Storm-proofing the Side Panel on a lightweight A Frame Design

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.  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,  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:

Ah well, to each his own. I would like to see the finished tent in the field though, so go to it! Perhaps some reinforcing along the ridge line?

Personally, I would prefer either the Phalcon or the Phunnel, although both are rather heavy wrt today’s weights. But you know my biases.

That second photo of Everest tents – a really sloppy pitching! Slack slack slack!

Cheers

“Slack, slack, slack”

Yes – it’s odd that they didn’t pitch better on such an easy site! I guess the weather was calm?

I think we can summarise this by saying that I’m a single walker who uses poles, while you walk as a couple and don’t use poles. Those are two parameters that change priorities.

The two most storm-worthy weight efficient designs are the A-frame and the tunnel. One of these works better for me, and one for you. I think we’re both making the most sensible decisions for our specific circumstances.

I’ll certainly post on how things go. May be some time though, as I don’t need the finished article till the Spring.

Ah yes – the ridge line. As I said above somewhere, I’m going to experiment with reinforcing the ridge with tape like the balloonists do.  Or perhaps even dyneema cord? Something low stretch. Not sure how that will play with a cat cut, or if it’s even necessary.

I won’t have the pole height to replicate the Saunders snow sleeve idea, so that’s not an option.

I’ve got a couple of old tents I can cut up so I’ll do some experiments.

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—

https://www.google.com/search?q=north+face+tuolumne+tent&biw=1408&bih=649&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjO9Pmk1rnPAhXKOz4KHZO7DowQ_AUICigD#imgrc=l78U44zRQSVPqM%3A

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—)

https://www.google.com/search?q=eureka+timberline&biw=1408&bih=649&source=lnms&tbm=isch&sa=X&ved=0ahUKEwj80u-92LnPAhUHwj4KHV6TB_AQ_AUICSgE

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).

Hi Tipi

Nice to get input from someone else who has actually used an A-frame in gnarly weather. Maybe you can reassure Roger that I won’t get blown off the mountain!

As you say, that Tuolumne does look similar to the Blacks, but a bit better executed.

Like the classic Bibler, it’s a design that sacrifices the livability of a porch for a small footprint. Outside of expedition mountaineering, I doubt that’s a tradeoff many people need to make, Nowhere to cook safely or store wet gear, and you have to keep the door closed in anything short of fine weather. How did you find it to live in? You must be seriously hard :-)

Surprising to see that they’ve revived it. Who is the target customer?

I like that old-style tubular vent, by the way. Used it on a tent I made years ago and it worked well. Never really understood why the eyelid vent seems have superseded it, though Hilly use the eyelid on their black label range so perhaps I’m missing something. An issue for another thread…

Yes – I guess you could say that the tunnels and hoops are the bendy-pole cousins of the A-frame. They all use vertical poles that don’t cross, and they all need front to rear tension to keep them functioning. Looked at from that perspective, the main difference between me and Roger is that he believes you need 1 or 2 intermediate pole sets to support the sides in the wind, while my experience with the old A-frames suggests that this won’t be needed in a small solo ridge tent of good design. As you know from your Tuolumne, the poles ain’t going anywhere, and a modern high-tenacity polyester has very little stretch, even when wet. So with sleeved poles under reasonable tension at both ends, there’s really nowhere much for the side panels to go, especially if they are guyed as well. With a hoop or tunnel, even with Roger’s fiendishly clever pole design, the poles are going to shift without side-support and you’re into a different ballgame.

Hi Geoff

For the record, I spent many years in an A frame tent, and I still have that tent! It had it’s limitations.
I have spent a few years in a 2-pole tunnel tent as well, and had trouble in a strong side wind. We had to hold the poles up for a while.

Personally, I think an A-frame is a pole-deficient tunnel … :-)

Your point about using low-stretch silicone-coated polyester and a high tension (and sleeved poles of course) is a good one. I would like to see the result. I think a good cat cut on the ridge line might be important.

Photos!
Cheers

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.

https://www.google.com/search?q=vintage+timberline+tents&biw=1408&bih=649&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjI0suIwrrPAhVLFT4KHYxxAjkQ_AUIBygC#imgrc=6m9Xl-qeYFo2PM%3A

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.”)

On second thought, maybe the old Eureka looked like this—

https://www.google.com/search?q=eureka+alpine+meadows+4+tent&biw=1210&bih=649&source=lnms&tbm=isch&sa=X&ved=0ahUKEwiOqdKMxrrPAhXI2T4KHaM2DMYQ_AUICCgD#imgrc=jOEyhHrSUq2XGM%3A

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.

If you wanna see a truly stout A-frame, just google “Rivendell Bombshelter”. rather cramped, though. But rugged.

Hi Paul

I spotted the Bombshelter when I was checking out the old Jensen backpack design.  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.

The Rivendell seems to have at least 3 configurations:  Tent itself as in Geoff’s pic.  Tent with rain fly.  Tent with fly and added weird looking vestibule.  What is what and which is which??

https://www.google.com/search?q=rivendell+bomb+shelter&biw=1408&bih=649&tbm=isch&tbo=u&source=univ&sa=X&ved=0ahUKEwjl-bLbr7zPAhWGKyYKHVYdAOwQsAQIKA

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

Your photos intrigue me. Would I be right in guessing that the yellow pole sleeves were added to the basic tent later? The sewing in photos 3 & 4 certainly looks that way.

Also, the way the poles seem to bend worries me a bit, as does their length. It looks as though the original pole lengths were increased by adding thinner extensions with eyelets. I am not sure that extra length is such a good idea, as it means the ridge cord is pulling upwards more than outwards. We found with our old A-frames that it was better to keep the ridge cord attachment only slightly higher than the ridge line.

I agree very much with the concern about the tension at the ground hem. If the hem flaps too much there is trouble. In the case of tents with vestibules (such as my tunnels), this is never a problem as the primary tension is at the ground level. Tension at the top of the pole arch comes partly from the ground-level guying and partly from extra guys from up top. For an A frame it might be necessary to stake the bottom of the poles in place.

Cheers

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.  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!

I bet that the orange REI tent as it is in those photos is the original design. (sleeves, poles…)

However I can’t find another one to comparing it to.

Yes, the yellow sleeves (it’s the same material as the sewn in floor) is original. The material is much more robust than the orange nylon body.

The poles (aluminum) are also original. Keep in mind the 4 poles weigh 864 grams (30.5 oz) by themselves, and the aluminum wall is 1/16″ thick. As a comparison, the single pole for my Chouinard Pryamid, which has to handle a lot of loading, is only 1/32″ thick — half of the REI poles. Of course I don’t know what alloy is used in either, but I would guess they are the same. There is a lot of tension on the poles in the pictures; the guys are as tight as I can make them and are held by 9″ Easton stakes. Hey, I thought you Aussies and Brits call stakes, pegs, or is that out of fashion?

Keep in mind the REI was the mass merchandiser and private label company of its time, if we ignore Sears and Montgomery Ward, so the tent wasn’t the most leading edge of the era, however in those days REI was pretty particular about its own labeled equipment.

Herein lies the problem for Geoff. As Franco alluded to earlier, a big factor is sturdy poles and stakes. How much of the total weight (800 gram shelter goal) will need to be allocated to poles? Also, if he uses sleeves for trekking poles in the front those sleeves will be harder to fabricate than stock diameter poles.

Poles for a proper A-Frame will need to be much more robust than poles for a tunnel or even the SD Flash (which is really a modified tunnel). In an A-Frame, the poles are pulling the fabric to create tension, poles under the fly in a tunnel are spreading the tension to the ground with a thinner pole.

Over the decades my go to shelters in 3 seasons have been simple tarps. Then I used a Hexamid for 5 years, switching to a Deschutes CF last year. When I expect really windy weather (fairly common in the deserts I hike in) I use a silnylon Trailstar. Winters in the mountains have me using a Scarp 1 for the past 6 years.

So, I don’t have a preference for A-Frames. But as Geoff stated, the center pole in a mid is inconvenient. If he can build one at 800 grams that is bad weather worthy, he’ll have something he probably could sell. In the 70’s tent designs started to ignore A-frames, they just were too traditional looking (heck not only were geodome tents popular geodome houses were too). As the A-frames became “old school,” so did the external frame pack. We now have a few companies making externals again (ZPacks and Seek Outside come to mind), so perhaps it is time to revisit the A-frame design. I’m interested to see what he comes up with, and he does understand the challenges and design requirements. Thus my enrhusiasm in this thread. One could say I am biased, as I prefer tarps and mids for most trips, but I am not going to say it can’t be done. Maybe with some input from the community and diligence on Geoff’s part we can see something special come of it.

Hi Nick

Yes, I agree that there was a fashion element in the switch away from A-frames, as I posted above. I dumped mine for a WinterGear Sapphire (the design that became the Terra Nova Quasar), which seemed so much sexier!

I’ve no desire to make tents commercially (looks like a hard way to make a living!), but if the design works I’ll share the details here for self-builders.

The thing with the A-frame, though, is that these days it has a very narrow range of application.

First, you have to be carrying trekking poles – separate poles would be too heavy compared to the alternatives.

Second, the poles have to use a twist lock if you’re going to sleeve them – the flick-locks are bulky and might cause abrasion.

Third, it’s pretty liveable for solo use but there’s poor headroom for two people, where a good tunnel or hoop would make more sense.

Fourth, you only need the strength if you’re camping above the treeline.

And fifth, you need to be walking in buggy areas, otherwise a mid is probably a simpler solution.

If you walk solo with Pacer poles and plan to do the GDT or a traverse of Iceland (ie if you’re me!) it’s ideal. For most others, not so much, I suspect…

This has been a great thread.  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.  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.  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:

the walls are sewn directly to the groundsheet to make a tube,
Thereby ensuring that any condensation on the inside of the tent will collect on the floor and get all your gear wet. Provision for ventilation is good, but for the ventilation to work you need wind. On a damp still night – HA!

The innovation was the rearward canted A poles, which they claimed did away with the need for bothersome front and rear guys.
Load of rubbish. That tent won’t stay up for more than 5 seconds without good end guys OR the ridge pole. Build one and see. Even with the ridge pole in place you will still need some stakes, and maybe some guys.

Prototypes are good – made of old sheets which come at $0

Cheers