Whoopie Sling Suspension

[tripitaka]

I've read this thread over the last 3 days or so. After meeting Grizz a few weeks ago, I thought the marlin spike stuff was cool but this is a new dimension!

Keep it up guys - I'm lovin' it.

C'mon Shug - do the video!!!

[GrizzlyAdams]

I've read this thread over the last 3 days or so. After meeting Grizz a few weeks ago, I thought the marlin spike stuff was cool but this is a new dimension!

Keep it up guys - I'm lovin' it.

C'mon Shug - do the video!!!

well, would you settle for shug being in my video ?

Of course, shug's would (will?) be funny...can you imagine the sound effects....

Grizz

[MacEntyre]

Great job on the video, Grizz!

The skipper of the offshore towing, salvage and equipment handling vessel I worked on years ago was a New England shell-back Scot named Roy, (may he rest in peace). He was very particular about chafe, and would cut it out of any line that might see a heavy load. That's how we avoided accidents.

Roy would point out that a Whoopie sling hammock suspension will tend to chafe the middle of the rope, where it runs around the toggle. You always want chafe to occur near the end, so that you lose little when you cut it out.

With a UCR, Roy would have put chafing gear on the eye, because that is where the toggle will wear out the line over time.

Of course, modern synthetics are relatively chafe resistant. The principle of use remains, though. We tend to use stronger, smaller lines to save weight, so chafe really becomes a bigger issue.

- MacEntyre

[GrizzlyAdams]

Great job on the video, Grizz!

The skipper of the offshore towing, salvage and equipment handling vessel I worked on years ago was a New England shell-back Scot named Roy, (may he rest in peace). He was very particular about chafe, and would cut it out of any line that might see a heavy load. That's how we avoided accidents.

Roy would point out that a Whoopie sling hammock suspension will tend to chafe the middle of the rope, where it runs around the toggle. You always want chafe to occur near the end, so that you lose little when you cut it out.

With a UCR, Roy would have put chafing gear on the eye, because that is where the toggle will wear out the line over time.

Of course, modern synthetics are relatively chafe resistant. The principle of use remains, though. We tend to use stronger, smaller lines to save weight, so chafe really becomes a bigger issue.

- MacEntyre

great point! Would that my gear saw so much use that I'd have to be concerned about chaffing

One point though about the whoopie sling versus UCR---hanging from different trees mostly will move the point of wear around on the whoopie sling (different suspension lengths) whereas on the UCR the wear spot will always be in the same place.

I knew I'd seen a picture here somewhere of a loop with some abrasion protection....back a few posts....here.

Grizz

[Frawg]

One point though about the whoopie sling versus UCR---hanging from different trees mostly will move the point of wear around on the whoopie sling (different suspension lengths) whereas on the UCR the wear spot will always be in the same place.

From the relativistic viewpoint of an ant crawling on the constriction, I'm not seeing how that's the case. Certainly the UCR constrictor stays next to the tree, but the location of its buried part varies with different suspension lengths, as with the whoopie sling. Also, both will chafe invisibly inside the constriction section.

There was a little discussion of wear in the original UCR thread and Samson has a technical bulletin on Rope Inspection & Retirement that's worth a glance.

Mathlete side note: wouldn't the chafe distribution along the bury reflect the pdf (function, not file) of your tree spacing history?

[angrysparrow]

I think he means the eye that goes around the toggle as being the point of wear, not the constriction. There is a certain amount of chafe, and deformity introduced in the bend around the toggle. That is often at a different place along the cording with a whoopie, but on the UCR you always hang on the same eye.

[Frawg]

I think he means the eye that goes around the toggle as being the point of wear, not the constriction. There is a certain amount of chafe, and deformity introduced in the bend around the toggle. That is often at a different place along the cording with a whoopie, but on the UCR you always hang on the same eye.

My bad, AS -- thanks for redirecting my gaze! Guess I'd repressed that thought. It was one of the things that originally nudged me back to the UCR from the whoopie. Felt like I was sawing through the tree strap holding the toggle, when it wasn't popping off the toggle during adjustment.

[GrizzlyAdams]

I think he means the eye that goes around the toggle as being the point of wear, not the constriction. There is a certain amount of chafe, and deformity introduced in the bend around the toggle. That is often at a different place along the cording with a whoopie, but on the UCR you always hang on the same eye.

right, that's what I think Mac was referring to.

Mathlete side note: wouldn't the chafe distribution along the bury reflect the pdf (function, not file) of your tree spacing history?

ooohhh, that's good, but it's better than that I think. A pdf suggests a point associated with a tree spacing, but the wear on the inside is one-dimensional, you might suppose it to be proportional to the constriction strength. So what we really have in time is the super-imposition of exponentially decaying curves, where the super-imposition is a function of the various tree spacings. You could even weight each component differently depending on occupant weight. So I'm smelling transform methods here...what's your pleasure? A simple engineer's discrete FFT? A discrete mathematician's z transform? Try to impress the girls with a Hadamard transform?

Grizz

[Frawg]

...ooohhh, that's good, but it's better than that I think. A pdf suggests a point associated with a tree spacing, but the wear on the inside is one-dimensional, you might suppose it to be proportional to the constriction strength. So what we really have in time is the super-imposition of exponentially decaying curves, where the super-imposition is a function of the various tree spacings....

**

I guess I'd like a gamma distribution -- they're shape shifters and you don't really need to know what you're doing to use them.

...You could even weight each component differently depending on occupant weight. So I'm smelling transform methods here...what's your pleasure? A simple engineer's discrete FFT? A discrete mathematician's z transform? Try to impress the girls with a Hadamard transform?

Well, I don't let just *anyone* sleep in my hammock, so the weighting coefficients would be constant. Besides you can fold that stuff into the kernel of the transform. Why be old school?

The Hadamard is too checkered... not sure I'd want to use that; besides, it's too square to be cool. The z is unnecessarily complex, and the FFT has lost a step or two over the years. A Mellin's tasty in some spots, but probably wouldn't do here. <sigh> But they're all variations on a theme, no? Why choose a kernel before we have to...

But, really, if we're talking about the time history of hanging it may be more convoluted than we've touched on. Homomorphic processing might be useful, if you don't have any phobias about quefrency alanysis.

... and if this hasn't veered beyond reason into left field, I don't know what would qualify!

**Edit: pulling tongue from cheek for a moment, if we consider the additive effects of various hangers using the same hammock / suspension over the same set of trees I think you could consider the aggregate wear at a point inside the constrictor as a random variable that is the sum of the wears from each individual hanger. The aggregate pdf would then be the convolution of the pdfs of each hanger. If you do any of the Laplace-related transforms the convolution maps to a product of transformed pdfs. Taking the log of that maps to a sum of pdf related transforms that you still probably couldn't unmix.

[MacEntyre]

You scientists are too funny! Good engineers know that the chafe inside the constriction is insignificant, or no more significant than the rest of the normal wear and tear. Chafe is accelerated wear and tear, beyond the norm.