with opening times. The openings are well patronised, waterways upstream have many moored boats, marinas, and popular cruising anchorages.

"Several complimentary moorings are provided either side of the bridge for boats arriving out of sync with opening times."

I like that. Good idea.

psneeld said:

Bridge tenders and bridge commissions have a strict set of rules from the USCG...but as all operations that can appeal to politicians...they gain back a lot of latitude.

The Little River Swing and the Socastee have the..open on demand reg...unless just opened ...then maybe 15 minutes they'll do it again. I've seen that plenty of other times too.


So like in most things in life..the only rule is "there are no rules"...

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Never had to wait more than 15 minutes for either of those bridges. Both of them are directly adjacent to a 65' high rise bridge, so there is an alternate route for cars. The alternate route is 4 lanes and the swing bridges are 2 lanes. I've wondered why those two bridges aren't removed altogether since they are essentially redundant.

Lake Simcoe is in the middle of the Trent Severn waterway and as such it is necessary to have an air height of no more than 6.1M (20ft.) to clear the fixed bridges and as well there are many draw and swing bridges along the way. Bridge tenders are not in communication with the boats at all. Some say 3 short blasts of your horn when approaching while others are reliant strictly upon the tender keeping a keen eye. Waits are generally not too long but if a scheduled train is coming, boats just have to wait. No sense in hurrying around these parts, just relax and enjoy!

BruceK said:

Spit Bridge,Sydney`s only currently opening bridge, opens at scheduled times only.

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Here's a link to all the info we have on it including the phone number:
https://activecaptain.com/X.php?lat=-33.802544&lon=151.246225&t=h&z=15

I quickly looked around and you're right - this seems to be the only bridge that isn't on demand. That's pretty amazing for a populated city. Most at least limit openings outside of rush hour.

ActiveCaptain said:

You're able to tell the time to go for a waypoint along a route that's 18 miles ahead? What software does that?

It's pretty simple to see how far the next bridge is when you're approaching it. That's also often too late to make enough of a change to actually make the bridge in a comfortable way.

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Jeff, MacENC is one example. Once you are on a route, selecting he Route dialog box in the Navigation window will show you each waypoint in order, how far it is and time to go to get to it, dynamically.

In practice almost all the bridges or locks I was ever concerned with are pretty much in a straight line on the A, G, or O ICW. I'd simply set the next bridge as a "Go To" on the Furuno. I am still able to do simple arithmetic in my head and figure out what speed over ground (takes care of the current issue) i need to set to. I could tweek the speed to get it more precise if I liked as time went by. As noted in another post, a cushion of a few minutes is needed anyway. I disliked having to stand off any more than I had to, especially in Southeast Florida on a weekend.

That's interesting. I didn't know MacENC did that. Of course, there's no integrated capability to get the bridge opening times in that software but there are certainly other ways to manually do that.

My goal is to provide a comprehensive "Up Ahead" list that dynamically changes as you move. There are dozens of things that can provide - bridge openings are just one but it's one that I want so it'll be early!

What I did was include the times (for instance :15-:30) and the air draft in the waypoint name. Worked pretty slick.

First time I started using the bridge as waypoint (but not nearly so elegantly) was when we were chartering in SW Florida. Had this Maptech App on my Palm Treo, the guy who invented it turned me on to it on T&T ... ;o)

That was where the original idea came from!

And meeting in New Bern...that was almost a decade ago, George. Feels like a blink...

Coastal explored can give you the eta to a bridge that is an arbitrary distance away. Like MacENC, you can look at all the waypoints on your route and see the distance and eta. Just place a waypoint at the bridge, and it works as well as any eta calculator. Varying speed, either by throttle control or current influence will of course impact the eta calculations, but in my experience you are either running at a pretty constant speed, or the speed changes due to current cancel each other out over the route, so arrival time calculations tend to be pretty accurate. There will of course be exceptions, but so far I've found it works well.

Egregious said:

........... I've wondered why those two bridges aren't removed altogether since they are essentially redundant.

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I've wondered that too. Probably some influential people want them to stay.

The Ben Sawyer swing bridge just north of Charleston, SC needed to be replaced. The state offered a 65' fixed bridge but the residents demanded an exact replacement. They won. It's still a swing bridge with rush hour restrictions.

Accurate data would be good, last week heading north we came to a bridge that was listed at 21' but was actually 25'. We had researched all the bridges on our route for that day and we air draw 35' antennas up or 23' antennas down.

As all the bridges for that day were meant to be either above 35' or below 23' I left my antennas up, needless to say we came around a bend and had to scramble to lower antennas going through a Georgia shoaling area for a grumpy tender on a Sunday morning.

We have met some real nice bridge tenders and others who seem to be having a bad day.

Look forward to the AC program Jeff.

ps I needed a canary yesterday between Charleston and here 15 m south of Georgetown

Bridge height is a complex and non-standard thing. First, seeing 25' when the bridge is listed at 21' is easily explained by tide. The one nearly standard thing is that bridge heights are almost always listed at high tide.

But it gets worse...

Few bridges are flat across the opening. There is usually an arch since they achieve more strength that way. So what should the height boards and charts provide as a measurement? The center or the edge? There's no standard although Florida, thank you, is one place where all measurements at height boards are "low steel." They will sometimes have a sign telling you how much extra is in the center, but not always. It is usually 3-4 feet on ICW bridges.

Other states have no standard. We just passed a bridge in NC (Onslow Beach Bridge?) where the height board noted that it was the height in the center.

Nautical charts have no standard. You're never really sure what a height measurement means except it's supposed to be for high tide.

In ActiveCaptain, there will often be a note about these things where any information was available. My wife is responsible for all bridge data and has spent years developing accessory information about bridges from different states and countries to get more info when needed. All of these bridge issues happen in other countries too. And on rivers and areas protected by locks, normal pool is generally the height although many bridges list heights by summer and winter pool. Even then, they're not taking the other factors into consideration.

gwkiwi said:

Accurate data would be good, last week heading north we came to a bridge that was listed at 21' but was actually 25'. We had researched all the bridges on our route for that day and we air draw 35' antennas up or 23' antennas down.

As all the bridges for that day were meant to be either above 35' or below 23' I left my antennas up, needless to say we came around a bend and had to scramble to lower antennas going through a Georgia shoaling area for a grumpy tender on a Sunday morning.

We have met some real nice bridge tenders and others who seem to be having a bad day.

Look forward to the AC program Jeff.

ps I needed a canary yesterday between Charleston and here 15 m south of Georgetown

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As Jeff mentioned tide swing makes the difference. You did have accurate data, you just didn't use it all (height of bridge and height of tide. ) I am curious what bridge you are speaking of that is near a Georgia shoaling area?

I don't recall any shoaling issues at Causton Bluff,which is the 21ft bridge in Georgia, nor at Skidaway, which is 22. I was chatting with a friend the other day who had just gone through both, and back again through Causton(having some work done at Thunderbolt) with a 6 foot draft sail boat.We were talking about the "usual suspects" shoaling wise in the area, mostly for old times sake for me. Made no mention of any issues near these bridges and he has to open them both.

Other states have no standard.

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Which goes to show that the United States is not that united. How about radio contact? Channel 9 in some states, channel 13 in others.

And if they are willing to spend several million dollars building a bridge, why can't they install and maintain clearance boards?

And aren't high rise bridges cheaper in the long run when you consider staffing, maintenance and inconvenience to motorists and police or fire vehicles?

Actually in the US, the Coast Guard regulates bridge clearances and supplies NOAA with the clearance data. Unless the height is charted as "at center" the definition of clearance is the least height within the horizontal clearance of the channel. Clearance guide boards are also regulated by the USCG, and are a guide to minimum height within the channel. Personally I never found it all that confusing, I knew where the tide was and I knew the height of the bridge.

Funny, I just talked to my buddy again and he reminded me that Skidaway draw bridge is no more, no wonder he didn't say anything about clearance!

caltexflanc said:

Clearance guide boards are also regulated by the USCG, and are a guide to minimum height within the channel.

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Wrightsville Beach bridge has height boards that measure the height at the center, hightest point, of the bridge. It was unusual enough that we edited the bridge information ourselves to note it. I have to admit that it's the first one I've seen like that - but it was very clearly labeled.

We also found really dumb colors of height boards on some of the NC bridges. White lettering on a green background that gets sun bleached is a really poor choice.

It seems hard to believe that there is much regulation on this especially since so many bridges don't even have height boards. And many that do face them inwards so you can see them really well when you're passing through the bridge but not during the approach.

ActiveCaptain said:

Wrightsville Beach bridge has height boards that measure the height at the center, hightest point, of the bridge. It was unusual enough that we edited the bridge information ourselves to note it. I have to admit that it's the first one I've seen like that - but it was very clearly labeled.

We also found really dumb colors of height boards on some of the NC bridges. White lettering on a green background that gets sun bleached is a really poor choice.

It seems hard to believe that there is much regulation on this especially since so many bridges don't even have height boards. And many that do face them inwards so you can see them really well when you're passing through the bridge but not during the approach.

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Might be worth having a chat with the CG. Here is the CFR on clearance gauges.

33 CFR 118.160 - Vertical clearance gauges. | LII / Legal Information Institute

ActiveCaptain said:

Wrightsville Beach bridge has height boards that measure the height at the center, hightest point, of the bridge. It was unusual enough that we edited the bridge information ourselves to note it. I have to admit that it's the first one I've seen like that - but it was very clearly labeled.

We also found really dumb colors of height boards on some of the NC bridges. White lettering on a green background that gets sun bleached is a really poor choice.

It seems hard to believe that there is much regulation on this especially since so many bridges don't even have height boards. And many that do face them inwards so you can see them really well when you're passing through the bridge but not during the approach.

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I found that 50% of the bridges give a center height, 50% a low steel height and 50% a height st the fenders.

Wxx3 said:

I found that 50% of the bridges give a center height, 50% a low steel height and 50% a height st the fenders.

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And that's the problem, you don't know how the measurements are taken at the bridge you're about to pass through.

After 81 miles today on the ICW and one bridge that only opened on the hour (Wrightsville Beach) and three others that opened on the half hour or hour I must say the bridge tenders were very courteous.

One bridge tender said they couldn't open because there was an EMS emergency on the island and would not open for quite awhile, we removed some hardware to squeeze under instead of waiting for an undetermined time and were pleased we did as it ended up being a fatality that had some waiting for quite awhile.

After reading some interesting exchanges on Active Captain about some of the bridge tenders we were expecting the worst but were relieved how polite all the tenders were.

Thank you ....

gwkiwi said:

After reading some interesting exchanges on Active Captain about some of the bridge tenders we were expecting the worst but were relieved how polite all the tenders were.

Thank you ....

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The vast majority of times we've encountered bridge tenders, they've been courteous and to us they always have been, although one we talk to regularly is short and grouchy sounding. Just his style. Most of the ones we've heard who haven't been nice have typically had good reasons. They were dealing with boaters who obviously had no idea how things worked. Either people upset over waits at scheduled bridges or those not wanting to lower antennas to clear. There have been a couple with discussions of whether they could clear or whether they could if they lowered antennas and the lack of certainty on the part of the boater led to confusion where a quick straight answer would have avoided issues.

We went through Alligator River swing bridge yesterday. That bridge tender has to be the best in the world. He times it all and makes the whole process enjoyable.

Today we're docked at Atlantic Yacht Basin just south of Great Bridge. I heard an exchange on the VHF that was unbelievable. A barge was going south while a few recreational vessels were headed north. Both recreational vessels call the bridge to request the opening. They respond about their hourly opening. The bridge opens and one recreational vessel goes through. The other talks to the barge to let them go first (they were moving and I don't think I would have passed at the bridge either). After the barge goes through, the bridge tender closes the bridge. The second recreational vessel calls to ask what's going on. The bridge tender complains that the boat didn't let them know he wanted to go through. He protests that he DID tell the bridge he wanted to go through and got a confirmation. I heard it myself. The bridge tender says, well, they just had a shift change and he guesses the other tender didn't tell him. But too bad, he's got to wait an hour.

That should have been a Coast Guard complaint. My wife told me to not get involved - not sure why but I listen to her in things like this. The poor guy had to sit circling for an hour.

After almost completing the whole Erie Canal I must say the bridge tenders especially those who on the western part of the Erie have to take care of multiple bridges sometimes several miles apart have been great.

The lock guys 34 that we have dealt with have also been very good, I am impressed by their courtesy and willingness to help.

Even the other day a lock would not open and it took 90 minutes or so to get a generator to arrive to power it up and the lock guy was so apologetic, it wasn't a big deal we all just tied off to the wall and took a stroll but you could tell that operator took the lock failure problem personally.

now that's pretty cool it reinvigorates my belief in good people.

In the back of my mind, I'm worried the bridge will break down, leaving us stranded at the end of navigable water.



"D" Street Bridge, Petaluma, CA, entering turning basin.

rwidman said:

And that's the problem, you don't know how the measurements are taken at the bridge you're about to pass through.

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In most cases I've found it to be labeled as to where the measurement is taken. The clearance sign normally says "clearance at low steel", "height at center", "X amount of feet more clearance at center", etc.