Samson Ropes Provides Whoopie Sling Info

[Knotty]

I wrote to Samson Ropes about Amsteel whoopie slings asking where they would fail. Here is their response.


Using Amsteel Blue whoopie slings for suspending hammocks is a very interesting application. Thanks for the link to the thread on the hammock forum, it's a good discussion.

Recently the reduction to 60% of average break strength for Amsteel Blue whoopie slings was suspected to be a low value. Testing showed that it is actually around 80% depending on the size of the rope. On every test done the break location was at the point of the adjustable whoopie tail exit.

In collusion, the locking brummel has less impact on break strength reduction than the "sudden transition in size where the adjustable section exits the bury". If a traditional buried eye replaced the brummel, the same strength reduction would be expected because the adjustable bury exit is the weakest link.


Best regards,

Mark Pederson
R&D Engineer


Samson: The Strongest Name in Rope
www.samsonrope.com

[Albert Skye]

Good work, thanks!

Please convince them to do some D:d testing (because that data is fundamentally useful); ideally, a plot like this. When I requested that data they said they didn't have it, but perhaps you can talk them into doing it.

[mike99]

Good work, thanks!

Please convince them to do some D:d testing (because that data is fundamentally useful); ideally, a plot like this. When I requested that data they said they didn't have it, but perhaps you can talk them into doing it.

Usefull for a sheave, but doesn't each side of an eye or loop only have to support half the load? If the bend only reduces the strength to 50% or more than i dont see how it has effected the breaking strength of the rope. It should still be 100%. A sharp bend creates a fatigue point so it might matter in use over time and be important as the rope weakens there, but thats a more complicated test.

You do have to make the eye at least 3 prefably 5 times longer than the diamter so that the two legs dont connect to the splice at a wide angle.

[Albert Skye]

[...] i dont see how [...]

Testing D:d would be useful in understanding the behaviour of HMPE (the plot in the link is for wire rope, and I'm told the performance of HMPE is likely to worse).

Of course, a spliced eye (close to twice the strength of a single line) can tolerate significant loss of strength efficiency before falling below the strength of the single line, but a line passed round a sheave/pin/toggle and loaded on both legs cannot.

In short, it depends how one uses the cord.

[mike99]

Yes i said it would be usefull for some things.

In the case of whoopie slings i suspect that it doesnt have any noticeable effect because of the doubling at the eyes, at least for D/D ratios of 1 or greater. If you splice two eyes to each other you get a D/d of about 1, hasnt there been break tests on that?

[gargoyle]

thanks knotty good info.

[Trout]

I have no idea what he said.

[Knotty]

I have no idea what he said.

Bottom line is that a whoopie will break where the adjustable tail exits the bury.


I guess we don't need the question mark anymore.

[opie]

Bottom line is that a whoopie will break where the adjustable tail exits the bury.


I guess we don't need the question mark anymore.

And Im taking a stab here, But I believe because thats the only place in the sling where there is a single stretch of line.

The section between the end of the dead eye bury and the beginning of the adjustable bury is the weak link in the sling.

[opie]

Thanks Knotty.