Tunnel Tents Tutorial and State of the Market Report – Part 2: Details and Commercial Models

[David Drake]

Roger, would you say the primary purpose of the double fabric wall in winter is structure or insulation? Are both about equal? If insulation, why is a double wall better than an equivalent weight in extra sleeping bag/quilt insulation?

Obviously the double wall is important for severe winter weather, just curious as to why.

[Josh Leavitt]

Details of the bet: After a fine string of literary gems from BPL, I quiped to some one else in the industry that this "state of the market report" was nothing more than a product launch. I was then called paranoid and a few other things. So I said that I could prove it, and the bet was made. "so roger, you are cool with me building your tent, right?" Was a nice one liner as it was dual purposed.

No rodger you do not get a cut. I will how ever be sending you a bill for advertising stunts. Dont worry BPL readers, my services are not dependant on products being sold.

Are we going to see some content between the commercials over here, its getting pretty stagnant.

[Mary D]

Josh, folks around here have wanted to get hold of one of Roger's homemade tents for years (or at least for the 6 years since I started lurking on this site)! If this SOTM report manages to get them into production for those who've been salivating all this time, so much the better!

And if it doesn't, maybe it will at least encourage folks to at least consider tunnel tents and, perhaps, persuade some overseas manufacturers to sell some in the US. Or maybe some of our wonderful "cottage" manufacturers will come up with one!

[Roger Caffin]

Hi David

> the primary purpose of the double fabric wall in winter is structure or insulation?
Well, my single skin tunnel tent has a bathtub groundsheet anchored to the fly via netting, so I think I could say that it has essentially the same techncial structure as my double-skin winter tent.

That leaves insulation. Yes, the inner tent does provide some insulation, in several ways:
* The wind-resistent fabric blocks cold wind from blowing across my face and my quilt. I think this is a very significant benefit.
* The DWR-treated inner tent can block condensation falling off the fly from hitting my quilt: it runs down the outside of the inner tent.
* The wind-resistent inner tent blocks spindrift from reaching me, my quilt and my gear.

> why is a double wall better than an equivalent weight in extra sleeping bag/quilt insulation?
The latter two reasons above answer that one. It's about preventing moisture from reaching my gear.

Cheers

[Bjørn Grenness]

Being Scandinavian I have grown up with tunnel tents. I have always wondered why Americans prefer geodesic tents. The weather is more extreme in many parts of the US than in Norway. Nearby all Norwegian explorers uses tunnel tents on trips to the Arctic and Antarctic, and in the mountains at home. American interest in ultra light backpacking is also strange (Ok, it's what this forum is about). Sturdiness and the ability to cope with extreme weather are essential, especially fore tents.

I find Coffin's two article about tunnel tents interesting. It’s impressing that Coffin has made the two MYOG-tents himself, but I can not quite understand the belief that his design is revolutionary. The weight and space is impressive, but it’s also easy to spot weakness of the construction.

If you look at the two pictures of Confin's tent covered with snow its apparent that the design is not well suited for snow. My Helsport- and Hilleberg tent’s would had none problems with that amount of snow. Of course it’s possible that the tents were not well pinched. But fore me the design look not well balanced.

It's also nearby impossible to pinch a tent alone in strong winds with the “American” system of pole feet and eyelets, compared with “Scandinavian” design with webbing and ladder lock. OK! It’s heavier.

Sorry fore being critical, but I really think that many commercial tent producers do a better job than MYOG-entrepreneurs.

[Roger Caffin]

Hi Josh

> I quiped to some one else in the industry that this "state of the market report" was
> nothing more than a product launch.
Splat. No joy. Me, I think you lost the bet.

For those curious as to the origin of these articles, let me explain. Early in 2011 Will Rietveld, who was at that stage the Senior Editor for Gear Testing, suggested to me that I write a Survey and Tutorial on Tunnel Tents. This arose from an internal discussion about a pop-up tent a few of us were having. I agreed. Will organised most of the tents. I started testing and writing. The articles were delayed by a hard diks crash, but eventually got back on track.

My comment about discussions with a gear manufacturer seem to have been misunderstood. For a start, let me make one thing very clear, by quoting from the email sent to me on 12-Apr-2012 by the gear manufacturer:
"I just read your article in BPL and that prompted me to write."
This refers to Part 1 of this series. I started work on this series of article early in 2011 – around March I think. A year ago.

Sorry Josh, but if you were betting on it being a product launch, I think you lost the bet.

Cheers

[Roger Caffin]

Hi Bjørn

> I can not quite understand the belief that his design is revolutionary.
I don't think I suggested that anywhere. Before making my own I had a Macpac Olympus for many years, and I think that was clearly stated in the articles.

In fact, I find the whole idea of 'revolutionary designs' fairly silly. Most good gear designs are quite old; it's usually the 'new revolutionary designs' which turn out to be market failures. New materials – yes, and sometimes they lead significant technical improvements.

About the only market segment I can think of where new designs are significant improvements over things available 50 – 100 years ago are small canister stoves. And much of these improvements are due to technology. Oh well, that and we did not have those canisters (or that fuel) 100 years ago!

> two pictures of Confin's tent covered with snow its apparent that the design is not
> well suited for snow.
There are quite a few pictures of 'my tent' in the snow. Which ones did you have in mind?
Readers might bear in mind that we have spent many nights in the snow with our tents, and taken a lot of bad weather, and slept well.

> It's also nearby impossible to pinch a tent alone in strong winds with the
> “American” system of pole feet and eyelets, compared with “Scandinavian” design
> with webbing and ladder lock.
I am confused here. My tents and several from other countries around the world all use 'pole feet and eyelets', so I don't this is in any way an 'American' system.
And I have always managed to pitch my tent single-handed in bad weather.

Cheers

[Bjørn Grenness]

Hi Roger!
>I don't think I suggested that anywhere. Before making my own I had a Macpac Olympus for many years, and I think that was clearly stated in the articles .In fact, I find the whole idea of 'revolutionary designs' fairly silly.

No, you did not. But it seems to me that many of the positive comments on this Forum suggest so. I agree with your comments on `revolutionary designs`.

>There are quite a few pictures of 'my tent' in the snow. Which ones did you have in mind?
I think of the two pictures in the article were the snow covers the tent. Your tent is bending down, and the fabric is not stretched out properly. Of course it can be bad pitching.

>I am confused here. My tents and several from other countries around the world all use 'pole feet and eyelets', so I don't this is in any way an 'American' system.
And I have always managed to pitch my tent single-handed in bad weather.

The use of the terminology "American" and "Scandinavian" design is of course not the point. None of the "Scandinavian" tentmakers uses 'pole feet and eyelets': I used "American" because I don't know any American tent-maker who uses webbing and ladder lock.

My main point is that it’s easier to raise a tent in storm alone (metrological storm, 9-10 on Baufort`s scale) with the "Scandinavian"-design.

[Roger Caffin]

> I think of the two pictures in the article were the snow covers the tent. Your tent
> is bending down, and the fabric is not stretched out properly. Of course it can be
> bad pitching.
Ah – I think that the photos were of my (commercial) Macpac Olympus tent in heavy snow. Yes, they had got a bit slack during the night. They were taken a very long time ago, when I was maybe a bit less careful. In one case the tent was pitched in quite hot weather in the evening, and it suddenly snowed overnight. The cold weather made the nylon fabric expand, so the tent slackened off a bit.

"American" and "Scandinavian"
OK, understood. However, I must say that the pole foot and eyelet design works very well if done correctly. I have never had any problem with the pole foot slipping out. And it is lighter.

> My main point is that it’s easier to raise a tent in storm alone (metrological storm,
> 9-10 on Baufort`s scale) with the "Scandinavian"-design.
I will simply disagree here. I've tried both pole designs during our testing, and found no difference. It may be slightly easier when one end of the pole sleeve is closed, if you are on the right side of the tent.

Cheers

[Josh Leavitt]

rodger

So when they asked you if they could build your tent, you gave them an answer? Interesting……I'll ask again, so rogder its cool if I build your tent right?

Given the particulars of the bet, I still won, its not being contested. No where did we discuss time frame and intent. It became a defact product launch, by intent, manipulation or otherwise. Given current details, and my supposed interest in the design, I'm very interested to see how this actually plays out. New bets wagered.

[Roger Caffin]

Hi Josh

It's a free world.

> New bets wagered.
Details? I am – we all are, curious.

Cheers

[Derek Goffin]

As no-one else is saying it I feel I must. Josh if as a small manufacturer you made money out of playing games with the enthusiasm of your potential clients, deceiving them. I hope it was a lot or it will not have been worth it

[Stuart Murphy]

I don't thing Josh is contributing anything useful to this particular thread through what appears to be making ambiguous and disparaging comments about Roger.

Josh, if you have a point to make come out and say it.

[James Marco]

Hi all,
I was examining some of the engineering stuff with tunnel tents (not my usual forte.)
One of the things that seems to jump out at me is the loading on the poles.

As Roger said, the loading needs to be symetrical around the poles. In one section he wrote that the failure modes usually occured on the sides of the tent, though. And I agree that sleeves are inherantly stronger than clips for this reason.

I would submit that a tapered pole may better withstand this pressure. With Rogers poles he simply uses the same diameter arrow shafts. The taper could be approximated using two different diameter poles. One smaller size for the top 33-50% of the curve. It has low live wind loads and static loads from materials. The sides need more strength to support averything above it and takes up the brunt of the wind.

I noticed that the pole connections could be interlocked much as they are in fishing rods where curves are quite important to the perfrmance of a flyfishing rod. In a flyfishing rod, maintaing a fairly smooth arc between the butt and tip results in the best transferance of casting energy to the line hence quite a bit of effort has been expended in pole design, and joint function wich can be reused to our benefit. From the perspective of a tunnel tent (with no snow/ice load, of course.) it appers that the actual static stress on the hoop is almost all tension (Well…aproaching infinity as the angle goes to 180" with the wind) as we go to the top. Only as the tent deforms under wind loads does it pick up any other stresses. A stiffer pole on the sides should mostly prevent that… By guess and by gosh, it looks like about 1/2" at the bottom to about 3/16" at the top (given the changing slope.)

Sort'a thinking out loud…

Anyway, I would suggest you contact a couple rod manufacturors and see if such a pole is possible, and the cost of placing joints every 12-15" around the perimiter. Probably a bit lighter anyway. And, it would do away with internal guys, simplifying things, even if there was no weight savings.

[Roger Caffin]

Hi James

With all respect, I think you may be over-analysing this one. My reason for saying so is that the loading on the poles varies a huge amount, depending on the weather and how the guys are set. There is no single situation.

Strong sideways wind: high sideways loading from the fabric to the poles, but properly set guys take a lot of this load. However, if the tent moves, then there is a fair bit of variation in stress at the top of the poles.

Snow loading: high sideways loading, but in the opposite direction, bulging the poles outwards and taking stress off the middle section. Here you need the horizontal internal guys.

> it appears that the actual static stress on the hoop is almost all tension
Not so. There will be high stress on the outer part of the pole, but there will be roughly equal (matching) compression on the inner part of the pole. 'Outer' means on the outside of the curve, 'inner' means on the inside of the curve. However, if you look at the failure modes of wrapped poles and pultruded poles, you find different things. Here the structure of the pole itself comes into play.

Pultruded poles split full length when bent. This is because the plastic or epoxy holding all the fibres together fails down the middle. It is actually quite weak. But it means that the compressive forces are very significant, and this translates into a high shear force on the epoxy.

Wrapped poles fail with an abrupt break at right angles, when the fibres on the very outer face fail in tension. The shear forces are handled by the 2D wrapping.

I have had poles fail at the top of the arch and half way down the sides. Yes, both positions – but under different conditions.

Hope this helps!
Cheers

[Simon Gunn]

Enjoying the articles Roger, looking forward to part three as I have been procrastinating about which tunnel tent for some.

A couple of points which may need to be checked:

* I think you may have included the pegs in the weight of the Nallo 2. 2.3kg should be with all the bells and whistles.

* I haven’t been able to see the Macpac Olympus model first hand like the Hilleberg’s. But from what I have seen on the web the latest model’s dimensions don’t match what you have listed. It looks wider (1350mm) and has a sloped inner at the rear which would (I expect) cut down on the usable space from the full 2200mm groundsheet length. Are you refering to an older Olympus model or are their web descriptions off?

You seem a bit sceptical of the larger tunnel designs (which are on my shopping list). Do you have any specific reasons as to why? I had noticed that the pole span of a Hilleberg Keron 4, Nallo 4 and Kaitum 3 is quite different to a Keron 3 or Nallo 2. The bigger tents are larger but don’t have the same near vertical walls of the smaller tents as the pole has a flatter curve more like a ‘pop-up’. I had seen that useable space might be less per person in these larger models but hadn’t thought that would affect performance. Any thoughts?

[Roman Vazhnov]

Just for the record – there is new interesting 3-person Helsport model for 2012:
Helsport Fjellheimen Superlight 3 Camp

[Jason Elsworth]

Thanks Roman. Hilleberg now have a video on the Anjan http://www.hilleberg.com/home/products/anjan/anjan3.php.

[Roger Caffin]

Hi Simon

Nallo wt: the weight of the fabric always varies, and that makes the tent wt vary. Happens to everyone, and well-known. Listed wt is without stakes.

Olympus Sitting Space: yes, typo, being fixed. It should be 200×110. The width shown is an approximation overall. The widest bit is more like 120 cm, but the ends are narrower. Let's just say the sitting space is quite adequate for two. The 135 cm is across pole feet, which is of course even wider.

Larger tunnels – probably OK in many cases. The problem is how do you get increased width without either a) increased height, or b) a flat top, or c) sloping sides. So imho the 2-man size is about optimal for stability. But if you really need a 3-man tent, then look at the Hilleberg ones. You might note however that Macpac, who REALLY do know tunnel tents and extreme weather, don't make a 3-man Olympus.

What to buy? That *really* depends on what sort of use you are planning.

Cheers
Roger Caffin

[Roger Caffin]

Hi Roman

I would have loved to have included the Helsport Rondane Light, but they were not interested in the USA market.

Cheers

[J C]

Fibraplex have recently listed new pole designs, one of which is for the Hilleberg Soulo, which is advertised as having a pre-curved middle short pole. Now maybe they are using some sort of Aluminium join as you do, but it doesn't sound that way.

I've never understood why you couldn't make a CF pole around a curved metal mandrel of constant radius. You would still be able to slide the forming mandrel out.

http://www.fibraplex.com/tentpoles2B.asp

[Roger Caffin]

Hi Jeremy

They may be using an aluminium centre section with lots of curvature.

> why you couldn't make a CF pole around a curved metal mandrel of constant radius
You could … IF (and only IF) you could find a mandrel of absolutely CONSTANT curvature and CONSTANT cross-section – to within microns.

Cheers

[Stuart Murphy]

I don't know how it's laid up etc. but from looking at bicycles it is obvious that carbon can be fashioned in all kinds of shapes including curves for forks.

The fact that nobody seems to have bothered for tent poles is probably a function of economics and market demand rather than the material/technology as such.

Is there something I'm missing here?

Cheers
Stuart

[James Marco]

Yeah, you can certanly bend carbon. In fact, they could probably be made a bit lighter with a known finished radius in mind. Mostly, the material will shrink slightly when curing. This would eliminate some of the internal compression that contributes to the failure mode. So, really, the only problem would be extracting the mandrel evenly at the end…perhaps with some rollers. It might be easier to simply use a slightly larger form of heavy wax, then melting it out when you were done with the preliminary curing. Several methodes that could be used that I can think of, so, yeah, the reason it is not done must be economic.

[Rakesh Malik]

"I don't know how it's laid up etc. but from looking at bicycles it is obvious that carbon can be fashioned in all kinds of shapes including curves for forks. "

I had the same thought while reading this thread, because my road bike has a carbon fiber monocoque body.

It's probably economics. Carbon fiber bike frames are quite a bit more expensive than steel and aluminum, and even titanium frames, and I'm sure that manufacturing cost accounts for a significant part of the difference.

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