Bridge Clearance

[Sazaisan]

Greetings all,

I am getting close to purchasing my first boat and need help with a bridge clearance issue. The entrance to the marina I plan to dock at is restricted to 42 feet. I would like to get the biggest boat possible that will allow me to pass under the causeway at 42 feet. I have discovered that a 1997 Beneteau 281 Oceanis has a 38'8" clearance and that seems like quite a nice boat and is something I think I would be happy with. Does anyone know of any other boats that are in the 28 foot (or longer) range that will pass under a 42 foot bridge?

Thanks, Sazai

[Kevin84]

What are you planning on using the boat for? Day sailing, weekending, long term cruising or liveaboard? Size isn't everything. Also, is that marina your only option in the area or do you have other choices?

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[Tx J]

There are a few other factors to consider besides published clearances and the boats' air draft (38'8" seems a little short for that boat?).
Stuff like masthead nav lights, windex, and antennas will/may add a few feet to your height. Tide levels and just plain wave motion can add a couple of feet +-. And most bridges are curved/arched, so not sure if the published clearance is the max at center, or minimum above all of the channel.
The effect of storms and associated winds can also affect water levels greatly too, especially in bays; and Murphy's Law states that such effects will be worse when you need to move to a hurricane hole somewhere else on short notice, just when you need it most.

We used to sneak Hobie cats under the short(er) parts of the old Queen Isabella causeway, but it was best to heel it over like crazy as you went under it , and setting up the course angle vs. wind and chop could be tricky.
If under sail, the bridge and its' piers also do weird things to the wind, so you need some momentum, especially for a wide one.

[ddsailor25]

I wouldn't base your purchase just on mast height restrictions unless like Kevin said that's your only option for marinas. If you looking at boats with that restriction, the Cape Dory 28 or 30 should fit under that bridge.

Dave

[casual]

Probably as good a choice as any. I see you are lake sailing and need not concern yourself with tides. At 39 ft 3 ft for what ever you mast mount should be ok.

[Sazaisan]

First of all, thank you to everyone for your helpful responses.

Answering Kevin84’s questions, I plan to use the boat as a liveaboard for part of the year (winters in Minnesota can be brutal, my choice of marina is set, and the 42 foot restriction is something I need to work with. Tx J mentioned “air draft.” This is something I have not heard of before. Can anyone explain what that is to me? The 38’8” bridge clearance is the spec from the Beneteau company web site and seems to be acknowledged by other Beneteau owners. My target marina is located on the Indian River (Florida) and probably less susceptible to height changes caused by tides. Regardless, transiting the causeway would be done after verifying the clearance and taking tides into consideration (transit would be done at low tide just in-case there is a cause/effect there). If there is any real concern I would remove anything ancillary such as antennas lights, etc. to prepare for transiting the causeway. Finally heeling the boat over is an additional consideration. The transit could be done during high wind and a significant reduction in overall height could be achieved (could probably gain an additional foot) using this maneuver. ddsialor25 mentioned the Cape Dory 28 which has a mast height of 39’6” and is right at the max height of the causeway. Thanks for that suggestion.

Again, thank you to every one for your input. Additional comments welcome.
Sazaisan

[Kevin84]

Actually, rivers can have higher tidal changes than some harbors. The marina I docked my old boat at was on a river and we would have up to 6 feet differences between low and high tide.

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[Stumble]

Sazai,

Is transiting this bridge something you will need to do often or just once to get the boat home?

For a one time thing there are large water bladders than be used to heel a boat over far enough to get it under the bridge. Trying to use the sails... It's possible, but not advised. There are lots of swirling wind currents under bridges, and it isn't at all uncommon for the wind to die completely, or back 180 degrees while transiting.

http://m.youtube.com/watch?v=WGAzt-8minI

[Stu Jackson]

Originally Posted by Sazaisan

Tx J mentioned “air draft.” This is something I have not heard of before. Can anyone explain what that is to me?

The distance between the waterline and the top of everything on the top of your mast so you don't hit the bottom of the bridge above you.

The term is used a lot in Europe on the canals for the low bridges there. Same concept.

Doesn't mnatter whether you're just coming down to get away from winter or using the boat for sailing, sooner or later ya gotta get under the bridge.

Why not buy a boat that will fit?

[roverhi]

Might want to investigate a boat with mast in a tabernacle. That allows you to lower the mast for low clearance access. With a tabernacle, you can get a boat as large as 40' though that would probably pushing the limit.

[RKsailsolo]

Is it folly to refit a tabernacle on a Leapord 38 cat?

[CarlF]

First, get local knowledge of the bridge clearance. If the 42' number comes from the marina, you can be sure their lawyers have insisted on a very conservative number. Many of the bridge measurements on the charts also understate the clearance as no one reports a reading that is too high.

If you aren't going to do it every day, you can cut it very close ("creeping" speed) and make some preparation. Definitely plan to take anything that goes above the hard top of the mast down (although stainless whip VHF antennas will just bend and come back). Once you've done it a few times, you'll know by the water height on the bridge piers whether you have enough room.

You might look at ketches. A Cape Dory 30 ketch has a bridge clearance of just over 38'.

A Bristol Channel Cutter 28 (which is much bigger below than a typical 28' boat - and pricey) has a 41.5' clearance.

[markpierce]

Motorboats typically have a lower "air draft."

[Sazaisan]

Hello again. Quite a bit of useful information on this. I think I will get enough input to make the correct decision. As I said in my initial post, I am buying my first boat so after I get it docked at the marina it will most likely remain there for some time while I take lessons and assemble the basic sailing skill set. Having said that, if the boat fits under the bridge once, it will fit again. The tabernacle idea is a good one, but I don't think that is something that is a retrofit option. I have noticed that some of the shorter boats that are able to be trailered use this mast method. I think the boat would need to be designed with a tabernacle mast from the beginning. Does anyone have any experience with tabernacles? Are they sturdy enough? What are some manufacturers/model numbers of boats that use this system?

Thanks again everyone.

Sazai

[roverhi]

You should be able to convert any reasonable sized boat with a deck stepped mast to a tabernacle. Seem to remember there is a video of lowering a tabernacle mast on a Westsail 32. Our W32 had the tabernacle base but never tried lowering it. It consisted of a base with an axle and reinforcing plates welded to the mast that the axle passed through. Would have required adding a link plate to the cap shrouds that would allow a pivot in a horizontal line with the tabernacle axle to lower the mast.