Oct 16, 2012 at 6:05 pm #1295135
@maiaLocale: Rocky Mountains
Companion forum thread to:Oct 16, 2012 at 6:29 pm #1921939
– -K.T.- –Participant
Excellent! I can't believe it's been nine years.
I'm tall so I settled on a 9×9Oct 16, 2012 at 6:35 pm #1921944
@jephotoLocale: New Zealand
Excellent. I look forward to reading it in more detail later. For years I have been saying we need more pegging points on tarps and shelters.
I don't think I am ready to replace my Trailstar with a rectangular cuben tarp yet, but you never know.Oct 16, 2012 at 6:44 pm #1921954
@empacitatorLocale: Western Australia
Thanks for a great article Ryan. Very well written.
I prefer a mid for the simplicity first, weight savings second, it's nice to know that it's easy to pitch and ultra reliable when needed
I also find them heaps of fun to combine them with different inners, bivies, ground sheets etc :)Oct 16, 2012 at 7:24 pm #1921973
@glacierramblerLocale: NW Montana
Fantastic. Really–articles like these are why I re-upped my BPL membership.Oct 16, 2012 at 10:31 pm #1922028
@nickbLocale: Los Padres National Forest
I totally agree. Seeing this article coming up this week was one of the reasons I re-upped my membership just the other day.
Lots of good info here. I read through it quickly but will definitely be through it again, much more slowly and carefully to glean all the great info out of it.
Thanks.Oct 17, 2012 at 6:18 am #1922077
@jamesdmarcoLocale: Finger Lakes
Thanks! Clear and to the point.
Good staking technique is important. A few items that you didn't mention in regards to stake strenghth.
1) Angular displacement
Angular displacement is when a tarp uses low angles of incidence to the direction of the stress. We all know that angling a stake is stronger, this is not what I am refering to. Rather, the vector the stress is exerted from the tarp to the stake. A low pitched tarp, or "storm pitch" (Summit Lake pic with scouts 2011 in article)will exert a stress about 15 degrees to the ground. A taller pitch (Markus' Blue tarp in the article) pulls at ~40 degree angle. Given equivalent ground pressure, the stakes closer to a shear (0 degrees) will hold better. As you mention, though, the deflection is best described non-linearly. It applies to all staking points.
This is why adding a 1 "arm length" (about 3' or 1 meter) guyline to stake outs helps. The 8×8 tarp with a 42" center pole in front (Summit Lake pic, 2012) Adding a 3' tie out to the front corners decreases the angle from about 40 degrees to about 30 degrees.
Also, using longer tieouts on a narrow tarp is equivalent to using a full width tarp, in holding power. Ignoring wind catching, adding "arm length" guylines to the front corners will increase holding power to the tarp pictured at Summit Lake, 2012. Of course, you will also pick up more wind, a trade off.
2) Wind force
Wind force is something else that you don't mention. A nearly ideal shape would be a hemispherical shape or approching it. A good example is the pyramid, or, a shaped tarp from a tunnel tent. (Example: Exped Sirius allows only the tarp to be used.)This allows wind to be both deflected AND "sucked" back onto the tarp. (The wind force would actually create a tear drop bubble, but I am talking "ideal", here.)
This allows wind deflection from all sides, but is more expensive, in terms of weight, than the more usual 3 sided shelters UL'ers are fond of. Wind pressure will cause a vacume inside the tarp causing it to pull up, AND, push down. Often stronger stakes are needed where the "pulling up" force is greatest, usually the open, higer side. You can allow the wind through the tarp (after deflecting rain) to alleviate the air pressure differences by NOT pitching tightly to the ground. As you mention, stronger stakes are needed for higher areas("ridge lines") and areas that trap air pressure in high winds.
In more constant high winds, a "Diamond" pitch works better than a "Shed" pitch. The longer pitch angle of a diamond, along the diagonal, will hold better. The angle also reduces stake out patterns around the two sides allowing a higher density of stakes on the fully sheltered, upwind side. The trade off is reduced roof effectiveness by removing about the first 1/3 as a wind shelter (though this often stays much dryer than outside, it has less three dimensional protection.) The more enclosed 2/3 will be far better against winds/rain and have far less pressure against each stake. Since the wind is allowed to enter the shelter, from the sides, you gradually reduce the air pressure pulling up on the stake holding the peak.
Ground clutter has a lot to do with wind velocity, as Roger mentionesd in his articles. Indeed, weather staions often have higher towers for measuring wind speeds.
3) Multiple stake use (2 stakes in the same loop): You mention this but do not describe it. When using two stakes, I angle both away from each other creating a "ground claw" aginst the tarp.
4) Stretch vs Impact (Wind Hammer) One of the great weaknesses of cuben tarps is the lack of stretch. Like a hammer hitting a nail, simply resting a 10 pound sledge on a nail is not as effective as pounding it with a 1 pound hammer, both for driving and pulling a nail. This is an extream example regarding tarps, but the same principle applies. A "snap", nearly instantaneous, will pull a stake with light wind speeds. A stretchy elastic will distribute the same pressure over time. Example: Given a stake that takes 30 ft/pounds of force to pull it. A single snap of that pressure distributed over about .01 sec will pull it. If I distribute the same pressure over .5 sec, it is never in danger of pulling loose. A looser pitch means more snapping, but the danger of pulling a stake can be (largly) removed when tight pitches cannot be done due to ground variations, and/or, obstructions.
Silnylon can streatch a lot. Nylon absorbs water and stretches. Temperature softens it and it stretches. Pressure does the same. So, there is a built in "shock absorber." Cuben tarps do not have the same properties. I often recommend heavy duty hair ties, or, "shock cord" on cuben tieouts to supply the stretch needed for good stake holding for the above reason.
A nice, tightly pitched tarp can often do the same by gradually increasing pressure on a stake as wind speeds increase. But, this can be fiddly to set up requiring good ground. The elusive "perfect pitch" escapes everyone, sometimes.
Anyway, I would suggest many shaped tarps are designed incorrectly with the wider, taller living space closer to the door. Dynamics dictate a more "igloo" like design with the door open towards the smaller, narrower end (with the living space behind it.) As with the trailstar, this supplies good storm protection for the occupent and better overall wind stability by supplying a more storm resistant "tear drop" shape. Perhaps it could be placed into the wind? Hmmm… anyway…
I really liked the article! Thanks again, Ryan.Oct 17, 2012 at 6:36 am #1922083
@ikeLocale: Central Michigan
The original version was very influential in cementing my style as a poncho tarper. This updated version should inspire up and coming ultralighters to experience their surroundings in this beautiful and simple way.Oct 17, 2012 at 7:01 am #1922094
@vdealLocale: West Virginia
I great article in the original style of BPL. These are the reason I keep re-upping my membership. Keep them coming.Oct 17, 2012 at 7:27 am #1922108
That was beautiful man, great comeback. Thank You RJOct 17, 2012 at 7:46 am #1922111
So according to Ryan, Silnylon is stronger than Cuben Fiber with the only limiting factors being weight and stretch in comparison. In fact, Cuben Fiber has a high failure rate in his tests.
You cuben afficionados okay with that?Oct 17, 2012 at 8:45 am #1922124
@davecLocale: Crown of the Continent
80" by 90" spin tarp at 8k. I've spent the summer thinking about a small mid for solo trips, but keep coming back to the ability of my tarp to adapt to conditions.Oct 17, 2012 at 9:35 am #1922136
Tarp camping in bad weather ? hmmmm
if only there was a tarp that was enclosed on all sides, with maybe a full zip door, and a nice waterproof floor-maybe bathtub shaped, oh … and free standing :-)Oct 17, 2012 at 10:04 am #1922146
@ikeLocale: Central Michigan
"You cuben afficionados okay with that?"
Absolutely. For field use, personal and anecdotal experiences have been excellent. Some interesting reading from the past:
The myth of tarp durability"Oct 17, 2012 at 10:30 am #1922158
Good article, I really learned a lot about tarp use. I've been considering the switch (from ultralight tent) and this article gives me more confidence about my biggest concern — weather conditions — and helps me know what kind of things to practice toward getting comfortable with the transition.
Related to your photos, I would like to offer a suggestion that your scouts — and any anyone else who ties lines to trees — consider the technique of "cribbing" those lines. That is to pick up small downed sticks and place them under the line as you go round the tree. Held in place by pressure, the sticks (or a cloth padding) will help to prevent bark abrasion and 'girdling' the tree as wind on the tarp causes movement in the line.
— BSA LNT MEOct 17, 2012 at 11:23 am #1922182
–Oct 17, 2012 at 11:41 am #1922189
Great article. I've been loving my mid, but there are definately advantages to a flat tarp and developing these skills is a worthwhile pursuit.
"If the simple assumption is made that each stake will absorb an equal amount of force, then the same 120 pounds is distributed among five stakes, imparting only 20 pounds of force per stake."
Should be 25.Oct 17, 2012 at 12:05 pm #1922198
Now I'm curious which manufacturers are considered to be capable of the "very high manufacturing quality and seam design" with cuben fiber.Oct 17, 2012 at 12:17 pm #1922209
Great article. I have been backpacking with a tarp for years and I love it for all the reasons you stated but especially the weight factor. Right now I am using the Equinox 10'x12' Globe Skimmer Ultralite tarp that weighs 18.8 oz. It has plenty of room for me,my son and our gear,dog and room to party if the weather turns on you. I could get a few ladies from the Swedish ski team in if necessary.
Art what you have added to the tarp makes it a tent. :)Oct 17, 2012 at 12:32 pm #1922217
OK, now where do I find an 8'x 8' cuban fiber tarp with all the attributes listed above? I have been considering switching to a MLD TrailStar or a tarp for some time.Oct 17, 2012 at 12:51 pm #1922223
Great job. Thanks, Ryan.Oct 17, 2012 at 1:29 pm #1922233
Can anyone comment on their experience with the MSR cyclone stakes? They look like a twisted red-rope licorice. A tad heavier, but look like they'd be even better than some of the stakes reviewed in the past. Not sure how easy they'd be to pound into packed soil, however. I like to carry one or 2 heftier stakes, like the Easton nails, in addition to my ti shepherd hooks. I also use a small snow-stake instead of carrying a potty trowel, dual use whenever possible.Oct 17, 2012 at 2:25 pm #1922258
@chinditsLocale: Cntrl ROMO
Excellent read and comments. I never knew there was so much contemplation over what the average 11B calls home in the field. It seems strange that with so many rocks in the area, one doesn't just reinforce your stake points with rocks unless there is a lot of snow. I often set up shelters with out stakes and never use them when I'm in the field with the green machine. Actually getting stakes in the ground where I recreate isn't always possible, but piles of rocks are always close at hand. Of course endless deep sand is problematic too, but I don't frequent those places recreationally.Oct 17, 2012 at 3:41 pm #1922286
@glacierramblerLocale: NW Montana
OK, now where do I find an 8'x 8' cuban fiber tarp with all the attributes listed above?
Without having heard Ryan's thoughts on it, he did mention in his gear list at the end of the Anaconda-Pintler photo essay that his 8×8' tarp is from ZPacks.
I'm definitely thinking about ordering one myself.Oct 17, 2012 at 4:08 pm #1922291
@dpexLocale: Pacific NW
Perhaps a silly question, but:
What is the best way of establishing a mid-tarp tie-out point, that is, a point that is not a grommet hole on the edge of the tarp?
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