Benchmark time for Tarp Set Up?

Paul and Jack,

I ordered two STLs recently (from JRB- what a coincidence!) and I suspect they will be sufficient to keep an A-frame pitch taut when attached to the ridgeline tie-outs. My reasoning is, if you pitch your tarp with the poles at an angle as suggested above, when the tarp sags, the tensioners will automatically pull the poles closer to vertical and keep the tarp taut.

Frank,
Thanks for the Ray-Way knot link.

I’m going to be experimenting with Dr. J’s method of using one piece of line on each side of the tarp. It goes from stake to tarp loop to stake etc. down the length of that side of the tarp. This creates more & smaller panels allowing it to take a higher wind load. Maybe I’ll add Vick’s elastic loops too.

re. staking in rocky alpine terrain: This is where I mostly camp. Sometimes I only bring a few stakes because I know I’ll be mostly girth hitching boulders and the like by passing a bight of guy line through the small loop at it’s end. I find this to be much faster, easier and stronger than using stakes in these conditions.

Al

Al, I’ve seen pics of the “method of using one piece of line on each side of the tarp”. This looks like a very neat arrangement for adjusting tarp tension. I’ve yet to try it, but hope that it works out.

The question I have is how does “This creates more & smaller panels allowing it to take a higher wind load”. Wouldn’t just as many separate guylines (one guyline at each of the tarps tie-down points) produce the same number of panels? What am I missing?

Paul,

I think the discussion has muddled the causes and effects.

You are correct that it’s the number of number of attachement points that determines the number of panels and that the one guyline idea is involved with convenience for tensioning … two separate aspects of tarp pitching each contributing to a different part of the result.

One thing I’m concerned about with the single guyline method is that a single stake failure leads to a large part of the tarp failing.

Jim, Many thanks for the swift reply. That’s what I thought.

Good point on a single point failure. I suppose that re-adjustment is real easy to tighten up the rest of the continuous guyine on that side of the tarp. That’s the benefit of this approach, correct? I would guess that this ease of adjustment would still be available and work. Also, I’m guessing that after readjustment of tension there would be no more flapping than if one stake holding a single separate guyline pulled out, right? What’s the down-side between the two? If the tarp didn’t fall down when the stake pulled out due to complete loss of tension on that side, then after easy readjustment possibly without leaving one’s sleeping bag, only that one panel would not be tied down – no different after readjustment than if separate guylines were used and one stake had pulled out. Now, the question is, will the trekking poles supporting the tarp ridgeline fall over and the tarp collapse when one stake pulls out? My guess is that it might since it was windy enough for one stake to be yanked free of the ground and that now even tension on the corner guylines on that one side is gone. Anyone have any experience or a more educated guess on this point?

Hate to be a spoilsport but…
If you use a single line through all the pullouts and one stake out of the 4 or 5 fails, then ALL the pullouts on that side will loosen…radically. In the wind, potentially, that is enough to let a gust catch the now non-aerodynamic tarp and jerk everything else loose. If you use one line per stake, the failure of one stake is frustrating but not catastrophic.

Vick, you’re no spoilsport. Read the prev. posts again – that was Jim and my point exactly. From my perspective, it’s good that a more experienced person like yourself and Jim joined in here – it confirms my suspicisions and will save me from having to experience this myself in order to learn from it.

PJ,
Here’s what Dr.J says in “Advanced Tarp Camping” under “techniques”.

“This picture shows the kind of innovation needed to optimize tarp performance in high winds. Here, a single long guyline is threaded through each of the tarp’s side guyline tie-outs, with a series of six tent stakes securing apex points along the guyline. By adding only a single additional tent stake along each side, you are able to distribute panel tension across more panels, resulting in a tauter, more wind-resistant pitch”

My interpretation of this statement is that tensioning each guypoint from 2 directions rather than just 1 line perpendicular to the tarp edge adds considerable structure.

Interpret that as you may and look at the photos or ask the good Dr. for an in-depth explaination.

The stake failure issue is a significant one. I can envision solutions but don’t know if they’re worth the downsides. A much more catastrophic concern is if the line fails. Then that entire side’s connection to the earth is gone.

To avoid these problems and still maintain 2 directions of tension to each guypoint, tie the ends of a guyline to adjacent tarp guypoints with enough slack to secure the center of the line away from the tent. This allows the stake to be moved roughly parallel to the tarp edge for optimum stake location. If stake or line fails, each guypoint is still attached to a stake. The end guypoints will also have a guyline connecting them to a single stake. This maintains Dr.J’s formula: # of stakes on a side = guypoints+1.

Of course, you could double guy and stake each guypoint from 2 directions, but then stake# escalates to Guypoints x 2.
Al

If you had four pegs on side of your bivvy and four guy lines, then when the wind blew each peg would take 25% of the strain.

I imagine that by having the extra peg and a single guy line, (All other things being equal) that each peg would only take 20% of the strain created by the wind.

In other words, I guess a stake failure is less likely to occur with the single line setup but when it does, as discussed above, the consequences are likely to be bigger!

Al, Thanks for the clarification from DrJ’s writing. I’m not sure that I agree totally with him entirely on the all (some, yes) of the points he makes of the single guyline benefit. His other theory in the article seems very sound, showing much more understanding of the subject than I possess. However, in all but one case, when I’ve “nitpicked” with him via email over some minor technical/engineering issue, I’ve been wrong and DrJ’s been right. Probably if we analyzed his approach mathematcially (e.g. a vector analysis of the loading of the tieouts and tarp using both guylilne methods), I’d be wrong again, but just visualizing what is actually happening if a rectangular flat tarp has ‘V’-shaped webbing tieouts, I’m not sure that there would be too much difference in panel loading (not guyline and stake loading, which is improved) between the single guyline per tieout and the single continuous guyline. But, that’s just an off the top of my head, close my eyes and visualize the panel loading analysis. I’m probably missing some key point, that DrJ understands. Of course, I’m visualizing a static loading, perhaps with dynamic movement/shifting under heavy winds, the single guyline starts to make a real difference in pulling on the tarp from different angles as the tarp attempts to shift in response to the wind – that might be the secret. Maybe, the tarp in question does not have sufficiently wide ‘V’-shaped tieouts to simulate the pull that the single continuous guyline attempts to achieve? I believe that the primary determining factor in panel loading on the tarp will be how many tieouts are available for use and not primarily the guyline configuration used. Again, stake and guyline loading can be quite a bit different from the panel loading, hence one benefit of the single continuous guyline.

That single continuous guyline per side approach is nice in one sense that if you wanted to use the JrB’s self-tensioners, you’d only really need one per side (or two if wanted more “give” in very windy conditions). Two self-tensioners per side and the extra stake required for the continuous guyline approach might make a stake pulling free far less likely and make the whole system far more resistant to experiencing its inherent single point of failure (per side).

I’ll have to go take a look again (it’s been prob. 18mos) at the article you mentioned. Thanks for taking the time to post back and give me something more to think about – I do appreciate it.

Once all the frost is out of the soil here I’ll be trying the single line approach …. that’s 5-8 weeks away.

My interpretation of this statement is that tensioning each guypoint from 2 directions rather than just 1 line perpendicular to the tarp edge adds considerable structure.

It’d be great if Dr. J would weight in on this but I don’t think the single line pitch effectively delivers tie-outs that are tensioned from two independent directions … due to the tie out point being free to slide from side to side.

Al’s idea of guy lines tied to adjacant tieouts does deliver that result but then you lose the tension adjusting convenience of the one line approach.

One (maybe) new point I can contribute here is that stakes can be made much more reliable if you can find some nice sized rocks to plant on top of them.

Jims contributon about weighting your pegs down with weighty rocks reminds me of an unfortunte accident I once had. I was camping here in the UK and needed a few rocks for exactly what Jim had suggested. I looked into the nearby undergrowth, picked up a reasonable sized rock, only to find moments later this searing hot pain in my finger tips!!!. When I say hot, I mean HOT! I had chosen to pitch at a location that must have been vacated a short while before. The rocks were hot and I subsequently worked out that they had been used to make a fire surround and then after use, tossed back into the surrounding undergrowth.

So I ended up with a few blisters on my finger tips.

At least I now know that what my old scout master said about cooking on rocks is a real possibility.

So, yeah good point Jim, but a health and safety warning for everyone out there, watch out for hot rocks!!!!! Yep there’s danger on the trail at every turn. :-)

Carping again.
1)The idea that a single line with multiple stakes “transfers load to other panels” doesn’t work. You have the same number of pullouts on the tarp – that does not change – and the vector of forces on each pullout is identical to the force of an individual line on a single stake. — Think about it like this: If you had two stakes with a single loose line running through a single pullout, the direction of force *on the tarp* and *at the pullout* would be the same as the force of a single line and stake set between the V of the double stake/line arrangement – as long as the line can run freely through the pullout. You cannot even ‘transfer load to additional panels’ by *tying* the lines to the pullouts so they cannot slip freely. Even if you did that, the force vectors still split the difference between the lines. For example, force on line A at a 45 degree angle would impinge on the pullout at that force and angle, and force B at a 65 degree angle would impinge at that force and angle. The vector would split the difference at 10 degrees from perpendicular to the tarp. You would do as well and “distribute the force” just as well with a single line at 10 degrees.

2) The only ways to distribute load among the panels of a tarp is either to add pullouts (including in the centers of the panels as well as the sides) or to use a catenary cut with careful attention to the orientation of the bias of the fabric. Old Man Moss of Moss Tents was an artist at that.

3) If you want to reinforce a setup with additional stakes for a heavy blow, then by all means, tie the additional lines to the pullouts and stake them separately. If the lines run freely, the failure of one line will be the same as the failure of both lines. But if they are separate line/stake units, the failure of one will not necessarily result in the failure of both – although the remaining stake/line unit will be forced to bear the full load and might fail anyway because of that.

Vick = Bingo!

I think that sometimes when writing for a varied audience that simplified statements are made, as in the case of DrJ’s article.

When viewed from a very technical standpoint, an error is noticed. If, however, the article was intended for a group engineers or specialists in a particular field, more care and explanation would be given, as well as using more technically accurate precise wording.

Accomodations must sometimes be made when writing to an audience with varied backgrounds. I think that is what we might have here in this recent discussion regarding one point of DrJ’s article. We need to keep in mind the original audience and the original intent of the article, viz. teach advanced tarp camping techniques, and not finite element analysis or some other in depth very technical engineering design issue.

I don’t know about others, but at times IF I attempt to keep a post, on some subjects, short, I may make a statement which is NOT technically accurate precisely as stated in all cases. The choice is, “Do I make a simple statement, that in a rare case may be incorrect?”, or “Do I add two lengthy paragraphs of technical explanation that no one is interested in reading, just so a single statement will be technically accurate in all cases?”.

Vick,
Although I am often enlightened by your posts, Im afraid I don’t posess the education or mental horsepower to visualize the situation that you describe in your last post.

If you guys decide what you think the best tarp guyline set-up is, I would like to know about it. I do like the idea of tying shock cord loops on each tie out to absorb gusts and help with slack from wet tarps.
Al

Al, I believe Vick is right, hence my “Bingo” comment. Vick (if he read one of my earlier posts???) understood what I meant by vector analysis and number of tie-outs determining the number of panels. I’d really like to see a finite element analysis of a tarp under loading – that would be very interesting.

Keep in mind, that as I stated earlier, I believe that the problem is even more complex and that both Vick’s and my comments are mainly related to a static loading of the tarp. Dynamically loaded, the tarp will want to shift, bot the tarp and guylines are essentially, to some small degree, springs, and therefore subject to Hook’s Law (F=kx). Some lines of force on the tarp’s conceptual “panels” will go slack (or to zero), others will increase in tension. This dynamic loading will give DrJ’s single continuous guyline approach an advantage since the lines of force can change somewhat as the tarp attempts to shift due to wind loading. Also, in DrJ’s approach, since the three middle stakes are connected by, conceptually, two guylines, they don’t have half the force applied to them, they have the same force (but each conceptual guyline on a stake bears half the load) – the two end stakes being an exception.

I still think as I stated in a prev. post that the number of panels doesn’t really change, either statically or dynamically, since any shift results in the same number of panels but in different directions, so “straight” conceptual panels will become “diagonal” conceptual panels. I’m open to instruction here as maybe I’m forgetting something or not visualizing this properly.

Depends upon what you mean by “best”. Easiest to adjust – well,…you know the answer to that one already.

Strongest in wind – “the more’s the merrier.” You could end up adding so many stakes and guys (or larger, longer, better shaped stakes, and stronger guylines – either single or multi-guyline arrangment) that either the tarp fabric, or sewn seams, or the tie-down stitching is the weakest link – would depend on the tarp material and construction – not that such an arrangement is necessarily practical.

I would imagine that the conditions that exist on any given night might be better suited to one approach or the other.

OOOF! Are we getting esoteric or what? Maybe we need to model this. Naw…

Al,
Yep, we’re dancing a bit much on the heads of pins here. My best advice is to set up in the back yard and try things out. But don’t neglect to simulate stressful conditions.

Jacks’R’Better has elastic guys already made up. Or you can make your own as simply or as whoopeedo as you like. There are lots of different ways floating in these forums. Loops tied with water knots, loops where shock cord is stitched to lengths of gutted parachute cord, in-line lengths of shock cord – tied with water knots or slipped into gutted paracord and stitched, medical tubing in loops or lengths, etc.

Also “Naw…”

>>”…dancing on heads of pins…”
agreed, but feels more like the points to me!! Ouch!!!

Regarding the self tensioning lines, as made by Jacksrbetter, how are those properly used in conjunction with a treking pole? I like the concept of having the ridge guyed out with these tenioners, but it seems the rubber is right where you would loop the line before sending it to the stake. Would it be functional to use a short piece to tie the tarp to the pole, and then loop the tensioner piece to the pole as well?

Depends entirely on how your pole is made and how you generally attach your tarp to it. Some poles have a hole or strap you can put the line through. Some folks tie on with a clove hitch. The shock cord might have to be placed beyond that. One way: envision a continuous line with a length of shock cord tied somewhere in the middle so a loop forms in the line that is pulled out straight when the shock cord is fully extended. This is most easily done with water knots. 8 inches of 3/8″ shock cord is a good weight for ridge lines. But there is less benefit from putting shock cord on the ridge line than putting it on the side pullouts.

Back to the a-frame tarp set up. I will use rather standard leki 3 piece treking poles. From what you state, it seems I probably should not worry too much about self tensioning the ridge. (I want to try and keep the setup as effecient as possible). When you say place them on the side pullouts, are you referring to the four corners? So optimally I would attach shock chord to the triptease line? Are there any instructions on this site that might show how best to do that?

Thanks!

Yes, the 4 corners and intermediate points on the sides (1 or 2, depending on make or tarp. Let me see if I can post a pic or two in addition to this:

bungee loop with gutted parachute cord girth hitched to a tyvek poncho/tarp

Vick,
Thanks for the picture. I has seen many different diameter sizes of elastic line at local fabric stores. From other pictures I have seen, it looks like most are using 1/8″ diameter cord. That just doesn’t look strong enough to me, but then the 1/4″ diameter looks too thick.
Any input or ideas?