Think tank

[All U Get]

Hi all,
We got under the famed Wilkerson Bridge by heeling our boat 6 degrees. Thanks to the on-line help and the great group we're sailing with. We worked out a strategy while laying over in the Solomons and then had everyone anchor their boats and come back to the Dalmatian via Our Little Cape. With everyone hanging out the starboard side like rail meat, we listed three degrees. We then swung the dingy out on the boom to get to four degrees. The washdown pump and garden hose filled the dingy with water to get more than six degrees and we headed under. The whip antennas for the VHF were the only things to touch as we slid under. All the math we did really worked.:dance:
All U Get

There's a video if we can figure out how to publish it, just plain happy.

 

[caguy]

That must have been a nerve racking moment. Did you also use the tides?

 

[gettinthere]

Yikes! What was the board reading?
No tide to speak of, but wind driven levels can vary a lot there. "Normal" is supposed to be 64', if you had issues there, you'll have more issues further south. We've been seeing a lot of 62' & 63' board readings in northern Fla. Seems water levels are high all along this stretch so far.

 

[All U Get]

The board was 64.5 more or less. We've been clearing the 65's OK but it's always tense because there have been loose wires dangling below the beams. We measured ~ 63 for the mast head, 12 inches of lights, wind instruments, windex, and hard antenna. A static diffuser extends 6 inches above that and another foot for the VHF whips.

All U Get

 

[gettinthere]

You may have more issues ahead.

Our mast is 61' plus the same stuff you have, putting us at around 63. Our whip has not tickled any steel yet. But we keep seeing 65' bridges showing 64 and less on the boards, all down the north half of the Fl ICW.
We saw the 64.5 at Wilkerson and did not tickle the steel there.
We're in Indian River with virtually zero tide. All the 65' bridges are reading 64 to barely 65. Several bridges north of St. Aug seemed especially low, less than 63, but again there, we did not touch.
We don't remember seeing such skinny readings on the way north in May. I think the winds have driven the water levels especially high.

Worth looking into in my estimation. Good luck!

 

[Gunni]

Čestitam mornar! Bravo!

 

[RichH]

Good job.

Just remember that the Fl Highway Department has all those 'air gap' boards indicating the LOWEST clearance ... usually at the outer boundaries of the actual channel and where the bridge's 'structural arch/bow' is at its minimum over the channel.

Simple speak - there is usually more clearance for the FL AICW bridges if you stay exactly in mid-channel and exactly at 'mid span' .... sometimes the clearance, as indicated on those 'clearance boards', is measured from the bottom of the bridge's hanging 'range lights'.
The hanging-down range lights and the 'adjustment' of the 'clearance posting boards' have been the subject of litigation (what else!!), hence the 'conservatism' of what's 'indicated'. When in doubt ask the closest bridge tender .... by PHONE.

 

[All U Get]

Thanks Rich. When you're looking up those lights seem to be a foot lower and I've been running to the side of them just in case. Some bridges didn't have boards that we could see so we took it as "Plenty of Room".

All U Get

 

[gettinthere]

South carolina seems to have quite a few unmarked bridges.

We were extremely happy to have been able to go outside from Beaufort to Charleston & Charleston to St. Simons. And both mornings we were greeted by great dolphin shows!

 

[RichH]

This is what you need if your mast is 'close' to that 65ft. height:

http://www.amazon.com/Fluke-411D-La...286398&sr=1-2&keywords=laser+distance+measure

 

[Stu Jackson]

Higher tides next few days

Yikes! What was the board reading?
No tide to speak of, but wind driven levels can vary a lot there. "Normal" is supposed to be 64', if you had issues there, you'll have more issues further south. We've been seeing a lot of 62' & 63' board readings in northern Fla. Seems water levels are high all along this stretch so far.

Have you considered that tides WILL be higher since we have a full moon just passed? Spring tides. Yup, right in the middle of winter! :naughty:

 

[WayneH]

This is what you need if your mast is 'close' to that 65ft. height:

http://www.amazon.com/Fluke-411D-La...286398&sr=1-2&keywords=laser+distance+measure

ooooooh, NICE! But I had a thought. It would be nice to know BEFORE the bridge if you can fit under it. Does this one make triangle calculations? Pythagoras Calculations? The Fluke 416D does but it's $235. My wife can do these calculations in her head but I wouldn't trust MY figures with my boat's mast. :naughty:

Let's see distance to base of bridge pillar = x, distance to top of bridge pillar = y, height of bridge pillar = z so

z = sqrt of (y2 - x2) plus how much for the arch. Ah, heck if I can clear the pillars, I can clear the midspan.

On a different note, there's a drawbridge on the GICW in Louisiana that has a CLOSED clearance of 73 feet! If you give the Louisiana DOT 24 hour notice, they will open it for you. And I thought my 55 feet was tall.

 

[Rick I]

Here's how it's done. Saw this at Vero a few years ago.
http://www.youtube.com/watch?v=epz6BBZm__0

 

[Dan Johnson]

Ooh! Ooh!

Another stocking stuffer toy! Thanks, RichH!

 

[gettinthere]

Have you considered that tides WILL be higher since we have a full moon just passed? Spring tides. Yup, right in the middle of winter! :naughty:

Considering we did this over 2 weeks ago, I don't think the full moon played a part north of st aug. Locals have commented the tides are the highest they've seen in a while

 

[Chris Patterson]

I love watching that video. Yup, that feller sure has got some big ol' balls..

 

[Joe]

ooooooh, NICE! But I had a thought. It would be nice to know BEFORE the bridge if you can fit under it. Does this one make triangle calculations? Pythagoras Calculations? The Fluke 416D does but it's $235. My wife can do these calculations in her head but I wouldn't trust MY figures with my boat's mast. :naughty:

Let's see distance to base of bridge pillar = x, distance to top of bridge pillar = y, height of bridge pillar = z so

z = sqrt of (y2 - x2) plus how much for the arch. Ah, heck if I can clear the pillars, I can clear the midspan.

On a different note, there's a drawbridge on the GICW in Louisiana that has a CLOSED clearance of 73 feet! If you give the Louisiana DOT 24 hour notice, they will open it for you. And I thought my 55 feet was tall.

My binoculors have a distance/height calculator built into one of the lens barrels. You know the distance, measure the height angle through the viewer, use the calculator to solve for height. Takes about 10 seconds to determine the angle and then rotate the calculator to find your answer.

 

[Manureva]

it is easy, to get your required height and degree. the length of your mast would be your hypotenuse and the required heigth your opposite side, so sin -1 X required height divided by mast length should give you the minimum required angle to clear the bridge

 

[Ron20324]

Locals have commented the tides are the highest they've seen in a while

Maybe the moon is in perigee???

 

[All U Get]

Oops

Well what Roger said about getting tired last year is reallly true. We were heading out of Morehead Yacht basin and I miscalculated the tide under the bridge. I would have cleared but getting over the swell the boat lifted enough to catch my antennas. The windex must have flexed enough to bounce back. I'll have to take a trip up the mast to check it out.:cussing:

We anchored at the Atlantic Beach Bridge for 3.5 hours for the tide to fall again and we got through well below the beams. Anyhow we caught up to the group and had a nice evening of scallops we picked up at R E Mayo's.

La Dolce Vita

All U Get