Low Friction Ring strop methods survey

[Breaking Waves]

^^ the Hampidjan graph is specifically for dux, a heat set product, which amsteel is not. The specific curve/numbers change a little but the general characteristics of the curve are common across high modulus fibers (and wire).

I can’t comment on the soft shackle vs cow hitched strength argument. Would need to see test data. As we have seen here, actual testing can reveal things, different that we (or at least I) expected.

out of curiosity "these loops are often cow hitched in situations where the diameter of the attachment point is about the same as the line diameter, or at least not much more." you are saying that a pad eye rated to 9500lbs would have a bail 3/16" or smaller? Do you want to double check that for me, please.

I do agree the soft shackle is a more versatile attachment than the fixed loop. On the flip side I worry that it adds a level of complexity, on top of the ring connection construction, which is daunting for DIYers and could introduce construction defects which weaken the end solution.

The lab did offer to do another round of testing if we had “ improved solutions”.

[Seaworthy Lass]

Originally Posted by Breaking Waves

^^ the Hampidjan is specifically for dux, a heat set product. The specific curve/numbers change a little but the general characteristic of the curve are common across high modulus fibers (and wire).

I can’t comment on the soft shackle vs cow hitched strength argument. Would need to see test data. As we have seen here, actual testing can reveal things, different that we (or at least I) expected.

I do agree the soft shackle is a more versatile attachment than the fixed loop. On the flip side I worry that it adds a level of complexity, on top of the ring connection construction, which is daunting for DIYers and could introduce construction defects which weaken the end solution.

The lab did offer to do another round of testing if we had “ improved solutions”.

Given nothing failed at the LF ring end for all five samples you constructed, I can’t imagine loops could be improved over and above this, as the weak point is at the attachment end.

In practice, loop strops will be far less strong than tested (possibly less than half the strength tested) if cow hitched onto attachment points around the same diameter or even slightly higher. Load testing results on cow hitched loops have already shown this.

If we are trying to maximise the strength of strops used for LF rings, I do think soft shackle versions are the way to go. I agree though that they are harder to make if someone is not experienced with soft shackle construction, and also there is room for more error if some basic care is not taken. Even manufacturers get this wrong - eg I have seen Kohlhoff style soft shackles with diamond stoppers for sale with eyes that are barely one rope diameter in size .

SWL

[Breaking Waves]

Originally Posted by Seaworthy Lass

Load testing results on cow hitched loops have already shown this.

source?

Im just not sure what argument you are making ... of course all solutions, including the soft shackle, will be weaker when put around a smaller bend if that is where they are already breaking. The cow hitch testing I have seen has mostly been rope around rope (as in joining two) which has different dynamics than what we are talking about here - you have compression issues there which this case does not.

Originally Posted by Seaworthy Lass

Given nothing failed at the LF ring end for all five samples you constructed,

in fact the cow hitched one failed at the ring lol . . . but because it caused ring deformation rather than line weakness.

[Seaworthy Lass]

Originally Posted by Breaking Waves

source?

Evans Starzinger.

I bet you are now going to ask where and make me hunt for hours .
It may be that I am remembering incorrectly, but in one thread on CF a few years ago I recall him discussing a figure of 42% of system strength for full loops (85% for eye spliced loops) when cow hitched on.

Originally Posted by Breaking Waves

Im just not sure what argument you are making ... of course all solutions, including the soft shackle, will be weaker when put around a smaller bend if that is where they are already breaking. The cow hitch testing I have seen has mostly been rope around rope (as in joining two) which has different dynamics than what we are talking about here - you have compression issues there which this case does not.

Not an argument at all, I am just pointing out that in practice these loops are generally cow hitched onto attachment points that are not huge in diameter. The main point I was making (or trying to make ) is that system strength will decrease much more for a loop compared to a soft shackle, as there are only two legs in the former and four in the latter.

Apart from the added complexity of construction (not actually much harder if someone already makes soft shackles) I think soft shackles are a much better option for retaining LF rings rather than loops. Construction cost is lower, they can be significantly shorter, they are removable with the line still passing through and time taken is not much more than for the loops retaining LF rings. Bonuses all around .

A few of the designs you made up could be incorporated into soft shackles, it is not just the Bullseye weave.

Originally Posted by Breaking Waves

in fact the cow hitched one failed at the ring lol . . . but because it caused ring deformation rather than line weakness.

That is a surprise for me! (The whipped one also performed much better than expected).

Given the dyneema was probably bending between 1:1 and 2:1 in the cow hitch on the ring side, why do you think the failure of the loop was still at the pin end where the bend was nearly 4:1?

Edited to add: is it because the portion around the ring is a form of an additional loop, so loads seen in that portion are halved? Late at night here and my mind is getting fuzzy.

SWL

[Seaworthy Lass]

Originally Posted by Breaking Waves

source?

Bingo!
I found it.

There was initially some confusion in this discussion (mainly on my part) between loops on eye splices and full loops (and as well % of system strength or % of line strength being referred to when strength was discussed), but here is the reference. As the system loss with a 1:1 bend without any cow hitch is already around 50%, the 85% strength referred to here must be % of line strength (where maximum system strength is 200% line strength):

Originally Posted by estarzinger

This is a bit more complicated that that - for instance if a loop is around a 1:1 padeye, the strength is 100% (or 95%). But if that loop is around a payeye in a cowhitch it would be 85%.

I will call it quits for tonight as matchsticks are holding my eyes open (late at night on top of a couple of long flights).
Thanks for the interesting discussion.

SWL

[Seaworthy Lass]

Originally Posted by Breaking Waves

out of curiosity "these loops are often cow hitched in situations where the diameter of the attachment point is about the same as the line diameter, or at least not much more." you are saying that a pad eye rated to 9500lbs would have a bail 3/16" or smaller? Do you want to double check that for me, please.

You are correct. The pad eye is then the weak point in the system . I have heard cruisers complain of these ripping out of the deck (more commonly than breaking), so the strength of the attachment point and how it is secured does need serious consideration.

The soft shackles or loops (none cow hitched) with or without LF rings that take the highest loads on board our boat are all attached to the toe rail, which has a diameter of 36mm (D/d of around 5:1 or 7:1 depending on line diameter), so bending losses there are not the weak part of the system.

However, if loops were cow hitched onto this same toe rail (as the loops with LF rings would be), given there are bends that are somewhere between 1:1 and 2:1 in the cow hitch itself, I think breaking strength is likely to drop to very roughly 50% system strength. A soft shackle will not see this.

SWL

[Breaking Waves]

^^

As I said to dockhead recently: perhaps, perhaps not, testing would reveal

I can and have speculated with the best, but I learn something new from almost every test I do (which means my speculation, which is decently informed, was often wrong).

I do like the soft shackle base to the strop.