Managing Condensation in a Single Skin A-frame

[Sam Farrington]

Geoff,
Agree that with polyester fabric the sag issue is mostly eliminated. I think we both have posted to that effect. Dan’s observations were not about his own tent, but of a number of other thru-trekkers on the PCT who left the backcountry for the night(s) when the weather got nasty. Re: “The people who say they are happy with their A-frames are social hikers or bullshitters.” That’s a straw man, I think.

As for A-Frames, I sense that we have quite different approaches to what is OK for creature comforts, so will just stick with my earlier comments. And I cannot suggest what a multitude of others find OK, since I head for very remote places and seldom see other people for many days at a time.

The Crux WPB fabric was reported here a while back, and is heavier than what I am looking for to get a solo tent down to 2 lbs. or less. Wish I could get ahold of some of the fabric BD currently uses on its single walls, but when they first came out, there were a number of reports of puncturing or tearing, which put me off.

Regret I could not be helpful concerning the details on your A-Frame. If and when I can get a largish solo tent done at 2 lbs or less, it will be posted here in detail, and is an A-frame of sorts, but with a ‘side entry’ and vestibules, and 2 bowed sidewalls to increase interior space. At that time, I hope you will comment.

[HiLight]

Sam – The older BD wall fabric (yellow) seems little different from their newer, house branded green fabric, and yes, it’s somewhat fragile with regard to abrasion & puncture; the floor is fairly robust. The way the interior poles are inserted into female snaps makes it easy to accidentally poke a hole in the fabric, which is a source of damage to many of those tents. That’s also why I want to add two short sleeves the the rear corners of mine to act as pole guides.

Other than that, the fabric seems plenty strong to me, and it might work very well for a MYOG tent, if it could be found.

[Geoff Caplan]

Hi folks

I did look at transverse designs like the Duplex and Skurka’s High Route.

Andrew critiques his own design here: http://andrewskurka.com/2016/sierra-designs-high-route-tent-imperfections/

My first reaction was that they look like an intimidating build for MYOG, The geometry is complex and it would need a LOT of prototyping, I think. An A-frame is a bit less daunting for a first project. I can see that they would be pretty liveable and would take a fair bit of weather. But Andrew only talks about a design goal of surviving 40mph winds. Videos of transverse designs in moderate winds didn’t give me great confidence about performance in a major hoolie, and the porches wouldn’t be as sheltered for bad-weather ventilation. Where storm-worthiness is a higher priority than liveability, I still think that a well executed A-frame with sleeved poles at each end would take a significantly higher wind-load. For Sierra’s mainstream market, I can see why Andrew went for something with more all-round appeal. My design priorities are very niche indeed.

I prioritise storm-worthiness because of my hiking style. I have a muscle metabolism issue that makes me slow but steady. To get big thru-routes done I have to trundle along all day and basically sleep wherever I am in the evening. If that’s a high col, for example, so be it (within reason). Or I’ll be passing through national parks and have to stealth-camp high in storm-prone areas, as the official options are booked months in advance. Most lightweight hiking tents are getting pretty stressed at 40mph, while I want something closer to a mountaineering tent that would be rock-solid in moderate wind and safe in a hurricane.

Sam – so we’re both shooting for a storm-worthy solo for under 2lbs. Challenging, but doable I think. Look forward to seeing what you come up with. My own design will come in at 700-900 grams depending on whether I go with 20D or 40D walls, and single or double doors. Not too shabby for something that should take a major Alpine storm.

[Nick Gatel]

Agree on the complexity of MYOG for shelters other than a-frames and mids. A-frames and mids have proven themselves in bad weather, the trick being keeping weights down for your project. I have a Trailstar that did fine in 80mph gusts, and understand your complaint of large foot print and us older guys crawling on hands and knees to get in and out of it. I don’t have a lightweight a-frame that can handle high winds, because nobody makes one. It’s not because it can’t be done, a-frames just aren’t sexy anymore.

[Geoff Caplan]

Nick

I don’t have a lightweight a-frame that can handle high winds, because nobody makes one

You’re right – it’s an odd gap in the market. As we’ve discussed above, the relatively recent popularity of trekking poles has led to a revival of A-frame tarptents, as their main disadvantage (the weight of the poles)  is eliminated. But none of them seems designed for severe weather use, which is why I’m thinking of making one. I guess it’s just too niche a market to be economic.

I want the weather performance of my TrailStar with a smaller footprint, lower weight, easier pitch, and integrated floor/doors. I think it’s doable, and the A-frame is the only practical approach within my weight constraints (c 850 grams).

[James holden]

marc says his trekkertent 40D stealths are just fine up to 100km/h winds or so …

the key he says is to use the apex guy lines aggressively … basically as tight as you can as they tighten directly on the pole (not the fabric) with dyneema lines

i havent tested em to that level of winds … but they make tents in and for scotland … so they probably know what they are talking about in a high wind/rain environment

unfortunately his orders are backed up … the fall of the pound has resulted in a slamming of orders i suspect as the prices for his tents in USD are very attractive

;)

[HiLight]

The Edge 1 is an interesting 4S, mixed pole design. I wonder what the new model will look like.http://www.trekkertent.com/home/home/1-edge.html

[Geoff Caplan]

As a Scot I followed TrekkerTent from the start and have swapped a few emails with Mark.

It was the Stealth 1 that got me thinking about an alpine lightweight A-frame. But I can see ways of improving the storm-worthiness with little extra weight and realised that my mods would  be uneconomic for Mark to consider. He tests all his tents on the Scottish tops and the Stealth does pretty well. So with the extra strength I’m planning my self-build should be bomber for the weight.

I’m less convinced by the Edge – it’s quite heavy and fiddly to pitch, and the videos I’ve seen of it in the wind weren’t too convincing. Perhaps it’s too innovative for its own good. Mark has stopped production and is about to launch a new 4 season model – interested to see what he comes up with.

[HiLight]

I haven’t seen the Edge in action, but it looks like it would benefit from a few ridge mounted guy lines. If faced with serious wind, that’s what I plan to do with my Bibler-ish BD.

[Geoff Caplan]

More reasons to question the weather performance of transverse ridge designs

As a follow-up to Mark Fowler’s comments about transverse ridge designs above, I spotted this recent video from Yama introducing their prototype Mark II transverse Swiftline 1P. They launched their Mark I some time ago and pulled it as they weren’t satisfied. After more development they’ve come up with this:

https://www.youtube.com/watch?v=P-fSyJ1QNog

Their Cirriform looks like a very smart design, so it’s interesting that they’ve found it so tricky to develop a transverse that they’re happy with. Personally, I wouldn’t fancy pitching that in a wind, and I’m not convinced it would perform too well once it was up.

I’m still of a mind to think that transverse designs are a sod to develop and that they sacrifice a fair bit of storm-worthiness for the convenience of a side-entry.

[Mark Fowler]

Geoff, when I talked about transverse ridge designs I wasn’t really referring to these fancier designs where the poles are not placed directly opposite each other.  The guy in the video does seem to make a dog’s breakfast of pitching the thing.

The basis of the design I am playing with is http://andersj.se/talt-ul-1-del-1/ . I would spread the poles so they support the walls and link them with a spreader. He even has a set of plans you can download.

[HiLight]

Mark – That looks similar to the Sierra Designs Tensegrity form, but the UL 1 appears to have better protection for the storage/vestibule area. There are wind tunnel tests on the SD page.

 

[Geoff Caplan]

Hi Mark

That looks like a rigid-pole version of the Akto/Laser single bendy pole design. Another approach to this is the Aarn Pacer:

These would probably perform better than the bendy designs in wind. The bendys do OK if the wind is end-on (there’s a YouTube video of an Akto in a measured 80mph hurricane). But they don’t do well when the wind is shifting:

https://www.youtube.com/watch?v=JG4YeHwcXCY

I have a bendy version of this design, and don’t like it as I’ve said above. The plusses are a side entrance and nice views. But in addition to poor performance in sidewinds,  I’ve also found are that they have little space above your head and feet, they are difficult to ventilate, the vestibule is quite shallow and offers modest shelter, and the design is complex and fiddly to pitch. Your mileage may vary…

[Geoff Caplan]

HiLight

That SD Tensegrity is very much a valley design, I think, with a focus on liveability over weather performance. They set themselves a rather modest 25mph standard for 3 season tents. Quote from the wind tunnel video:

It just goes to show – when the wind gets up to 35 mph, you want to have your campsite somewhere else.

It survived a bit more than that, but it would have been scary. I don’t think I’d fancy it above the treeline! And as for snow…

[Roger Caffin]

It just goes to show – when the wind gets up to 35 mph, you want to have your campsite somewhere else.
Chuckle.
But more seriously – it’s for a different market. That’s OK, as long as you know.

Cheers

[HiLight]

Yep, the SD tent is definitely not made for serious weather. Of course, I have my doubts about some of the other shelter systems found on BPL. I’m surprised it fared as well as it did, though. That tarp extension is just bizarre to me. With no way to seal it up that area or reef the tarp, the outcome is predictable. I wish more manufacturers posted wind tunnel tests, so points to them for that.

[Geoff Caplan]

Well, I’ll give SD points for originality – they’re one of the very few gear makers to experiment and innovate.

From what they say, the boxy flared walls are designed to provide space at shoulder height. The odd gear panel seems to be designed for alternative use as an awning, but it sure looks like a wind-trap. There’s a huge mesh panel behind it that has very little protection and would be freezing in a cold wind. The adjustable grommets that allow you to use different fixed-length walking poles are a pretty neat idea though…

As Roger says, probably a nice tent for warm fair-weather camping, but not much for us to learn from, I suspect.

[Roger Caffin]

probably a nice tent for warm fair-weather camping, 
Remember they are after the mass-market lowlands 3-season novice. I imagine it might suit such quite well, although the $400 tag is not that cheap.
On the other hand, they do NOT use ‘fire-retardant’ fabrics, so as they say ‘limiting your exposure to FR chemicals’. FULL marks for this, as those chemicals are toxic.

Cheers

 

[Mark Fowler]

Hi Geoff

A lot of my thinking is based on the performance of my old Laser Comp 1 which weathered 12 hours of 100kph winds pitched on the NW side of North Ram Horn in Kosciuszko NP – totally exposed to the wind. The wind strength was measured at the Thredbo Top Station AWS (about 2km away and a little lower) as 80+kph with gusts just over 100kph. It was interesting getting 10 minute interval readouts of conditions in real time from the Bureau of Meteorology web site.

Up to about 80kph things were going well — no flapping or noise etc. In the big gusts the windward end (specifically the seam connecting the rear panel to the side) would flex inward taking tension off the side panels and allowing them to flap. In later versions of the tent Terra Nova has added a couple of tie outs half way down these seams. My proposed alterations would be to add poles (inverted V) to the ends of the tent and insert additional pegging points half way along the bottom of each side wall which starts to address Roger’s comments on the size of unsupported panels as the tent would now have three poles and better control of the panel bottoms. Other aspects of the tent, especially the poor ventilation and the increasing weight with the proposed changes, means that I think I can do better.

I spent my youth in a japara one person A tent and in any number of variants later on. I can understand your preference for the classic ridge tent with inverted V poles for simplicity, and our requirements no doubt differ a little, I don’t seek out snow although it is always a possibility so I am less concerned with the flatness of the roof.  My concern with the classic A design is head room and the distance between the poles. For one person tents the A design tends to waste space by being too wide or having to be quite high to provide head room. In a two person tent this ceases to be a problem. To me, for a 1 person tent, this is a good reason to incorporate side entry with vestibule by using a spreader bar between the more upright walking poles.

[Roger Caffin]

Hi Mark

Sounds a bit like a conversion to a tunnel :-) But it should be interesting.

Japara A-frames – yeah, I remember …

Cheers

[Geoff Caplan]

Hi Mark

It’s a case of different strokes, I guess. Given the popularity of the design with the Laser, Akto, Scarp and many others, there are obviously plenty of users who like it. It just doesn’t seem to suit me and my priorities.

A tip from TarpTent – they say that the key to the stability of the Scarp is the PitchLoc corners. it seems it took years of development to perfect this, so it’s something you might want to experiment with.

I hope you’ll keep us posted as your project progresses.

[Mark Fowler]

I hope you’ll keep us posted as your project progresses.

It won’t be until after Christmas.  I am off for 7 weeks doing the Australian Alps Walking Track. When I get back I will also have to do penance by dealing with a long list of household jobs but I do have the materials and am close to completing the design.

I agree that TT’s PitchLock ends would improve wind worthiness considerably.  The problem of guy lines not properly angled to handle panel movement is apparent in far too many tents. Some are only there for decoration.

[Geoff Caplan]

Hi Mark

Looks like an interesting trip. I hope you enjoy Boggy Plain and Misery Road – those Aussies sure know how to make a place sound enticing!

[Author]

Posts