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Old 09-06-2015, 07:35   #1
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Jacksonville Bridges vs Lagoon 450

Hi there. We have a lagoon 450 with an air draft of 75.6ft, there are two bridges near Jacksonville we want to clear that are listed as having a clearance at high tide of 75ft. At low tide we would therefore have a few inches to spare if the bridge was indeed exactly 75ft. Does anyone know what the tolerance for the listed height is? I would think they give some margin of error when listing the clearance height but I'm not sure I want to gamble my mast on that! Has anyone else taken a Lagoon 450 up to the Ortega River?

Thanks.
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Old 09-06-2015, 08:01   #2
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Re: Jacksonville Bridges vs Lagoon 450

75.6' top of mast or top and mast plus antenna(s)?

Not sure what you mean by margin of error. The listed height is suppose to measured at mean high high water, which is an average of the higher/highest tides.

If the bridge has height markers at the base, those are 'suppose' to accurate, but I've found differences in them on various bridges. My mast is 65' plus lights, anomemeter, antennas and I've gone under bridges listed at 65' at low tide where the marker boards were 67' and never touched, but gone under other 65' bridges when the marker board read 67+' and drug the antenna on the bottom of the bridge.

YMMV
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Old 09-06-2015, 09:03   #3
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Re: Jacksonville Bridges vs Lagoon 450

I'm only going off the Lagoon spec sheet so I'm not sure but I'll measure it today. Cheers.
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Old 09-06-2015, 10:08   #4
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Re: Jacksonville Bridges vs Lagoon 450

Wish I remembered the exact numbers we discovered but I crewed on a Lagoon 50 and we had the same dilemma in Jax. The Acosta Bridge was the problem...the charts had clearance listed from directly under the center of the bridge -however- the channel you cross through is not directly under the center but closer to the north shore, which means clearance is a few inches less.

We did the same thing, measured our mast, then took the dinghy up to the bridge at low tide to check the clearance gauges. It was a no go, but that was a larger vessel. Turned out to be another adventure to get back down to St. Petersburg hope you have better luck!
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Old 10-06-2015, 10:45   #5
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Re: Jacksonville Bridges vs Lagoon 450

some fyi. The charts in the west seem to use one of two notes. But MHW is the most common. However, The boards on Bridges are typically not a coast guard data. They are put there by other groups for different reasons. (see note from coast guard below). things 75 feet away from me always look a lot closer...

The conversation with the coast guard resulted from curiosity. According to the charts (43' MHW) at low tide (12 foot tidal range) our 46.5' mast 'should' clear. But I can tell you, we have carefully edged up to it at -3 foot tide... and we cannot clear!!!! The boards (put up by railroad) say 48'. My math based on mhw puts the clearance at 51'. but when we get near it, I can tell you it is only 45ft at Minus Low Tide! so I am still trying to crack that nut.

but YOU should be fine...... ?!?!? :-)
MHHW*
Mean Higher High Water
The average of the higher high water height of each tidal day observed over the National Tidal Datum Epoch. For stations with shorter series, comparison of simultaneous observations with a control tide station is made in order to derive the equivalent datum of the National Tidal Datum Epoch.
MHW
Mean High Water
The average of all the high water heights observed over the National Tidal Datum Epoch. For stations with shorter series, comparison of simultaneous observations with a control tide station is made in order to derive the equivalent datum of the National Tidal Datum Epoch.

Hello Mike,
The vertical clearance for the Ballard RR Bridge at mile .1 on the Lake Washington Ship Canal is 43 feet at mean high water (MHW). Mean high water is the average of high waters over a history. The numbers on boards in the water is something for the railroad, however, they represent clearance for under the bridge at given tidal conditions. Please refer to chart 18447.

Best regards,

Danny McReynolds
Bridge Management Specialist
Waterways Management
USCG District 13
(206) 220-7234 <tel:%28206%29%20220-7234>
d13-pf-d13bridges@uscg.mil


also...

Sir, please refer to NOAA's Tide Tables for the West Coast of North and South America, or
Tide Predictions - SEATTLEĀ*9447130Ā*Tidal Data Daily View - NOAA Tides & Currents.

Danny McReynolds
Bridge Management Specialist
Waterways Management
USCG District 13
(206) 220-7234
d13-pf-d13bridges@uscg.mil
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Old 10-06-2015, 11:31   #6
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Re: Jacksonville Bridges vs Lagoon 450

Keep in mind that water levels in the St Johns River below Jacksonville are strongly influenced by wind. So if you try, base your decisions on what you find for actual conditions, not what the tide predictor on your chart plotter says.

You might check with some of the marinas upstream from Jacksonville and downstream from Shands Bridge to see what they say. Green Cove Springs 904-284-1811 is one, and there are others.
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Old 11-06-2015, 08:39   #7
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Re: Jacksonville Bridges vs Lagoon 450

Howdy,

I have an Islander 32 tall rig. 50' overall. For years I have used a trick to get myself off of sandbars and under impossabel (impassable) bridges.

Unhook your mainsheet block from the traveler, swing the boom out as far as it will go and secure it with the preventer to hold in place. Bring your dink around, attach the block to it and fill the dink with water. Crank on the mainsheet and you will be surprised how far you can heel over. There is a video somewhere, I think on youtube where a person on a large ketch used 2 1,000 lb water bags attached to his masts and swung (is that a word) them to stbd. to get under a bridge.

Going under a bridge choose low tide or just before or after low slack so that the slackened current is against you. It will make it easier to stop if necessary and move you back out with no effort.
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Old 11-06-2015, 11:46   #8
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Re: Jacksonville Bridges vs Lagoon 450

I use to live on the Ortega river, so I know the area very well. There is only one bridge you need to worry about on the Ortega and it is the Roosevelt Boulevard bridge, the other bridge is a draw bridge.
I don't know the clearance there, but you could call Huckins Marina (904) 389-1125. They are located right beside the bridge. And yes, they were the builders of the PT boats in WW2. There is also Lambs Marina (904) 384-5577, which is past said bridge and they have many sail boats there.
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