minimum required mooring depth

[ramminjammin]

I have a 1985 tartan 30 , it is listed as draft of 4.9 feet.
I have to put in a mooring , the bottom is mud . I am wondering what is the minimum depth i should choose ? At low tide would six or seven feet be enough depth ?

thanks

[Idiens]

Depends how sheltered it is. I've seen centre keel boats on moorings in Granton harbour that take the ground (soft mud) on every tide. Not my choice, but it the mooring is sheltered enough and the mud soft enough you could used 5ft of water at low water springs. Those guys in Granton have to wait for the tide to go sailing or return to the mooring.

[ramminjammin]

Thanks
It is pretty sheltered i guess; to put it in 5 feet would be a great spot , but I have a good spot where it is six feet so I will probably put it there.

[Idiens]

A clear foot under the keel. Those Baltic sailors would love that, they are quite used to sailing the keel through mud.

[sailingfool]

just remember that mose tide table tell you mean low water, which is an average, half the time the water is lower than the mean, and more with the spring tide. see Tide - Wikipedia, the free encyclopedia if you want a refresher on terms. Five feet at spring low should be OK.

[DrB]

I have boat that has a 6' draft. We are mored in an area that has grass/mud bottom. Last year the lowest water that I was in (saw) was about 7.0 feet (On a real low tide day), which is a little too close for me. Most days the MLLW was just over 8 feet. Our harbor is somewhat protected, but not calm. We also were near a traffic zone, so we would get wave action. This year I asked to be moved to a less traffic area with a little more water. I'll find out tomorrow where exactly and if it has more water.

As a minimum I would suggest a MLLW of no less than 3 feet over your draft if a protected area that receives little wave action. So for your draft I would, think 8 ft ish should be fine. I would go twice your draft for a MLLW if your are in a lesser protected area or your in an area that gets a lot of wave action. If you can get into 10 ft of water with your draft, you should never have to worry about the touching bottom.

Edit: My transducer for my depth meter is on the bottom of my boat about 1 to 1.5 feet below water line, so if my gauge says 7 ft, I am actually in about 8 to 8.5 feet of water. So when I said I say 7, I was actually in about 8 ft of water for 6 foot draft boat.

DrB

[Maine Sail]

Originally Posted by sailingfool

just remember that mose tide table tell you mean low water, which is an average, half the time the water is lower than the mean, and more with the spring tide. see Tide - Wikipedia, the free encyclopedia if you want a refresher on terms. Five feet at spring low should be OK.

Huh?? 5 feet At low water leave him with just 3" under the keel. What if he swings into the mooring or high winds fetch waves that can diminish the trough depth?

For me 8' would be my absolute minimum and that's in a very protected area with zero wind fetch potential and max potential waves of less than 1 foot..

In Maine we can see spring tides of more 3' less than the mean marked depth on a chart...


P.S. It would hep us answer your question more accurately if you filled out your profile with things like what boat you have and where your home sailing waters are.. ME and FL have very different tides??

[JohnRPollard]

I think the varying answers are coming from regions with widely disparate tide range. Even with Maine's big swing, it's not too hard to keep several feet under the keel because it generally drops off quickly up there. Here on the Chesapeake, with small tide range, they recommend 1-2 feet below the keel at MLW. This will cover most spring tides, but sometimes you'll still get caught by a strong seiche. Yes, you could go to deeper water, but with so little/shallow drop off finding two more feet might quadruple your row to the mooring....