Whoopie Bury Length

[Knotty]

7/64" Amsteel Blue is rated at 1600#. Make it into a whoopie sling and it derates to to 960# (60%).

200# person in hammock with typical 30deg suspension angle will put 200# on the suspension. So now we're below a 5:1 safety factor. I wouldn't climb cliffs with those numbers but, for the moment, I'm feeling safe in a hammock.

Reduce the angle by just 10deg and the same person puts 300# on the suspension. Now we're just a bit better than 3:1 safety.

The big unknown is the dynamic loading, which is only exacerbated by using a line with almost not stretch. Lines which stretch will significantly reduce shock loading. Fortunately there will be some stretch in the hammock material.

Yet another chart:

[angrysparrow]

Now we're just a bit better than 3:1 safety.

Let's remember that if anyone is uncomfortable with the safety margin of 7/64", Amsteel is available in larger diameters. I actually prefer 1/8" for my own purposes (safety factor notwithstanding).

[opie]

7/64" Amsteel Blue is rated at 1600#. Make it into a whoopie sling and it derates to to 960# (60%).

Thats using a locked brummel. An eye splice being locked via stitching derates it by a maximum of 10%.

It would be interesting to find what the bury on the sling derates it to. Because if you use a straight bury and stitch lock it... the weak point isnt the dead eye.

200# person in hammock with typical 30deg suspension angle will put 200# on the suspension. So now we're below a 5:1 safety factor. I wouldn't climb cliffs with those numbers but, for the moment, I'm feeling safe in a hammock.

Divided by 2. So 100 pounds on each line.

Reduce the angle by just 10deg and the same person puts 300# on the suspension. Now we're just a bit better than 3:1 safety.

Again..divide by 2.

The big unknown is the dynamic loading, which is only exacerbated by using a line with almost not stretch. Lines which stretch will significantly reduce shock loading. Fortunately there will be some stretch in the hammock material.

Maybe a hammock/sling destruct test is in order?

50# bags at a time untill something gives.

[opie]

I just don't get guys who put 200lbs into a hammock and then publicize that a 1,000lb-rated line (expressly intended for non-human-safety applications) is good enough. All to save an ounce. Not in my book. YMMV and HYOH, though.

But if the ideal hang is around 30 degrees... Why wouldnt a line rated at 1000 pounds be suitable?

If the whoopie sling derates 40%, that leaves 600 pounds to work with. A 300 pound hanger hanging at 30 degrees only exerts 150 pounds on each line.

Part of my problem is that I'm an ex-caver, where rigging forces really were "life and death." Even though that's not normally the case in hammocking, I still don't rig my hammock over rocks I wouldn't want my backbone to do any destructive testing on! But that's just me. I'm such an amateur knuckle-head, that I want a generous margin of error when it comes to my spine relying on my DIY. LOL

Enjoy!

Rain Man

.

I hear ya there. Id never hang over water or something I wouldnt want to hit while sleeping.

[opie]

BTW... I suck at math so I wouldnt be surprised if Im missing something.

[TeeDee]

I've read a lot of speculation elsewhere on the rating of a buried eye splice versus a Locked Brummel eye splice.

There is no consensus.

Some say the Brummel derates the rope, some say it is 100%.

All agree that a proper stitched bury with a sufficiently long tapered bury is 100% or at the most 1% to 2% derated.

I think that Brion Toss may have destructively tested both splices, but not too sure. He makes statements in some forums that he has done destructive testing, but doesn't specify exactly the eye splice and the material used.

In his Book #5 he claims the Mobius Locked Brummel with no bury of the tail is 70% of the rope strength - what I call the Mobius Locked Brummel, he calls the McDonald Brummel. But he also claims that a Mobius/McDonald Locked Brummel in HM rope (Dyneema/Spectra) with a tapered, buried and stitched tail is rated at 100% of the rope strength.

Brion Toss has an interesting way of stitching a buried eye splice. When he is preparing the taper for the bury, he pulls one strand right at the point where the end of the eye is. When the tail is buried, this strand ends up right against the bury. He then uses this strand to stitch the bury. Makes a neat bury using the rope strand without cutting the strand until finished stitching.

Anyway, until somebody does some detailed, repeatable destructive testing on the Whoopie Sling with a Locked Brummel eye splice as Samson rope details and another with a stitched bury eye splice as Samson Rope details in their 12-strand class-2 eye splice, everything conjectured here (and elsewhere ) is simply that, conjecture. Until the testing is done with repeatable results, we'll never really know the answer to the question:

Does the adjustable bury splice derate the rope 40% or is it the Locked Brummel that derates the rope 40%?

[TeeDee]

....

If the whoopie sling derates 40%, that leaves 600 pounds to work with. A 300 pound hanger hanging at 30 degrees only exerts 150 pounds on each line.....

Nope - at 30 degrees each suspension line has the full weight of the hammock and occupant. The 300 lb hanger, exerts 300 lbs on each line at 30 degree suspension angle.

It is 150 lbs on each line if the suspension line is hanging straight down the tree - now that would be a nice trick

[opie]

Nope - at 30 degrees each suspension line has the full weight of the hammock and occupant. The 300 lb hanger, exerts 300 lbs on each line at 30 degree suspension angle.

It is 150 lbs on each line if the suspension line is hanging straight down the tree - now that would be a nice trick

I was misreading the chart...

SO Ameteel Blue has an average strength of 1600 pounds, and the whoopie sling derates it 40%. If my math is right, that leaves 960 pounds one could load in their hammock at 30 degrees.

Maybe Ill stop stitching and start using the locked brummel. Its what Im using on the guy lines and it holds fast.

[opie]

Thats using a locked brummel. An eye splice being locked via stitching derates it by a maximum of 10%.

It would be interesting to find what the bury on the sling derates it to. Because if you use a straight bury and stitch lock it... the weak point isnt the dead eye.



Divided by 2. So 100 pounds on each line.



Again..divide by 2.



Maybe a hammock/sling destruct test is in order?

50# bags at a time untill something gives.

Knotty, I was wrong... Sorry about my post.

[Hooch]

Ok, call me ignorant if you will, but what's a fid?