Storm-worthy single skin A-frame tent: sewn-in or suspended groundsheet?

[Roger Caffin]

Roger’s tents may have larger vents, but Warmlite has a truly lightweight system.
The Warmlite 2R weighs 1.41 kg. This is less than my 2-man winter tent (2.20 kg complete, with big vestibule) , but more than my 2-man summer tent (1.34 kg complete, good vestibule).
However, I think the weight comparison misses out the sad fact that the Warmlite has very little room at the low foot end except for your feet, while the big end has room only for your head. It has no room for packs, shoes, cooking or any sort of ‘living’. It has no vestibule space.

Not a reasonable comparison?

Cheers

[baja bob]

from the photos I have seen the 3R might be a better comparison to your tunnel tent. With two poles I think mine is 1.93kg. With 3 poles it’s 2.1 kg.

 

main difference is the 3R has no actual vestibule.  It’s 381 cm long and 152 cm wide.

[Sam Farrington]

When Warmlite was less than a half hour away, I used to visit them often to buy fabric and parts and jaw about tents and packs.  They steadfastly maintained that the front of the tent was a vestibule with a floor.  In fairness, I think they had to make the front of the tent very gradually sloped in order to create the tension needed to keep the tent taut with only two hoops.  (I’m making this short (no applause please) because the BPL gods just timed me out on making corrections to my last post.  If we had more typing space as before, it would not be so difficult to complete corrections.)

[Roger Caffin]

They steadfastly maintained that the front of the tent was a vestibule with a floor.
Possible, possible.
So where does one put one’s snow-covered boots, sharp spikey crampons, and very hot stove? On the groundsheet? Really?

In my BPL review of the modern Warmlite 2R I found that the construction quality was simply awful. Seams were a single line of stitching, with no reinforcing. And the design of the double-layer front door was (for me) incomprehensible.
That said, I note that the founder died some time ago.

Cheers

[Steve S]

Roger, I never suggested that my Warmlites are good winter tents. Jack Stephenson said they could handle high winds without breaking, but never said they could be pitched or taken down during those winds. He also neglected to say what the interior volume would be during a good storm. He mentioned optional interior guys to stabilize the poles and an optional middle pole for the three person model in his advertising. Those guys would dramatically reduce the interior space in the tent, and could only be used after pitching and would have to be disconnected before dropping the tent, so I did not order them. My two person tent was not designed to be highly tensioned in the way yours are; perhaps his expedition models are.

When I was in a good blow with one for the first time, it was in late spring. I was camped on snow on a ridge of complex geometry, but not at the edge, and could not have predicted the direction of the highest winds at the location where the tent was pitched. The winds at twilight were calm, the sky not threatening. During the night winds started, soon reaching their highest speeds for the evening. Where I was located the winds curled over the nearby ridge and formed eddies, resulting in fast gusts at times from varied directions. But as the winds began they were mostly rapid and from one side, causing the tent pole beside my head or shoulder to release tension by taking an s-shape, with the tent fabric compressing my sleeping bag and reducing the loft, while leaving a relatively small living volume in the tent. The poles, which in Warmlites are precurved, had twisted at the ferrules under the wind loads to form that s-shape. As Jack Stephenson claimed, the tent was undamaged by the wind. When the wind slowed somewhat after an hour or so, the poles returned to circularity, as did my sleeping bag’s loft.

At the apex of the storm I checked the three stakes normally used, and they held all night. I don’t remember adding stakes at the pole ends, but perhaps I did. It was a dry night, so my tent’s fabric did not relax. Perhaps that is why the tent survived until morning.

In the morning, my wind meter showed gusting to, iirc, 56 miles per hour. When I attempted to drop the tent between gusts — necessary before poles could be removed from a Warmlite — a gust hit at the wrong moment, side loaded a rear pole, and a ferrule snapped.

No big deal on a one night trip. Jack Stephenson neither responded to my comment in a letter nor changed his advertising copy. He did send me some ferrules.

The design does hold up to a blow while pitched. The geometry, seam design, reinforcement and sewing is up to the task. However, trekking in serious winter requires tents that are tougher while being pitched during a storm.

 

[Roger Caffin]

Hi Steve

Some very interesting comments, thank you for them.

The 2R has a single stake at the rear end, and the entire tent hangs off this stake. There are no other guying facilities. My biased opinion is that the single stake is a single point of failure, and (imho) very dangerous because of that.

My winter tunnel has 3 ground-level stakes at ground level and two extra guys from near the upwind pole to more stakes. Yes, it is designed to be highly tensioned – and that design works very well.

Where I was located the winds curled over the nearby ridge and formed eddies, resulting in fast gusts at times from varied directions.
Been there, had that, and it was bad.

causing the tent pole beside my head or shoulder to release tension by taking an s-shape,
Aaarrgghh! Utterly horrible! Lack of guys.

I have almost routinely dropped my tents in high winds (100 kph) without problems. But it has to be done the right way. I unhitch the lee end at ground level and ‘push’ the tent upwind. With the side guys at the windward end still in place, the poles stay curved and protected. That gets the tent flat on the ground, after which it is easy.

Cheers

[Sam Farrington]

Steve S’s post sounds very much like one posted on BPL years ago by a Canadian named Oliviere, I think.  I posted a link to his post containing a video on BPL, and think that Roger may have seen and commented on it.  As Steve relates, the poles twisted in place, totally distorting the rear of the tent.  I believe they were in open, snow covered country in Iceland, with pretty awesome winds, and they held up an anemometer I think.

Roger, after Jack passed away, his family continued the business, and are still doing business in Colorado.  I do remember your review, and do hope the quality has improved.  I never bought one of Jack’s tents, so no comment about quality in prior years.  However I do think his designs as a retired aeronautical engineer were very original and helpful.  (but not his politics)

A couple years ago, the family was kind enough to dig out and sell me some YKK coil zips and pulls that are listed as #3, but are sturdier than the no. 3’s sold today, and I appreciated their doing so.

Not having seen the Warmlite tents face to face, cannot be sure, but believe the catalogs say that the rear end cover does provide a small area for storage.   Among my purchases were a number of the Warmlite poles that are prebent, but not very sturdy, and could easily lose shape; and that may explain the ‘S” shape issues.  But they are an odd diameter, and fit nicely over Easton 340 tube for MYOG projects.

[Steve S]

Sam, the pole sections did flex some, but mainly the pole stress relieved by twisting at the ferrules. I was both happy and surprised that the 7000 series aluminum flexed rather than buckling and splitting, since that allowed it to recover when the wind slowed.

The pole that bent was the thicker-walled and wider diameter front. It was loaded by a larger surface area of fabric, stands taller, and has much more of the fabric close to perpendicular to the wind.

BTW, the rear on the two person is difficult to access, and has to be kept clear for ventilation. It cannot be called a vestibule. The three person, with two high ends, is a different matter with respect to rear space.

 

[Sam Farrington]

Steve S:  Yes, you are right on all counts.  Thanks for clearing things up.

[Juup Stelma]

Hi Geoff,

Coming back to your original post – the wish to make a solo A-frame

Your description makes me think of TrekkerTent. I am sure you know of this small company already, but just in case:

https://www.trekkertent.com/home/home/3-stealth.html

The cat curves on these tents, besides being good looking, probably help with stability.

The “open but close-able” ends might simply be a matter of two triangular panels at each end which overlap when closed – so to avoid the need for a zipper – and then – yes –  some clever guy points.

A sewn-in floor … could there be a two inch strip of some sort of wicking fabric where the walls meet the bathtub floor? That might intercept running drops of condensation and thus reduce any pooling?

Juup

[Daryl and Daryl]

I bought a 2 person Stepnenson Warmlite tent about 1971.  Used it on one snowy cold eastern Washington night and returned it.

I set it up and got in.  I was cold and wet.  Condensation immediately started forming as I changed into dry clothes.  Within 30 minutes that condensation turned into frost.  The rest of the night was like sleeping inside a freezer that needed to be defrosted.  When I brushed the walls of the tent it would “snow” on me.

Jack Stevenson allowed me to return the tent but wrote me a full page letter saying I had done everything wrong from a venting standpoint.  He said I should have left the vents closed.  I wasn’t willing to repeat the experiment.

 

 

[Geoff Caplan]

Thanks for all the advice folks – I’ve learned a lot. This is what makes BPL so great!

On more sober reflection I think I’ll ditch the idea of a single skin tent with sewn in groundsheet and revert to a modular shaped-tarp/insert solution.

From the advice here and elsewhere I’ve realised that sewing the groundsheet directly to the walls Warmlite style really could result in issues when condensation conditions are bad.

Plus I need a shelter that will work in a wide range of conditions, from the heat of the valley to serious wind-storms on the tops. This ideally requires an outer that can be pitched high and airy for venting, medium-low for liveability in moderate wind and rain, and hugging the ground bivy-like in serious weather where safety trumps liveability.

These different pitching options are much more practical to achieve without having to incorporate a sewn-in inner!

The simplicity of an integrated tent is tempting, but thinking it through I realise I’d have to sacrifice too much flexibility. Plus there’s nothing to stop me rigging the inserts so that they can be kept attached to the outer in dry weather for more painless pitching.

[Sam Farrington]

Geoff,

Thank you for your thread.  It raised a number of issues that are hard to tackle.  The original Jansport domes, the later Moss ones, and their progeny, addressed some of your issues by focusing first on an inner tent and making it as stable and self sufficient as possible.  Only then was a fly added for greater protection and stability for the inner.  This approach, particularly when used on self-standing tents, cornered the market for many decades, but did not last; perhaps because the result was tents that were too heavy for many who went instead for single walls and tarps.

But now we have more choices for materials, including strong carbon poles, and fabrics that are superior in a number of ways to nylon.  And various other components have become lighter, like the tiny McGizmo titanium snaphooks which unfortunately are no longer sold, just to cite a few examples.

We know that bathtub floors have routinely been attached to inner tents for ages, with no problems, so long as sufficient steps are taken to provide ventilation and prevent condensation. Only when that can be accomplished can a smaller second wall, in the form of a fly, be added that is attached to the framework supporting the inner tent, but not to the inner tent itself.  For this reason, I had trouble getting at the issues you raised about sewing a floor to a tent canopy because I was thinking in terms of sewing it to an inner tent, and not an outer fly that provides a second wall, but only over the occupied area, not the vestibules.

So what I’m shooting for is an inner tent that is almost self sufficient, including single wall vestibules, and needs only a small overlapping fly attached.  In mild weather, only the inner tent will be needed, with the small fly attached just in severe weather, either present or impending.

Needless to say, an inordinate amount of time has been spent building models and locating  light materials;  but am looking at a weight between 24 and 30 ounces.  It could go lighter, but I’m looking at woven materials with some elasticity, especially on the bias, as well as a mini-ripstop grid for added strength. The feeling is that woven elastic materials will withstand severe weather much better and last longer, compared to, say, DCF or other laminates.

Your posts, as well as those from others, eventually provided a better grasp of what you were getting at.  It’s just that I was not thinking in the same terms, and regret not being more helpful.

[Justin W]

I don’t have much to add to this interesting and excellent geek out on shelters, but there were a couple things perhaps worth addressing:

Someone mentioned condensation and how it is not possible to mostly eliminate it. Was wondering, if one had an IR reflector (a mylar space blanket or similar) placed between you and your tent fabric, and with also at least a slight air gap between the tent fabric and the IR reflector, wouldn’t that go a long way to minimizing condensation on the inside of the tent fabric (along with proper venting of course)?

Someone also mentioned about tent/shelter fabrics and possible improvements.  I have long thought that woven polypropylene with a thin polypropylene film heat+pressure bonded to it, remains an untapped potential for tent and tarp construction.  Consider this.

1. Polypropylene has a density of .91 g/cm3 compared to nylon 6’s 1.14 i.e. 20% less dense than nylon and polyester’s 1.38 i.e. 34% less dense than polyester.

2. It has more stretch than polyester, but less than nylon. (perfect sweet spot?)

3. It is completely hydrophobic with 0 moisture regain–even polyester has appreciable moisture regain as compared to PP and PP is naturally, permanently DWR i.e. doesn’t need coatings to repel and bead up water on its surface.

4. The tensile strength is only slightly less than polyester, but when weight/density difference between the two is factored in, then it can equal to exceed it (and if you chuck a little low grade, pseudo graphene into the plastic when hot/melted before extrusion, you can up that tensile strength to probably at least rival nylon 6.6’s tensile strength–informed speculation based on graphene being currently added to nylon and UHMWPE to up various strengths slightly).

5. (this one I’m not certain of, the first part). You most likely could easily modify calendering rollers to heat+pressure bond the PP film to the woven PP fabric getting an extremely waterproof fabric that will never peel, wear, etc off and thus lose waterproofness unless outright punctured.

6. The raw material is as low cost as polyester/PET, if not a bit lower, since a lot is made and it is more easily recycled than even polyester and nylon. (Melts at a lower temp etc)

I once contacted Ripstop by the Roll and pointed out some of the above to them, but all I heard back was crickets.  It is a shame, because if any company would be able (or willing) to pioneer such a material for backpacking use, it would be them. If I had significant spending money and connections to over seas factories/companies, I would jumpstart this myself, but I have neither.

[Roger Caffin]

Trouble is, polypropylene degrades quite fast under UV, and gets very weak when it does.

Cheers

[Justin W]

There are ways around that. It is easy to add UV inhibitors to the plastic before it is extruded into fibers. This is what often happens with UHMW-PE (particularly with the big brand names/companies of Dyneema and Spectra).  PE (polyethylene, of which Dyneema and Spectra are a form of) and PP have similar UV properties, and so UV inhibitors are often added to UHMWPE since it is a more expensive, high end, and sought after material that is known for its high tensile strength.

Nylon is also not particularly UV resistant either. Color can greatly affect that.  (And silicone coatings also helps).  For example, I once went up in a hot air balloon. I asked the captain did certain color nylon balloons last longer than others. He said absolutely and that black and dark blue were the longest lasting color nylons i.e. because they were inherently more UV resistant than other colors.

[Justin W]

Regarding the issue that Roger brought up, this article addresses this issue well and funny enough compares specifically polypropylene and nylon.
https://www.xometry.com/resources/injection-molding/uv-resistant-plastics-polypropylene-vs.-nylon/

But, if you want to cut to the chase (the important part is):

“Improving UV Resistance
While nylon and polypropylene are not generally seen as UV-resistant plastics, certain additives can improve their performance. These additives take the form of stabilizers, absorbers, or blockers.

Blockers – Fillers like titanium oxide or carbon black pigments can act as UV radiation blockers. These pigments help prevent the UV rays from reaching the plastic’s actual polymers and thus prolong the material’s lifespan.

Absorbers – Absorbers work by absorbing UV radiation and then converting it into heat. Typical organic absorbers include benzophenones and benzotriazoles. Benzotriazoles can be introduced in concentrations as low as 0.5% by volume and still significantly increase UV resistance.

Stabilizers – Stabilizers work by trapping any free radicals that get formed. This then minimizes subsequent degradation of the intermolecular bonds within the plastic. Stabilizers are also known as scavengers because they “scavenge” and collect any free radicals. Among the most common are the hindered amine light stabilizers (HALS).”

I earlier mentioned adding graphene to PP to improve tensile strength.  Not only would it improve tensile strength, but like carbon black, it would also improve the UV resistance. Granted, it would up the price a bit.  But with graphene, a little goes a long way.  As little as 2% powder can be added by weight to get those improvements. And note, this is low quality, pseudo graphene and not the high quality, hard to produce graphene (i.e. truly 2d sheets of same).  I can easily make the former graphene at home for relatively cheap.

For example, I once took graphite rods and used electrolysis via an AC powered car battery charger and certain chemical water solution to flake off particles of graphene (it was years ago and don’t remember all the specifics).

[Roger Caffin]

Long LONG ago I made a nylon dome tent, 7′ square. We (Sue & I) used it a lot camping out in the semi-desert next to Mt Arapiles, a world-class rock climbing venue. Excellent therapy around Uni exam time, for many years. Lots of sun. It had blue and yellow nylon panels.

After many years of use, the yellow panels went paper-like and shredded. The dark blue panels were still good nylon. (The poles were Jarvis Walker fibreglass fishing rod blanks I scrounged from the company manager. Very good stuff.)

Yes, UV absorption matters.

Cheers

[Justin W]

Thank you for sharing Roger.

Cheers also

[Sam Farrington]

Roger, please correct me if wrong; but seem to recall you posting that when using the tent only at night and/or in storms, UV is not a major issue.

It is interesting that some tent and tarp makers use only darker shades of silpoly, Yama Mtn Gear being a prime example.  And they probably have considerable knowledge of the issues discussed here.  I only use a tent from dusk till dawn, or once in a  blue moon when wind/rainstorms are so severe that it seems best to get under cover for a while, a good option to have when nature delivers its worst.

As for polypropylene, like Justin it seemed intriguing. and spent much time searching; but as Justin’s post suggests, finding a really ultra light version was daunting.  A lot of interesting stuff about protective clothing. but nothing to compete with sub one ounce fabrics.  So opted for silpoly in the hopes of producing something is this lifetime.  And while it would be nice to  make a tent with light earth colors; it seems clear that darker hues will be more serviceable.

On piste, I’ve never used a single wall since way back when toying with tarps.  For me staying dry in nasty weather trumps wipe-outs in single walls.  And do not mind being a woose.  As the greast blues singer said, ‘I’m built for comfort, not for speed.’

[Roger Caffin]

seem to recall you posting that when using the tent only at night and/or in storms, UV is not a major issue.
Correct.
But in those days (late 60s) Sue & I were rockclimbing for the weekend, going from Uni, so we usually got to Arapiles on Friday evening, pitched the tent, and left it up all Saturday and often some of Sunday. That is how that tent got so much UV.
We did also take the tent to SW Tassie for some extreme trips.

Wooses R Us.

Cheers

[Author]

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