Benchmark time for Tarp Set Up?

[Vick Hines]

1/8 inch is about right. I think you can find 3/16 and 3/32. Do a break test to satisfy yourself about strength. I think you will find that even the small round cord used in garments is plenty strong.

One product that will NOT be strong enough is beading elastic – a very small round cord. I don’t know the size, but it is almost thread-like. It will certainly break.

You need a cord that has enough resistance that you won’t stretch it fully during set up. Some stretch should remain in the line so it can absorb wind shock. The small cord has to be doubled to achieve the right amount of resistance – as in the loop shown in the photo in an earlier post.

[Peter McDonough]

I’m confused about this wind shock belief. If a load is being applied to a sting, then that is the load applied to that string. If an elastic is used as part of the string, then the load applied is still the same. I guess the only thing that might be a factor is impact force(I think thats what its called), or the duration of time over which the force is applied. With the bungee, the impact force would be applied over a greater period of time and that might save the tarp panel. However, for the amount of force required to tear the tarp panel, the bungee is already going to be stretched to its maximum, and most probably won’t do one any good in protecting the tarp. It might help with the tension after a night of rain(I just tension it really tight), or protect from clumsy campers, but I think the hassle outweights the benefits.

[paul johnson]

Peter, You are correct, impact loading and the resultant “surge” effect is reduced by the self-tensioners (note that is what JrB properly calls them, i.e. self-tensioners, not load absorbers or some such thing). You’re also correct, Newton’s Second Law of Motion (F=ma) applies here to extend the time that the load is applied over. Acceleration is a change in velocity and instead of going from zero to whatever, essentially, instantly, it accelerates over a very short period of time instead of instantly, and also a much greater relative distance is involved, obviously, in the acceleration, hence time to accelerate. So, the change in velocity from one moment in time to the next is reduced by the self-tensioners’ ability to elongate to a greater extent than the other components in the system (guylines, tieouts, tarp). The whole spring constant of the system changes and its response to dynamic loading due to the inclusion of the self-tensioners in the system. This, IMHO, is a minor/minimal benefit of the self-tensioners given the sizes of the loads the “fully extended” system could be “seeing”/experiencing. However, without performing either a carefully controlled experimental analysis with either load cells or strain gauges, or a mathematical analysis on an accurate model, no one can really say how much of a benefit this feature might be in this regard. Lastly, you’re right again, self-tensioning to reduce sag and the resultant flapping is the primary benefit of this system.

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