Air Draft

[bilbo]

Has anyone measured or recorded a ballpark air draft for a DS? Driving around I've seen a ton of drawbridges around here. Up to this point I've never had to deal with one in my boat but some areas I'd like to sail in has them around.

An example would be Matlacha Pass Bridge, with 9' listed clearance. Obviously I'm not making it under that one, but others are a bit higher like the drawbridge in LaBelle, FL. That one lists 28ft. There are warnings about fines for having to open bridges needlessly; not sure that's enforced or not but I'd rather not find out the hard way. Estimating by some of the one design dimensions it looks like it would be around 25ft. but I haven't been able to find anything concrete. It should be easy enough to measure when I get home but I'm bored on break so figured I'd do some internet research and maybe save myself the trouble.

[tomodda]

********CORRECTED MEASUREMENTS AFTER MEASURING FULL MAST************

The mast is 25' long from keelson to mast head (in other words, including the part under the cuddy roof). The keelson is maybe a few inches below the waterline, not enough to make a difference. I've always estimated my air draft at 22', AND WUZ WRONG! It's 25'. I tried not to squeeze under any bridges lower than 25', but from now on 28' min. Only time I've ever been a bit dubious was crossing under the VA 227 Bridge on Urbana Creek, Virginia, which I did under engine and sloooowly. All that being said, I lost a Davis Wind Indicator to a tree along a shoreline once, oops! Anyway, 25 feet is the answer to your question.

[GreenLake]

I don't think 22' is correct as measured from the water line. I'd go with 25' plus a reserve for the Windex.

When you are getting within a few feet of nominal, it's worth checking whether the information is based on the current water level. Some bridges where I sail have a marker on the side that's ruled with the remaining height. The number that you read just above the current water level is the one that you can use for that transit.

[tomodda]

Mm, on 2nd thought, 22' might be from the datum - cuddy roof. I have to take my (one-piece) mast down tomorrow, will measure it if I get the chance. Going to be a busy day, re pointing mortar, Woo-hoo! Not what I wanted to be doing for Christmas, that's for sure...

[tomodda]

I stand corrected! 22' is the mast height from the datum, in other words from the cuddy top on up, not the actual air draft. I just finished measuring my entire mast (I have a new-to-me one-piece mast, my old one had a tabernacle hinge). It's 24' 9", but the mast jack adds another inch (width of the "collar"), bringing us essentially to 25' air draft. Add in 6" of Wind Indicator, a bit of bounce from passing waves, and I'd not go under any bridge lower than 28' at the bare minimum, 30' better. This also explains how I managed to hit a tree branch along the shoreline, live an learn! Anyway, note that I've corrected my original post up above. Thank you for prodding me into the exercise of measuring the WHOLE mast, I took it off my boat and propped it up on sawhorses to measure properly.

[GreenLake]

You're welcome.

I've done the thing of sailing into branches and losing a Windex more than once. Also managed to raise the mast on the wrong side of some branches at the boat launch. That one I spotted in time and had some fun maneuvering around them without hitting anything on the ground level.

[bilbo]

Thanks for the replies! Our house was visited for the holidays by Influenza B so we all went “off the grid” for a little while. Thank you for the measurements tomodda. Now there’s something concrete.

I’ve trimmed trees a couple times with my boat, always at the ramp. I’m just glad I’ve yet to trim any electrical lines.

[GreenLake]

Please refrain from the latter. It might be worse than influenza.

Some inland sailing destinations have had issues with low hanging live wires. There was a moderately famous case that made the rounds of some other sailing forums.

So look up!

Our boat launch has wires that follow the street line. It's always fun when the motorboat people suggest we might pull across the street for taking the rig down...