Storm-proofing the Side Panel on a lightweight A Frame Design
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Roger – if you’re basing your views on A-frames on Paddymade bush tents I can see why you’re sceptical! I know it’s an Aussie icon. But let’s face it guys, it’s a crap design on pretty much every dimension. Â You’re not seriously comparing it to the Phortress?
While we’re waxing nostalgic on crap designs, here’s the first mountain tent I ever used – a single skin by Blacks of Greenock. An A-frame, but the poles aren’t sleeved so do little to keep the panels under tension. No vestibule or bug protection, and a zipless tunnel entrance. At the time, any self-respecting mountain tent had to be orange!
Back to my tapered version of the Phortress. Roger says “hum, it might handle the wind”. Well, I’ll remind you for a third time of Chris Townsend’s view that the Phortress was the most stable tent he’s ever used. I doubt that there’s anyone alive who’s evaluated more tents, so why wouldn’t you believe him? And my version would have a lower profile. I’ve survived many a Cairngorm storm in lesser A-frames. And there were owners in my club who swore by their Phortresses and slept untroubled while everything around them shredded. So that’s why I’m not too shaken by your scepticism…
I’ve still got to decide between the RSBTR 20d silpoly PU or the 40d silpoly for above ground. The 40d would only add 85g so I guess I should go with it. It’s only a 3-season design, but the added tear strength and lower bias stretch should improve performance all round, especially if I get caught out in snow. I won’t win any pissing contests on weight compared to, say, a Hexamid Solo. But I wouldn’t trust one of those US minimal cuben thingies in a real wind, and when I asked the manufacturers how they would survive in 60mph+ they didn’t seem too confident.
Roger’s idea of an intermediate pole is original, so far as I know. I’ve certainly never seen it. But this is a design that was used in the high ranges for 100 years. Maybe nobody’s done it because it’s not really needed? Time will tell.
I’ll leave you with pics of the tent used on the first ascent of Everest. Frankly, Â as A-frames go it doesn’t look that great a design. But it got them up there…
PS – Just noticed that on the version of the Blacks tent in the pic, the poles are sleeved, but in an odd way that doesn’t do much good. I guess they tried to improve it. The version I used looked more like this:
Geoff, my old North Face Tuolumne tent which I lived in for many years until it died of UV poisoning, looked very much like your last A-frame pic.
I don’t have alot of pics of my old North Face tent but here is one—note the A poles in front are inside sleeves. And note the snow tunnel door.
Here’s another pic poor quality but it shows the single back pole without a sleeve.
This tent got me thru many blizzards and hellstorms and I never worried about the poles breaking because as you say straight poles are very strong.
Here are some better pics of the Tuolumne taken by someone else—
http://www.ebay.fr/itm/Vintage-North-Face-Tuolumne-Tent-/171979364081
Imagine my surprise when I find out the Tuolumne is being made again by North Face!! See—
But my old Tuolumne had a rain fly—this new upgrade does not and is single wall—a non-starter for me.
(It must be remembered that Eureka came on the scene many years ago with their Timberline A-frame—)
Beyond all this, I see hoop tents like the NF Westwind and tunnels tents as modified A-frames. Think about it. You have A-frames and then you bend the A into a hoop or tunnel. (What’s the difference between a hoop tent and a tunnel? A hoop has different length poles, a tunnel has poles all the same length).
Thanks for the response. There used to be an old Eureka Timberline tent that had the usual double A frame fore and aft with the tensioned spreader pole on the ridgeline AND an added roof canopy pole to pull the A sides out from the top down. Weird to explain so I’ll look for a picture. Went out with a guy in the 1980s who had such a tent and helped him set it up so I remember.
My old Tuolumne had a fly with a small front door overhang but not much although I never got wet or spindrift or blown away by this set up. A few years into my Tuolumne experience North Face came out with a full length fly for this tent and it created a big vestibule for the thing along with a tapered back. It sort of looked fly-wise like my old NF Westwind—
Westwind (camping in a friend’s backyard, circa 1992). The Tuolumne had such a full length fly which created a decent “porch”.
The new Tuolumne is a single wall, stupidly in my opinion, as it has no apparent awning or vestibule, so like with some Warmlite models every time you unzip the door rain comes inside. (I believe Warmlite calls it an “Inside Vestibule.”)
Hi Tipi
That Westwind is a baffling design – do tents really have to be so complicated?
Thanks for the heads up on the Eureka – it’s something new to me. Seems like Roger’s idea of an intermediate pole isn’t so original after all!
What they seem to have done is design an A-frame with lightweight A-poles, and gone for high, steep, sides to enhance liveability. This would necessitate the ridge pole and central pole to keep everything stable. The tensioned ridge pole is interesting – it would allow you to use a lightweight DAC bendy pole instead of the heavy bargepole used on the Force Tens and still get much of the benefit. Like a lot of US tents, the fly doesn’t have a vestibule. Does no-one camp in the rain over there?
I doubt that particular tent is particularly storm-worthy, but it does suggest ideas for a fully 4-season version of my type of design. Teamed up with strong ski or trekking poles the ridge pole would help with snow load, and the middle pole would make it seriously bomb-proof. The new poles would be an exoskeleton in a single-skin version, and a quick calculation suggests it would come in at a bit over a kilo with 40d fabrics. Made with enough skill, that’s something you could take into very challenging places. I’m not aware of any liveable solo shelter on the market that could do that for a kilo. Hmmm…
Like a lot of US tents, the fly doesn’t have a vestibule. Does no-one camp in the rain over there?
I spent many nights in an old orange Timberline tent back in 1995-97 and it looked pretty much like this—
As you can see the fly awning is substantial enough to create good protection from rainstorms—just keep the door zipped in windy rain— although there’s no vestibule. The awning is created as you know by ridge pole extensions on both ends.
This is a true free standing tent as the fly corners attach to the tent itself and the fly pullouts are not required. I learned this the hard way one day when my tent blew away into some brush since like an idiot I didn’t stake it down.
The floor of this was worn out (and probably never that good to begin with when new) and so on saturated ground any body weight would sponge water up thru the floor (a common problem with many tents with poor water proofing and thin denier floors).
That Westwind is a baffling design – do tents really have to be so complicated?
(This is not my pic). I bought my Westwind in 1989 and used it extensively until 2001 when the fly died from UV exposure. Unlike some hoop tents, the Westwind tension and setup was achieved by the 4 corner stakes on the tent body, as above. It was a great little 4 season tent (see my pic above with the full vestibule).
Remarkably, the Westwind like the Tuolumne was discontinued and then reintroduced by North Face in a weirdly different configuration (silnylon etc). I believe the new Westwind was available in Great Britain only. See—
https://bamboogirl.wordpress.com/2012/08/30/tnf-westwind-3-review-the-northface/
I never thought of this tent as being complicated as it’s in a large family of similar hoop tents. In fact, I thought of several improvements NF could’ve made to this tough tent like pole clips and velcroed vents but it never really came back.
Hi Paul
I spotted the Bombshelter when I was checking out the old Jensen backpack design. Â The best info I can find is here:
http://www.oregonphotos.com/Rivendell-2.html
They only sold 300, so there’s not much about them on the web. But it does seem to have been as bomber as they claimed: there’s one account of it surviving a measured 100mph on Mount Shasta when the 13 other tents on the site were shredded. Here’s one of the few pics. There was also a version with a tiny aerodynamic vestibule.
It weighed 2.7 kilos. It’s very small, as you say, and they used relatively light silnylon. So I can’t see how the fabric could have weighed much more than 0.8 kilos. So that means the pole system would have weighed almost 2 kilos.
According to the source above, Jensen used a particularly stout ridge pole. And in contrast to the Phortress, they reduced the side panel size by inclining the poles backwards rather than forward. The ridge pole eliminated the requirement for front and rear guys which made it freestanding apart from the side-guys.
Of course the slanting A poles mean that the entrance extends well beyond the dripline and it’s barely bigger than a bivy. When they were trading storm-worthiness vs liveability they went 100% with storm-worthiness – a very specialised mountaineering design, I would say.
The unusual frame seems be the main design innovation, and according to the source they also paid very careful attention to cut and reinforcement.
Geoff,
Yes, you can do it but you need to solve a couple problems you have already identified, which are tension. My old A-frame tent doesn’t work as well as a mid or a 4-season tent, but it never failed me, even when almost everyone else had tents collapse in heavy winds.
Here is a link to some information on my 1960’s REI A-frame tent with sleeves at each end. There is some stuff like measurement and weights of the poles you might find interesting or helpful.
In the above picture the tension at the top is tight, tight, tight. But it is difficult to get the bottom as taunt. One solution in my mind are tie outs midway or below at each of the 4 pole sleeves. I am sure this will help a lot. The bottom is where I get most flapping and is the difficult place to get things tight. Also note that the seam is not along the ridge line, but perpendicular to it — I feel this helps with side tautness and it almost creates two panels. Something like this might allow you to make an A-frame with the same height at both ends… the extra room makes a big difference when one is tent-bound. Given that the tent is over 50 years old and there is a LOT of tension pulling from the ends, a seam like this can be strong.
Now is Roger right about a tunnel and extra poles in the middle? Yes, of course he is. But that doesn’t mean a light A-frame can’t be designed to handle wind and bad weather, but not epic bad weather or Everest, which isn’t what you are looking for (40 mph wind max).
For years my bad weather tent was a Sierra Designs Super Flash. It handles wind better than a Trailstar or a Scarp 1 with crossing poles, both you are familiar with. But it is small and it weighs over 6 pounds. These Flash tents were standard issue for the US Antarctic Program.
I bring this up, because you might want to look in a sleeveless modified arch middle pole below a perpendicular seam, if it can be meet your weight requirements. This would be less material than a modified A-Frame like the picture in you OP. The pictures show how SD used 3 arches without sleeves to create this storm worthy shelter. Might help get the creative juices flowing.
Hi Nick
Thanks for the thoughtful input.
That old tent of yours looks about as basic as an A-frame can get! Though it seems to have served you well.
I agree that getting tension along the bottom is probably trickier than along the ridge. I suspect that one reason you got flapping is that the side guy is too high, and also only at a single point. Â If you look at the Phortress in the first post you’ll see that the side guy is lower with a wing shape that spreads the tension more evenly across the panel.
I’d been wondering how to place the side guy, and Franco has explained to me why Phoenix kept it low. The ground effect means that there’s little wind-speed by the ground, so you can move it up a bit without getting much flapping. But if you move it too high, you’ll start to get flapping below the guy as there’s little tension between the guy and the ground – it’s mostly between the guy and the ridge.
Also, the ends on the REI are flat. With the UK-style design, the pegs holding out the rain porches will help tension the bottom – I know this from quite a few designs I’ve used. Finally, instead of the single end-guy used on the Phoenix, I’ve been thinking of just the arrangement you describe, with guys attached near the top and bottom of the sleeved poles and angled out to the sides. Something a little like this (best pic I could find):
The vertical seam idea is interesting. As you say, it might help tension the side. Another seam to seal, though. The triangular panel idea I mention in the OP is a variation of this, but your suggestion would be easier to implement while keeping the geometry simple.
The Sierra tent is an interesting beast. The Antarctic credentials are impressive, though with 6lbs and 20 stakes you’d really hope it would perform well!. Clearly a central pole of some sort would add stability. But I’m not sure I want the weight, and there have been many strong A-frames that didn’t seem to need it. As I mentioned in a recent post above, it becomes more interesting to me if I make a full 4-season version designed for snow-load, where I think it might come into its own.
Lots to chew on. Though I do hope the final result will be able to handle much more than 40mph! The Phoenix could handle at least double that, and if you look above you’ll see that simple A-frames were used by the Mallory expedition on the North Ridge of Everest, and by the summit team on the first ascent. ! The potential is there, if I get it right.
Nice blog, by the way. I’m going to explore it!
This has been a great thread. Â As an old guy who remembers the switch from straight to flexible poles a couple of comments:
Notice that many of the A frames and the old Paddymade (Australian manufacturer established in 1930) japara tents – the shape was referred to as cottage tents – have a 30 to 45 cm wall created by the guying in the case of the Phortress and design in the case of the Paddymade tents.  This provides increased internal volume and could be emphasised by panel design.
Many of the design ideas I have played with involve the use of the walking poles in the centre of the tent combined with the use of a spacer bar between the walking poles to improve head height which, allows a side entry with vestibule.The walking poles U shape can be centred with the tent either side running down to smaller pole structures (3 pole tunnel?) or slightly offset to a single smaller pole structure. Â This minimises the weight of the poles but may become a problem if snow loading is significant.
The A-frame is such a simple concept that it’s hard to find innovations. But I’ve just spotted the Trailwise Fitzroy from the mid ’70s.
That’s not a hole in the side, by the way – it’s a cutaway to show the rear tunnel entrance and the dual venting.
This was sold as an expedition tent, with panels cut so that they didn’t flap and the ability to take a high load of wet snow.  The innovation was the rearward canted A poles, which they claimed did away with the need for bothersome front and rear guys. Despite having higher and steeper walls that most A-frames, they didn’t feel the need to sleeve the poles and the ridge pole was optional. No porch – presumably to keep the footprint small.  The poles are T6061, so it seems that they didn’t have access to 7-series aluminium.
The only report I can find on the web says it performed well, when other tents were collapsing.
Two other things I find interesting.
First, the walls are sewn directly to the groundsheet to make a tube, like the Stevenson Warmlite. I was planning to do this myself and rely on really good through-venting between front and back. Â It’s simple, fail-proof, and allows the tent to be sealed up against spindrift and dust.
Second, I was planning to use that kind of double door arrangement, with separate bug and draft doors. In my experience this gives unmatched flexibility. It will cost about 65 grams compared to a single door, but I get the ability to adjust between unrestricted airflow on warm, bug-free nights to total lockdown in storms, with every gradation in between.
Mark – have you seen the Aarn Pacer tents? They look similar to your design. According to Franco they are pretty bomber, at about the same weight as an Akto.
But personally I find the A-frame design more liveable for solo use, and it’s a lot simpler and less fiddly.
It’s designed to work with the PacerPole. The Pacer handle design is brilliant in the hand, but tricky when using them for tent poles. Aarn solves this cleanly with a webbing pocket:
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