Self-tensioning lines

Sounds pretty simple: a microprocessor for control, a load cell to sense the tension, a motor, gearbox and winch to do the work, some batteries to power the whole thing …

Hum….

That's funny Roger. But seriously have you ever had that problem? Dacron and spectra, are both advertised as being basically non stretch. Try pulling on a piece and see how much it moves.

I would think that the fabric, being much thinner and weaker, will stretch much more and the rubber bands won't help with that. But this is just my gut opinion and not actually based on any experience.

A foot of 1/8 inch bungee cord makes my HH tarp self tensioning for a night.

Hi Nia

Oh yes, I sure have had that problem. Have a look at this page:
http://www.bushwalking.org.au/FAQ/FAQ_Pegs.htm
For some experiments I have done on cheap nylon cord for instance. Very affected by the cold.

Nylon fabric is also known to expand in the cold. That's why some shelters are made of polyester: less expansion. You will often find the guys limp at 10 pm when they were tight at 5 pm.

Bungee cords on the guys? OK for mild weather, I'm sure. For a hammock – I question whether you could get something strong enough (and carry it). OK for the tarp cover perhaps.

The more modern synthetics – dacron, Dyneema, Spectra and even Vectran, have less stretch it is true, but they do have other problems.

Problems … :-)

Hi Roger,

Sure there are better and worse materials to use. Nylon is about the bottom of the list. But you also mention Dacron which is also basically 0 stretch and has been around since 1941. I guess that’s modern era. :)

As far as stretchy fabric, that’s a problem. And I have had to retention a silnylon tarp even when staked directly to the ground. I don’t really know how much a rubber band or bungee would help. It seems it would just add more tension and stretch the material farther. Plus it seems like it would bounce around quite a bit in the wind, maybe a lesser concern for hammock users as they are likely protected by trees.

Old canvas tents like vango force tens had thick rubber bands on the peg out points. Paradoxically this was to allow for the way the material got *tighter* when wet, and prevent ripping the hems in rain and wind.

Solid rubber bands are less stretchy than shock cord, but heavy. I guess another technique for the main ridge guys could be to run them over tree branches and tie rocks to them.

Gravity doesn't weigh anything, though it always seems to make my pack drag. :-)

Hi Nia and Rog

You are right of course, and that is why I haven't used nylon guy ropes for some time. They stretch far too much. I have used Spectra on my summer tent for some years now, and it works better, but the nylon fabric in silnylon still stretches in the cold. Ah well.

I found that thin Spectra can have problems. Stuff 0.5 mm thick has a breaking force of 150 lb, which should be fine, but you can't hold it, you can't put tautline hitches in it, and … and it frets on my titanium snow stakes and breaks. Epic story there, which may appear here at BPL 'soon'. I lost 7 out of 8 guys in one 14 hour night.

So I am looking now at thicker Spectra or perhaps softer Dacron (with similar strength of course). The stuff has yet to arrive, so this is a work in progress.

My objection to bungee cords really only applies to extreme weather conditions. (Unfortunately, we just had that in spades – in the snow here in Australia.) The stretch then is just too much. And yes, the stretch lets the fabric flutter, which can be bad all round.

I don't have a really good solution, except to get dressed around midnight and climb out into the gale and reset the guys… I suspect a few of us have done that too?

Cheers

The best solution I've found is to cut rubber hoops from motorcycle inner tubes. Butyl rubber is pretty strong and is weather and sun resistant. It's a low cost solution if you don't mind carrying a few ounces more to save those midnight excursions. I just tie larks heads in them through the pullout tapes.

Here is a link for an excellent DYI self-tensioning answer to tarp guy lines. I use this method with my silnylon hammock fly. It works perfectly and simple to make.

http://www.tothewoods.net/HomemadeGearTarpTensioner2.html

I do use self-tensioning lines, but was merely inquiring why I haven't seen them here on BPL.

Mine consist of feeding a 12" piece of shock cord through the tie-out loop (I don't use them on the ridgeline, just on the sides and corners), and fastening them via a clove hitch to the main guy line. You can get a much better idea of the process at http://www.hammockforums.net/forum/showthread.php?t=3731

There are a couple of methods listed there.

You can also get "commercial" STLs which are similar to the MYOG ones at tothewoods from JacksRBetter (likely better known for their quilts in the UL community than their hammock). You can see them at http://jacksrbetter.com/index_files/Self%20Tensioning%20Lines.htm

I do use nylon cord (1/8'), but it is because the weight:$ ratio is pretty bad in lines. That and I can't effectively use small diameter lines (I have retarded fingers or something). I'm sure that I'll eventually go away from nylon cord, but I'm happy with it at present. 6 12" sections of shock cord are ridiculously light for the advantage they can be to many.

I like to make tensioners from loops of the 1/8 or 5/32 inch elastic used for waist-drawcords.

Tensioners do several things. They take up the slack as a nylon fly absorbs moisture and begins to sag or as a non-stretch fly gets weighted with surface moisture. They absorb wind shock – a greater threat to a tarp than steady wind loading. That protects the fly in general and the pull-outs in particular and helps keep stakes in the ground. Tensioners extend the safety range of ultralight tarps and flies.

Tensioners can do their jobs only if used properly: They should be stretched so half their extension is used and about half remains. That way, they can take up slack as the fly sags and still have some give to absorb wind shock. The pull and configuration of tensioners will be different for tarps/flies of different weights, material and configuration. In general, I start with 12 inches of elastic cord in a loop so the pull is doubled. If that does not give a tight set-up when pulled half-way out, I go to a larger elastic or "third" the loop so three strands are pulling instead of 2. This seems necessary only on large tarps(12×14 super-catenary).