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Go Back   SailNet Community > On Board > Gear & Maintenance
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  #1  
Old 12-05-2006
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Bulletproof my mooring

I have a 35' Pearson resting on a homemade mooring in 10' of clear water in the Virgin Islands. My problem is I am off island sometimes for long periods of time so I worry about my mooring breaking. I'd like to construct something I feel comftorable with. I have two Helix screw anchors with 15' of 1/2 chain on each connected to two 30' 3/4" nylon pennants. I also have two 45' 3/4" pennants running to each screw head. All over a bow roller. I use anchor bends instead of thimbles because they just clang and rust away. I don't use a mooring ball because it just bobbles the end of the chain off and on the bottom till it rusts through. My lines get twisted and the boat dose'nt swing right. How about a bridel plate with a swivel ? Should I chain the two screws together ? How about braided polyester mooring lines ? I hear they resist chafe better. Any good ideas?
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Old 12-05-2006
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I would get some serious weight on the bottom. I don't know what you are allowed to put in the water there. I'd guess something over 500lbs would do you, but others on here probably have better input than I on that area. Regardless of that, I'd get about fifty feet of the heaviest chain you can possibly handle, secure that to your weight, and then go to your 15' of half inch chain (or more) and then 10' of nylon to the chock(plus whatever you need on deck). I'd buoy it at the end of the 1/2" chain. This will keep your line off bottom to minimize abrasion. You want the heavy chain on bottom for it's weight-it will give you a catenary and make the pull on your weight horizontal. As it stands, I believe you have too much potential vertical pull on your screw anchors. I'm also concerned that you have only 4-5 feet of water under the keel, but don't know enough about your moorage to say if that is safe for all conditions.
As far as your lines fouling-you've got four lines out with two doing no work, I don't think a swivel is going to remedy that problem. Try to construct everything out of chain and use the line just for shock loading.
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Old 12-05-2006
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Actually, the Helix screw anchors are proven to be better than most mass-based anchors. By using anchor bends, instead of spliced thimbles and shackles, you're losing about 40% of the strength of the rope... They do make titanium or plastic thimbles, which are far less prone to rusting.

Depending on the size of the Helix Screw anchor, one should be sufficient to hold your boat...but YMMV. If you have to use two, it might be better to have the two chains joined to a three-way swivel, underwater, and have a single heavier chain coming up to the boat. Properly hot-galvanized chain should last a fairly long time.

However, catenary isn't as much of an issue when you're using properly sized helix anchors that are properly bedded, but having sufficient chain to allow for storm surge is a very good idea. The catenary curve can help absorb shock loading to a small degree, but the bulk of the shock loading absorption will have to be provided by the nylon pennants. BTW, oversizing the lines is probably a bad idea, as they will not stretch under the given load, and your boat will suffer from the shockloading.

Last question—what are you using for chafe protection? None of this matters if the rope chafes through. And you haven't mentioned any sort of chafe protection outside of using a bow roller. Also, is the bow roller large enough to handle two lines of the size you're describing?

Sailaway's points about the buoy are excellent...keeping the line away from the bottom is an excellent idea.
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Last edited by sailingdog; 12-05-2006 at 06:44 AM.
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Old 12-05-2006
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John...I'm with the "Dawg" on this one except that I think the 3/4" inch lines are not oversized enough! NOTHING short of a hurricane will load the lines enough to damage the boat and in a hurricane, the line WILL stretch! My own boat SNAPPED a 1.5" line in Ivan and another one was totally FUSED due to heat from stretching! My boat is quite heavy s you may not need that much but my initial reaction to your post was that your line was too small!
I would shackle 2 such lines from a SINGLE chain as SD suggests and provide them with breathable chafe protection (not hose). Use a "keeper" on your anchor roller to insure that the lines don't jump out in heavy seas and insure that all surfaces on the roller will not chafe the nylon.
I agree with SD about chaining the 2 helix anchors together IF YOU MUST and then using a very robust 3 way swivel to run one chain up to the boat.
If your Helix's are EACH capable of handling hurricane force winds with your boat then I would suggest using ONE as the primary anchor taking ALL the load and then using the other as a backup by running a longer length of chain to it from the swivel so it receives no load unless the first anchor or chain lets go. Trying to use BOTH anchors at the same time will result in one being loaded (AND UNLOADED)at a time and I think you are better off with some load on just one at all times.
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Old 12-05-2006
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Cam-

IIRC, your boat is a good deal bigger than his...and has a lot more mass..

The bit about the breathable/water permeable chafe protection is a good one. Water will cool the nylon and help prevent fusing from internal friction and heat.

It would also help if you said how large the helix anchors you're using are as well as the type of sea bottom you're anchored into.
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You know what the first rule of sailing is? ...Love. You can learn all the math in the 'verse, but you take
a boat to the sea you don't love, she'll shake you off just as sure as the turning of the worlds. Love keeps
her going when she oughta fall down, tells you she's hurting 'fore she keens. Makes her a home.

—Cpt. Mal Reynolds, Serenity (edited)

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Old 12-05-2006
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Correct me if I am wrong, but it sounds like you live on the VI. Rather than just leaving the boat for long periods of time, after upgrading your mooring arangement, I would arrange with a trusted friend/acquaintance to check on your boat periodically. I would offer use of the boat or some other kind of indirect monetary compensation, i.e. dinner out at a nice resturant, tasteful gift, etc. Nothing like having actual human eyes ensuring that all is well.

Romaine
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Old 12-06-2006
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Camaraderie's point of using the screw anchors in stages is eminently a sensible one. I am approaching this from a mooring versus anchoring standpoint and that is why I lean towards alot of weight on the bottom. What Cam is heading towards is what happens when you pop out that screw anchor. It's not going to reset itself; having the second shackled on will just make the first part of the new rode. My preference to weight is that, even if it were to drag a bit, it is always set. Any anchor that drags may or may not reset, and you will not be there to observe it. If you drag on your mooring weight it will stop as soon as strain moderates. Worst case the strain will moderate when your keel touches bottom in shallower water and you are facing damage to your keel. When your anchor lets go and you drag you will be facing much more damage, but it will be readily observable because your boat will be laying ahull on the beach or reef. I see nothing wrong with using the screw, but I'd have it stoutly chained to a good weight.
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Old 12-06-2006
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A properly designed, sized, installed, and maintained screw helix anchor is not likely to pull out.

It won't reset ever...but it is very, very unlikely to pull out. If you have properly sized nylon mooring pennants between you and the mooring chain, the shock loads on the screw anchors won't ever get high enough to pull them from the bottom.
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You know what the first rule of sailing is? ...Love. You can learn all the math in the 'verse, but you take
a boat to the sea you don't love, she'll shake you off just as sure as the turning of the worlds. Love keeps
her going when she oughta fall down, tells you she's hurting 'fore she keens. Makes her a home.

—Cpt. Mal Reynolds, Serenity (edited)

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Old 12-07-2006
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Wow, Thanks everyone for all the great advice. Where do I start ? First of all I don't live in the VI any more. I am back and forth from the states as often as possible. I see to it that everything including my mooring is maintained. My long distance relationship is difficult but Iam unwilling to give it up. Let me backtrack. I have 2, 6' round shaft Helix anchors. Each rated at 10,000 lbs holding power. Anchors are in medium packed sand. My bow roller is oversized and has a keeper. I use flexable reinforced hose zip tied on my lines for chafe gear. My biggest problem seems to be, I have expensive heavy chain that won't let my boat swing a full circle and the last few feet to the pennant bounces off the bottom constantly, quickly wearing it through. I can actually hear the links on a calm day inside the boat. I am kind of tired of babysitting this problem after 15 years. Interesting engineering insight on all chain to the boat by Jeff.Lefebvre@ntsociety.org. Anyone have or had experience with the hazelette elastic mooring system? Thanks, John
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Old 12-07-2006
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John...just a quick note to sugget you get rid of that hose chafe guard and replace it with canvas. Just read a note from Evans Starzinger detailing how para-anchor systems with nylon rodes were failing WELL below the breaking strength of the nylon due to the HEAT of stretching back and forth. A hose makes this problem worse right at the worst place for heat. You need something that provides protection from chafe in the worst weather but also lets the rode get WET and cool...hence canvas is a good choice.
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