Calculating ACTUAL bridge clearance

[markpierce]

Knowing your air draft and bridge clearance can be critical.

[reed1v]

Be aware that bridge height is not to be relied upon down to the inches, nor even the foot. Steel expands and contracts with temperature, sags under loads and barometric pressures, changes with wind speeds, and stretches with age. Should leave at least a foot safety margin. Also be aware that some bridges have electrical cables hung underneath. You do not want to hit those with your mast(s). finally you are financially responsible for any damages you cause to the bridge, cables, or pipes.
If you hit the bottom of a bridge, your mast can get stuck,causing your boat to turn sideways, and sink if there is a current running under the bridge.

[buzzstar]

Originally Posted by emcmia

You would be well advised not to cut it so close, especially given all the variables. I recently lost all the masthead accoutrements when a powerboat came by with a 2ft wake. Expensive!

Both the advice and the example need to be emphasized!!

It at least appears the water bags in the videos would be a good way of getting the extra margin you would want. I am unable to recall which one, but there was a fairly extensive discussion of techniques, including the water bags, that was on one of the Yahoo sailing groups' forum a couple of years back. Maybe heavy water would work better. The trig calculations should be easy, but achieving the proper angle for the dangle could be troublesome.

With all of the information, and your mention of a drawbridge, it seems there are viable options. Let us all know what you eventually decide.

[CaptNemoO2]

Out of curiosity, where in Jamaica Bay are you planning to keep the boat? I can only think of Broad Channel or Mill Basin. Are you open to other places to keep the boat, or is the boat going to be at a private residence that you own or know the owner (as in much cheaper than a marina)?

Also, the Marine Parkway bridge does open, though requires advanced notice outside of 8am to 4pm Monday through Friday.

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[reed1v]

Of course, he could just let his boat flood so it barely floats. That should give him another two to three feet of clearance.

[OrangeCrush]

Thanks all, I like the creative thinking on this.

I'm definitely not talking about taking chances with my new boat and I will exercise due diligence at every crossing. I'm really just trying to figure out what my cutoff should be for maximum air draft, and what boats I need to rule out completely so that the stress of passing under the bridge never outweighs the joy of getting the boat I want. I will ask every potential seller about air draft and I will measure myself before buying.

Emcmia, that is very cautionary tale about your bad luck with a wake. That is indeed a factor that I could not control for if I was cutting it too close. I was (wishfully) thinking a wake wouldn't raise the mast height much, but rather make the boat pitch around its center of gravity. Your experience definitely says otherwise.

Capt Nemo, I kept my last boat in Mill Basin at a slip at Dimeglio's Boat Yard. I trust the guys there and I don't think I'll find a better rate anywhere in the city. They're raising the Mill Basin bridge (the Belt Parkway) to 60ft of clearance, so I've been thinking that was my limitation. I completely forgot that the Gil Hodges Bridge is only 55ft until last week, so now I am crossing boats off my list that I thought were real contenders. I'm also considering the 79th St. Boat Basin, although that would be a mooring and the largest boat they can fit right now is 35 feet. Gateway Marina and the one in Gravesend Bay were WAY more expensive last I checked, and I'm guessing Sheepshead Bay is too. I'll ask around again, but it's probably not worth nearly doubling my annual slip fees for an extra foot or two of boat.

Right now I'm thinking that if I can confirm that a specific boat I (desperately) want is no higher than 54 feet off the water, it could still be worth it. I think paying attention to the tides and calling ahead when necessary could be bearable in the long run, and if it becomes too much of a pain I can also pony up for a better placed marina later on. On the other hand if I filter it down to 50 feet as a maximum air draft, I could enjoy the luxury of not thinking about it at all and I still have some good boats left on my list, like the Cabo Rico 38, Cape Dory 36, Southern Cross 35, and Bristol 40.

I think this is still technically one of those "good problems" to have, and I welcome any more thoughts and opinions you all have, including about the boats on my list. Thanks!

[Montanan]

Originally Posted by goat

Why all the calculatin'?

goat

This is a great idea. Such a perfect use for my kegs of beer on my day cruiser.

As an alternative, one can just lower the water below the bridge.

Reference the following weblink.

Ingenious Design Lowers the Water Under a Bridge to Let Tall Ships Pass

[OrangeCrush]

Originally Posted by Montanan

As an alternative, one can just lower the water below the bridge.

Or we could just flood the bridge and sail wherever we want!

[reed1v]

Be sure to check the decks carefully any Cape Dory boats you might buy. The Cabos are first class construction. Bristols right behind, and then the SC. Capes are way, way behind.

[OrangeCrush]

Originally Posted by reed1v

Be sure to check the decks carefully any Cape Dory boats you might buy. The Cabos are first class construction. Bristols right behind, and then the SC. Capes are way, way behind.

Thanks Reed, good to know as I hadn't heard that point of view. Although I haven't been out on a CD, I've been getting the feeling that they are a bit overrated and overpriced in general... used to be at the top of my short list but now closer to the bottom.

Any opinions on quality of the Baba 35 or the Valiant Esprit 37? Or how about the Tayana 37 or Corbin 39 (if I didn't have to worry about the bridge)?

[kas_1611]

Originally Posted by OrangeCrush

Keiron,

Thanks but I believe you are confusing the European system with the US way of doing things, which as usual is perhaps a bit less logical.

HAT would make a lot of sense as it is a more conservative reference point to use, but in the US they generally use MHW on for charted bridge clearance figures. This means that even though the clearance is listed at 55ft for the bridge I'm talking about, on a spring tide there will actually be less than 55ft of clearance. Depths are calculated from MLLW, which is the average of the lowest of the two low tides in a day, but again it is not the lowest tide possible. This means that you could run aground with a 5 foot draft where the chart says you have 5 feet if it was around the time of the full moon.

I am not trying to defend this system but I did read someone make the argument that weather alone could make the tide higher or lower than it should be, so captains should be aware of the need to adjust their calculations anyway, and that using the MHW and MLLW is more accurate even if it's less conservative. Then there is the question of rivers, which are even more variable depending on seasonal rainfall.

Let's hope those tide boards that show clearance at the base of the bridge are accurate at least...

Jack

Jack you said it!!

HAT and LAT just make total sense rather than using an "average" which changes daily . It's a bit like why you guys have to have your channel markers the wrong way round, never understood that one either.

By using MHW and quoting a clearance of 55ft you are not actually giving an accurate clearance as it is not the MINIMUM clearance possible. Given the American love of suing I'm surprised no one has. As the stated clearance is not under anything but average conditions. Weirder and weirder said Alice.

Oh well it keeps us all on our toes and despite what many would say we do love our cousinbrothers over "the pond"

Keiron

[reed1v]

Originally Posted by OrangeCrush

Thanks Reed, good to know as I hadn't heard that point of view. Although I haven't been out on a CD, I've been getting the feeling that they are a bit overrated and overpriced in general... used to be at the top of my short list but now closer to the bottom.

Any opinions on quality of the Baba 35 or the Valiant Esprit 37? Or how about the Tayana 37 or Corbin 39 (if I didn't have to worry about the bridge)?

All good boats. The Baba and Tayana are virtually the same boats.Comfy, woodwork everywhere, cruising boats. Decks again may be an issue since they mostly were teak over plywood. Both rather a different breed than the Valiant and Corbins. But again, all four have sailed around the world many times. All four built for long distance cruising, not so the CD. Plus the CD has no real shearline worth looking at . Looks like a whale's back.

[OrangeCrush]

Originally Posted by reed1v

All good boats. The Baba and Tayana are virtually the same boats.Comfy, woodwork everywhere, cruising boats. Decks again may be an issue since they mostly were teak over plywood. Both rather a different breed than the Valiant and Corbins. But again, all four have sailed around the world many times. All four built for long distance cruising, not so the CD. Plus the CD has no real shearline worth looking at . Looks like a whale's back.

Thanks again, Reed. Since you're being so generous with your opinions I'll keep asking... How about the Rafiki 37?

I'm well aware of the teak deck issues on all these older boats and I wouldn't consider a teak deck unless it passed the survey with flying colors. I don't mind maintenance that I can do myself but I definitely don't want a boat with any serious underlying weaknesses.

Also, any more boats that you think are missing from my list so far? My basic criteria are that it be heavy, comfortable and bluewater capable, 35 to 40 feet, full keel or very very robust fin, very sturdy with no serious build issues, with a strong preference for a cutter rig. The Crealock 37 and Hans Christian 38 also look good but I'm a little less optimistic about finding a decent one in my price range, which is about 50-75k. The Morgan 382/383/384 is another thought, not my favorite but it's on the cheaper side so I might find a pristine one that's well equipped for offshore.

Any obvious boats missing from consideration?

[CaptNemoO2]

Originally Posted by OrangeCrush

Capt Nemo, I kept my last boat in Mill Basin at a slip at Dimeglio's Boat Yard. I trust the guys there and I don't think I'll find a better rate anywhere in the city.

I can understand that. Trust is a big issue.

Originally Posted by OrangeCrush

They're raising the Mill Basin bridge (the Belt Parkway) to 60ft of clearance, so I've been thinking that was my limitation. I completely forgot that the Gil Hodges Bridge is only 55ft until last week, so now I am crossing boats off my list that I thought were real contenders.

Are they going through with that? Last I heard it was still a proposal, nothing was planned for making it a reality.

Originally Posted by OrangeCrush

I'm also considering the 79th St. Boat Basin, although that would be a mooring and the largest boat they can fit right now is 35 feet. Gateway Marina and the one in Gravesend Bay were WAY more expensive last I checked, and I'm guessing Sheepshead Bay is too. I'll ask around again, but it's probably not worth nearly doubling my annual slip fees for an extra foot or two of boat.

I was going to suggest Sheepshead Bay since there is a large sailing community there. It is also a whole lot more convenient to actually going sailing. Though while not being at a dock is a draw back, you're not limited to certain boats due to mast height. And the biggest advantage is being a few minutes away from sailing, with no worries about draw bridge schedule or tides. You will use the boat way more if you could be sailing in 10 minutes verses an hour or more. I don't know where you live, or how much you pay now, but there are a few places here on the South Shore in Nassau. My old yacht club is in Bay Park. It may be a bit more money than other places, but you get a pool, and a cheap place to store a dinghy or two. I don't remember what the dues were, but I believe it was $35/ft for the season. My 12 foot center console rib cost me an extra $150 to keep there. It's about 45 minutes to the ocean through the Atlantic Beach Bridge, but if it's nasty in the ocean, you can sail in Reynolds Channel, or right in front of the marina. And there is a Tayana 37 there too. If you live in the town of hempstead, there's room here in Freeport. 10 minutes to the draw bridge, and another 5 to 10 to the ocean.



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[hrsail920]

I watched the video, very impressive. But, how do you get the initial listing of the boat?