Rethinking the Double-Walled Tent

[Diplomatic Mike]

That's a great looking tent Roger. I really want to buy a Warmlite tent, but lack of a vestibule keeps on stopping me. If the Warmlite tents had vestibules liks Rogers tent………

[Chris Townsend]

The Akto and Photon both have silicone nylon flysheets. The Akto is slightly bigger with a roomier porch for cooking and more stable in strong winds. Just summarising by weight is rather limiting – there are other important factors. The Akto is my favourite tent for year round Scottish use, where the weather is usually wet and windy and in summer biting midges are a big hassle. It wouldn't be my first choice for calmer, drier or more sheltered places though or for places where cooking in the porch was unwise (it's standard practice in Scotland).

Hillberg's lightest two person tent is the Nallo 2, a roomy tunnel that I carried solo the length of Norway and Sweden back before the Akto appeared. It weighs 4lb 3oz.

Hilleberg does make a tent designed for pitching with trekking poles – the single skin Rajd – but the ventilation is poor.

Generally Hilleberg tents are designed for exposed mountain camping. They're unnecessary for forest camping or dry places. I wouldn't take one to the desert SW or the High Sierra.

[Lynn Tramper]

Big Sky has to get honourable mention if we're going to consider "double tents" with mesh inner.

I would love to have a pattern of Roger's tent. I have this feeling that one of those made out of cuben fibre would be an awesome project! I really like they way the pole sleeves are designed to take the stress out of bending the CF poles. Then again, cuben is very unforgiving in terms out cutting and sewing things just perfectly (because it doesn't stretch), so may not work as well as silnylon. Even a silnylon replica of Roger's tent would be a fun project…hint hint hint.

[Roger Caffin]

I would really love to see my two designs in commercial production. REALLY! I would welcome any approaches.

Making these particular designs out of Cuban – tricky. The design details have been optimised for silnylon, and I would need to do a bit of work to make sure that Cuban could handle the localised stresses at the seams. I have tested Cuban samples and found some problems here. But just because it might be difficult doesn't mean it couldn't be done. That Cuban does not stretch – yes, that has implications as well.

The summer tent has been reproduced, with variations, by a few people. You can see their versions starting at http://www.bushwalking.org.au/FAQ/DIY_RNCTents.htm
The biggest problem for many people will be making the corners for the poles: I used a lathe and a precision tube bender. getting the RIGHT carbon fibre tubing is also tricky: there are many psuedo CF tubes out there which are totally UNsuited to the job. And some which are really a bit of an overkill.

Cheers

[Ross Bleakney]

OK, I updated my posts with Big Sky's numbers and the Nallo 2. Now, getting back to my original post, I again ask (rhetorically this time) if the standard ultralight approach makes sense. The standard ultralight approach is that while a double walled tent makes things a bit warmer (and offers other advantages which, for the moment, we will put aside) the difference in weight is too large — you are better getting a heavier sleeping bag, rather than a double walled tent (for relatively mild conditions — no snow, mild winds, infrequent rain). For most of the items on the list, I think this is true. The only items where the double walled approach might actually be warmer is maybe the Terra Nova Photon (for one person) or Stephenson's warmlite 2R (for 2).

Fully enclosed single walled single person shelters seem to range from about a pound to a pound and a half. This makes the photon only about 2 to 8 ounces more. Eight ounces more insulation in your bag with a single walled tent would probably be warmer, but I doubt two ounces would.

Similarly, if the Stephenson's Warmlite 2R is really only two pounds twelve ounces, it is quite warm for the weight. With the exception of the Refuge X, most of the two person tarp tents are about two pounds, making the Warmlite only twelve ounces more. Spread between two people, this adds only six extra ounces of insulation. This may be enough to make the single walled tent better, but I would be curious as to how often the phenomenon Will Rietveld mentioned occurs. Does it occur with various temperatures? Does it occur when it rains or when it is dry or both?

[Martin Rye]

Mike I did a walk last week with a well known TGO Challenger who had a Warmlite tent. I want one and no porch is not an issue. They cooked on a heat resistant pad in the tent in bad weather with no problems and used the door as a porch via treking poles – see the link for some pics.

http://summitandvalley.blogspot.com/2008/07/dartmoor-bloggers-gathering-unabridged.html

[Chris Townsend]

My experience is that double-wall tents are warmer than single wall ones and that double-wall tents with solid fabric inners are warmer than double-wall tents with mesh inners. But the difference is not enough to make me carry a lighter sleeping bag than with a single wall tent or a tarp. For me the big difference between double wall and single wall tents is condensation. Most of the single wall tents I've used in conditions where I would want a tent rather than a tarp have had inadequate ventilation and condensation has been copious. Those with adequate ventilation have not been wind resistant enough. The exceptions are floorless tents like the GoLite Hex 3/Shangri-La 3. However not being bug proof these aren't suitable for summer. I have yet to find a single wall tent with an attached floor that I really like.

[Ross Bleakney]

> My experience is that double-wall tents are warmer than single wall ones and that double-wall tents with solid fabric inners are warmer than double-wall tents with mesh inners. But the difference is not enough to make me carry a lighter sleeping bag than with a single wall tent or a tarp.

That makes sense (and did the other things you mentioned and they are part of the trade-offs of single versus double walled tents). The thing that was so surprising to me was the number quoted by Will Rietveld as the difference between the outside temperature and the inside of the tent: 17 degrees (F)! Now granted, that is the the high number — but if even 10 degrees is common, that would allow you to take a lighter sleeping bag. Perhaps that big a difference only occurs with really cold temperatures.

[Diplomatic Mike]

Thanks Martin.

[Franco Darioli]

Taking note of the above info is then up to us to determine what maybe the best personal solution, I cannot see how any of them will have a universal advantage over all the others.

Anyway, what I would like to know now, ROGER, the ghost that is standing inside your rear vestibule, does it have a name ?
Franco

[Roger Caffin]

> the ghost that is standing inside your rear vestibule, does it have a name
????????????????????????????

Are you talking about the photo of the inside of the tent with my wife sitting to one side? If so, what you can see there are:
1) overlaps in the no-see-um netting making two grey columns
2) a stringybark gum tree some distance away

One part of the overlap makes a mosquito seal between the two hanging door halves without the weight of a zip. The other part of the overlap is just excess width of netting which has to be there to allow me to pull the doors wide open – otherwise the corners make a slight problem. In hindsight, the excess is probably superfluous.

Or have I missed the question entirely?

Cheers

[John G]

Post by Roger Caffin:
While I do agree that you don't need a real double-skin winter tent for summer use, I will also argue that you don't need a full netting inner tent in summer either. My single-skin summer tent is fully bug-proof because there is an inner netting wall between the groundsheet and the roof at the sides and there are full netting doors at the ends. Needs to be so in Australia!

The point here is you can eliminate the netting *roof* at no penalty: the design is fully bug-proof as it stands. There are extra benefits of doing it this way: you don't have all that extra weight of the unnecessary/useless netting roof, and you get more headroom as well.
End Quote.

For summer use, I agree – the roof netting is just extra weight since I have to use the outer fly anyway because the rain is so unpredictable (the high heat causes sporadic thunderstorms even on days with clear blue skys). However, condensation isn't a problem, since the night time temperatures are way too high (75*F or more).

For late spring and early fall use though, carrying the inner mesh is easier than waking up to wipe down the condensation, and worrying if I waited long enough for the sleeping bag to dry. The inner fly gets lots of big drops of condensation all over it, because the humidity is usually around 85%.

For actual spring & fall use, the humidity is lower (maybe 65%), but the night time temperatures are lower, so even more condensation results.

[Miguel Arboleda]

Anyway, what I would like to know now, ROGER, the ghost that is standing inside your rear vestibule, does it have a name ?

Actually I had exactly the same reaction when I first saw your photo! I did a double take with the shadowy figure created by the mesh in the back.

[Franco Darioli]

Miguel can see it too, it must be real…
Franco

[Derek Goffin]

Terra Nova Laser — 3 lb. 8 oz. I dont think this is right. The Laser is sold at 1.29 kilo which I make 2 lb 13 ounces. I understood it was 7 ounces lighter than the Acto, and I know it is about 28 ounces lighter than my Nallo.

[EndoftheTrail]

The Vaude Hogan Ultralight and the smaller/lighter Hogan Ultralight I tents are two more good options — very lightweight for self-standing double wall tents. No direct experience, but they've gotten good reviews — one right here @ BPL. Check them out at vaude.com

[Ross Bleakney]

> Terra Nova Laser — 3 lb. 8 oz. I dont think this is right. The Laser is sold at 1.29 kilo which I make 2 lb 13 ounces. I understood it was 7 ounces lighter than the Acto, and I know it is about 28 ounces lighter than my Nallo. <

I don't think it is right either (now that I look at it a bit more). I'm sure how much it is though. I originally quoted the weight from prolite:
http://www.prolitegear.com/terra_nova_laser.html
They do have a different weight for "minimum weight". I'm not sure what that means. If it means leaving the fly at home, I don't think it makes sense to list it as the weight. If it means without a footprint or not counting the bag, then I think that is the proper weight. Regardless, I do think that ProLite made a mistake in their conversion — they say "Packed Weight 1.42Kg (3lbs 6 oz)" — that is wrong. If "Packed Weight" (whatever that means) is 1.42 KG, then that equals 3 pounds 2 ounces. So, it seems that at worse, the tents weighs 3 pounds 2 ounces. So,

According to Prolite:
Minimum Weight: 1.19Kg (2lbs 10 oz)
Packed Weight 1.42Kg (3lbs 2 oz)

According to Terra Nova Web Site:
Minimum Weight: 1.19Kg (2lbs 10 oz)
Packed Weight 1.38Kg (3lbs 1 oz)

Since the Terra Nova minimum weight was verified by Prolite, I'll assume their "packed weight" is accurate as well. I probably shouldn't have posted any weights (since it is reinventing the wheel and opened the possibilities of inaccuracies). So, I updated my post to point to the list of double walled tents (which has all the tents mentioned).

[Martin Rye]

I own a Terra Nova Laser and use lighter guy lines and mini line-loks and total weight 1350kg total. It is a light and large tent for one with more usable porch space than an Akto.

In the damp UK the solid inner offers protection from condensation and I have measured several degrees of warmth in the Inner compared to the porch or outside.

[Richard Mueller]

Ben,

Have you tried just using the mesh inner tent without the fly when dew has formed at night? I'm wondering when there is going to be dew at night if just the mesh inner tent keeps the dew out or if you have to use the fly when there is going to be dew to keep the dew off your sleeping bag and inside the tent? Any thoughts or experience on this would be helpful.

[Roger Caffin]

Dew forms when the moisture in the air touches something which is cooler than the critical temperature. This (dew) temperature may be only a few degrees cooler than the surrounding air.

A mesh inner will not stop the moisture in the air from entering the tent, so it can (and will) condense on anything cool. Now, this may not include the outside of your sleeping bag: one would expect that to be a few degrees warmer than the surrounding air. But it certainly could condense on the mesh tent itself, as the fabric can easily cool a few degrees below the ambient.

This is why a good tent, and especially a double-skin tent with a fabric inner, is so useful in humid conditions. Your body heat keeps the inside just that little bit warmer, which helps to limit the amount of condensation. It bottles up warm air. A tarp on the other hand cannot do this, and it therefore very susceptible to condensation.

Cheers

[EndoftheTrail]

Absent the fly, if dew will form, it will most likely form on the cold tent floor around you — not on your bag (as Roger explained above) — and also not on the mesh itself — as the mesh will likely be at the same temperature as the circulating air.

With tent fly deployed, if dew will form, your presence will warm the air around you and "push out" the formation of condensation onto the underside of the fly — and safely away from the inner. This is more likely when the dew point is "right" and when there is insufficient breeze to circulate out the moisture. The combination of inner tent (even an all mesh one) and separate outer tent (fly) does a pretty good job keeping the inner condensation free. Depending on conditions, of course, but more often than not, I find the underside of my tent fly bone dry as well.

[Tim Marshall]

I'm not sure i agree with the idea that mesh won't hold warm air in the tent. Roger, on your site you state that you don't use noseeum mesh in your tens and i think that may be what has lead you to that conclusion. However noseeum mesh doesn't breathe that great. In fact tents using that mesh are always hotter inside (even with no fly) than it is outside. My bug bivy is almost too hot sometimes. With that said i have little to no experience with condensation using the shelter without a fly, but it has been my experience that noseeum mesh will trap air pretty well.

-Tim

[EndoftheTrail]

Agree, and adding to what Tim wrote above…

A "solid" fabric only looks and feels solid to us. To air molecules, it may as well be completely full of countless giant gaping holes. Noseeum mesh, of course, will be even more so. We are therefore talking about a difference in degrees.

An "all mesh" inner tent with fly deployed does indeed block winds (the great majority) and trap warmth — and thus function the way we expect a "double wall" tent to function in most all three-season conditions.

A fabric inner will block winds and trap warmth in a still greater degree than an all-mesh inner. That can be a very good thing in the "right" condition — or it can make for an unecessarily warm/stifling inner tent.

Having used both mesh and fabric inners — for most all three season use — except at places with blowing sands — my preference is mesh over solid fabric. When using solid fabric inner — I like multiple zippable/closable windows to promote cross-flow and hi-low venting when desired.

[Roger Caffin]

Hi Tim

> Roger, on your site you state that you don't use noseeum mesh in your tens
Keeping ALL the FAQ up to date is a problem. The couple of photos I included here recently did actually show no-see-um mesh. (They were the 'legs' photos.)

I agree that some no-see-um meshes breathe less than others. As Ben said, it is all a matter of degree.

Cheers

[Tim Marshall]

is there a way to find the no-see-um mesh that breaths the most without buying it from every supplier to test?

-Tim

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