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

[Geoff Caplan]

Hi

I think my flirtation with floorless tarps may be coming to an end. Sharing my living space with bog, thistles, dung, slugs and other delights is beginning to get a bit old. So my next project is a single skin A-frame along the lines of the Tarptent ProTrail or the Yama Cirriform.

US-focused designs tend to go for a gap around the flysheet paired with a suspended floor and plenty of mesh in the walls for side-ventilation. Ventilation at the foot end tends to be limited.

Suspending the floor like this adds a good deal of complexity to the build and also complicates pitching.

I’m focusing on a design that will be storm-worthy for mountain camping in 3.5 season Scottish and Nordic conditions. This pretty much necessitates a fly that reaches down to the ground, which will reduce airflow through any mesh in the side walls.

Plus, the side mesh would be an issue with wind-driven dust or snow (though the Yama does have an ingenious closure system using a running cord to mitigate this).

So I’m tempted to dispense with the mesh walls and sew the groundsheet directly to the fly. With the low flysheet I’m not convinced that side-mesh will add much to the ventilation.

Instead, the idea is to have a well-sheltered vestibule at the head and foot ends that can be kept open in all but the worst weather to provide a vigorous through-draught. If the wind is strong enough to force me to close both ends, I’ll have plenty of draught anyway, plus I may fit a couple of vents as well.

My first thought was that sewing the groundsheet to the fly would be a recipe for a sweatbox. But then I remembered that the venerable Stephensons Warmlite tunnel tent does precisely this – it is a long-lived design with many diehard fans.

I also remembered an interesting little bivy tent from Turner Lightweight Tents which implements the idea of a sewn-in groundsheet paired with well-sheltered vestibules to promote airflow. I’ve been in touch with the designer and despite the small internal volume he says that the airflow has ensured that condensation isn’t a significant problem.

So I’m beginning to think that this isn’t such a daft idea after all. I get a simpler build and an easier pitch, while a proper rear vestibule (which can be adjusted from inside) should hopefully still give me enough airflow to keep condensation at bay.

Clearly, this won’t be a warm design. But I’m of the Chris Townshend school that the job of the tent is to keep off the weather, while keeping warm is the job of your clothing and sleep gear. My thinking is that if you go for a small and very lightweight shelter you simply have to accept that it will be a bit draughty if you want to keep the condensation at bay. I’ll implement adjustable solid panels in the front and rear doors so I can keep the draught above my bag if needed for comfort.

I’m a newbie at this game, so before I get too invested in the idea I’d very much appreciate input from all you more experienced tent-makers. Do you think this has a decent chance of working?

[Sam Farrington]

Geoff,

Please consider the phenomenon known as ‘horizontal rain.’  It can blow right through a partial vestibule, and did so many times before I switched from tunnel shaped tarps to tents.  Guess it was just a strong aversion to sleeping bags wet at the foot.  At least it was a tunnel, not an A-frame, so my head did not get soused every time when sitting up.

As far as Warmlite is concerned, please recall than many of their tunnels had both inner and outer coated walls, which made it a bear to install the poles.  However, the double walls did reduce inner condensation somewhat, because the colder outer was separated from the warmer inner.  They also tried laminating mylar sheets to the single walls, again with only limited success.

And good ventilation is always an essential part of controlling inner condensation, but it is not a trade-off. Way I look at it, some form of inner wall is also essential to stay dry inside in all weather.  Part of that can just be inner netting doors behind the front and/or rear vestibules, netting that you would want anyway to keep out insect and other pests.  Recall the tales of scouts at Philmont who woke up with rattlers crawling into their sleeping bags at night for warmth.  Fortunately, scorpions may be more cold-blooded.  That leaves just the ceiling to be truly double walled; so a rear vestibule may be used to extend floor space; thus allowing a smaller double ceiling; but in turn requiring double doors at the front vestibule that open and close both singly or together.

Contrary to Mr. Turner’s approach, the overworn approach to designing tents with A-frame shapes may limit development of new approaches to these old problems.  Hope this provides food for thought.

[Geoff Caplan]

Hi Sam – thanks for the input!

But I find that the “which geometry is best” debate never really goes anywhere because each design offers pros and cons and everyone has different priorities. I’ve spend hundreds of nights in A frames of various designs, so know what I’m letting myself in for. I know they’re not trendy, but I like them.

I’m designing the shelter to take heavy weather on long hikes at the lightest possible weight. I’m mainly a walk-and-sleep kind of hiker, so I’m not looking for luxury.

In big winds, bendy poles are the main cause of failure in lightweight tents. On the other hand I already carry 2 robust walking poles that will survive any kind of wind or snow load. If I’m to bring the shelter home at around 850g, I’m restricted to a walking pole design. Robust bendy pole tents tend to weigh significantly more than that and I don’t see any need to pay that price.

Of the limited wind-worthy geometries available with 2 straight poles, I much prefer the A frame for solo use. It has plenty space at the head and foot for sleeping without contacting the outer, and there is decent room to sit up inside the front entrance. The footprint is modest. And it’s relatively easy to build.

I’ve used single pole mids and transverse ridge tents and don’t enjoy the walls being so close to my face and the foot of my bag – especially under load from wind or snow. The other options are either too complex for an inexperienced MYOG builder, or are restricted to use below the treeline.

Clearly, other folks have different priorities – which is why there is room for so many different designs.

A properly designed A frame will do just fine on the North Coll of Everest, so I don’t see any problem with weather resistance. I’m drawing on well established principles and it should be pretty quiet at 40 mph and undamaged at higher speeds. I have enough experience with them to be confident of that.

Another advantage of the A frame is that it plays well with with a single skin design. I will be fitting adjustable twin mesh/solid doors at both ends, with a generous waterproof bathtub to catch any splash while the vestibules are open for venting.  This is much less practical with side-loader designs.

As you say, that only leaves the roof as a single skin. If I need any more warmth or drip protection in extreme conditions, I’ll have mountings to rig a very light inner curtain. This would effectively give me a full double wall design and true 3.5 season functionality that should handle anything except for massive snowfall, which isn’t on my agenda.

So for my needs this design will be lightweight, robust and adaptable with acceptable liveability.

My last dilemma, as I posted, is whether to suspend the floor with mesh or sew it directly to the wall. I’ve just revisited Ryan’s review of the HMG Dirigo, which I realise is yet another example of a sewn-in floor – and no one seems to have found this a major problem. I’ve spotted some other examples too, including the classic Bibler design which has been used by millions over many decades. So at the very least, it’s not a show-stopper.

So I think I’m going to go for the sewn-in option and rely on through-draught from the sheltered front and rear vestibules. I haven’t seen any other lightweight design that really offers this – most have a flat rear that can’t be left open in rain. I get a simpler build and more failsafe pitching, and it’s easier to defend from driven dust and snow. With a fly-to-the-ground design I don’t think I’m missing out on much airflow, so it feels like the right tradeoff.

[Steve S]

Stephenson Warmlite tunnel tents rely on end vents. No mesh along the floor. He thought (iirc) that on the tapered designs the low rear vent and high vent above the door were important, but he had a vent below the door as well. He felt that the door should remain closed (but not the vents above or below) so the circulation generated by human warmth would tend to move moisture up and out. The rectangular tents had high and low vents at both ends; so relatively stagnant air in the middle and, I assume, more condensation. He pushed double skin main tent bodies — both waterproof — as a fix for areas of heavy condensation. My single skin tapered Warmlites have seemed to handle condensation fairly well — in the relatively wet Oregon Cascades. But maybe I just don’t know any better.

BTW, I’ve used very lightweight frost liners in winter in an A-frame design — in my experience they work really well to keep the frost on the outer from snowing on you in a storm.

[Sam Farrington]

Steve S, It may be just a matter of you settling for “fairly well” vs my desire for gear and self to remain fully dry when mother nature is dishing out her worst.

“A properly designed A frame will do just fine on the North Coll of Everest …”

Can’t say I’ve been up there, Geoff; but all the photos I’ve seen were of tents with the bendy poles.  Granted, I would not try to use my carbon arrow shafts on the North Coll, or anything like it.   Some places you just have to carry more sturdy everything, including poles.

Agree with the sewn in floor.  Have been caught too many times in situations where the ground turns into a stream bottom.

As far as A-frames go, admit that sleeping under shelter halves in basic training did prejudice me against them.  They are the oldest design of small tents that I know of, and I think they suck for a number of reasons, the least of which is that when one key peg goes in the middle of a storm, down goes the tent.  The next least of which are the soggy claustrophobic single walls.

But I see you are set on a tent build.  No better way to find out.  Go for it.

[Geoff Caplan]

Sam – if you can show me a freestanding double-wall alternative that can handle 60mph+ gusts and that I can bring in for under 900 grams I’m more than open to ideas! Not convinced that such a shelter exists though. Clearly, trekking-pole designs trade off comfort for lightness – as I say it all depends on priorities.

In the UK, Scandinavia and the Western Alps finding good peg placements is rarely a problem. My design will pitch with just 5 pegs in calm weather, but can be battened down with many additional pegging points as required. Lots of pegs spreads the load – and the secondary locations only need a 10 gram titanium hook, so it’s not a big deal weight-wise.

And in any case, lightweight bendy pole designs also need lots of pegs in the wind.  Even at almost 3x the weight of my own design, the Suolo still needs reliable pegging points:

The last few years I’ve been using a TrailStar – an A-frame gives a much more convenient living space so will be an upgrade for me!

[Geoff Caplan]

Steve – interesting to hear from someone with direct experience of the Warmlite!

I’m increasingly confident that sewing the floor direct to the fly Warmlite-style won’t be too much of a problem. Remembering that the Bibler and many other mountain tents work this way has swung it for me.

In my experience, double mesh/solid doors at head and foot help a great deal. In warm weather you leave the solid doors open. In cold weather you zip them up enough to deflect the draught over your sleeping area, but it still carries out the damp air. And in driven dust or spindrift you close them to defend the living space and simply put up with any condensation.

I wonder if Stephenson was right about temperature differential driving the venting? What’s your view? In my experience it’s wind that makes the difference, and the ability to leave the vestibules open in all but the worst of the weather. Luckily, where I camp still air is rarely an issue!

[Sam Farrington]

Geoff, I agree that 26 oz is a good goal for a non-DCF solo tent.  However, wind tunnel testing is way beyond my budget.  I used a less travelled area near the peak on Mt. Washington for my Goondie (There is a photo on my OP); and Bald Mtn. behind my house, has some pretty good open ledges; but I’m not keen on climbing up there as winter approaches.  So I think you’ve priced me out of the running.  But am glad you can see the comfort issues for trekking or other pole designs that are basically versions of A-frames.

And for stormy mountain weather, wherever you go, we would probably agree that site selection has a lot to do with the function of any shelter.  However, I don’t think the kinds of solo flexible pole self standing designs, like the heavy Suolo, or a Hubba, are designed for storm level winds.  No one would put a little cap fly on the top of a wind tent, and indeed, it was those horizontal wind and rains that were reported in BPL to create leaky Suolos.

More disastrous, though, are the hoops, whether they be the long one on the Hubba and its progeny, or the  several hoops on the Suolo.  A hoop, which forms a parabola when flexed, would not be my choice for high winds, because when they strike the side of a hooped tent with near horizontal walls, large force can overbend and snap a pole.

Instead, a pole framework for a self standing tent should be made of flexible poles that form gothic arches; that is, a less parabolic shape that comes to a point at the top of the arch; thus creating a more aerodynamic shape much less vulnerable to the force of winds.  Although a Gothic arch is less bent, and thus creates less convex internal space, it beats a saggy A-Frame hands down for sit-up space and elbow room.  Unfortunately, I’ve only seen one tent that attempted crossing gothic arched poles, from EMS, and it was not at all well designed.

But you might liken it to the elbowed poles on Roger Caffin’s tunnels.  Each pole has three elbows, the top two sections forming a slightly gothic arch, and with the walls guyed out is extremely stable in high winds.  For a side-entry self-standing solo, however, I wanted the poles to cross at the head and foot ends with permanent guying at the crossing points that hold the poles in place without the need for pegs at the corners.  That is something I learned from the Goondie; when the poles are guyed out, no pegs are needed to hold the bottom corners of the poles firmly in place. And this should work even better with the downward force on the pole crossing points.

So, my current tent project uses the above mentioned guys from the pole crossing points to stakes at the head and foot ends of the tent, and two more stakes at the points of the front and rear vestibules that also serve to keep the tent taut.  A fifth stake is carried to add a guyline from the rear vestibule of the tent facing high winds when they may occur.

As I may have noted, the tent will be double wall with a WPB inner ceiling.  I like a tent that can stay buttoned up, albeit with protected vents, to avoid condensation, and the second ceiling will add strength and greatly simplify pitching because it can go up first.  So as said, I’m not keen on the idea of using partially open vestibules for ventilation in storms.  I’ve survived warm and dry in too many storms only with tents buttoned up.

I don’t think this will be a tent for heavy snows, because even though the self standing framework reduces the stress on the pegs, there could be enough stress to pull the pegs out of the snow in high winds.  So it is intended only to be a three season tent, as recommended by Roger some time ago on a BPL thread.  That is AOK for me.  I mostly play homebody during season four, reading, working on the house, and on MYOG projects of course.

[Geoff Caplan]

Sam

I agree that Roger is on to something with his angled poles – I’m no physicist, but it’s pretty obvious that you’re getting more strength out of the material if you go that way. So yes, the gothic arch is surely going to beat your basic rounded romansque arch, weight for weight.

Given the clear advantages it’s odd that no one would take up Roger’s design for the commercial market – I guess they’re not set up to produce the poles cheaply enough. There’s an opportunity there for someone to build a business around a better pole geometry.

Hilleberg classify the Suolo as black label and they know what they are doing – but I’ve played with one and it does need very substantial guying to perform to spec. And as you say – the design of the venting is odd. My design should be pretty much as robust at 1/3 the weight, at the cost of a little liveability. That’s the right tradeoff for me.

You and I are old enough to remember the days before bendy poles, when we lugged around thick, straight shafts of aluminium. They were heavy and the shelter geometries were a bit inconvenient, but pole failure was unknown and the tents were bomber. We abandoned them when the bendy poles came out for the superior lightness and liveability of the new designs, but we sacrificed wind performance. Now that most of us carry strong poles for walking, the old geometries are experiencing a revival.

These days you see broken poles after every big storm. As you say, to make a really bomber bendy-pole shelter that doesn’t rely on guys you really need a geodesic design with multiple poles – but they are egregiously heavy and tedious to erect, so they’re only used for expedition work.

If you want a shelter that can take a big storm you can either go light and inconvenient or prioritise liveability at 2 or 3 times the weight. With current materials I don’t think there’s any way around this. This is particularly true for solo designs, which are less efficient weight-wise.

[Roger Caffin]

it’s odd that no one would take up Roger’s design for the commercial market – I guess they’re not set up to produce the poles cheaply enough.
An Easton Product Manager did try for the full design, under licence from me.

But the tent as a whole is far more expensive to produce, and the Easton Sales Dept did not want to sell anything in volumes of less than hundreds, without leaving their desks, and with a wholesale cost of under $100 each. Eventually Easton got out of the tent market.

So there you have it. The tent is more $$ andthe volumes are smaller. The mass market vendors think there are easier pickings elsewhere.

Cheers

[Geoff Caplan]

Yes – I suspect that the benefits of your design are too niche to be attractive the the mass market.

After all, most tent buyers go out a couple of times a year when the forecast is good – your basic Vango or Big Agnes will handle this fine – they don’t need the performance or sophistication of the Caffin.

And the thru-hikers will prioritise lighter HMG/ZPacks type designs as the expense of liveability.

I suspect that the true market would be the top end currently dominated by Hilleberg – the kind of people who will fork out well north of US$1k for a high-performance shelter.

They are either serious users, or well-off vanity users who want to be seen with the best kit.

And they would be manufactured by a small and highly trained team in an artisan workshop under direct supervision of the management, on the Hilleberg model.

They would be horribly costly, but I’m pretty sure there would be a market for a small range.

It would never get the VC investors excited, but it could be built up organically with very little capital and might make a solid little business.

There’s very little risk that the big boys would copy the design and undercut the business – the niche is too small to justify the effort.

All it would take is the right entrepreneur to work with you. I’m surprised no-one has seen the potential.

Not that I’m telling you anything you don’t already know…

[Roger Caffin]

Hi Geoff
Right on all counts. ALL counts.
Cheers
PS: I sold a few I made, typically for >$1k. The buyers were happy.

[Sam Farrington]

Geoff,  Re; “With current materials I don’t think there’s any way around this. This is particularly true for solo designs, which are less efficient weight-wise.”

Yes, that is the riddle I’m working on.  There are some beautiful MYOG designs on these forums using DCF; but with conflicting reports about durability, and with issues about making tents out of inelastic materials, I passed; which meant somewhat heavier fabrics weighing around one oz/sq/yd,  That doesn’t rule out a 3 season stormworthy solo double wall tent under 30 oz; but it is proving to be a challenge.

However, here is an old well designed but inexpensive  Eureka Crescent, heavily remodeled and used for many years until the fly wore out.  It is self standing, except for the front guyline, has 3 flexible poles, is double wall, and pitches in one motion once the poles are installed on the ground; so it is a quick and dry pitch:

The beaks ventilate well; and provide enough cover in windy storms.  But it had one major flaw; there was not enough space inside to comfortably prepare and eat a meal, especially if the pack was sheltered under one of the beaks.  And if I leaned back, I hit the rear inner wall.  It required 4 pegs, plus a fifth for the front guyline.  The mods included a better silnylon floor, beaks and poles.  But it revived the hope of a slightly larger solo tent that could check all my boxes, and led me to begin work on a self standing solo with a bit more room and lighter fabrics, fixtures and carbon poles.

I mention this because it gave me some confidence that with lighter and more durable materials now available, a slightly larger tent with as many features is possible.  Que Sera!

[Murali C]

If the floor is sewn to the fly, I find that the fly tends to move a bit when you move on the floor. I think it is not a big deal unless it pulls on the fly a lot. And then of course, if you don’t have a big vestibule to remove your wet rain jacket etc, then your floor could get wet. Without a floor, you have the whole canopy to spread out, remove clothes etc and then place the floor and unpack.

[Roger Caffin]

With a good vestibule, you can shed the wet gear in some degree of comfort before you get onto the groundsheet.

The first thing Sue does is to spread out her 1/8″ CCF foam layer and sit on that. Then she gets out her airmat and inflates that, on top of the (protective) foam.

Cheers

[William Chilton]

My last dilemma, as I posted, is whether to suspend the floor with mesh or sew it directly to the wall. I’ve just revisited Ryan’s review of the HMG Dirigo, which I realise is yet another example of a sewn-in floor – and no one seems to have found this a major problem.

The Dirigo has a floor which is sewn in at the head and foot end, but is suspended from mesh at the two sides. When condensation is bad, you can get a little pooling of water in the corners of the floor.

The Dirigo has no vents, so you might be able to lessen the condensation, but I suspect that with a sewn-in floor there will be some circumstances where you get some water collecting on it.

[Geoff Caplan]

William – thanks for the feedback. I suspected that I would have to deal with some pooling as you experienced in the Dirigo.

As you say, hopefully the stronger airflow that my design would offer will help minimise the issue. I’m also going to have more volume at the foot than in most tapered A-frames – most of the commercial ones are so small that you’re more likely to get condensation and to contact the wall with your bag.

But a little pooling in the worst conditions is not a deal-breaker for me. If I’m awake I’ll simply mop it up, and I sleep on quite a thick mattress so there’s no reason for my bag to get wet. I’ll make a protected storage pocket for my electronics to ensure that they remain safe.

In my way of thinking, condensation is simply something you have to live with in small tents. It can be problematic in any kind of design, and for me the trade-offs for the sewn-in groundsheet concept are still making sense.

[Steve S]

Geoff — My usual use case, given the snows of the Oregon Cascades, involves camping on snow in subfreezing overnight temperatures. Usually cool nights even in August, so there are 2 choices — solid door open or closed. The mesh door is usually zipped or it would be hanging in the front (floored vestibule) area. In my experience keeping the solid door closed (but with vents high and low) has led to a less drafty tent with little condensation, so a closed door seems to be a win-win due to the high-low ventilation scheme.

I use a breathable bivy in any tent. Insurance against brushing against tent walls and the occasional drop of water should seam sealing fail or cold rain lower the tent skin temperature suddenly on a warm night when the humidity is high inside the tent, thereby causing condensation on the interior of the skin. An example is offered by one night when I was camping on coastal island during the summer. A cold front came through and after the initial heavy down burst and violent wind it was wet all night. My tent’s interior skin was damp and I had 3 drops on the bivy in the morning where the seam sealing (years old) seemed to have failed. The floor, iirc, was dry. I had to avoid touching the tent wall while dressing and such. I do not see how physics allows one to avoid a wet wall on a single skin tent under such conditions.

So Geoff, no matter how you ventilate your tent, I suggest you make the tent roomy enough to do any needed tasks while successfully avoiding touching the walls.

[Sam Farrington]

Geoff, a few points:

“But a little pooling in the worst conditions is not a deal-breaker for me. If I’m awake I’ll simply mop it up, …”

This is something I would never accept, and would not carry a shelter that left me and my gear wet during torrential rains.  IMO, that defeats the whole purpose of lugging around a near 2 lb. tent.  I’ve heard the “simply mop it up” refrain on BPL for decades, often to justify single walls and tarps, and I think it is self delusion.  I only keep quiet most of the time because of being vastly outnumbered.

You mention the straight pole supports of yore, as being better than ‘bendy’ poles.  An early experience was with a scout group chaperoned by a couple of our dads in an all night storm of snow and freezing rain.  In those days, all you saw was A-frames, but we had more spacious tents, based on a lean-to shape, and supported by two of those long straight poles, and two support struts in the back made of the same light tubing.  They were state of the art and  made of single wall Egyptian cotton.  And we even ditched our tents, which kept the floor dry, and pounded in plenty of burly stakes to hold the poles in place.

Three of us came through the storm dry; but when we got out of our tent, the dads’ tent had totally collapsed when the poles were blown down, and the only way they could stay warm was to wrap themselves up in their tent on the ground.  Not long after that, Jansport came out with its wedge dome tents that were lighter nylon, bathtub floored, double walled, bendy poled, and free standing.  Needless to say, I switched to those and never went back to A-Frames except as I noted, in basic training.  But even those tents kept us dry, and eventually better tents came along, like the Moss tents.

It is a PITA to carry around a two pound tent when often it is not needed, and only seldom are we caught in a deluge.  But it is the deluge that justifies the weight, particularly when trekking for several weeks in the mountains and the odds of being nailed by a few deluges are high.  So I was amused by an old post from Dan D. about his PCT trek.  When the deluges struck, many trekkers hiked out and went to motels.  But there are many places in Colorado where that is not feasible on longer treks, and maybe if one has to do that, they shouldn’t be there.

Only wish we had lighter WOVEN fabrics that would make for shelters that withstand the elements.

[Roger Caffin]

“But a little pooling in the worst conditions. . . ”
This is something I would never accept, and would not carry a shelter that left me and my gear wet during torrential rains.
There could be some distance between ‘a little pooling’ and getting really wet.

Anyhow, under certain circumstances it is not possible to avoid a little water on the floor. At -10 C with a little fog, you WILL get some condensation on the floor where it is touching the snow underneath. Unavoidable.

So we have a 1/8″ CCF foam mat under our airbeds and any condensation stays under it. The CCF mats get rolled up and carried in a silnylon stuff sack, and often get dried out during the day or the next evening.

This is how I would interpret ‘a little pooling’.

lighter WOVEN fabrics that would make for shelters that withstand the elements.
I suggest that at some stage one might run into the strength of the fibres as a basic limit. At this stage UL becomes SL: stupid light. Me, I want to know that the tent fabric will handle the storm. If that costs me an extra 100 g, so be it.

Cheers

[Geoff Caplan]

Steve – your experience-based input is very useful! I was dithering over whether to bother with vents, but based on your reports on the Warmlite I guess that this is something I should add to the design.

Then the issue becomes how to implement it. There’s a guy in the UK who did some practical experimentation measuring through-draught and concluded that most vents are much too small. I suspect that GoLite got it right with vents that were much bigger than average:

I also agree that in a single skin it’s important to have enough space to enable packing etc without touching the walls. In particular I think that many A-frame designs are too small at the foot. The lack of volume encourages condensation, and the lack of space increases the risk that the foot of the bag will contact the wet walls. My design will have enough space at the foot to enable me to sleep either way round. This enables me to point the foot of the shelter into the wind for optimum storm performance without worrying about having to sleep with my feet above my head, and also to enjoy views through the door of an evening. The weight of the extra fabric is so minimal that I can’t see the case for the tiny designs that are currently trendy.

Sam – I think you’re overdramatising the issue – I won’t be getting wet. Any pooling will be a minor inconvenience. It’s not as though a double wall prevents condensation – it’s merely a different way to manage it. I know someone with an Akto, for example, and she experiences quite severe issues with condensation at times. And as Roger says, a double wall doesn’t protect you from floor condensation.

This can all be managed, I think. Like Roger I sleep on a 1/8 foam pad to protect my sleeping mat from ground condensation. (If you’re in the UK, I persuaded Ultralight Outdoor Gear to manufacture this mat so we don’t have to re-import a British product from the US). And in difficult conditions I have the option of erecting a lightweight DWR curtain which effectively turns the design into a double-wall, or to use Steve’s strategy of a lightweight bivy to add protection and warmth.

And like Roger, I suspect that an effective ultralight woven fabric like the old cottons wouldn’t be practical. Essentially they were the same as the modern woven and coated fabrics – just much heavier. They relied on brute bulk to keep you dry, combined with inefficient DWR coatings. And in extended rain they leaked and got egregiously heavy. So I’m not clear what advantage you would envisage?

[Geoff Caplan]

Quick PS – a recent post here points out that the mesh-suspended floor has its own weakness – on tricky ground where you can’t achieve an optimal pitch it can leak far more water than any pooling condensation would cause with a sewn-in groundsheet.

Add to that the complexity of making it defendable from draughts and driven snow or dust and it confirms my growing view that it’s more trouble than it’s worth – certainly for European conditions.

https://backpackinglight.com/forums/topic/tarptent-dipole-li-review/page/3/#post-3762021

[Roger Caffin]

most vents are much too small
I make mine adjustable. The vent at the windward end is like an end door, with zips up both sides. In fine weather I can pull the zips down on both sides and have a really big vent. Despite its size, rain does not come in (unless I go too far!) because there is a hood over the opening. In bad windy weather, the vent is made much smaller.

The weight of the extra fabric is so minimal that I can’t see the case for the tiny designs that are currently trendy.
Perhaps ‘trendy’ is the very right word here? Fashion, not function?

the mesh-suspended floor has its own weakness – on tricky ground where you can’t achieve an optimal pitch it can leak far more water than any pooling condensation would cause with a sewn-in groundsheet.
Ah, but is what is implied here is not the only possibility. I use a mesh-suspended groundsheet on my blue single-skin tent, but the groundsheet has 150 mm (6″) high side walls all around. Ground wobbles don’t matter. I actually had the entire floor floating in 20 – 30 mm of sudden rain once on a very flat hard site (helipad). It was bizarre! But the floor was seam-sealed so we stayed quite dry inside. The water eventually flowed away.

Cheers

[Steve S]

Geoff, making a waterproof skin tight against blowing snow suggests you want to carry a loud carbon monoxide detector with you, or that you won’t use heat and are assuming that high carbon dioxide levels will suffice to awaken you to the need for fresh air. I suppose you could make long or baffled chambers for the snow to collect in, but that sounds heavy. I personally prefer to live with some spin drift.

Does the Golite design have low vents?

The Warmlite tents have large vents. The base vents are roof overhangs where the floor ends before the roof does. Simple, with the floor extended in mesh at an angle, so that the extended roof provides a drip guard. In the front the mesh door is the extension overhung by the solid door, while in the rear the floor extension is tied back and remains available; allowing it to be repositioned, if necessary, to lie against the mesh, thereby limiting air flow.

The top vent is brilliant in its simplicity, but might be hard to duplicate with an upright pole. This shot on the Warmlite website shows the vent: https://www.warmlite.com/wp-content/webpc-passthru.php?src=https://www.warmlite.com/wp-content/uploads/2018/06/Yellow-Top-Gold-Ends-2X-front.jpg&nocache=1

The top of the door is mesh; a single piece of fabric forms a gutter by the way it falls, allowing gravity to remove any rain penetrating the mesh. Allowance is made for tying up the panel at the middle top, if necessary.

I have never closed the vents; nor has water penetrated past them, that I have noticed. (I started using Stephenson tents in the early half of the 1970s.)

I’m not impressed by the Golite vent, but your tent poles are challenges for the Warmlite method. Perhaps the X-mid vents would spark an idea.

Roger’s tents may have larger vents, but Warmlite has a truly lightweight system.

 

 

[Sam Farrington]

Geoff and Roger,

You are not the first to question that I am ‘bone dry’ inside my tents.  That may be because I no longer camp in the winter season, but only in the other three seasons.  Or perhaps because you have encountered harsher weather in the 3 seasons.  In any event, although it cannot be proven here, I’ve trekked in some really ghastly weather in the shoulder seasons.

However, please note that my tents continue to be double wall, and now intend to make the inner ceilings solid, but breathable, using some older GoLite poncho fabric that is very light.  That leaves the front and rear of the side entry design with netting inner walls that are there to keep out pests and provide ventilation, not to mention protection from condensation inside the outer vestibule walls.  Plus there will be protected vents near the tops of the vestibule beaks.

I’ve also reached the Mao-like conclusion to take a step back to take two steps forward; in that the design of the solid inner ceiling will protect the inner tent during pitching and striking.  But that said, even with conventional double wall wedge domes with inner walls that are mostly netting, I’ve not experienced any noticeable moisture inside my tents for a long time.

I think that may be due to greater ventilation with the side entries.  I did experiment with doing away with the rear entry to gain space, reported at: https://backpackinglight.com/forums/topic/81307

There was some concern about condensation inside the rear walls without the rear entry; but it proved to be  unwarranted, and the addition of rear top vents should make it even less likely.

And please note that the conventional double wall design allows a bathtub floor to be sewn to the inner tent, while the outer fly is attached to small buckles that fit over the ends of the bendy poles that are also held in place by sleeves on the inner tent.  The conventional double wall design just appeared to work so well; as long as the solid inner ceiling could keep out water during pitching.

Please also note a clarification that my reference to lighter woven fabrics had in mind fabric woven with spectra or dyneema thread, or the like, and that should have been stated.  I think that the bias stretch on woven tent fabrics provides valuable elasticity even with polyester threads that are less elastic than nylon.

Sorry for the overdramatisizing, and am glad to hear that you both have adequate moisture control in your tents; and Geoff, that you expect your design will address those issues. In my defense, I encountered many moisture issues early on, but finally licked them, and flinch when thinking about the many times I’ve observed other backpackers shivering in the muck.

You may think that the double wall will add to much weight; but the netting to keep out pests will be there regardless, the only addition being replacing a netting ceiling with a solid one weighing ~1.13 oz over an area of less than 2.5 square yards. It will work wonders if it works.  If not, you guys can have a good laugh and some I told you so’s.

[Author]

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