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Old 25-10-2008, 20:51   #1
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homecrafted mooring

Any suggestions for a relatively inexpensive homemade mooring adequate for a 50' catamaran houseboat?

mud/sand bottom...average depth 5'

I am awaiting a quote from Dor-Mor for 1000 pound pyramid and am anticipating severe sticker shock.

I searched the CF archives but have not found anything yet.

cheers,

mm
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Old 25-10-2008, 21:17   #2
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Not sure of the exact cost, but a friend had a concrete mushroom made for his mooring. Think it was about $1000 installed. I am looking into screw type moorings. Seem to have a good reputation and may be less expensive than mushrooms and pyramids.
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Old 25-10-2008, 21:36   #3
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The mushroom types were traditional for a long time but the screw types have proven themselves pretty well.
Helix Mooring Systems Inc
The Benefits of Helix Mooring Systems

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Old 26-10-2008, 03:25   #4
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I also recommend the helical anchor systems:

A few previous CF discussions:

Safe Reef Anchoring

Big ole Claw anchor for semi-permenant mooring?

Mooring-building one

Storm Preparation

See also: Mooring Buoy Guide
http://www.coralreef.noaa.gov/outrea...ing_buoy_g.pdf
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Old 26-10-2008, 04:50   #5
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mm,

I think the answer to your question depends on your anticipated use of it. If you want the boat to be able to withstand a hurricane on the mooring, the helix is your best bet. Maybe three of them set in a tripod arrangement.

If you're just looking to ride out 30-40 kt blows, and plan to move the boat to a safer location for worse conditions, a hunk of concrete might do the trick. The locals here on Nevis form up a 5' x 5' square on the beach, place some rebar in it, and pour about 18" of concrete. A friend with a large-ish power boat drags it to the desired location. If pulled fairly straight up, it can be dragged. The attachment point is bent rebar. About 60' of heavy chain, 20' of heavy nylon line made up to a swivel, and a pickup float on 3/8" line completes the project. In about 15' of water, there's enough scope to keep from dragging in normal conditions.

I kept my 12 ton sailboat on one of the local moorings for a couple of years with no dragging. Winds occasionally got up to 35 kts. I went with the concrete mooring after I got a quote on a helix from a guy over in Antigua--US$3,000, which included his travel to and from Antigua.
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Old 26-10-2008, 05:57   #6
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For a 50' boat, 45 kn of wind, we suggest a bloc of concrete of 2600 kg (5800 lbs) or about one cubic meter ( 61 cubic inches).

This mass could be shared in several blocs, ex. three blocs of 2000 lbs each.
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Old 26-10-2008, 13:43   #7
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Thanks everyone!!

I like Huds idea as I am looking for a compromise between efficacy and cost.
I presume the holding power of such a system is really based on the vacuum created by the flat surface as it buries into the sand/mud.

Thanks again,

mm
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Old 26-10-2008, 14:20   #8
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What I found when snorkeling on the mooring is that the concrete block partially buries itself over time, I guess from the tugging of the boat back and forth. So you're right, there's going to be some suction working on it. That helps, because concrete loses about half it's weight due to the water it displaces.

Your challenge will be making sure you can line up someone with the horsepower to move it from where you cast it to where you want it located in the water.
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Old 26-10-2008, 14:32   #9
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Aloha Mango,
If there are no restrictions on what you use I would chain two heavy diesel engine blocks (without fluids of course) together and drop them for a mooring. Steel or cast iron weighs about double of what concrete does under water.
Kind regards,
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Old 26-10-2008, 15:24   #10
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Hey skip'r,

Probably anything other a than helix type would be unlegal (sic) here. So that's what I'll do, I suppose.
As far as weight of iron vs concrete goes, a slab works on vacuum. That is even the main principal of the Dor-Mor.
Since we are talking about a houseboat, I could even use a spud system though it would take a bit of engineering and the location of suitable pipe.

Thanks everyone for the input

mm
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Old 26-10-2008, 16:48   #11
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Quote:
Originally Posted by Hud3 View Post
mm,

I think the answer to your question depends on your anticipated use of it. If you want the boat to be able to withstand a hurricane on the mooring, the helix is your best bet. Maybe three of them set in a tripod arrangement.

If you're just looking to ride out 30-40 kt blows, and plan to move the boat to a safer location for worse conditions, a hunk of concrete might do the trick. The locals here on Nevis form up a 5' x 5' square on the beach, place some rebar in it, and pour about 18" of concrete. A friend with a large-ish power boat drags it to the desired location. If pulled fairly straight up, it can be dragged. The attachment point is bent rebar. About 60' of heavy chain, 20' of heavy nylon line made up to a swivel, and a pickup float on 3/8" line completes the project. In about 15' of water, there's enough scope to keep from dragging in normal conditions.

I kept my 12 ton sailboat on one of the local moorings for a couple of years with no dragging. Winds occasionally got up to 35 kts. I went with the concrete mooring after I got a quote on a helix from a guy over in Antigua--US$3,000, which included his travel to and from Antigua.

Iron re-bar?
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Old 26-10-2008, 17:20   #12
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Iron re-bar?
I share your concern. Re-bar is made from un-treaded scrap steels. It would rust away in no time.

A bronze plate with a hole drilled in it would have been my choice.
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Old 26-10-2008, 21:24   #13
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Helix are great but you need special gear to install them and remove them. Actually we have a growing problem here with used helixs not being removed. Once the top has rusted/worn away they are near impossible to get out.

Engine blocks are just too small.

Disc shaped concrete block of at least 4000lb. If you can, a concaved bottom will dramatically increase the suction, this is good. Use rebar in the block and try to find some monstrous 2" plus steel for the mooring lug. Put 2 lugs in so when the 1st is worn you have a spare, not just a big lump of useless concrete. Don't piss around with 3/4" or anything like that BIG is best. Either that or cast a 6" hole right through the block for putting the chain through (shackle back on itself.

Block to 4 times high water depth 1 1/2" chain (ex ships stud link is fantastic but similar is fine. Doesn't need to be galvanised) to 1 or 1 1/4" steel ungalvanised swivel to length of 1" minimum, 1 1/4" better POLYESTER rope (3 strand is fine, 8 braid better) which is twice high water depth plus waterline to the bollard. Use anti-chafe hose. Splice nice loop boat end. From loop a high water depth length of 1/2" rope to a pick-up buoy.

Assemble on beach on the low water mark. Weld all connections if at all possible. Tie a couple of 44 gallon drums to the weight and wait for the tide to come in. Float block into position and then USING A KINFE ON A LONG STICK cut the ropes between the drums and weight. DO USE A LONG STICK WITH A KNIFE, the drums will pop up fast with power.

Simple and easy yet strong mooring. Check swivel as it is usually the 1st thing to go. How long depends on local conditions. The big chain should last years, like 10-20 maybe more especially lying in mud. Headrope many years unless chafe gets it.

Considerations -
If decent wave action can happen add concrete and make head rope 3 times high water depth plus w/l to bollard in length.

Mooring laid, open cold beers, done.

When you are not on the mooring it just lies dead in the mud so no wear and very little O2 so no rust. The only moving bits is the buoy rope and the buoy.

That's a simple mooring like we use down here and we anchor on the edge of oceans as in land one side and 7000 miles of open ocean all the way to Chile on the other. We generally would have a length of smaller 3/4" or 5/6" chain between the stud link and the head rope though but then we moor more in 30-40ft than 5. We have a less than 1% failure rate.
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Old 30-10-2008, 18:40   #14
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GMac has good advice, we made a mooring here in the UK using an old tractor tyre (tire) to pour the concrete into, we made a small hill in the sand before pouring the concrete so it had a dished bottom, we also managed to get a load of steel punchings from a local metal fabricator that cost a case of beer and made the concrete more dense, two lugs is a good idea, get as big lugs as you can.
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Old 11-01-2009, 23:04   #15
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Lightbulb

BUMP!
I got some huge brake drums from the local cement truck folks and made up a mooring with them spaced apart with disk brakes from another shop. I've heard railroad wheels are the shiznit but have no sourcing info...
We are in 21 feet at high tide with 2 boats on the mooring weighing in about 18klbs combined...
No movement to date in mud/sand bottom through storm surges of 60kts to date.
My .02
Mike Sr.
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