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post #1 of 13 Old 07-25-2008 Thread Starter
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Accurate Draft?

Just purchased a new boat, have only been sailing for about 1 yr and will be sailing in the Keys. The boat has a wing keel advertised at 4' 8" draft. From where? My other question is once loaded with people and gear, it will ride lower in the water, so what will be the safe distance from the lowest point of the keel? When looking at the charts in the Keys, there is a lot of shallow water, and I do not want to miscalculate the draft of the boat. Hope this is not a stupid question.
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post #2 of 13 Old 07-25-2008
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Basically, add a foot just to be safe... If you figure you need six feet, when you're a little off... you'll probably be okay... if you figure on five feet, you're going to go aground a lot.

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post #3 of 13 Old 07-25-2008
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The draft is given from the design water line, which may be entirely different from where the current water line is.
If in doubt take a stick and measure - in any case do what SD recommended and give yourself an extra foot. or more.
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post #4 of 13 Old 07-25-2008
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In the keys, you don't have an extra foot to play with in many places so I would simply hop overboard with a tape measure (or a lead weight and string and measure your loaded boat waterline to the bottom. Usually loading the boat for casual cruising does not add more than a few inches. My guess is that 5.5' will be sufficient bottom clearance for the tough parts and you'll probably have 6 inches to spare. A wing keel is difficult to un-ground...and expensive in the keys too!....so you are right to try to get a very accurate measurement. While you are measuring...it is a good time to re-calibrate your depth sounder in a place where you now KNOW the depth for sure!

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post #5 of 13 Old 07-25-2008 Thread Starter
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Thanks for all the suggestions.

I will check the make sure the depth sounder is correctly calibrated, and after loading, measure the depth to the bottom of the keel! All these are much appreciated!
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post #6 of 13 Old 07-25-2008
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As an alternative, don't worry about the waterline on your boatans absolute keel depth, adding a foot as mentioned should suffice for chart navigation purposes. You need to know the exact depth difference between your sonar transducer and the bottom of the wing keel. No matter how many people and how much gear you pile on that will always be the same ... of course you need to turn the sonar on and remember that the sonar gives the depth from the transducer not the actual depth.

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post #7 of 13 Old 07-25-2008
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We have our depth sounder calibrated to show how much water there is BENEATH the keel. Since we draw 6'9", in 8 feet of water, it shows 1.25'. With the alarm set to whenever there's less than 5' of water beneath the keel, we tend to avoid running aground most of the time.
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post #8 of 13 Old 07-25-2008
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You might play around with the numbers for different boats on this site as well. Sail Calculator Pro v3.52 - 2000+ boats One of the things it'll give you is the pounds per inch immersion for different boats. You need to know this so that you have an empirical reason for denying your mother-in-law access to the boat.

There's any number of ways to set up your depth sounder; the only important thing is to remember how you've set it up! 'Notherwords, pick one reference point and stick with it.

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post #9 of 13 Old 07-25-2008
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my boat is suppose to have a draft of 4'3" - i tell everyone including myself that it is 5' - and when i see water less than 6' my heart rates goes up - i also think my depth gauge maybe off a bit and read shallower than actual as i have checked it against other boats that i have followed into and out of anchorages - so do i lie to myself -- YEP - do i lie to everyone else - YEP - and have i convinced myself that i draft 5' --YEP - do i believe my depth gauge is accurate - KINDA -- and do i stay out of trouble - you betcha
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post #10 of 13 Old 07-26-2008
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Am I the only one lands on beaches with a sailboat?
My sounder is on the bottom of my rudder therefore things are safe unless i land on sand where I lift the rudder...
I'd recommend a good study of charts and a good investment of a chartplotter... Once you mark your draft on chartplotters, they would warn you about shallow waters...
PS: The equipment and people wouldn't drop the draft more than a couple of inches... The hull is shaped so the heavier it gets, more square footage lifts you up...

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Last edited by merttan; 07-26-2008 at 11:04 PM.
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