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Old 07-14-2012
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Minimum Depth For Slip?

I hope to purchase a new boat soon, and want to stay in my existing marina.
The only issue is that my marina is mainly power boats, and small sailboats, so it is real shallow.

It appears that at negative tides, I might not be able to get out, which to me is not a big deal. There would probably be around a foot of soft mud under my keel, which i don't believe would hurt my boat. I am a scuba diver, and would personally dredge the area under the keel.

One reason i don't want to move is because it is a very nice, clean, and quiet marina. Some of the other marinas around me are a little ghetto. The boat is currently at a marina that is around a foot deeper, but keeping it there is not an option.

I have guys in my marina that have said anywhere from 1-3 feet is acceptable. One person said as long as the keel is off the bottom at negative tides. I once saw a marina that was so shallow, they had troughs dug for keels, and the boats were pretty much resting on the hulls at low tides. They could only go out at high tide. This seemed kind of extreme to me.

So my question is, what is the minimum amount of water you would want under your keel in your slip?

I appreciate any and all constructive advice.
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Last edited by BlueWaterBlair; 07-14-2012 at 10:33 PM. Reason: spelling
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Old 07-14-2012
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Re: Minimum Depth For Slip?

I looked at a First 345 a few years ago, and the first 8 inches or so of the keel were stained from sitting in the mud. Did not seem to do much harm. As long as it is soft, and you are OK with not being able to move the boat at low tide. Too much of a restriction for me, though it was a very protected spot.
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Re: Minimum Depth For Slip?

Paul,

I feel i could get out at low tides, but probably not at extreme negative tides.

I would definitely not let it sit in the mud. If i had to dredge a foot or so for those extreme negative tides, i would do so.

We have a negative tides this week, and will measure at that time.

Thanks for the input.
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Re: Minimum Depth For Slip?

Having moved this past year because of shoaling I would say that if you'll be having problems at anytime other than an hour or so around low it's not good. Now if you only go out for a week at a time and don't plan on day sailing that's different. It sucks having to wait an hour or two to bring the boat back in. The tides never agree with your schedule.

The occasional sinking in mud isn't going to kill a boat, they do sit on the keel when pulled. My boat would be on the bottom in slip during low tides once a week or so (6-12"). The keel just sank into the mud. I don't like the idea of it bottoming out all the time. It does put a strain on things that don't happen on the hard, i.e. waves pushing on the side. I'd be even more concerned if I had a fin keel, my boat has a keel that's 4' long on the bottom so weight is distributed somewhat. In fact one of the other sailboats (not a very well maintained boat) in the marina sank at the slip from bottoming out and having the keel bolts loosen.

Trying to dredge out your slip is a long, hard & I think futile proposition. The slip will likely fill back in again.
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Old 07-15-2012
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Bolt on keels are not designed to be loaded up on the hard. A grounding is a grounding intentional or otherwise.
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Re: Minimum Depth For Slip?

If you can live with the restricted access, which is rightly pointed out to be most often disconnected from your plans, it doesn't sound like there would be any detriment to your boat. For now.

As a general rule, shallows only get shallower as sediment continues to wash in. Not always the case, but most often. Or, little shoals move around with current, storms, etc. It seems you would have little to no room for a one foot shoal.

If this marina is your best option, I would give it a try. Little to no damage would be expected. It may wear the anti-foulant off the bottom of your keel. But I would want a plan B, if the inconvenience was too much or I found myself stuck on a little shoal as I entered or exited.
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Re: Minimum Depth For Slip?

If the wind picks up and waves are formed you will pile drive the keel into the boat. Even wakes from the power boater's will do this. I have 2 friends that lost their boats this way.
Your boat shouldn't rest on the keel when on the hard. It should be resting on the pads, which are placed under the bulkheads that hold the weight of the boat. You will weaken the structural grid which the keel is bolted on, if you continue to place all the weight on it.
I would find another marina.
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Re: Minimum Depth For Slip?

I have a similar situation. We don't have normal tides, but do have wind tide. Boat draws 4' 10" and I probably have 1-1.5 ft. under the keel in the fairway on most days. Boat is wing keel and spade rudder. Bottom is silty sand / mud. If the wind blows out of the west over 20 kts. for a day, I generally can't go out. In the slips here, the keel washes out a hole, so when the water is too low to get out of slip, the boat is still generally floating freely in the slip. If the wind blows out of the west at 25 kts. or more for a day or two, the water is mostly blown out of the creek and the boats settle down on their keels on the bottom. The dock lines go tight (nylon stretches to accommodate the situation if lines are not too short...you adjust length over time to accommodate the rise and fall in the slip). The tight lines steady the boats in an upright position. This is not really different from situation when you put boat on blocks in the boatyard. Problem comes if there is something hard below..a sunken log or rock or similar. In just a very few slips, the boats don't settle down upright, and in such cases, when they go over on the side, they could put unusual forces on the keel or contact the pier where damage could occur.

Settling down in the sand/mud upright, being steadied by the lines to pilings is a frequent occurrance here, and as far as I can tell, boats are not damaged. My current boat has been in such a slip for over 12 years, and no problems. But it would be nice to be able to go sailing regardless of tide/ wind tide conditions at any time, however.

Also, you have to give some consideration when you go out as to what the water depth will be when you come back in.
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Re: Minimum Depth For Slip?

Quote:
Originally Posted by BlueWaterBlair View Post
......There would probably be around a foot of soft mud under my keel.......
I may have misread this as there being a foot of water between your keel and the soft mud. It seems you are saying the mud is a foot deep, then gets hard?

As just pointed out, you need enough water to prevent any wakes or fetch from repeatedly pounding you into the bottom. However, that can and should be a matter of inches. My original point was, having that little room for error is very likely to be problem somewhere along the entry/exit, unless you are just tucked up against shore and it progressively gets deeper away from your slip.
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Re: Minimum Depth For Slip?

The problem with shallow water is that when under power, mud is sucked up into the engine cooling system, and that causes real serious problems.
Don't ask me how I know.

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