Are our suspensions systems safe

[Floridahanger]

Check the labeling on those Walmart straps, Floridahanger. The 400# may be the "working" strength, not the "break" strength. If so, they would be rated about 1200# "break" strength, which is what everyone is referring to here on the forum.
(Maybe you're not such a dare-devil after all )

You may not want to know the info after I find it. But I will get it. I hope I'm wrong.

[dingbat]

I see a lot of the 5:1 safety factor being throw around in this thread. In my line of work, for fall protection, the 5:1 ratio is used to determine working load for hardgoods, ie. metal. Softgoods (any cordage or webbing would come under this) we use at 6% max of breaking strength which is more like 17:1. Minimum breaking strength in our systems are 5000lbs, and it's rare we are on anything below 7000lbs.

Now I'm not recommending that folks use 11mm kernmantle static line for their suspensions (I certainly wouldn't), just passing on some information so folks without any other background can get a sense of how far they are pushing things.

Softgoods also get inspected before and after each use, and retired after 5 years from in-service date regardless of condition. A real common issue we see is weld abrasion, particularly where soft goods are girth hitched to one another and in knots in cordage. Always make sure your knots are well dressed and tight to start, then load them as gently as possible on their first uses. Another thing to look out for is exposing softgoods to anything that could also harm your skin: Sunlight (UV breaks down plastics), dirt (makes micro abrasions in fibers), abrasion, chemicals, etc.

The stuff I use at work is pretty bomber, but even so, over the years I have seen some instances where the extra safety factor came well in to play. Usually some sort of complacency was involved in these instances. Just because a piece of gear has not failed you the last X number of times you've used it does not mean you can pull it out without thinking, or start asking it to handle extra strains, and expect the same results. Short of not taking part in an activity, complacency is the one factor in allowing or avoiding a failure you have complete control of.

In reference to the thread's title, nothing is safe when it comes to suspending yourself off the ground. Some practices are just safer than others.

[Caveman]

Man... If you want to know if they are going to hold you... there's only 1 way to find out! FOR SCIENCE!

[Rain Man]

I too use dynaglide. The safety magin is exactly that. If you are using a 30 degree hang angle, then technically one could use dynaglide safely to about 400lbs before I would be sketchy.

You addressed (1) rated strength and (2) angle, but what about (3) knots, splices, and bends over hardware, and (4) dynamic (effective) vs. static (phony) weight?

Solving for 2 unknowns out of 4 would get me quite a "sketchy" answer in math class.

Rain Man

.

[DemostiX]

I hope elders besides Rain Man would agree with my advice on this. (I am pleased to follow up and expand on someone who I know from his experience as a spelunker -- cave diver -- knows a whole lot about good use of cordage.)

There's more to cordage than breaking strength. If you don't want to know enough about cordage to understand why people who would benefit from a light load carry heavy stuff, then

1. give yourself a big margin of safety in breaking strength to cover all you don't want to learn or be concerned about or might make you anxious and spoil fun.
   
2. Margins of safety for engineers are 5-15 as multipliers
3. Right off the bat, your normally hung hammock puts twice the load on each rope you likely thought it did.
4. Dropped loads, so called dynamic ones, snap ropes, especially ropes of UHDPE like ours especially easily. Unless you are put to and get removed from hammock and sleep like a swaddled baby, you need more strength than you think.

[Xtrm tj]

Sometimes when I am laying up in my hammock and I look up at my Dynaglide UCRs, I can almost hear Sgt Rock saying, "You're Gonna Die".

That is a true statement....he really pounds that in your head during his ucr video...lol

[Floridahanger]

I use the 7/64 Amsteel for my cordage, but my straps are Walmart cargo straps rated ~400lbs. It's definitely not for the weight savings as much as the $ savings. I'm sure I could get lighter and less bulky straps from any of our cottage vendors, but, I don't have the funds for them. The WW straps are ~$5 for 2, 12' straps I make into 4, 6' straps. I've tested and was happy with them.

I still use my original straps for 3 years now. Also, I always check them everytime I remove them from the trees and everytime I remove the toggles.

Check the labeling on those Walmart straps, Floridahanger. The 400# may be the "working" strength, not the "break" strength. If so, they would be rated about 1200# "break" strength, which is what everyone is referring to here on the forum.
(Maybe you're not such a dare-devil after all )

You may not want to know the info after I find it. But I will get it. I hope I'm wrong.

OK, I have the info and here it is...

*gulp*

500 lbs(227kg) Break Strength
167 lbs(76kg) Load Limit

*Yikes, I'm gonna die!*

Even though I inspect before and after every connection, I still know it can fail anytime and I limit the height to how high I'm willing to fall. The older I get, the lower that height is. January, I fell from lack of ensuring my whoopie was on the knot of MSH. I'm currently just at a low chair height

If over some rocks or roots, I will switch to stronger backups. Until then... "let it ride" *yikes, again*

[JToon]

Quick question here regarding my suspension. I have an ENO double which is supposedly good to 400 pounds, which I do not doubt. I have changed out the ends with continuous loop amsteel 7/64. Was I an idiot to do this? My wife and I lay in it occasionally in the back yard our combined weight is almost 300 lbs. Did the continuous loop now become my weak point?

[gmcttr]

...Did the continuous loop now become my weak point?

That would depend on what connects the CL to your suspension. But in general and without digging out the pertinent test reports, a CL of Amsteel Blue will have a strength ~ 1.5 times the minimum breaking strength of a single leg of amsteel. Since the MBS of 7/64" amsteel is 1400 lbs the CL should be good for at least 2100 lbs.

I think you'll find the weak link is still the hammock.

[wgiles]

The tension in your suspension is related to the angle of the suspension lines. If your suspension was exactly horizontal, the tension would be infinite and any suspension line would break. If your suspension lines were vertical (an impossible arrangement in a hammock). the tension in your suspension lines would be one half of your weight. Since the suspension lines must be at some angle from the horizontal, the tension in each side must be somewhere between 1/2 your weight and infinity. At a suspension angle of 30 degrees from the horizontal, the tension in the line would be equal to your weight. If the angle from the horizontal is less than 30 degrees, the tension will be more than your weight. A ridge line on your hammock allows you to keep the hammock end angle at 30 degrees regardless of the angle of the suspension. With a ridge line, the suspension lines tend to be more horizontal, so the tension in each suspension line is greater than your weight. The extra tension is taken by the ridge line. The breaking strength of your suspension is dependent on the size of the rope or strap, the efficiencies of the knots, splices or sewed connections, the sharpness of the bends and the condition of the line. It is common to assume that the efficiency of the knots or splices is 80% and the line condition could reduce the efficiency to 50% or less. It is entirely possible for any of the common suspension lines to fail. The biggest culprit in strength loss of synthetic lines, whether rope or webbing is UV deterioration. Black is generally least affected by UV and white is generally most affected by UV. If you leave your suspension out in the sun for any length of time, it will lose a significant part of its strength. All that this says is that you can calculate the safety factor of a new, properly applied suspension line, but you can't calculate the safety factor of an old, worn suspension line. Most of the reason for the high safety factors quoted is shock loading. If you don't get into your hammock gently, you could easily double the tension in the suspension lines for a short time. It's the same if you squirm around or bounce in your hammock. That is the reason for using shock absorbing lanyards on fall protection harnesses.