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bungee to reduce wind stress
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Bob Gabbart
(bobg) - F
bungee to reduce wind stress on 01/22/2006 08:29:50 MST Print View

I've read that it is a good idea to attach a bungee to tent tieouts to reduce stress on the fabric during brief strong wind gusts. Does anyone have a recomendation of bungee to use that does not absort water?

Thanks,
Bob

Douglas Frick
(Otter) - MLife

Locale: Wyoming
Re: bungee to reduce wind stress on 01/22/2006 09:38:14 MST Print View

>Does anyone have a recomendation of bungee to use that does not absort water?


Try surgical rubber tubing (for ready-made tensioners, look in fishing supplies). Also check out Jacks R Better's Self Tensioning Lines. I just bought a pair and used them the last two nights to guy out my hammock fly in 10F temperatures. They worked fine.

Edited by Otter on 01/22/2006 09:42:52 MST.

Vick Hines
(vickrhines) - F

Locale: Central Texas
Re: bungee to reduce wind stress on 01/22/2006 10:51:36 MST Print View

You can make good tensioners from the small elastic cord used for waist drawstrings. If it absorbs water, it isn't much. The inside is tightly packed rubber. The cord I use is, I think, 3/32". You can make tensioners as simple or as complicated as you like. The only issue is keeping them tied. Most folks make a loop. You can close a loop of 12 inches of elastic with a water knot and ensure it won't come undone with a drop of Superglue. Or you can gut some parachute cord, slip 3/4" of elastic in the end and bar tack it with a sewing machine. Then you can use less elastic to form the loop. Insignificantly lighter and less stretch. Sometimes that's a good thing.

Edited by vickrhines on 01/22/2006 10:52:10 MST.

Douglas Frick
(Otter) - MLife

Locale: Wyoming
Re: Re: bungee to reduce wind stress on 01/22/2006 12:41:50 MST Print View

>small elastic cord


Good solution, Vick. The guys for my hammock are made of this and I've had them soaking wet before. All I did was stretch them taut and pluck them once or twice and they were pretty much dry, or at least didn't hold enough water to wet anything else. I still haven't arrived at a satisfactory knot arrangement; thanks for the tips.

Stephan Guyenet
(Guyenet) - F
Re: Re: bungee to reduce wind stress on 01/22/2006 13:52:04 MST Print View

I've wondered about using these to keep my silnylon tarp taut overnight when it gets wet. It always loses a lot of tension and it makes me nervous. I've thought about using line tensioners but I'm afraid they'll reduce the overall structural integrity of my tarp in the wind because they'll "give" and allow the fabric to sag and become a sail in strong gusts. Does anyone have experiance with this?

Douglas Frick
(Otter) - MLife

Locale: Wyoming
stretchy cord v. JRB Self Tensioning Lines on 01/22/2006 17:30:16 MST Print View

The 9 ft. Jacks R Better Self Tensioning Line weighs 0.5 oz., of which 0.3 oz is the stretchy band (I suspect surgical tubing would weigh about the same). The 9 ft. guy line on my fly also weighs 0.2 oz. I put a piece of stretchy cord under mild tension, and the weight of 9 ft. of tensioned stretchy cord was 0.5 oz. It appears the weight penalty is 0.3 oz. either way, unless you take Vick's suggestion to combine a short length of stretchy cord with regular or parachute cord; this could save 0.1-0.2 oz. (The rounding error on my scale is large enough to prevent a more accurate estimate.)



I've found that the stretchy cord works well for keeping tension in a wet and drooping silnylon fly, but I haven't tested the setup in high winds.

Edited by Otter on 01/22/2006 17:31:30 MST.

Mike Storesund
(mikes) - F
Re: Re: Re: bungee to reduce wind stress on 01/22/2006 17:32:23 MST Print View

>> "I still haven't arrived at a satisfactory knot arrangement" <<

Try using a sheet bend for closing both ends of the loop. It is designed for joining two pieces of different diameter or slicker ropes that will not hold a square knot. With the elasticity of these type cords, you can easily get different diameters as it stretches.


http://www.iland.net/~jbritton/sheetbend.htm

Edited by mikes on 01/22/2006 17:33:23 MST.

Peter McDonough
(crazypete) - F

Locale: Above the Divided Line
Another Way on 01/22/2006 17:46:18 MST Print View

Here's the setup I use to be able to tighten guylines from underneath the tarp. In my neck of the woods, the ground is so full of rocks titanium skewers are not an option, so I use some MSR GroundHog stakes, which have a loop of cord attached to the top. I run the tarp guyline through this loop and then to underneath the tarp, where I have the other side of the guyline run as well. I tie a truckers hitch between the two, and then at any point in the night I'm able to tighten up the guylines without getting out from underneath the tarp.

Vick Hines
(vickrhines) - F

Locale: Central Texas
Re: bungee knots on 01/22/2006 19:07:43 MST Print View

Knots:
Sheet bends won't hold. Try waterknots: two simple overhand knots one on one end, one on the other with each knot tied around the other line. Done right, the knots jamb against each other.

Vick Hines
(vickrhines) - F

Locale: Central Texas
Re: Re: Re: bungee to reduce wind stress on 01/22/2006 19:09:51 MST Print View

Structural integrity:
The tensioners won't hurt the tarp. They prevent 'shock loadings' from wind gusts from exceeding the strength of the tarp/pullouts/total system. The give in the tensioners doesn't contribute to flapping. And if you pull the tensioners out all the way, they will still take up that early morning sag but will make the tarp just as tight as solid lines would. I prefer to leave some give in the elastic to take up wind shock.

Edited by vickrhines on 01/22/2006 19:15:05 MST.

Vick Hines
(vickrhines) - F

Locale: Central Texas
Re: stretchy cord v. JRB Self Tensioning Lines on 01/22/2006 19:12:37 MST Print View

Weight of tensioners:
If you use 3/32" cord the weight is way less than the weight of rubber tubing. I haven't checked lately, but I think they weighed in at 0.15. That is for 6" of elastic on 8" of gutted parachute cord with two 3/4" overlaps subtracted from the total length.

Douglas Frick
(Otter) - MLife

Locale: Wyoming
Re: Re: Re: Re: bungee to reduce wind stress on 01/22/2006 20:28:31 MST Print View

> closing both ends of the loop

I don't have a loop. I tied two half hitches to secure one end to the tarp and cranked them down with pliers; they hold. That leaves the other end free. A taut-line hitch doesn't hold on itself. Mostly I've been tying a clove hitch on the stake, then untying it each morning by slipping it off the stake. This works fine with round Ti stakes, but doesn't work with MSR Groundhogs.