Companion forum thread to:

Storm Resistance of Ultralight Shelters: Part 1, Introduction

This data is something I've very much wanted to see in shelter reviews/SOTMs!

Above timberline in the Wind Rivers would be another good place to do such testing!

I've always wondered why no wind tunnel testing! If it's done, nobody seems to admit it. Of course in the real world, the wind, especially during thunderstorms, seems to come from several directions at once.

Edited by hikinggranny on 01/31/2012 16:02:11 MST.

"I've always wondered why no wind tunnel testing!"

A real wind tunnel is extremely expensive and impractical for something like a tent.

Years ago some tent manufacturers used to test their products this way. They placed a large slab of plywood over the top of the entire bed of a pickup truck and fastened it down. They erected the tent on the plywood and fastened it down. Then they drove the truck at each specific speed up to about sixty or seventy mph. They noted when the tent would begin self-destruction. I know that some tent users would be interested in the results of higher speeds than that, but I don't know if I would want to be around a pickup truck with that kind of load if it was faster.

--B.G.--

The German Outdoor Magazine includes windmachine tests in their testing of tents.

Here is the link to the article for the 2011 test of twelve two-person trekking tents

And here is the article for the 2009 test of 9 dome tents

And here is another article from 2009 about six storm tents
http://www.outdoor-magazin.com/news/produkte-neuheiten/video-zelte-vor-der-windmaschine-was-halten-sturmzelte-wirklich-aus-6-zelte-im-outdoor-test.358911.3.htm

Some of the videos are interesting to watch.

Manfred

Edited for missing third link that wouldn't work. Copied it now directly.

Edited by Orienteering on 01/31/2012 16:46:39 MST.

This is going to be awesome! I LOOVE these articles. And they're doing packs and trekking poles next? I can't wait!

One day, just one day, Roger's going to make those enticing tents of his available for the rest of us to stop drooling over and actually get a chance to try out for ourselves! Over and over again we're told what fantastic shelters these are and that they are the bee's knees, but how are we ever going to know unless we can try them out? I can make tarps and such, and with a lot of time (which I don't have lot of) and painstaking learning curve, could probably make such a shelter... but when will it be worthy of a winter storm or typhoon? My sewing and especially patterning skills aren't that high yet.

Roger, quit teasing us!

Well all this has me thinking about the strength of my MYOG tarps. Now that I now more about sewing and what goes into a good tarp I doubt they're going to hold as well as they could. I think I'll go ahead and keep the Shangri La-1 that I just ordered and use that for nasty weather.
One idea to increase the strenght of a tarp would be to add more tie outs. All other things being equal I wonder whats better, a couple more tie outs or a bit heavier matieral? Maybe I'll add more tie outs to my MYOG tarp and see how that works.

I'd like to see BPL do something similar to Outdoor Magazin vis a vis using a wind machine. I know it's not necessarily indicative of the real world but it presents a more "controlled" (fairer) comparison. Video of the tents at a range of angles to the wind source would be nice too. It would also make it a heck of a lot easier/quicker to do testing. That shouldn't replace field testing but it would be a useful adjunct.

I personally would like to see the scope of the testing broadened to include non lightweight/ultra-light shelters. Just because I'm on BPL doesn't mean everything I own/buy is ultra-light (eg. maybe I favour longevity or strength over the lightest possibly weight). Certainly some of the things I use are light but not all. Whether philosphically or cost motivated... it doesn't matter, people use a range and mix of equipment types. Including "heavy" shelters would also provide one metric of the compromises ultra-light brings compared to heavier alternatives -- something of value to both schools of thought (an objective measure that can then be used by readers to arrive at the "perfect" shelter based on their own set of priorities.

One more thing for the wishlist... Please include the role of pole diameter as poles are often cited as the weak link (there seem to be few reports of fabric failure in tents that are newish/not UV damaged, though that may be increasing given the trend towards ultralight).


Note: Catastrophic vs non-catastrophic definitions don't seem to currently accommodate a bent pole?

Edited by stu_m on 02/01/2012 02:09:22 MST.

> Roger, quit teasing us!
Miguel - find me a reliable manufacturer who is willing.

Cheers

> Catastrophic vs non-catastrophic definitions don't seem to currently accommodate a bent pole?
Maybe, maybe not.
A bent pole is not a catastrophic failure: that much is obvious.
I suggest that it might qualify as a non-catastrophic one. Certainly, something has failed.

Cheers

Agreed Roger. It was a matter of semantics -- the current defintion of non-catostrophic doesn't seem to allow a bent pole to be classified as such.

I'd also be interested in seeing your tents commercially produced.

Maybe an existing cottage manufacturer you trust could make small runs basically in response to "group buy" orders that arise from time to time of interested pple on this forum (and elsewhere)?

Very good. Looking forward to these hard facts, graphs and conclusions. I do have one wish though (or requirement), please use the SI-unit, m/s when talking about wind speed. If one thinks about it, km/h is highly irrelevant, when m/s is very easy to get a grip on.

I've always wondered if Rogers tent - very fine handwork indeed - does have any problems with the pole shape, or rather links? There should be a concentration of stress at the "sharp" angled links. Unless of course, the pole angles happen to be aligned with the applied forces.

Looks like I'll have to renew my subscription after all...

Thank you for the article. I hope this pace and quality isn't just a new years promise that'll fade away in February. ;)

> Non-catastrophic failure is characterized by the simple criteria that upon removal of the load, shelter structure and performance properties are fully restored

A bent pole is permanent damage, certainly falls into catastrophic.

Non-catastrophic is more like a compromise in functionality. I like the term and the comparison, it's very descripting of what we can expect from a shelter.

Fascinating subject, I love this one.

Yeah, I can see a problem with aerodynamics...and pickup trucks.

Anyway, Roger did some older writeups here: http://www.bushwalking.org.au/FAQ/DIY_RNCTents.htm

Pretty good stuff. He will no doubt be expensive on the order of Stephenson's...not my place to say more. The 2 and three hoop designs do look pretty good for silnylon. With cuben, the angles will create problems as Ryan mentioned.

Again, cuben is actually a plastic film, like a plastic drop cloth, but reinforced with high strengh fibers. The fibers don't give much and create a mesh (asymetrical) that needs attention to bonding and force flow modeling to design properly. Small tarps/tents that you see on the market right now, are not really well engineered to take advantage of the materials strength properties. Hikers tend to get locked into a design without a lot of seams, but (again, as Ryan says) the seams need to be oriented with the mesh in the cuben directing the strength to pole "pockets", stake down points and guyout attachments. Sewing AND bonding seams results in seams that are as strong or STRONGER than the material.

Example: A fair off hand modeling scheme would be to orient the cuben fibers diagonaly...say 4 panels on a square tarp. This would allow the seaming to pick up any stake loading/pole loading. Better than common designs out now but quite wastefull of time spent sewing and stitching. This by-guess and by-gosh engineering will cover the worst of the cuben's tendency to rip loose like in Ryan's picture above. But most cuben fabric is asymetric, having more strength on one direction than the other. When forming sails, they overlay fibers in the direction of the stresses and laminate the entire sail at once. Not something a home or cottage manufacturer could easily do.

For example, the Hyperlite Mountain Gear Traverse Shelter pictured in a recent article seems to have a badly oriented front panel. Shame on one of the favorite manufacturers. ;)

This series might have me re-think using shockcord loops for my LDPE shelters. I figured shockcord would absorb the force from gusts though it obviously causes panel deflection, but I'm confident my main tieout points could take 50 pounds of force. The LDPE material itself stretches some so it likely wouldn't be too good in snow aside from it's as slick as you can get. We haven't had enough snow here to test this year.

I always thought stout shockcord would be good for silnylon as well since its seams stretch with moisture. Then you don't need to re-tension during a storm.

Great start, Ryan! I'm already anxious for the hopefully soon-to-be installments!

"It is my hope that this ongoing research into the storm resistance of ultralight shelters contributes a meaningful body of data, observations, conclusions, and knowledge that will help us explore more hostile environmental conditions with less weight on our backs. In addition, I hope to spur both do-it-yourself enthusiasts and commercial manufacturers to pay close attention to their designs so as to improve their performance beyond casual summer environs. I believe that the market demand for “ultralight” shelters capable of withstanding harsh storm environments is increasing, and that the current product market for stormworthy ultralight shelters is sparse, underserved, and ripe for opportunity."

I couldn't agree more, and I've had this same thought every freaking day myself! I'm super-excited to see this evolve. Thanks for going for it on this one.

Miguel - find me a reliable manufacturer who is willing.

Roger, I've been reading your thoughts on all this since you first started your own website, with all the examples of your train of shelters over the years, plus your comments here on BPL.

Just teasing you back. I really appreciate your designs and what you've put into them and realize the problems you have in trying to make them commercially available. Just wish I could make one myself. I've always loved tunnel tents, especially your designs.

i can be wrong on this .. but, in the world of Root cause Analysis, a bent pole has indeed "failed" (as would be an alternator belt that has cracks), whereas a broken pole is a catastrophic failure.

i think too that Rolls Royce uses a very nice term " a failure in progress", for things like relays gone intermittent and times when it's talking to you, but you are not understanding what's about to take a dump.

Very NIce article. it reads to me that Ryan is returning to his roots here, and we are moving in the correct direction. it's all good.

question for Roger C. the tent guru :

if i pre-bend my poles, (as on the little walrus swift that Dondo so graciously gifted me with) .. in a situation where the mfg expects the rear pole to be installed with a ridiculous** amount of bending .. does this make the pole ultimately stronger (as i suspect) or weaker, considering it gets hit with equal loadings.

** - is WELL into it's capacity to elastically deform.

--
peter is going to take now another look at the 'ol Akto, and with the idea of taking a gore out of the fly to spread tension more evenly. Bo Hilleberg is really asking a lot for one panel to go so many different directions.