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  1. #61
    Senior Member WarmSoda's Avatar
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    Tapering

    Sorry I'm late to the conversation. From what I have learned so far about eye splices, the main purpose to use a Brummel is to lock the splice in place during times when there is no load on the rope. If you are going to lock the splice with stitching, then the Brummel is not needed and needlessly degrades the rope strength. During times when the rope is loaded, the load will hold the splice in place. So a straight bury has higher strength than a Brummel, but still needs extra stitching to lock the splice in place. It doesn't need to be a lot of stitching, since it is only for situations with no load on the rope.

    Ok, now that I got that off my chest, I have an idea to run past you guys.
    Assumptions that I will believe are true:
    1) The weak point of the whoopie sling is at the adjustable bury on the side of the tail exit. This makes sense because the loop on the other side effectively divides the forces over both halves of the loop, while the tail holds no load, so the single line takes the whole load by itself.

    2) Degradation in rope strength is caused by bending and tight curves in the rope. The higher the degree of bend away from straight 180 degrees, the higher the loss of strength. This is why tapering helps, it forces the fibers of the sheath to form a more shallow bend and there fore conserving more strength.

    If both of those are true, then, the way I see it, the only way to make the whoopie sling for any given rope stronger is to add a buried taper inside the single line with the wide end starting just where the tail exits the adjustable bury and tapering down inside the single line. This would help to simulate the taper that would be there if the sling where not adjustable and the loop was just buried with a taper at the end. With this new fixed taper, you can have it both ways, you can have an adjustable bury AND a taper to help with strength conservation.

    So what do you think? It should make the sling stronger and would reopen the debate as to where the weakest point would be, in the adjustable bury or the fixed eye bury.

    WarmSoda

  2. #62
    Senior Member opie's Avatar
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    Quote Originally Posted by WarmSoda View Post
    Sorry I'm late to the conversation. From what I have learned so far about eye splices, the main purpose to use a Brummel is to lock the splice in place during times when there is no load on the rope. If you are going to lock the splice with stitching, then the Brummel is not needed and needlessly degrades the rope strength. During times when the rope is loaded, the load will hold the splice in place. So a straight bury has higher strength than a Brummel, but still needs extra stitching to lock the splice in place. It doesn't need to be a lot of stitching, since it is only for situations with no load on the rope.
    My destructive testing indicates that neither degrades the single line strength of Amsteel Blue 7/64

    http://www.hammockforums.net/forum/s...3&postcount=32

    Nor does the whoopie sling derate the rope, at all.

    Quote Originally Posted by WarmSoda View Post
    Ok, now that I got that off my chest, I have an idea to run past you guys.
    Assumptions that I will believe are true:
    1) The weak point of the whoopie sling is at the adjustable bury on the side of the tail exit. This makes sense because the loop on the other side effectively divides the forces over both halves of the loop, while the tail holds no load, so the single line takes the whole load by itself.
    The slings I destroyed gave in the fixed eye. None of the buries was a source of failure.

    Quote Originally Posted by WarmSoda View Post
    2) Degradation in rope strength is caused by bending and tight curves in the rope. The higher the degree of bend away from straight 180 degrees, the higher the loss of strength. This is why tapering helps, it forces the fibers of the sheath to form a more shallow bend and there fore conserving more strength.
    Yes, I can see this. The slings I used all had tapered buries. But they still failed, on average, at the lines rated limit of 1600 pounds.

    Quote Originally Posted by WarmSoda View Post
    If both of those are true, then, the way I see it, the only way to make the whoopie sling for any given rope stronger is to add a buried taper inside the single line with the wide end starting just where the tail exits the adjustable bury and tapering down inside the single line. This would help to simulate the taper that would be there if the sling where not adjustable and the loop was just buried with a taper at the end. With this new fixed taper, you can have it both ways, you can have an adjustable bury AND a taper to help with strength conservation.

    So what do you think? It should make the sling stronger and would reopen the debate as to where the weakest point would be, in the adjustable bury or the fixed eye bury.

    WarmSoda
    Check out the link I pasted above...
    I am not a gram weenie. , But Im starting to see the merits!!!

    Kris' Splicing

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  3. #63
    Senior Member WarmSoda's Avatar
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    Quote Originally Posted by opie View Post
    The slings I destroyed gave in the fixed eye. None of the buries was a source of failure.

    Check out the link I pasted above...
    Okay, I watched the videos. I paid attention to your setup and I'm not surprised the the slings broke in the eye. The post you are using is not round, it is hexagonal, with 30 degree bends. If you are testing the breaking strength of a taper or a bury, then you can't introduce a bigger bend in the rope than the area you want to test. The bigger bend = the weakest link.

    You can't claim that the bury is not the weakest part of the rope by introducing an even weaker part ( like a knot or a significant bend) and proving that the rope doesn't break at the bury.

    I know I read somewhere, but couldn't find, information on the diameter of the eye vs strength. That would tell us the optimum diameter of the round post that would make your experiment a better test. I imagine electrical conduit or chainlink fence post that will fit over your hexagonal post will improve things.
    Quote Originally Posted by opie View Post
    My destructive testing indicates that neither degrades the single line strength of Amsteel Blue 7/64 ...

    Nor does the whoopie sling derate the rope, at all.
    This just doesn't jibe with the information from Samson about the degradation of the slings. I don't want to discount your test, but I would feel better if it was consistent with other sources of information. Although, I am very impressed with the strength of the slings, how did you figure that 280 psi gives 1600 lbs tension??
    Last edited by WarmSoda; 12-12-2009 at 16:34.

  4. #64
    Senior Member opie's Avatar
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    Quote Originally Posted by WarmSoda View Post
    Okay, I watched the videos. I paid attention to your setup and I'm not surprised the the slings broke in the eye. The post you are using is not round, it is hexagonal, with 30 degree bends. If you are testing the breaking strength of a taper or a bury, then you can't introduce a bigger bend in the rope than the area you want to test. The bigger bend = the weakest link.
    But they broke well past what samson says they should have done. And they didnt break at any of the bury points. The bury points are supposed to be the weak link, and these broke, on average, at the rating of the line. That tells me, that even though the posts may have introduced a weak point, its moot as they broke at the rating of the line.

    Quote Originally Posted by WarmSoda View Post
    You can't claim that the bury is not the weakest part of the rope by introducing an even weaker part ( like a knot or a significant bend) and proving that the rope doesn't break at the bury.
    I can because thats not where they gave it up. I may have introduced a weaker part, but that still did not derate the rope below its maximum weight rating.

    Quote Originally Posted by WarmSoda View Post
    I know I read somewhere, but couldn't find, information on the diameter of the eye vs strength. That would tell us the optimum diameter of the round post that would make your experiment a better test. I imagine electrical conduit or chainlink fence post that will fit over your hexagonal post will improve things.
    Once again....1600 pounds...

    INCH MM LBS/100 FT KG/100M SAMSON AVERAGE STRENGTH LBS SAMSON AVG STRENGTH KG SAMSON MIN STRENGTH LBS SAMSON MIN STRENGTH KG ISO/BS EN919 METRIC TONNES
    7/64 2.5 0.30 0.45 1,600 730 1,400 650 0.73

    Samsons Whoopie Sling splicing instructions say...

    AmSteel® and AmSteel®-Blue Whoopie Slings have a break strength of
    60% of the published average ROPE break strength.
    That means it should have broken below 1600, well below. Even if we take into account the email Knotty got from Samson, which brings it to 80%.

    Quote Originally Posted by WarmSoda View Post
    This just doesn't jibe with the information from Samson about the degradation of the slings. I don't want to discount your test, but I would feel better if it was consistent with other sources of information. Although, I am very impressed with the strength of the slings, how did you figure that 280 psi gives 1600 lbs tension??
    Knotty received an email from Samson stating the derate was closer to 20% and the weak point was the tail exit of the adjustable bury. My testing did not show that. Now.. Im not a testing lab nor am I certified in anything.....

    280psi being exerted on a surface area of 11.78 inches divided by 2. There are 2 cylinders on the machine and their combined effective piston surface area is 11.78 inches. Im only using 1 cylinder. 11.78 divded by 2 = 5.89 sq inches. 5.89 x 280 = 1649.2.

    I guess if I wanted to be more accurate, I could take into account the hoses and fittings past the valve. Some say that will take as much as 5% of your psi.
    I am not a gram weenie. , But Im starting to see the merits!!!

    Kris' Splicing

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  5. #65
    Senior Member TiredFeet's Avatar
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    Quote Originally Posted by WarmSoda View Post
    Although, I am very impressed with the strength of the slings, how did you figure that 280 psi gives 1600 lbs tension??
    280 * (11.78/2) = 1649

  6. #66
    Senior Member Albert Skye's Avatar
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    I suggest testing a few unmodified pieces to find the real breaking strength. Put a buried eye splice in each end and cover the hex posts with some pipe.

  7. #67
    Senior Member opie's Avatar
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    Quote Originally Posted by Albert Skye View Post
    I suggest testing a few unmodified pieces to find the real breaking strength. Put a buried eye splice in each end and cover the hex posts with some pipe.
    Future testing is going to be done via slings made from 3/16 Amsteel Blue using carabiners to attach the pieces to be tested. I will re-test the 7/64 whoopie sling. The machine has mounting points, but they are located in the wrong area. So Im going to make up some slings with the 3/16 to properly locate the biners so its a straight pull, from biner to biner.
    I am not a gram weenie. , But Im starting to see the merits!!!

    Kris' Splicing

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  8. #68
    Quote Originally Posted by opie View Post
    . A 300 pound hanger hanging at 30 degrees only exerts 150 pounds on each line.

    i believe a 300# hanger hanging at a 30 deg angle exerts 300# on each line

    in my experience, a 20 deg angle (146% of bodyweight on each susp. end) is hard to do.
    ...that's 20 deg susp. angle after line is weighted. you might be able to pull the line to 0 deg on an unweighted hammock, but after weighting it will almost always be more than 20 deg (146% weight)
    Last edited by warbonnetguy; 12-12-2009 at 22:01.

  9. #69
    Senior Member opie's Avatar
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    Quote Originally Posted by warbonnetguy View Post
    i believe a 300# hanger hanging at a 30 deg angle exerts 300# on each line

    in my experience, a 20 deg angle (146% of bodyweight on each susp. end) is hard to do.
    ...that's 20 deg susp. angle after line is weighted. you might be able to pull the line to 0 deg on an unweighted hammock, but after weighting it will almost always be more than 20 deg (146% weight)
    Yes.. I was wrong there. I forget who it was that set me straight on that one.
    I am not a gram weenie. , But Im starting to see the merits!!!

    Kris' Splicing

    Kris on Facebook

  10. #70
    yeah, saw that after i posted

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