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Old 15-04-2012, 10:15   #16
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Re: Chain Stoppers

Mike--

One alternative for using the Maxwell Chain stopper is to have two ¼” SS plates made up that are, say, 1" on a side and 2” fore and aft larger than the Maxwell Stopper. The machine shop can drill and tap the bolt holes for the Stopper and 2 additional bolt holes each fore’n aft of the chain stopper so that you would have a total 8 bolts through the deck to carry the shear. The Stopper would rest on one “Base Plate” (that could be electro-polished), above deck, and have the second, matching plate as “Backing plate” on the underside of the deck. With the Maxwell Stopper sized for ½” chain (13mm) your plates would be, roughly, 5-1/8” wide by 12-5/8” fore’n aft giving the plate a bearing area on deck of 64.84 sq. in. and a shear area (in the M12 bolts) of 1.40 sq. in. (or a shear capacity of 63,000# for typical 50ksi SS bolts). In cross grain compression teak can sustain roughly 6900psi before crushing. However, assuming the Stopper were loaded to the full capacity of the bolts, the maximum compression load of the base plate on the teak would only be in the range of approximately 1000#. Frankly, the best alternative would be to remove the teak decking at the stopper and weld a mounting plate to the deck itself with a somewhat larger stiffener on the underside of the deck to transfer loads into the steel deck but, assuming you don’t want to damage the teak, the foregoing would work so long as the end-grain in the teak where the bolts are drilled through is treated with epoxy to prevent water infiltrating the end grain.

FWIW…
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Old 15-04-2012, 10:37   #17
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I have never used a chain stopper. My boats have had vertical ideal windless with gates on the hawsepipe.Big gear and the chain had low leverage against the windless. On newer windless you do nit want to load the gypsy. I guess in a run away circumstance a chain stopper is good. Most stoppers I have seen would not be substantial enough to hang in that kind of load. Course jedi tells us his saved the day. So I like the idea of a pawl with lines run back to the spring cleats. I took the skin off my hands with a run away chain. But it was my error. Took a flash if a moment and my hands were torn up. This was mostly due to the hawsepipe nit being located well. Moving it forward would allow more contact with the windless. A job I need to do but is complicated. Seen lots of pictures post hurricane With bows ripped off znd holes in decks from loads directly put on chain. A few snubbers are first 8defenseThat's why I asked why. Good conversation. Thanks
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Old 17-04-2012, 05:32   #18
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Re: Chain Stoppers

Sy Gilana has given a great description of the problems associated with high winds at anchor. I anchor over 300 days a year and during winter in the Med there are some regular storms. When other boats share the anchorage and get into difficulties a very common tale is that anchoring systems that they had used for years fail in stronger winds.
Think how you will control the chain, communicate with helm etc what works at 30 knots often does not work at 50K.
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Old 17-04-2012, 06:02   #19
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Quote:
Originally Posted by noelex 77
Sy Gilana has given a great description of the problems associated with high winds at anchor. I anchor over 300 days a year and during winter in the Med there are some regular storms. When other boats share the anchorage and get into difficulties a very common tale is that anchoring systems that they had used for years fail in stronger winds.
Think how you will control the chain, communicate with helm etc what works at 30 knots often does not work at 50K.
Exactly. Also rethink the "need no windlass" strategy before loosing body parts or the boat...

cheers,
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Old 17-04-2012, 18:53   #20
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Re: Chain Stoppers

[QUOTE=Andrew Troup;931420] self-acting, pawl type stopper - - devil's claw or chain hook.

use an endless loop of climbing tape, hitched to the chain with a Kleimheist hitch (a prussic is nearly as good, and easier to remember). The advantage is that, apart from being about 0.2% of the cost, and 5% of the weight, it's easier on the chain, and if I have to 'cut and run' (originally a nautical term) I can literally do just that.

(pawl on bow roller) – it was a good idea on a vessel small enough (in relation to crew numbers and strength) that the anchor could realistically be weighed, even in bad conditions, by human effort,

contingencies (what if the windlass seizes or strips: how do you lower the anchor under control in deep water or strong wind)


I really like this idea of the enless loop. There are so many anchor related items so far forward that can hurt you and the loop belayed aft by tag line parmits release before you go forward, lets your crew control the initial drop from aft; lets you torque it tight from aft; lets you handle it if the brake fails. We have a really large Maxwell with rope gypsie and 320 feet of heavy chain. My anchors are 55# and 75# and we will be adding a Manson about 120#. Any of these clutches look to me like hand slicers waiting for meat.
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Old 21-10-2012, 02:18   #21
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Re: Chain Stoppers

Hi All, thanks for the valuable input. I thought I would give you an update.
I designed and made my own stopper, and we are thrilled with it. It works as intended. Attached is a drawing and a photo of the final product in situ.
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Old 21-10-2012, 02:38   #22
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Re: Chain Stoppers

I had this stuff made in stainless 10 mm olate, but of course it could be thicker...
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Old 21-10-2012, 02:46   #23
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Re: Chain Stoppers

Quote:
Originally Posted by sy_gilana View Post
Hi All, thanks for the valuable input. I thought I would give you an update.
Looks great. You want to think about going into production. The commercial ones are not cheap.
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Old 21-10-2012, 03:02   #24
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Re: Chain Stoppers

Nice job!
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Old 21-10-2012, 03:35   #25
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Re: Chain Stoppers

In fact, it's a commercial product (Sea-Dog : Quality Marine, Industrial and Rigging Hardware), but the sampling was not suitable for my boat, so I asked a local metal turner to make a similar stuff ( and it was cheaper, among 15 euro, less than 20 USD)
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Old 21-10-2012, 05:00   #26
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Re: Chain Stoppers

Quote:
Originally Posted by noelex 77 View Post
Looks great. You want to think about going into production. The commercial ones are not cheap.
HAHA, you might have an idea there, the 316 Stainless only cost me 65 Euros, including the studs. Used 12 welding rods, and half a cutting disc. So all in it was about 4 hours of work and approx 75 Euros. I think these go for about 400 Euros, and they only have four bolts too close together.
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Old 21-10-2012, 07:21   #27
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Re: Chain Stoppers

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Originally Posted by pupuce View Post
I had this stuff made in stainless 10 mm olate, but of course it could be thicker...

I prefer a chain grab hook. The plate shown withthe tiny cross section at the footof the groove is sure to part at the worst possible time or possibly be forced closed in a pinch around the chain. They are available in SS but galvanized is just fine. The rating is comperable to the chain. Put one of these in the center of your bridle. Once the load is slacked from the windlass and transferred to the hook it will stay attached. As the windlass picks up the chain the hook will fall free. Use one to apply a safety line from the chian to the mast or other secure fixing point. 10 to 20 bucks at GRAINGER Supply for 3/8"

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Old 21-10-2012, 11:23   #28
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Re: Chain Stoppers

This thread has gone in two different directions.

Chain hooks, and the slotted plate, don't help in the situation the OP describes, because they cannot protect the windlass during the chain retrieval phase.
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