Kedge/Stern Rode Sizing

[thinwater]

Originally Posted by Muaddib1116

...
When I see that a Crosby shackle has a WLL, a Proof Load of 2x, and a UBS of 5x, and given Crosby's place in the market, I have some faith that they've done the work to make those numbers mean something. Then I look at the specs for my duplex anchor chain, made by Ketten-Walder a well respected German manufacturer of lifting equipment, where they have a WLL of 11,690lbs and a UBS of 23,380lbs for a factor of 2x. This is a very different value, but from everything I've heard, Ketten-Walder also knows what they're doing.

Mantus has duplex shackles, they're the only supplier of them that I've seen. Do they manufacture those themselves? or are they made to contract by somebody else? They use a 4x WLL to UBS. Did they do a full test protocol to determine that? Did their contract manufacturer? or did they do enough tests to failure to determine a reliable breaking strength and then divide that by 4 for the WLL as a matter of course?

1stchainsupply states that G40 chain has a 3x WLL to UBS factor, and all other chain they offer is 4x. New England Ropes has a higher tensile strength on their ropes than the same size offered by Samson, but neither offers a WLL just an Average Strength.

Actually, that sounds more like a healthy skepticism. There is a lack of uniformity.


But the difference between nylon rope and steel is a separate issue. Nylon is well known to fatigue at high load factors, particularly when allowed to go slack between cycles.

[B-Baysailer]

I was looking at the mantis website and didn't see duplex shackles all I saw was 316 shackles .there swivel has a duplex pin for the chain side I assume ?

[B-Baysailer]

Oops mantus

[Muaddib1116]

https://www.mantusmarine.com/m2-chain-hook/

Scroll down, there is info on the duplex shackles. In some email to Greg a little while ago, he confirmed that all shackles 7/16 and larger are duplex. They are also stamped 2205 and are significantly magnetic.

[B-Baysailer]

Thanks I guess they don't show them under shackles just chain hooks

[Fore and Aft]

We use a Fortress FX23 for a stern anchor on our 32 foot yacht. Mostly with 14mm rope, we have a length of chain that can be shackled on if needed. But usually our 13 year old paddles it to shore in his kayak so we forget the chain. Those Fortress anchor's really dig into the sand, we can winch the yacht broadside to the tide without the anchor moving. To retrieve it normally one of us dives on the anchor and gets towed back to the yacht.
Cheers

[Jammer]

Originally Posted by Muaddib1116

How should you size your rode for your stern/kedge anchor? Should it be the same strength as your primary anchor rode? or can you size it down?

You should size it to match the stern/kedge anchor's holding ability. In most cases that will mean a smaller rode than the bower.


Most people would use minimal or no chain on a kedge to keep the ground tackle light when rowing it out.

[Muaddib1116]

Originally Posted by Jammer

You should size it to match the stern/kedge anchor's holding ability. In most cases that will mean a smaller rode than the bower.


Most people would use minimal or no chain on a kedge to keep the ground tackle light when rowing it out.

That makes sense, but the I think Fortress is the only anchor brand that I know of that publishes holding power.

My bower is going to be a 50kg Sarca Excel. I have a FX-37 as a stern/kedge, and I'm getting a Spade A-200 (aluminum version of 55kg Spade) as a backup bower/stern/kedge.

I'm still trying to decide on rope/chain type/size, but I think I'll use a shackle to connect the chain length, and I can keep a couple different lengths. A short length to use with my Fortress FX-37 and longer one if I use the Spade A-200.

[Don C L]

Personally I think it makes the most sense to use a Fortress or Danforth for a stern and/or kedge since you probably won't be swinging on it and they have great holding power for their size, shape and weight.

[Muaddib1116]

Yeah, the Fortress will be the stern/kedge anchor generally, the aluminum Spade is really a spare bow anchor that because of the aluminum construction is light enough to use as a big kedge anchor in a pinch.