Stretchy cord for tent guy lines?

[chris smead]

Hey there. I have a Zpacks Hexamid solo plus.
While I love the weight and space, I'm finding its hard to get a tight pitch, and thought the wind flapping might get irritating.
I thought about using stretchy cord for the guy lines.
Any reason I shouldn't?
Anyone done this before?

[Ken Thompson]

So the plan is to pull that stretchy cord tight to attain a tight pitch? How is that going to work when all the stretch is used? How will you get a tight pitch if you don't pull them tight?

There must be a reason why guy lines are static.

[David Gardner]

You could make loops of shock cord a couple inches long and attach them to your tie-outs, then attach non-stretch cord to the loops. This gives enough stretch to get a nice tight pitch and also to absorb gusts of wind. The picture below shows such a loop; the end is just out of the bottom of the frame. I have measured the tension on guy lines for an A-frame tarp, and came up with 10-15 lbs. on the side tie-outs and 25-30 lbs. on the ridgeline. Much lower than I expected actually. In any event, at those tensions all of the stretch in the loops is not used up.

If you use stretchy cord for the entire length of your guy lines they may stretch too much in strong winds and let the whole tent flap around. Have only used the loops of shock cord on A-frame tarps though, so can't say for sure how the loops would work on a pyramid type tent.

[Jennifer Mitol]

Yeah, not sure the stretchy cord is going to help you any.

Play with the position of the pole and that will fix your pitching problems. After I got mine I'd taken it on several weekend trips and was a bit frustrated…so I pitched it in the back yard and spent a lot of time and effort trying to figure out why it was slack and what I could do about it. Turns out the pole needed to be at a bit of an angle and you have to make sure the guy lines pull straight out. Pitch the shelter, look down at the pole and see if the guys are in a direct line from there – you'll see what I mean when you do it.

Once I figured it out I was able to get a great pitch every time.

Good luck!!

[Roger Caffin]

And when the wind blows, the guys will stretch, and the tarp will flap to perdition.
Bungee cord may be great for appearances, but it's hopeless for performance (except for very short loops as David mentioned). Get the pitch right, as Jen suggested.
My 2c.

Cheers

[Glenn S]

While we're on the stretchy cord subject…
I've been contemplating using shock cord loops, like David mentioned, as a means to keep my Sil taught overnight. I'm unsure about what diameter would be a good mix of stretchiness and still maintain a proper degree of rigidity. I'm sure this would pertain to the OP's quest as well.

So what size shock cord do people buy for this?

[K C]

I wouldn't use shock cord for the main tie outs, but small loops about an inch in diameter attached to guy lines works well for mid-panel tie outs. Especially on cuben where the tie out is only taped on, to preserve integrity of the weak bond.

[Matthew Perry]

Jacks-R-Better self tensioning lines.

http://www.jacksrbetter.com/shop/self-tensioning-lines/

[David Gardner]

I use 1/8" shock cord:

http://www.amazon.com/T-W-Evans-Cordage-SC-108-050-50-Feet/dp/B00DKA4TSQ/ref=sr_1_3?ie=UTF8&qid=1395804462&sr=8-3&keywords=shock+cord

(How does a person embed a link in their post?)

[William Chilton]

David, for embedding links, look here

[William Chilton]

Christopher, are you using lineloks or similar? If not, I think you'd find them a better solution than stretchy cord.

[chris smead]

Yep I just received some from zpacks last week. They definitely help. But for some reason I've still got some flappy sections.
Perhaps I do need to just experiment in the backyard until I get it right.
Thanks for the input everyone!

[James Marco]

I just use heavy duty hair ties. Longer, and it is too stretchy, letting the tarp flap. I pull them out till they just stop streching. Then set the tarp. There is enough give in the braided material and elastic to more'r'less adjust to mosture takeup and rather heavy winds up to about 40mph. You can double these if you need more. They weigh less than an ounce for the entire tarp.

The elastic prevents wind hammer on the stakes/tarp loops. By reducing an "impact" to a "push," things stay in service much longer. They auto-adjust for wet sil-nylon tarps, though there are limits and they do not help with snow loading.

You can double the loops before tying a good knot, a square knot will slip.this will double the strength.

[M Blick]

To get a taut pitch you would have to fully tension the stretch cord from the start; thus eliminating any advantage IMHO. It appears your Hexamid comes with Spectra lines from the start; it would be a shame to replace such wonderful lines with heavy shock cord. I understand Cuban Fiber doesn't stretch, so you likely won't need to make adjustments once you have a proper pitch.

For quick adjustment and tensioning of my guy lines I use Nite Ize Figure 9s. I always change out OEM guy lines for lighter and stronger Dyneema throw lines such as Samson Zing-It, but Zpacks designed that tarp right from the start with Spectra cords.

[Colin Krusor]

"To get a taut pitch you would have to fully tension the stretch cord from the start; thus eliminating any advantage IMHO."

Why? That would only be true if you used very thin shock cord. If you use a small bit of adequately stout bungee, tied into your spectra guy lines, the shelter should be taut long before you exert enough force to stretch out the bungee. The simplest way is to tie in the bungee so that it bridges a loop of your guyline, such that the guyline loop becomes straight when the bungee is maximally stretched. I posted about a variant on that method about two years ago:

http://www.backpackinglight.com/cgi-bin/backpackinglight/forums/thread_display.html?forum_thread_id=60007

I use smaller lengths of bungee now (about 3" total, with 1" showing). The Jacks'R Better cord-in-tube design accomplishes the same thing. I use a bit of bungee in the guylines for the reasons James Marco already mentioned: it protects against potentially destructive snapping in gusty winds. Too much elastic and you get the out-of-control flapping that Roger warns against. Too little elastic (or none, as in standard guylines) and you get high forces on the materials of the shelter when it snaps in gusts. Even the most tautly pitched cuben shelter will snap in strong gusts because cuben shelters almost always have a few wrinkles that give some areas of the material a little slack. About 1/4" to 1/2" of stretch in the guylines, from a stout bit of bungee, spreads out snapping loads but does not allow "flapping to perdition".

[Roger Caffin]

Colin has a good point there for Cuban.

Cheers

[Adam Kilpatrick]

I like Colin's points above too.

[M Blick]

Good point Colin.

I think my folly comes from my lack of knowledge about cuben fiber. I get things TIGHT whether a tarp over my hammock or the fly over a tent. I have never worried about wind damaging my gear. When I read the OPs' question, I just thought, "shelter is flapping, make it tighter and even". I attribute my success in beating the elements to an even taut pitch which ensures that any strong gusts exert their force across all of the achor/guy points. I don't carry an anemometer but I've been in storms strong enough to include cherry-size hail.

The bury of the bungie is truly beautiful workmanship; did you do that or is it the JRB product?

[Colin Krusor]

Thanks. The JRB product is pictured above in Matthew Perry's post. I think the JRB rubber tubing method might have been invented by BPL member Denis Hazlewood, and first described by him in a post in 2009.

My buried bungee idea performs the same function, but requires thicker braided guyline to accomodate the bungee. The difference in weight between 100lb test guyline and 500-800lb test guyline (that will expand around a bungee) is less than 3 grams for a 3 foot length, but some people have misgivings about using the heavier line on principle. Also, it's more expensive and it can be difficult to find in short lengths.

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