Cruisers & Sailing Forums (https://www.cruisersforum.com/forums/)
-   Anchoring & Mooring (https://www.cruisersforum.com/forums/f118/)
-   -   Mantus Chain Hook (https://www.cruisersforum.com/forums/f118/mantus-chain-hook-117902.html)

Cotemar 29-12-2013 14:10

Re: Mantus chain hook
 
Here is a nice video to show how strong Soft Shackles really are.

He is testing a 1/8" Amsteel Soft Shackle with a tensile strenght of 2500lbs.

His comment was that the Amsteel is rated at 2500 pounds, but he would estimate he put more like 4000 pounds on it. He goes on to say that a splice does not degrade the line as was thought.

MVI 7656 - YouTube

colemj 29-12-2013 14:23

Re: Mantus chain hook
 
I have no doubt Amsteel breaks at higher loads than they published (it had better not break at lower loads). I was just pointing out that Samson publishes breaking load for that line, and not working load. They are confusing on that point since they publish working load for their other lines and do not make a clear distinction of the change for the Amsteel numbers.

Regarding the Mantus hook problem, didn't Mantus change the design so that the slot was captured by a gate after hooking it to the chain? I seem to remember something about a gate on that slot now. Seems easy enough to install one if you don't have it.

Mark

estarzinger 29-12-2013 14:44

Re: Mantus chain hook
 
He has some other soft shackle test data on his site . . .this is with NER line

Note: everything here is breaking strength, NOT SWL

# Shackle Type Line size Breaking force Rated strength strength % of line strength
1 Single 3 / 16 7,082 6,100 116%
2 Single 3 / 16 6,288 6,100 103%
3 Single 5 / 16 15,995 14,500 110%

Approximate Breaking Strength 5/32 Amsteel 3/16 Amsteel 1/4 Amsteel
4,000 pounds 5,400 pounds 8,600 pounds

I don't know what safety factor we should apply, certainly 2:1 and perhaps 4:1

At 2:1 those translate to SWL: 2000lbs for 5/32, 2700lbs for 3/16, and 4300lbs for 1/4".

I will have some more data on this, from my new test bench, in January

Nicholson58 29-12-2013 14:53

Re: Mantus chain hook
 
Quote:

Originally Posted by Cotemar (Post 1426005)
I am using two Falcon Line Master Mooring Snubber for 5/8 line on my Catamaran.

Falcon Safety Mooring Line Snubber / Compensator - 5/8"

Worked great on my Mono hull also.


Is that your normal set-up? I think that part of the duty of the snubber is to transfer the load away from the bow roller & windlass. I take my snubber/bridle to the port or starboard bollards.

colemj 29-12-2013 14:54

Re: Mantus chain hook
 
Quote:

Originally Posted by estarzinger (Post 1426324)
I don't know what safety factor we should apply, certainly 2:1 and perhaps 4:1

For use connecting a snubber to a chain, I would be happy with 2:1 or even 1:1. The chain is stopped off the windlass with a very strong fitting, so a broken bridle connection is not dangerous.

Mark

Kenomac 29-12-2013 15:03

Re: Mantus chain hook
 
We've had no problems using either a standard chain hook or the Ultra chain hook along with an oversized rubber snupper as seen in an earlier post.

Nicholson58 29-12-2013 15:07

Re: Mantus chain hook
 
Quote:

Originally Posted by Cotemar (Post 1426289)
Here is a nice video to show how strong Soft Shackles really are.

He is testing a 1/8" Amsteel Soft Shackle with a tensile strenght of 2500lbs.

His comment was that the Amsteel is rated at 2500 pounds, but he would estimate he put more like 4000 pounds on it. He goes on to say that a splice does not degrade the line as was thought.

MVI 7656 - YouTube

I don't see how he has any idea what load he applied. No load cell/scale. He only demonstrated that the line would part where its single strength rather than at the splices or doublers. I'm sure the manufacturer's data or independant tests such as by Practical Sailor or other folks is adequate data.

If you make a loop of line as shown in post 2 you reach a theoretical 2X load capacity less the stress concentration of the knot. Its about the same as a rolling hitch or prussic knot.

Cotemar 29-12-2013 15:10

Re: Mantus chain hook
 
1 Attachment(s)
Quote:

Originally Posted by colemj (Post 1426303)
I have no doubt Amsteel breaks at higher loads than they published (it had better not break at lower loads). I was just pointing out that Samson publishes breaking load for that line, and not working load. They are confusing on that point since they publish working load for their other lines and do not make a clear distinction of the change for the Amsteel numbers.

Regarding the Mantus hook problem, didn't Mantus change the design so that the slot was captured by a gate after hooking it to the chain? I seem to remember something about a gate on that slot now. Seems easy enough to install one if you don't have it.

Mark

They have a New Mantus Hook Gate which makes it nearly impossible for the Mantus Hook to come off the chain… and yet easily opens to unlock

estarzinger 29-12-2013 15:20

Re: Mantus chain hook
 
Interesting . . .but if you have that gate . . . .do you still need all the rest of the hook's "features" . . . .would the gate would be a good addition to just a standard hook, which is rather smaller and lighter than the Mantus.

I have two of the 'pre-gate' Mantus hooks and don't like them. They did fall off, but are harder to get on and off when you want to than a normal hook.

Cotemar 29-12-2013 15:56

Re: Mantus chain hook
 
8 Attachment(s)
Other than the snubbers non-captive chain hook just popping off for no reason in wind, wave, shock load or tides.

The only real worry I have with chain hooks is that when you back down on them the snubber stretches a lot and if some un-notice chafe snaps the snubber, then the chain hook becomes a heavy projectile. On My Catalina 380 I used to walk back to the cockpit so as not to get hit with anything as the snubber stretched on the anchor being set.

Sid at SailAway 29-12-2013 16:24

Re: Mantus chain hook
 
@ Cotemar...I know that there is probably no problem with breaking strength on the soft shackle, but do you worry about chafe with a synthetic fiber acting as a chain hook? I use the Mantus as well and in a years time it has come off twice. Both times laying on the bottom in five foot of water in a tidal switch. But I've never worried about it chafing through. No disrespect intended..Thoughts on this? Sid

Mantus Anchors 29-12-2013 16:55

Re: Mantus chain hook
 
Quote:

Originally Posted by Celestialsailor (Post 1426262)
I've not yet had a problem with my Mantus chain hook. My feeling is that somehow it ended up lying on the bottom during a low tide.

guys just an update we are making injection molds now, but if you want the gate now just email us and we will 3D print one for you....
all we need is you address and the size hook you have...
Mantus Hook Locker! -

Cotemar 29-12-2013 17:32

Re: Mantus chain hook
 
2 Attachment(s)
Quote:

Originally Posted by Sid at SailAway (Post 1426388)
@ Cotemar...I know that there is probably no problem with breaking strength on the soft shackle, but do you worry about chafe with a synthetic fiber acting as a chain hook? I use the Mantus as well and in a years time it has come off twice. Both times laying on the bottom in five foot of water in a tidal switch. But I've never worried about it chafing through. No disrespect intended..Thoughts on this? Sid

Amsteel Soft Shackles have excellent abrasion resistance.
Excellent flex-fatigue resistance
Excellent wear characteristics
Extremely lightweight
Extremely low stretch
Floats
Lightweight
Maximum strength-to-weight ratio
UV stabilized

Here is a Soft Shackles being used on a 72’ Nordhavn as he circumnavigates. This boat weighs in at 240,000 lbs

JonJo 29-12-2013 21:35

Re: Mantus chain hook
 
Cotemar,

I might have misunderstood - but you seem to suggest you back down on the 'rode' with the snubber attached and have a fear something will break.

2 Items, the load you apply backing down should be factorially smaller than the possible load from wind and waves - so if there is a fear of breakage (from backing down) something is too weak.

But why do you back down with the snubber attached, why not back down with only the chain and then apply the snubber?

We would deploy 3:1 and then back down. If an modern anchor does not set at 3:1 then there is an issue (poor holding, something in the anchor toe) we would then deploy whatever scope is needed and then attach the snubber. If you deploy all the chain and back down and something is not quite right, you have it all to take in again.

But I might have misunderstood what you were describing.

And we use a standard chain hook which works perfectly, can be applied and removed single handed and we always have the weight of the chain keeping it in tension. If the chain hook touches the seabed - we are hard aground.




On other aspects - I was under the vague impression that 'conventionally' cordage had a 4:1 safety factor? Our trampoline was guaranteed for 10 years, is now 13 years old and has not a break in it (we are quite a way south of the tropics) - though we do replace the individual securing cords, maybe every 2-3 years.

Jonathan

Celestialsailor 29-12-2013 21:51

Re: Mantus chain hook
 
I almost never back down on my chain around the gypsy. I always use the snubber to do so. Why stress it?


All times are GMT -7. The time now is 20:17.

Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2021, vBulletin Solutions, Inc.


ShowCase vBulletin Plugins by Drive Thru Online, Inc.