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Old 04-03-2015, 09:16   #1
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Trusting junk?

Well I know I am opening a can of worms with this post but here goes...

My girlfriend and I are sailing Starship, our 40 foot Valiant, to Kodiak next month. We live and work remote on Afognak Island, AK and have what we think is the perfect mooring site for our home. The site we have in our minds is an embayment at the back of a larger bay. The bay is about 150 yards north/south and maybe 500 yards east west. The average depth is around 20-30 feet on low tides and about 50-60 feet on high high tides. The predominant wind is North-East which usually brings the worst weather. We would only be on the mooring throughout the summer (April-August) and we will visit the boat most days as it is a 15 minute skiff ride away.

We know the mooring types and sizes we should be using but practicality will dictate our set-up (on Kodiak heavy things are hard to come by and not cheap). At this point we are looking at a setup with 3 55 gallon drums filled with rock,rebar, and cement each weighing around 400-500lbs. These will be tethered with the largest chain practical to a swivel to a slightly lighter chain to the can. Our painter is stout.

We will have to create this mooring on site, and it will be just the 2 of us available. Any other ideas or constructive criticism is welcomed!
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Old 04-03-2015, 11:02   #2
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Re: Trusting junk?

Do you have diving equipment to work under water?

I would fabricate three big sandscrews if the bottom allows that.
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Old 04-03-2015, 11:10   #3
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Re: Trusting junk?

So with three drums you are talking about a 1200-1500 lbs. mooring anchor. I think that sounds quite adequate.
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Old 04-03-2015, 12:06   #4
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Re: Trusting junk?

Quote:
Originally Posted by denverd0n View Post
So with three drums you are talking about a 1200-1500 lbs. mooring anchor. I think that sounds quite adequate.
That's the thing with moorings: they are under water and weight works different there vs on land. As soon as you take rock and concrete into the water you loose what, 40% of the weight. What is left won't be enough. Steel gives much better results, i.e. you need a heavy material or use much more of the lighter material.

That is why I recommend sand screws. If there is rebar, you can weld up sand screws, which anchor to the seabed.

For weight I would bury a couple of train wheels into the seabed.
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Old 04-03-2015, 12:23   #5
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Re: Trusting junk?

Your Valiant displaces 23,000lbs. With rigging, gear and whatnot easily 25,000lbs. I don't think 1,200-1,500lbs mooring block is nearly enough in the worst case scenario. Especially since you're in Alaska and not in some placid lake or lagoon. I'd go with at least 3,500-4,000lbs.

If you plan to use that mooring for a few years what about getting a junked car, fill it up with cement and using that as a mooring block? Would need a hand from someone with a hydraulic lift or some such but may be worth exploring. I am always told by old salts that there is never too large of a mooring block or a chain.
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Old 04-03-2015, 12:34   #6
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Re: Trusting junk?

You just spent $30k on a boat and now you're going to trust it's safety to a bunch of junk? Spend $1000 on a great anchor like a Mantus
Mantus Anchors | Product Categories Galvanized Steel Anchors
and your boat may survive.

But first go read this thread
http://www.cruisersforum.com/forums/...ng-126073.html
and you'll learn a lot.
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Old 04-03-2015, 12:36   #7
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Re: Trusting junk?

Quote:
Originally Posted by s/v Jedi View Post
That's the thing with moorings: they are under water and weight works different there vs on land. As soon as you take rock and concrete into the water you loose what, 40% of the weight. What is left won't be enough. Steel gives much better results, i.e. you need a heavy material or use much more of the lighter material.

That is why I recommend sand screws. If there is rebar, you can weld up sand screws, which anchor to the seabed.

For weight I would bury a couple of train wheels into the seabed.
The numbers are pretty simple: you loose 200 kg from buoyancy for each 200 liter drum. So, your 400-500 lb estimate of weight in air is significantly reduced when you drop them in the sea.

However, the density of normal concrete is around 2.5, so the drum, filled with just concrete would have a weight of around 500 kg in air... a bit more than your estimate. And adding as much steel scrap as will fit improves it considerably.

The usefulness of such a mooring depends a lot upon the nature of the bottom. If the bottom allows the drums to work their way into deep mud they should have greater holding power than if the surface is hard sand or rock. Also, having your total mooring pendant long enough to have decent scope at high water will help, just like it does with an anchor.

So, it can likely be done your way... depending on the details. It's always the bloody details!!

Good luck with it, and keep your new girl safe!

Jim
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Old 04-03-2015, 12:40   #8
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Re: Trusting junk?

So concrete is about 140 lb/cf
Gravel mixed with sand will be 90-110 lb/cf depending on how well the soil is compacted.

A 55g drum has a volume of 7.3 cf.

Underwater concrete drum will weigh 555lb each.
The sand/gravel drum will weigh 260 each.

Have you considered tying off to shore on one or more sides?

If no one else ever uses the bay, get yourselves 5 spools of anchor line and tie off in 4 directions. The 5th line doubles up in the direction storm winds come from, but leave it somewhat slack so it only take load after the first line has stretched some.

If there are other users, hug in close to shore near the source of storm winds and run double lines towards the storm winds, plus the other 2 lines 45* to either side, and set 2 or more anchors away from shore to keep you from being driven aground. I would put a row of small buoys along each line ashore to advertise their presence to others using the bay.

All this is predicated on having something on shore to tie off to, large (very large) rocks or trees. If it is a sand beach then look for some sand screws. To deal with chafe you will want some metal cables or chains long enough to go around each rock or tree and out to the first buoy in the water where it will shackle to the end of the line. The end of the line should have an eyesplice around a thimble at its end. For shorter term use in less hostile locations a less durable arrangement would probably suffice.
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Old 04-03-2015, 12:56   #9
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Re: Trusting junk?

Just find another old monohull with a lead keel preferably one with a gasoline engine, and then just start the engine, and it will explode and sink, and there you have a mooring weight.
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Old 04-03-2015, 12:59   #10
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Re: Trusting junk?

A couple of issues...

1) barrels are absolutely a terrible idea. Once on the bottom they have a tendency to skid, or worse they can actually roll. For a concreet anchor a better design is a wide flat rectangle. Built a box frame from a sheet of 4x8 plywood and add some sides and rebar. This adds a lot of contact surface to prevent skidding. Commercially large flat cylinders are prett commn as well, with the attachment in the middle of a flat side. Large trackto tires are commonly used.

2) your weight is substantially below recommended. A 40' boat is normally suggested to have 4,000lbs of submerged weight as a minimum. For concrete this would work out to just over a 6,000lb block, or 1.5 cubic yards.


The massive weight and cost of deadweight anchors is why they aren't used very much. Since even a shank less anchor will provide substantially more holding power for the weight, and just getting them into place can be a real pain.
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Old 04-03-2015, 13:20   #11
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Re: Trusting junk?

Quote:
Originally Posted by jjlyons View Post
...At this point we are looking at a setup with 3 55 gallon drums filled with rock,rebar, and cement each weighing around 400-500lbs. These will be tethered with the largest chain practical to a swivel to a slightly lighter chain to the can. Our painter is stout.

We will have to create this mooring on site, and it will be just the 2 of us available. Any other ideas or constructive criticism is welcomed!
I agree that the mass is not sufficient and that the form of the barrels is far from ideal. In addition, since you're fabricating onsite you'll need to construct a platform that can float and then safely release at least 1,500 lb. for your proposed design, since all three barrels have to go down together, and ideally something up to a better spec'ed design weight. I think one of your challenges is the depth and tidal range. From your description you need a solution that works in 50' of water, at the very least.
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Old 04-03-2015, 13:30   #12
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Re: Trusting junk?

Drums full of crap are generally just that.

What kind of bottom is it? Rock? Mud? Gravel? Makes a difference in what mooring will work. I'm suspecting you either want a diver to put in augers, or a barge to bring in a truly massive dense deadweight. If neither one is possible, I would expect the boat to just not be there one morning.


It isn't easy, or generally recommended, but in 20' of water you CAN probably install the augers from the surface, if the bottom is sand/gravel/mud.
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Old 04-03-2015, 13:38   #13
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Re: Trusting junk?

When San Diego, CA, had "free anchorages" years ago, the officially OK'd anchoring system (approved by Harbor Police) was at least one V-8 engine block with the crankshaft still in place, that had been steam cleaned.

You could use up to three engine blocks.

Heavy chain (1/2" to 3/4") was insert into one of the cylinders, went around the crankshaft, and came out another cylinder. The chain ends were shackled together and a lighter chain (3/8" to 1/2") was run out 100-200 feet. Then a length of anchor chain (5/16" to 3/8") was fastened to it and run up to the boat or anchor ball. This section can be replaced every year or two if needed.

Over time the engine blocks bury them shelves into the bottom. Hard mud, sand or pebbly gravel bottoms work / hold best.

Just how well do they hold? When the City of San Diego got rid of the free anchorages they had to use a 800-ton floating crane/barge to pull up the engine block "anchors".

They did not come up easily!

You can rig the engine blocks on shore and float them out with 55-gallon drums or log rafts. Position them and either cut the lashings or flood the drums and down they go. Be VERY careful doing this as they are under a lot of load.

The other thing used was railroad car wheels, with chain threw the center. Same various sizes of chain. The RR wheels can also be floated out, although they are much heavier than the engine blocks so require more floats or a bigger raft.

Old railroad track can be cut into 10-ft lengths and welded or chained together to make a dead weight anchor.

It really depends what you have up there, but there is usually some old junk cars with engines in them that you can use. Probably be some chain or wire cable too.

Good luck - it's a real adventure making / setting these "anchors".
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Old 04-03-2015, 13:52   #14
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Re: Trusting junk?

We circumnavigated Kodiak the summer before last and Afognak sits right at the top of the island which means the bay he is talking about is almost certainly soft mud and should provide excellent holding.

I agree with others using barrels is not a good idea. They are the wrong shape, won't bury themselves into the mud easily and will rust away to nothing exposing whatever "junk" you have inside them.

There are a lot of abandoned canneries up there with literally tons of heavy equipment lying around completely rusted and forgotten. Most of these are owned by native corporations and maybe you could approach them for some old engine blocks or heavy scrap.

Alternatively, get an over-sized Mantus, Rocna or Spade anchor and it will continue to bury itself deeper and deeper into the mud. With some serious spring lines, well protected from chafe, attached to your serious chain this will hold whatever is thrown at it. Our Spade is 110 pounds and in Kodiak it was "throw it and forget it." That anchor loved burrowing deep into the mud and held like superglue wherever we went. Since you are only 15 minutes away you can check on her every other day.

Doable in my view.

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Old 04-03-2015, 14:54   #15
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Re: Trusting junk?

When I lived on Nevis, in the Caribbean, I kept my boat on a "home-made" mooring. The weight was a concrete block measuring about 5' square and 12"-14" thick. Bent rebar was embedded in the block to make the connection point for shackle and chain. The block itself was reinforced with rebar. The locals would make these up on the beach in plywood forms, and then drag them to the desired spot.

The guy that made mine used his Bertram 30' sport fisherman to drag the block. Once he got it off the beach, he and some husky friends hauled up on the block to take some weight off, cleated the lines, then dragged it to the position they'd chosen. The blocks slowly work their way in to the sand.

Concrete is about 2,400 kg/cubic meter, according to Google. So the 0.77 cu meter block my boat was moored to weighed about 1,850 kg (4,100 lb). Water is 1,000 kg/cubic meter, or 770 kg for the volume of my block. That makes the effective weight of the concrete block 1,080 kg (2,400 lb). My boat weighed about 12 tons, and the mooring held fine in some pretty brisk winds and bumpy waves.
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