the levitating tarp

[ibgary]

I haven't noticed any wear on the tarp from being in contact with the ridge line. Actually there is little contact due to the tarp being pulled out on the ends. The TRL is as Nanok said slightly slack. It usually hangs down an inch or 2 under the tarp. Some times i hang clothes from it to protect them from weather. It's still close enough that in wind the tarp gets support.
I'm probably not explaining this well.
TRL clips to the tree strap carabiner and runs under the tarp to the other tree strap carabiner. The tarp is connected to it on one end with a prusik around the TRL and larks headed to the tarp. The prusik allows me to center the tarp over the hammock. The other end of the tarp has a dutch wasp also larks headed into the tarp.
When I set the TRL, it has a slight sag, it's not a deliberate sag I'm just not trying to make it super tight. Then I adjust /tighten the prusik to center the tarp.

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[KBr00ks]

Interesting. Thanks!

Did you two collaborate, or just separately arrive at similar solutions?

[Andy Pandy]

The idea of a flexy RL is interesting. I guess you could achieve the same effect with shock cord loops at the tarp RL tie out points. I'd be a bit concerned about RL tension allowing my tarp to flap too much in the wind though. Have you found that to be an issue with the stretchy RL cord? I thought people didn't like stretchy paracord RL for the same reason.

[nanok]

Interesting. Thanks!

Did you two collaborate, or just separately arrive at similar solutions?

hehe, we didn't collaborate, we both arrived at somewhat similar solutions independently (which is interesting in itself). it seems our approaches are a little bit different, but still has in common one fundamental idea: using the hammock attachement point (tree straps) to support the tarp. it's really nice as this means we have some alternates already tested (like using a dyneema or partially dyneema ridge line etc), and some more data "from the road" than just mine

[nanok]

The idea of a flexy RL is interesting. I guess you could achieve the same effect with shock cord loops at the tarp RL tie out points. I'd be a bit concerned about RL tension allowing my tarp to flap too much in the wind though. Have you found that to be an issue with the stretchy RL cord? I thought people didn't like stretchy paracord RL for the same reason.

yeah, i've been amused by that as well: the common consensus is that stretchy ridgelines are bad, but it seems to me it is because you cannot make them really straight (or tension them a lot, as the two things go together). when you tension a stretchy line which is supporting more than its own weight, the line will sag and reduce the tension this way, while a non stretchy line can be pulled to much more extreme (shallow) angles. but this is exactly what we don't want, according to my testing, putting the sag where we want it is actually much more effective than trying to remove it alltogether. i still don't like paracord as a ridgeline, as i find it quite heavy, but it will work nicely in a pinch.

the flapping in the wind does not happen because of stretch, but because of lost tension (when tieouts or ridgeline are not under tension anymore, they are slack, or partially so), this basically cannot happen with a resonable stretchy line which was stretched "enough", as it will absorb significant amount of movement before going slack. at least in my testing so far, it has never been a problem, but i consider it still "early days". (but oth my entire existence seems to be a test lab, so maybe that's how it goes :P)

what does happen because of stretch is what i would call "resonant vibration", basically the tarp will start to tremble in the wind like a guitar string. this cannot be avoided with any kind of line, as there's always some flexible stretch somewhere in the system, by changing line all one can do is slightly change the frequency (remeber the tarp fabric itself will have some stretch). one way to reduce the chance of that is to weigh the tieouts down to intoroduce a non-linear force component in the system (weight doesn't vary with how much you pull on the line, as gravity is not an elastic field at our scale). but the even simpler solution, which i think works in most situations, is to either readjust tension on some tieouts, or reposition some tieouts, to change the resonant frequency.

shock cord would be too stretchy and too little range of stretch. a long slightly elastic ridgeline has the advantage that it has a very wide range of length, which means you can do this trick with it: set it up high, and then bring it down low to where you want. the shock chord would run out of stretch quite quickly for that, after which it tends to snap (or load the static line it is doubling, if like me you set them up in parallel). what i was considering to try is a mixed ridgeline, where the part common with the tarp is dyneema, and the rest is stretchy (which basically turns it into some sort of dyneema reinforcement for the tarp ridgeline, one might say), but it might be overkill to be honest.

[nanok]

Thanks for the thorough explanation, nanok.

Another question (for ibgary as well): With the tarp ridgeline running under the tarp, do you find that the downwards tension from the guylines makes the ridgeline more apt to abrade the tarp on the underside, especially at the edges?

In a "traditional" setup the ridgeline is also running under the tarp (I do this too), but exits at a more "flat" angle and doesn't contact the tarp with much pressure.

that's a very good point you bring up, which i forgot to mention: i prefer this method with the ridgeline above the tarp, indeed when putting the ridgeline under, there will be some "hotspot" of tension in the area where the edge of the tarp meets the ridgeline, which might become problematic. if the rl needs to be under the tarp for some reason (which i personally don't like that much, as it doesn't allow the tarp to take the shape it needs to, it is true in my experience even for non-cat-cut-ridgeline tarps, but it's a different topic), then some thought needs to go into rerouting the ridgeline on exit, so it does not "turn up" right at the edge of the tarp, but a little bit more outwards. again, using separate line to bring down the ridgeline (instead of using the corner tieouts) in this case might be the most robust and simplest solution, or maybe could be used as backup for high winds etc, to be installed only once the tarp is in the desired position, in order to unload that part

[Andy Pandy]

What range of RL height adjustment can you achieve? At some point the guys and RL will be too slack and flapping everywhere. If you crank the tarp right down low, and then slacken the guys, how much height can you gain before you lose too much tension in your tarp and need to go and reset the RL?

[KBr00ks]

After studying your first photo, nanok, I realized your ridgeline is indeed above the tarp, and that looks like it would work. But ibgary, I can also picture your system and think it seems reasonable.

Would love to see more photos from both of you, if possible.

My next question was essentially the same as Andy Pandy's above: is there a lot of "fiddle factor"? A traditional tarp seems pretty easy to set up -- no need to go back and forth balancing the tension between ridgeline and guylines.

[ibgary]

I think what Nanok and I do is basically the same thing. We both use a continuous line. His is above the tarp mine is below. Attaching the tarp to the RL and being able to adjust the tarp on the RL is IMO easier than adjusting both tie out as is required if using the method of tying from the tarp to the anchor on each end with a different line.

I learned different setups from watching Shug and Derik Hansen. Then I settled on the system I like best. I like the RL under the tarp in part because it allows me to use it as a covered cloths line. A possible down side is getting some dripping off the line, solved by using string or a safety pin as a drip stop.

Check out some more videos from Derik and Shug. Most of what I know came from them. Is sector 8 secure?

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[ibgary]

Pics
Why I no longer use shock cords on my tie outs.

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