Anchoring a Cat...Correctly

PDQ issues applicable across all PDQ Yachts (or if you can't find a place for something, it probably belongs here for now)
lauraj
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Re: Anchoring a Cat...Correctly

Postby lauraj » Thu Sep 10, 2015 1:17 pm

Our boat came with a bridle that has a very nice stainless steel chain hook. (centered on eye spices and a ring)
Just hook the chain link between the prongs and tension does the rest. Very quick to set and take off in emergency.

Dan White
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Re: Anchoring a Cat...Correctly

Postby Dan White » Thu Sep 10, 2015 7:32 pm

That sounds great. If you get time, could you post a picture?

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thinwater
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Re: Anchoring a Cat...Correctly

Postby thinwater » Sun Sep 13, 2015 6:43 pm

The only problem with the chain hook is that if the wind dies and it rests on the bottom, there is a signifigant chance it will come off. I have tested many styles for mag articles.

Keep it off the bottom.
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Main Event II
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Re: Anchoring a Cat...Correctly

Postby Main Event II » Mon Nov 02, 2015 8:32 pm

I think you need a video to explain that one..... :-)

Iriemon
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Re: Anchoring a Cat...Correctly

Postby Iriemon » Wed Jan 27, 2016 12:00 pm

A rolling hitch is an easy knot that takes 5 seconds to tie once you've done it a couple times. I've used it to bridle off a cat on both rope and chain rode hundreds of times and never had it slip or come undone once. It's easy to undo. It's a great knot to know for many other uses as well.

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Re: Anchoring a Cat...Correctly

Postby Kats Cradle » Wed Oct 05, 2016 11:06 am

We always use a bridle. It takes only a few seconds. A 15 ft line w/eye splice on the port cleat. Pay out rode to desired scope. attach rode to 15 footer with bowline. pay out rode until 2 lines are equal Cleat rode. Done

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thinwater
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Re: Anchoring a Cat...Correctly

Postby thinwater » Tue Oct 18, 2016 5:58 pm

Kats Cradle:

Do you mean a cow hitch on a ring?
Image
That is all I could come up with following your instructions.

I tested a bunch of knots, including this and a rolling hitch for Practical Sailor a while ago. I have a rig with a load cell to pull things apart.

Rolling hitch on chain. Always slipped at 500-700 pounds. Though many say it works, I found many circumnavigators, including some well known names, that have found it to slip and no longer use it. They use either a camels hitch or 2 rolling hitches.

Cow hitch. Slips at 300-700 pounds on chain or ring, depending on the rope and chain or ring.

It seems both will hold more than setting tension (you only have about 270 pounds in reverse) and most storms (50 knots = 800 pounds), but not everything that is possible.

In this case, so long as the end of the rope is also cleated, it might slip a few feet, but even the slightest pull on the bitter end would lock it down. It also weakens the rope about 50%, since it is basically a low efficiency knot. But since rodes only fail due to chafe, that won't be where it breaks anyway.

Neat.

---

Also, where did you get the SS ring? I friend of mine with a 38' cat used this method, but the ring failed at the weld the 2nd use in fair weather. Apparently the weld was surface.
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thinwater
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Re: Anchoring a Cat...Correctly

Postby thinwater » Fri Oct 21, 2016 1:30 am

Some test results and thoughts, based on the ring method. I have a test stand with a load cell. I have also measured wind loads with the load cell.

I used 1/2" nylon 3-strand.

At ~ 250 pounds untying is difficult with fingers. Line unlayed in the knot, but recovered when untied. About 30 knots.
At 650 pounds it took 3-5 minutes working with pliers to untie. It had slipped 8 inches. About 45 knots.
At 2200 pounds the line broke in the knot (40% efficiency). About 65 knots.
The rap ring started to distort at ~ 600 pounds and looked like a pear at 2200, but did not show any signs of cracking.

As for the strength of the ring:

I re-tested using a 7/16" SS bow shackle. Certainly this will not break.

At 250 pounds and 650 pounds, the untying problems were similar.
At 650 pounds it had slipped 12 inches.
Line broke at 2100 pounds. Not actually statistically different. No shackle distortion.

So, unless there is more information, I see some serious problems here. In an kind of real wind, the knot will seize, and the knot reduces the strength of the rope 60%, which may speak to durability. Perhaps with just the right matching of ring and rope it would be functional, but it will always weaken the rope.

The best alternative grab I am aware of is a prusik hitch in spectra webbing, which will hold to about 1500 pounds on this line without damaging the rope or seizing. Tandem prusiks will hold well over a ton.

My actual favorite, since I nearly always anchor in 6-7 feet of water, is to end a 70' rope with an eye and clip that. Zero chance of failure and no weakening. If I needed more depth I could carry another length with eyes in each end.

It's a tough problem. Any other ideas?
Writing full time since 2014.

http://sail-delmarva.blogspot.com/2017/ ... store.html
"Keeping a Cruising Boat for Peanuts"
"Singlehanded Sailing for the Coastal Sailor"
"Faster Cruising for the Coastal Sailor"


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