Air draft and ICW bridges

Jan 22, 2008
101
Hunter 40.5 New Bern NC
In theory would this work (I don't think I would have the nerve to try it ) I have a Legend 40.5 if I see the tide boards reading 64 ft of clearance I will "ding" my vhf antenna on the bridge girders ,at 1800 rpm I'm cruising at 7 knots with a Flex-O-Fold 3 blade prop which at that speed and rpm will cause the stern to squat a good 6 inches at 2000 rpm maybe about 8 inches (can you say over propped) ??? my question in theory.......with the stern squatting 6 to 8 inches would that reduce the air draft????
look forward to your replies
Capt. Ron
 
Jun 14, 2010
2,081
Robertson & Caine 2017 Leopard 40 CT
Yes, in theory. It would increase your aft-leaning angle, and assuming your mast is stepped somewhere just forward of amidships, the deck level should not be raised by the bow wave.

My question: Do you feel so confident in the accuracy of tide boards and tide tables that you'd risk your mast by making a 7-knot approach with little margin for error? I'd creep up on it if it was close.
 
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May 24, 2004
7,129
CC 30 South Florida
Have not worked out the math but it seems to me that a squat of 6 inches at the stern would only translate perhaps as 2 inches at the mast at best. There are other factors like for how long can the boat hold the squat before its depth starts decreasing. The strength and direction of currents will also influence the depth of the squat. I think at best is a poor gamble; the tried and true methods are to plan arrival and approach at low tide or to heel the vessel.
 
Oct 2, 2008
3,807
Pearson/ 530 Strafford, NH
We are always checking air draft. With speed we ride up on the bow wave being higher in the water. Yes we've bent antennas and anchor lights. Going slow we clear at our desired height.

All U Get
 
Jan 22, 2008
101
Hunter 40.5 New Bern NC
We are always checking air draft. With speed we ride up on the bow wave being higher in the water. Yes we've bent antennas and anchor lights. Going slow we clear at our desired height.

All U Get
I'l' stick to idle speed and a low or falling tide, wouldn't hurt near as much....kiss vs a SMACK
 
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May 27, 2004
1,964
Hunter 30_74-83 Ponce Inlet FL
Please notify us when and where you plan to try this method CR.
I'll sail over to watch!
 
Aug 22, 2017
1,609
Hunter 26.5 West Palm Beach
If I had to cheat on air draft, I'd be more likely to run my main halyard over to my tender that I had a fat boy run along side the boat & try to pull the sailboat over into a little bit of a heal with the weight of the tender. I would need a good reason to try even this trick. Waiting for proper tide would still be my first choice.

If you are going to try that other trick, you might want to invest in some nylon bolts to mount your antenna with. Spare nylon bolts are cheaper than antennas.
 
Oct 22, 2014
20,989
CAL 35 Cruiser #21 moored EVERETT WA
Ggrizzard. If you go take pictures. This could be a viral YouTube video in the making. Maybe American Home Video entry. They have a 100,000 grand prize.
 
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Webone

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Apr 30, 2010
50
Jeanneau 45.2 Saugatuck, MI
I have 64.5 draft, went from NC to FL, made them all but scrap ant. several times and always went thru questionable ones on low tide, (had to wait 3 times, couple hours at most) even pulled up to the fenders and walked to boat thru.
It seems to me if the stern is squatting, with the mast forward of the moment it might actually lift a little.
 
Jun 4, 2004
292
Hunter 49 123
I went thru the dismal swamp with a reported 64 ft bridge (there is no tide in the canal and the Corp of Engineers keep the level to around 6 ft deep). I have a 63' 4" clearance to the top of the wind instrument, I also have a 3 ft vhf antenna and a 4 ft SSB/DSC antenna. Going under the 64 ft bridge was a nail bitter (remember not tide or wake to worry about - sort off). The metal antennas scrapped the bottom of the bridge. I lost the bird spike on the wind vane because it was hit by one of the antennas. One of the unknowns and my concern is when you are under the bridge and a wave/wake hits your boat you may bounce and hit the bottom of the bridge. I continued all the way to Miami with a couple of nail bitters/scraping the bottom of the bridges with antennas. I did go out from FLL to Government cut because there is a fix bridge in between FLL and Mia. The worse case was a bridge in Fl that had a 6 inch difference between hi and lo tide and no high board.
 
Jan 22, 2008
101
Hunter 40.5 New Bern NC
I went thru the dismal swamp with a reported 64 ft bridge (there is no tide in the canal and the Corp of Engineers keep the level to around 6 ft deep). I have a 63' 4" clearance to the top of the wind instrument, I also have a 3 ft vhf antenna and a 4 ft SSB/DSC antenna. Going under the 64 ft bridge was a nail bitter (remember not tide or wake to worry about - sort off). The metal antennas scrapped the bottom of the bridge. I lost the bird spike on the wind vane because it was hit by one of the antennas. One of the unknowns and my concern is when you are under the bridge and a wave/wake hits your boat you may bounce and hit the bottom of the bridge. I continued all the way to Miami with a couple of nail bitters/scraping the bottom of the bridges with antennas. I did go out from FLL to Government cut because there is a fix bridge in between FLL and Mia. The worse case was a bridge in Fl that had a 6 inch difference between hi and lo tide and no high board.
I have been thru that bridge several times always bang the antenna, last time it took off the windex and bent back the shaft
 
Jan 22, 2008
101
Hunter 40.5 New Bern NC
Ok, I said in theory, I didn't say I was going to try it....... I know some of you will be disappointed to hear that.
Regards
Capt. Ron
 
Oct 2, 2008
3,807
Pearson/ 530 Strafford, NH
Ggrizzard. If you go take pictures. This could be a viral YouTube video in the making. Maybe American Home Video entry. They have a 100,000 grand prize.
Only if you have a baby or family pet in the video.

All U Get