## Re: 3/32" Hammock Hanging Rope?

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• To engineer the straps/ropes how big of a safety factor do you plan on? If I weigh 200 lbs. and hang at 40°. then my static load on each rope is 155 lbs. is a
Message 1 of 22 , Aug 4, 2004
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To engineer the straps/ropes how big of a safety factor do you plan
on?
If I weigh 200 lbs. and hang at 40°. then my static load on each
rope is 155 lbs. is a rope with 5oo lbs. breaking strength enough?
1000 lbs? 1500 lbs?

--- In hammockcamping@yahoogroups.com, "Ray Garlington"
<rgarling@y...> wrote:
> --- In hammockcamping@yahoogroups.com, "Mirage" <mirage@p...>
wrote:
> This is what I have evolved to. I found the bulk and weight of the
> 30 ft of webbing rather too much for my tastes. I used what I had
> to make two 10' "tree huggers" (rather long, but some trees here in
> the PNW really require it).
>
> One thing about ropes & trees. I've noticed that most of the
> rubbing/friction is in the first 1/4 turn of the rope around the
> tree. By the time you get to ropes about 5/16" diameter there is
no
> significant damage (but some slight cosmetic scraping). I made
some
> pads to protect this 1/4 turn, and a similar idea might work on
the
> thinner cords. You might try some thick wall tubing for that
area
> to act as a pad.
>
> Concerning breaking strength: I found the following rule of thumb
> for nylon rope on the Internet. (I have observed that woven
> polyester rope seems to have slightly higher breaking strength
than
> predicted by this formula.)
>
> breaking strength = <circumference of line in inches> x 2,400
>
> so
> 1/8" cord - .3927" in circumference = 942 pounds breaking strength
> 3/16" cord - .589" C = 1413
> 1/4" rope - .75" C = 1809 pounds breaking strength
> 5/16" rope - .98" C = 2356
> 3/8" rope - 1.18" C = 2827 pounds breaking strength
• ... Hey Mirage, I was asleep at the wheel last month when y all were talking about knots for the hammock to rope junction. What is this whipping to 10 foot of
Message 2 of 22 , Aug 4, 2004
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Mirage wrote:

>
>I then whipped the hammock hanging lines on the end of the hammock,
>leaving about 10' of line to hang from on either end.
>
>
>
Hey Mirage,

I was asleep at the wheel last month when y'all were talking about knots
for the hammock to rope junction. What is this whipping to 10 foot of
line knot that you use?

Rick
• ... Hi Jon, I would want the weight to be suspended from the webbing against the tree for two reasons: - eliminate roll down - spread weight across the full
Message 3 of 22 , Aug 4, 2004
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moneymakerjk1 wrote:

>What about short sections of tubular nylon sling as a cover for the
>line as it goes around the tree? A one or two foot length wont weigh
>that much I suspect. I used to be a Ropes Course instructor, and the
>stuff is pretty hardy.
>
>jon
>
>
>
Hi Jon,

I would want the weight to be suspended from the webbing against the
tree for two reasons:
- eliminate roll down
- spread weight across the full width of the webbing

I have used the Hennessy Hammock style tree huggers and think they are a
good solution. They are also easy to make at home. What this is, is a 2
or three foot piece of webbing with the ends folded over and sewn into a
loop. To tie the hammock up to the tree, the hugger is either wrapped
around the back of the tree (big tree) or wrapped a couple times around
a smaller tree, ending up with the two loops equidistant from the
hammock. Then the rope is passed through the loops and tied with a
hennessy hammock knot.

I would not think that passing the rope through a piece of tubular
webbing would do much to protect the tree from anything except abrasion
(which is not the damage I am concerned about) or to reduce roll down.
BTW, the damage I am concerned about is pressure damage to the live
cambrium layer under the bark.

Risk
• ... Thus far I have done well with straps with a breaking strength of 300-600 pounds. I figure that with a breaking strength of 950 pounds, the 3/32 T-100
Message 4 of 22 , Aug 4, 2004
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Ralph Oborn wrote:

>To engineer the straps/ropes how big of a safety factor do you plan
>on?
>If I weigh 200 lbs. and hang at 40°. then my static load on each
>rope is 155 lbs. is a rope with 5oo lbs. breaking strength enough?
>1000 lbs? 1500 lbs?
>
>
>
Thus far I have done well with straps with a breaking strength of
300-600 pounds. I "figure" that with a breaking strength of 950 pounds,
the 3/32 T-100 cord is probably strong enough. All I know about stretch
is that the line is said to stretch less than one percent at 95 pounds
of tension.

Another cord I might think about would be the 1/8 inch Pulse Line which
is also about 900 pounds of strength.

This is just an experiment for me. I will not guess any conclusion
until I actually try it. I know that I will be *very* surprised if 3/32
inch cord is sufficient. But if it is, this offers considerable space
and weight savings, as well as a little cost savings.

Risk
• ... hammock, ... knots ... foot of ... Initially, I was using 1/8 polypro line to whip the folded ends (instead of knots) together, then using a larks head
Message 5 of 22 , Aug 4, 2004
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--- In hammockcamping@yahoogroups.com, Rick <ra1@i...> wrote:
> Mirage wrote:
>
> >
> >I then whipped the hammock hanging lines on the end of the
hammock,
> >leaving about 10' of line to hang from on either end.
> >
> >
> >
> Hey Mirage,
>
> I was asleep at the wheel last month when y'all were talking about
knots
> for the hammock to rope junction. What is this whipping to 10
foot of
> line knot that you use?
>

Initially, I was using 1/8" polypro line to whip the folded ends
(instead of knots) together, then using a larks head from the straps
or rope to hang the hammock.

I just took it one step further, once I decided to go back to rope
and tree huggers. Instead of whipping with 1/8" line first, I just
use my 3/8 hang line and whipped it to the end, leaving the long end
comming out the end of the folds.

I'll post pics as soon I I get them back from my dads camera (I
borrowed my sons, and forgot it only has 16Mb and the pics turned
out poor as well).

Shane "Mirage"...
• ... plan ... As a practical example: Hennessey uses line with a breaking strength from about 1600 to 1800 pounds depending on the model. If the webbing used
Message 6 of 22 , Aug 5, 2004
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--- In hammockcamping@yahoogroups.com, "Ralph Oborn"
<polecatpop@y...> wrote:
> To engineer the straps/ropes how big of a safety factor do you
plan
> on?

As a practical example: Hennessey uses line with a breaking
strength from about 1600 to 1800 pounds depending on the model. If
the webbing used by the Speerians really is 800 pound breaking
strength, and they are not reporting problems then you can see that
Tom has built in a large safety factor.

It will be interesting to see if Rick ends up risking the 3/32"
which is typically used for working loads around 100 pounds. On a
positive note, it seems like it should work if the webbing he's been
using really only goes to 800 pounds.
• ... live ... Apx what pressure (in psi) will cause damage? We could calculate (or measure) the localized pressure being generated at the outside bark surface
Message 7 of 22 , Aug 5, 2004
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--- In hammockcamping@yahoogroups.com, Rick <ra1@i...> wrote:
> BTW, the damage I am concerned about is pressure damage to the
live
> cambrium layer under the bark.

Apx what pressure (in psi) will cause damage? We could calculate
(or measure) the localized pressure being generated at the outside
bark surface and stay above that figure. The exterior bark would
also act as padding serving primarily as a safety factor.

My experience with trees has been that they can survive quite well
even if cut through to the wood so long as decay does not start at
the injury site. You have to ring a tree most of the way around
(cut through the bark) to kill it.
• ... Ray, you overlooked something in your comparison. The Hennessy, with its intergal ridgeline, generally puts more tension on the hammock support
Message 8 of 22 , Aug 5, 2004
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--- In hammockcamping@yahoogroups.com, "Ray Garlington"
<rgarling@y...> wrote:
> --- In hammockcamping@yahoogroups.com, "Ralph Oborn"
> <polecatpop@y...> wrote:
> > To engineer the straps/ropes how big of a safety factor do you
> plan
> > on?
>
> As a practical example: Hennessey uses line with a breaking
> strength from about 1600 to 1800 pounds depending on the model. If
> the webbing used by the Speerians really is 800 pound breaking
> strength, and they are not reporting problems then you can see that
> Tom has built in a large safety factor.
>

Ray, you overlooked something in your comparison. The Hennessy, with
its intergal ridgeline, generally puts more tension on the hammock
support ropes/straps because it typically is hung so that the hammock
support ropes/straps are more horizontally than a Speer hammock.
Sometimes, this difference in tension is quite severe and it is not
obvious that Hennessy is using a greater safety margin. This extra
tension would also carry over to the other discussion concerning tree
damage. (While the internal ridgeline does help in getting a
consistant 'hang', it is not without its drawbacks.)

Youngblood
• ... Yes, but our goal should be leave no trace -- and this means no visible damage to trees. Many public (and some private) campgrounds already have
Message 9 of 22 , Aug 5, 2004
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In a message dated 8/5/04 10:35:38 AM, rgarling@... writes:

My experience with trees has been that they can survive quite well
even if cut through to the wood so long as decay does not start at
the injury site.   You have to ring a tree most of the way around
(cut through the bark) to kill it.

Yes, but our goal should be leave no trace -- and this means no visible damage to trees.  Many public (and some private) campgrounds already have restrictions against tying anything to trees because of damage caused by careless campers.   Any scarring or bark loss, even if it causes no long-term damage to the tree, should be considered unacceptable to an ethical hammocker.
John Wilson
• ... John, I agree that my concern is at a higher level than killing the tree - and I know Ray s is as well. I am concerned about scars from damage to any
Message 10 of 22 , Aug 5, 2004
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Quoting navjohn@...:

>
> In a message dated 8/5/04 10:35:38 AM, rgarling@... writes:
>
>
> > My experience with trees has been that they can survive quite well
> > even if cut through to the wood so long as decay does not start at
> > the injury site. You have to ring a tree most of the way around
> > (cut through the bark) to kill it.
> >
>
> Yes, but our goal should be leave no trace -- and this means no visible
> damage to trees. Many public (and some private) campgrounds already have
> restrictions against tying anything to trees because of damage caused by
> careless
> campers. Any scarring or bark loss, even if it causes no long-term damage
> to
> the tree, should be considered unacceptable to an ethical hammocker.
> John Wilson

John,

I agree that my concern is at a higher level than killing the tree - and I know
Ray's is as well. I am concerned about scars from damage to any portion of the
tree's live portion - under the bark.

I am a little less worried about a little surface scrape of the outer bark,
which is only some friction against the dead outer layer of the bark. But this
is because I usually am using a tree that will seldom/never have another hammock
hung from it.

I guess it is not truely leave no trace, in the same way that stepping on grass
is not actually leave no trace.
>

Rick
• Hey Risk, as far as stretch, the amount of stretch per unit of load should be higher for the first unit of load than for subsequent units. Sorry, which means
Message 11 of 22 , Aug 5, 2004
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Hey Risk, as far as stretch, the amount of stretch per unit of load
should be higher for the first unit of load than for subsequent
units. Sorry, which means that if you get 1% stretch with the first
95 lbs, that the next 95 pounds should be less than 1% stretch. So
for 450 lbs, you are looking at maybe 4% stretch or less.

Good luck with the experiment, and thanks for posting your ideas.
Hopefully the knots you use won't reduce the ultimate tensile
strength too much. Maybe put a big mattress under you when you do
the testing ;-)

Bill in Houston

--- In hammockcamping@yahoogroups.com, Rick <ra1@i...> wrote:
> Ralph Oborn wrote:
>
> >To engineer the straps/ropes how big of a safety factor do you
plan
> >on?
> >If I weigh 200 lbs. and hang at 40°. then my static load on each
> >rope is 155 lbs. is a rope with 5oo lbs. breaking strength enough?
> >1000 lbs? 1500 lbs?
> >
> >
> >
> Thus far I have done well with straps with a breaking strength of
> 300-600 pounds. I "figure" that with a breaking strength of 950
pounds,
> the 3/32 T-100 cord is probably strong enough. All I know about
stretch
> is that the line is said to stretch less than one percent at 95
pounds
> of tension.
>
> Another cord I might think about would be the 1/8 inch Pulse Line
which
> is also about 900 pounds of strength.
>
> This is just an experiment for me. I will not guess any conclusion
> until I actually try it. I know that I will be *very* surprised if
3/32
> inch cord is sufficient. But if it is, this offers considerable
space
> and weight savings, as well as a little cost savings.
>
> Risk
• Hey Risk, as far as stretch, the amount of stretch per unit of load should be higher for the first unit of load than for subsequent units. Sorry, which means
Message 12 of 22 , Aug 5, 2004
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Hey Risk, as far as stretch, the amount of stretch per unit of load
should be higher for the first unit of load than for subsequent
units. Sorry, which means that if you get 1% stretch with the first
95 lbs, that the next 95 pounds should be less than 1% stretch. So
for 450 lbs, you are looking at maybe 4% stretch or less.

Good luck with the experiment, and thanks for posting your ideas.
Hopefully the knots you use won't reduce the ultimate tensile
strength too much. Maybe put a big mattress under you when you do
the testing ;-)

Bill in Houston

Now I know that my climbing rope stretches much farther relatively on a
long fall than a short one.

Oh and I use a bouldering crash pad when I'm experimenting. Fortunately
I have yet to need it.

Tom

P.s. Now were is that piece of wood... Ah yes,, knock knock
• Yeah, I was afraid I wasn t making sense. The rope will stretch more as the load increases, you are right. It s just that in the first 95 pounds (or
Message 13 of 22 , Aug 5, 2004
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Yeah, I was afraid I wasn't making sense. The rope will stretch more
as the load increases, you are right. It's just that in the first 95
pounds (or whatever) the rope will stretch more, as the individual
fibers and strands shift against each other and lay down flat against
each other. One the rope is taut and all the strands are compacted
against each other, it will be relatively more difficult to stretch.

Bill in Houston

--- In hammockcamping@yahoogroups.com, "Thomas Peltier@G..."
<Thomas@G...> wrote:
> Hey Risk, as far as stretch, the amount of stretch per unit of load
> should be higher for the first unit of load than for subsequent
> units. Sorry, which means that if you get 1% stretch with the first
> 95 lbs, that the next 95 pounds should be less than 1% stretch. So
> for 450 lbs, you are looking at maybe 4% stretch or less.
>
> Good luck with the experiment, and thanks for posting your ideas.
> Hopefully the knots you use won't reduce the ultimate tensile
> strength too much. Maybe put a big mattress under you when you do
> the testing ;-)
>
> Bill in Houston
>
>
> Now I know that my climbing rope stretches much farther relatively
on a
> long fall than a short one.
>
> Oh and I use a bouldering crash pad when I'm experimenting.
Fortunately
> I have yet to need it.
>
> Tom
>
> P.s. Now were is that piece of wood... Ah yes,, knock knock
• as the individual fibers and strands shift against each other and lay down flat against each other. _________________________ Which would explain why short
Message 14 of 22 , Aug 6, 2004
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as the individual
fibers and strands shift against each other and lay down flat against
each other.
_________________________

Which would explain why short falls tend to be harder on ropes than long
falls.

Tom
• ... BTW Recently purchased 30 of 1 polypro. heavy link webbing. It weighs 5.5oz.
Message 15 of 22 , Aug 7, 2004
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--- In hammockcamping@yahoogroups.com, "Thomas Peltier@G..."

BTW Recently purchased 30' of 1" polypro. "heavy link" webbing. It
weighs 5.5oz.
>
• ... If ... that ... with ... hammock ... tree ... Since this comes up from time to time, I decided to upload a MSExcel spreadsheet of mine that shows the
Message 16 of 22 , Aug 20, 2004
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--- In hammockcamping@yahoogroups.com, "Dave Womble" <dpwomble@y...>
wrote:
> --- In hammockcamping@yahoogroups.com, "Ray Garlington"
> <rgarling@y...> wrote:
> > --- In hammockcamping@yahoogroups.com, "Ralph Oborn"
> > <polecatpop@y...> wrote:
> > > To engineer the straps/ropes how big of a safety factor do you
> > plan
> > > on?
> >
> > As a practical example: Hennessey uses line with a breaking
> > strength from about 1600 to 1800 pounds depending on the model.
If
> > the webbing used by the Speerians really is 800 pound breaking
> > strength, and they are not reporting problems then you can see
that
> > Tom has built in a large safety factor.
> >
>
> Ray, you overlooked something in your comparison. The Hennessy,
with
> its intergal ridgeline, generally puts more tension on the hammock
> support ropes/straps because it typically is hung so that the
hammock
> support ropes/straps are more horizontally than a Speer hammock.
> Sometimes, this difference in tension is quite severe and it is not
> obvious that Hennessy is using a greater safety margin. This extra
> tension would also carry over to the other discussion concerning
tree
> damage. (While the internal ridgeline does help in getting a
> consistant 'hang', it is not without its drawbacks.)
>
> Youngblood

Since this comes up from time to time, I decided to upload a MSExcel
spreadsheet of mine that shows the results of the analysis I did of
the forces associated with using an integral ridgeline. I hope it
will clear up the point I was trying to make. Basically without an
integral (or tensioned) ridgeline the forces are just Force 1... I
try to hang my homemade versions of the Speer Hammock such that Angle
1 is at 30 degrees or so. With the Hennessy Hammocks, Angle 1 is
typically less (my guess is somewhere around 15 to 30 degrees?)...
depending on how taut you tie the hammock. This means that Force 1
might be higher when using hammocks with an intergral ridgeline and
that the tension on that ridgeline can sometimes exceed the tension
on the hammock ropes (ie, Force 3 exceeds Force 1 on my
spreadsheet). My thinking is that the ridgeline cord may be the
first thing to fail if a hammock with an intergral ridgeline is
overstressed due to hanging it too taut, and I say this because my
observation with the HH that I had was that the ridgeline cord was
not as thick (and therefore not as strong) as the hammock ropes while
my analysis (which hasn't been scrutinized) suggests that maybe it
should be. The spreadsheet is in the Files section under my folder.

Youngblood
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