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Old 04-04-2014, 18:05   #1
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Anchoring in a shallow lake

Hi all; Not having a dock, I need to raise and lower my mast each time to transport to the boat ramp when I'd like to sail. Since the lake is within walking distance I thought I might try anchoring semi-permanently there. My public dock attempt didn't turn out too good. Chop was so strong during a wind that I pulled a cleat out of the dock and loosened others even though I had multiple lines and used the pilings in addition to dock cleats. I've observed it gets extremely choppy in just 10 mph wind and have been somewhat hesitant to try. Boat is a 23 O'day. I have an 8lb danforth and a 12 lb plow anchor. Was thinking of going double off the bow. Over a week's time you can expect winds from all corners but mainly from the North. (Central Florida) Lake is approx 20ft deep on average. (Lake is up a bit above average) No real coves or protected areas to talk about. It's about 3500 acres. What are your thoughts? Anyone else anchor on a similar lake? Thanks much.
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Old 06-04-2014, 14:15   #2
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Re: Anchoring in a shallow lake

The conditions on Your lake seem to be similar as are dominant on the lakes here, in Poland. We use here mainly Med mooring - stern to ponton/dock (better to the piling if one is available), bow on anchor - several metres of chain + as long as possible rode of lightly elastic rope.

Cheers

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Old 06-04-2014, 14:25   #3
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Re: Anchoring in a shallow lake

Can you drop a seasonal mooring or screw anchor? Makes more sense than hauling a massive anchor on a small boat.

Assuming it will be permitted, look for a used 50# or larger, add a float and make a mooring. I think a used CQR would do. My uncle used to use a well-stripped and cleaned engine block. Where we live, all moorings are required to come out for winter. Probably not an issue for you.

Consider also that you will now have to apply a barrier coat and anti-foul paint. Will this effect your insurance?
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Old 20-04-2014, 18:06   #4
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Re: Anchoring in a shallow lake

Sorry for not answering quicker. Was down ill for a bit. Much better now

Thanks Tomasz. I'll keep that method in mind. With an outboard I'll have to adjust a bit.

Thanks Nicholson58; I think I'll try a mooring of some type as you suggest first. I have good anti-foul coat as I was prepping it for salt water. Should I use the same length of rode per depth as I would coastal?
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Old 20-04-2014, 18:40   #5
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Re: Anchoring in a shallow lake

It can be tricky absorbing the nasty chop you get with decent wind in shallow water.
Moorings do not help with this.

The notion of laying (semi-permanently) a decent sized anchor (eg 50#) with a decent length of rode is more appealing to me, but there's still a problem:

When it's shallow, chain catenary doesn't help arrest the snubbing, either at the boat or at the anchor, and the elasticity of a nylon rode is a double-edged sword.
Chafe (external damage) is one problem, particularly where the rode comes aboard, and internal deterioration of the rode (due to heat generated by repeated stretching) is another.

One possibility is to use all-chain, with alternating floats and sinkers attached along the rode at intervals*. The one nearest the anchor should be a heavy sinker, and the one nearest the bow should be a large float. When you are not on the mooring, the large float will act like a mooring buoy for pickup: it should be large enough to hold up under the weight of the remaining chain.

This makes a very "soft" action, but durable rode, which will continue working reliably despite long unsupervised periods. You can use discarded (preferably aluminium, but failing that, galvanised) LPG bottles for floats.



*Don't make all the intervals the same ! (possibility of resonance)
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Old 20-04-2014, 19:27   #6
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Re: Anchoring in a shallow lake

Very Interesting. I am looking for a method for long unsupervised periods as you picked up on. I'll have to come up with hardware to attach the chain to boat bow. Maybe a simple clamp to a bow cleat. Then devise a method to prevent the chain from rubbing the deck. What length would be suggested for 20ft?
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Old 20-04-2014, 19:52   #7
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Re: Anchoring in a shallow lake

Quote:
Originally Posted by Conair1 View Post
Very Interesting. I am looking for a method for long unsupervised periods as you picked up on. I'll have to come up with hardware to attach the chain to boat bow. Maybe a simple clamp to a bow cleat. Then devise a method to prevent the chain from rubbing the deck. What length would be suggested for 20ft?
For chafe protection, with chain, one possibility would be to take a long piece of synthetic webbing and "parcel"/"weave" the chain with it, at the point where it comes aboard. It might get rather slimy though, if you're leaving the 'mooring' unattended for a while.

I wouldn't go much more than 100' at a guess, but without knowing more about your situation it's hard to say.

Does the level of the lake change appreciably with severe rainfall events?

Is there the need not to occupy too much space when you're not using the mooring?

The setup I describe does not rely on length for cushioning, although extra length will help in extreme (eg hurricane) conditions.

Scope/catenary is not nearly as beneficial in shallow anchorages as it is in normal (or particularly, in deep) anchorages.
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Old 20-04-2014, 19:55   #8
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Re: Anchoring in a shallow lake

The practice of using full-time permanent moorings is well established and there is a lot you can read on this. You can find expert write ups if you use your favorite search engine.

Given that the wind will change directions you will need a swivel and an anchor heavy enough to withstand pull in any direction for storm conditions (even thunderstorms can approach hurricane force, if only briefly in gusts).

For a 23 foot sailboat you'll need hundreds of pounds of iron. (I'd use at least 250). Concrete should be even heavier because it's less dense in water. If you don't want to hire someone with the equipment to handle that size mooring, you can make a temporary one yourself:

For a temporary mooring you can use 3 heavy anchors set in different triangulated directions, all joined by heavy chains and tied together at a large galvanized swivel 5/8" minimum. From there you can use a top chain that's a little lighter. I'd use 3/8" minimum for your size boat. The top chain is attached to a float and swivel. The rope pennant to attach your boat is attached to that. It should be 10-15 feet of 5/8" or 3/4" minimum with a spliced thimble at the chain end, and spliced loop for your bow cleat. You'll want at least 5:1 scope overall from any direction and all metal should be galvanized American made hardware (no cheap imports, and no stainless from anywhere). Go with brands like Acco or Crosby or Chicago and you're much better off. Make sure all shackles are seized with Monel or stainless wire. If you use zip ties they're not as reliable, but they MUST be black for UV resistance.
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Old 20-04-2014, 20:29   #9
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Re: Anchoring in a shallow lake

You will want to add backing plates under your cleats unless you have already done so.

Ann
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Old 21-04-2014, 04:10   #10
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for a permanent mooring block, if permitted, you may fill an old dinghy with concrete, wait for the concrete to harden, and send it to the ground by deflating, where you need it to be.
not the most environment-friendly method, cause the dinghy and concrete block will stay down there forever, but i have heard of many diy mooringblocks done like this here in the Med. Dont forget to have a big chain embedded in the block to attach your mooring chain or rope...
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