When Things Go Wrong

[Addie Bedford]

Companion forum thread to:

When Things Go Wrong

[Lynn Tramper]

Thanks for the thorough reply Roger. Like half of us on this site, we would just LOVE for a production model of your version 10 or version 11 or whatever version you are up to . Like the other half of us, I would also love to get a pattern for MYOG to play around with, eg, cuben. Maybe you and BPL could come to some arrangement!

That aside, I am thinking about making poles like yours to replace my Nallo poles. How are the pole angles joined together, and what is the angle? How do you insert them (fully assembled before sliding into the sleeve)?

[Roger Caffin]

Hi Allison

Yes, I am afraid my replies on some subjects tend to be lengthy… :-)

The carbon fibre poles may flex but cannot be bent permanently. So the bends are done via the joiners: they have bends in them. The angle is about 28 degrees.

Could you do this to a Nallo? I don't think it would work as the end bells will be the wrong shape. There would be lots of slack and creases.

Yes, the poles are first extended and then threaded into the sleeves. It isn't hard – that's how the Olympus and other Macpac tents work of course. Sleeving the poles makes the tent a lot more storm-proof.

I have not tried making this sort of tent out of Cuben fabric. Silnylon is quite elastic, while Cuben is not. I have some reservations about how well the design would take the rigid fabric, given the inevitable slight wanders in sewing along the seams. It can be done with a cat tarp I know, but … an expensive test.

Pattern – email me direct. [email protected]
See also http://www.bushwalking.org.au/FAQ/DIY_RNCTents.htm

Production version – yeah, my dream too!
Winter tent is V5b; summer tent is V10.

Cheers

[Lynn Tramper]

Thanks again for the thoughtful reply :) I really appreciate the lengthy ones!

I agree RE: cuben limitations. I wonder if there is a cheaper 'rigid' fabric I could do a mock-up with?

>Could you do this to a Nallo? I don't think it would work as the end bells will be the wrong shape. There would be lots of slack and creases.

What do you mean by "end bell"? Do you mean the joiners wouldn't work well in the Nallo sleeve (too narrow, too wide, wrong shape…)?

>So the bends are done via the joiners

On your website, you state "At present I make my own bends out of stainless steel tubing". Has the availability of pre-made bends changed (eg Fibraplex custom)? Or is this still the biggest limitation to making a Caffin tent?

>Sleeving the poles makes the tent a lot more storm-proof

Agreed again. This is one of the advantages of yours and the Nallo design IMHO, but the flex needed to use a continuous CF pole on the Nallo is too great, as I'm sure you know. Sleeved poles on the fly also allow you (in theory) to use the fly and inner separately, or to pitch and remove the inner with the fly still protecting you and the inner tent from rain. I used this feature a lot on the older MacPac tunnel tents, but it seems they no longer have this option :(

Thanks again for your knowledgeable replys.

[Rog Tallbloke]

> I wonder if there is a cheaper 'rigid' fabric I could do a mock-up with?

Tyvek?

[Lynn Tramper]

TYVEK!! Great idea Roger. Cheers :)

[David Ure]

nm

[Lynn Tramper]

Heavens no, no one (I think) is saying that those tents are inferior to tunnel tents. Quite the opposite in some ways. It's more a question of efficiency in terms of weight. The Soulo is a one person tent, and the 2-person Staika is almost twice as heavy as Roger's tent or the Nallo2.

[David Ure]

nm

[Rog Tallbloke]

> TYVEK!! Great idea Roger. Cheers :)

Welcome. :-)

Added advantage is you can use tape or glue and peel it apart for adjustments until you get a suitable shape.

I'm thinking of having a go at a tyvek tent with some complex curves in, and without a suitable computer program to work out the shapes, this seems to be the way to go. Now if I could just find a suitable glue which won't clog the needle come stitching time, I'd have built in seam seals too!

[Roger Caffin]

Hi David

There are three different conditions to consider:
Heavy snow fall (downwards force)
Strong wind (sideways force)
Heavy snow and strong wind (multiple forces)

The poles on the Soulo are much longer than on a tunnel tent: this inherently makes them easier to bend, buckle and collapse. However, they are 9 mm diameter – rather large. Also, the sides are much more 'wall-like' which makes them more susceptible to a wind. Granted, we are talking about extreme conditions here. As a solo tent it still weighs 2.1 kg – heavy!

The Staika has 10 mm poles! Blimey! I guess it will take a bit of snow, and wind, if well-guyed. It does weigh 3.7 kg too!

Both of these tents will have significant problems in bad weather, when the spindrift is flying. They have large holes in the roof, and the snow WILL come in there to land on the roof of the inner tent and filter down the sides, pushing them inwards. This would also be a problem with flying rain.

Yes, these are both good solid tents. But they are not designed for the worst conditions. And I suspect that Hilleberg would have no problem with my comments.

For reference: my summer 2-man tent with full insect proofing and groundsheet weighs 1.26 kg. My 2-man winter tent weighs 1.8 kg. The carbon fibre poles are 7.5 mm OD. So lighter weight with full storm-management is possible, in principle. Getting it is another matter.

Cheers

[Roger Caffin]

Hi Roger T

> Now if I could just find a suitable glue which won't clog the needle come stitching time, I'd have built in seam seals too!
When you do, let me know! I have not found anything yet, and a gummed-up needle is a right pain!
You could try using an oiler – that would probably work.

Cheers

[Rog Tallbloke]

Hi Roger C,
Do you mean a device for oiling the thread/needle on the sewing machine?

Regarding your cf poles: fo you put some sort of strengthening ferrule on the ends to prevent damage from the angled ss jointing pieces?

[Roger Caffin]

> a device for oiling the thread/needle on the sewing machine?
Yes. You can get them for commercial high-speed machines where the needle can otherwise get a bit hot … and melt the thread.

> cf poles: do you put some sort of strengthening ferrule on the ends to prevent damage from the angled ss jointing pieces?
The tubing I use is not pultruded kite stuff which splits easily (eg Avia). It is 5-layer bidirectional wound CF tube meant for high-impact arrow shafts. That means there are 2 complete layers of winding around the tube, and that is pretty strong. In addition, the CF thread is less stretchy than an Al ferrule so a ferrule would not add much to the circumferential strength.

However, the very end of the CF tube is susceptible to localised stress and impact damage under extreme conditions. I have known a pole break at the end when the user did not fully insert the SS joiner.
.

.
Let me hasten to add that I have a handful of aluminium tent poles which show exactly the same damage – I got them from a gear shop as scrap. You can break anything if you try!

So it can make sense to add a very high tensile aluminium ferrule around the end of the CF tube in some cases, to prevent incidental damage. I have done this for my winter tent using 8-10 mm lengths of snug-fitting Easton arrow shaft 7075 T9 tubing and high-strength epoxy. (Yeah, lucky to get such a good match in sizes.)
On my summer tent I do not use external ferrules as they don't get such harsh weather..

Cheers

[Rog Tallbloke]

Thanks for the info, and correcting my typo. :o)

I'm using gold club shafts for my A frame setup on my GG spinnshelter. I don't know what the construction details are, but I'm looking for some alloy tube of the right diameter to slip inside as my joint piece goes over the outside.

[Roger Caffin]

Hi Rog T

> I'm looking for some alloy tube of the right diameter to slip inside as my joint piece goes over the outside.

Exact internal diameter? I may be able to offer suggestions.

Cheers

[Rog Tallbloke]

I'll bring my verniers home from work monday to measure it.

How about this for a bargain. Arrived this morning. An old 'Peapod' made by Ultimate Equipment in Halifax, UK many moons ago, only done one night outdoors. £30. Total weight inc bags, pegs , poles and all is 5lb 11oz. Not too bad for a properly stormworthy and warm winter tent for two.

Some of Rogers arrow shafts and joiners might get the pole weight down a bit from the rather hefty 1lb 2oz solid fibreglass set which came as standard.

On the subject of the relative stormworthiness of domes vs tunnels, this article and the video it contains graphically demonstrate the point about tunnels deforming to shed the wind while geodesics just get blown away.

http://www.outdoorsmagic.com/news/article/mps/uan/5054

[Roger Caffin]

Hi Rog T

Nice looking tent, especially for £30. Lots of guy rope attachments too. Weight – yeah.

> Some of Rogers arrow shafts and joiners might get the pole weight down a bit from the rather hefty 1lb 2oz solid fibreglass set which came as standard.

Um – I would need to know what the radius of curvature is for the front and rear poles. It is possible to do some quite alarming things with Easton poles by giving them a 'prebend', but you can NOT do that to CF tubing. It is straight! In this case I suspect that the radius of curvature would be too small for straight CF by itself, but Easton poles might take enough prebend.

Short segments of CF with several bend-joiners? Maybe. Not sure how it would look, but not impossible.

Btw: Fantastic video! Thanks.

Cheers
Roger

[Rog Tallbloke]

Hi Roger C,
Thanks for that. I was considering a combination of prebends for the tight radius at the rear, and attempting a shape similar to your tents for the front in cf.

The costs are a bit high though. I'll test the old nylon first to check it's worth it. The PU proofing seems good though, and these were 5000mm head fly and floor on strong nylon – hence the weight. It'll probably get used for motorcycle camping mostly so weight isn't that much of an issue anyway.

The video is awesome isn't it. :-)

[Chris Townsend]

Roger T, I'm surprised any of the old Peapods are still around! Versions were made with aluminum poles so you should be able to get Eastons or equivalent poles and ditch the fiber-glass. It was a great tent in its day and the weight is pretty reasonable.

I remember one problem with the Peapods was that the long unsupported sides deformed in strong winds and heavy snow. Adding long guylines to the apex of the poles and pegging them out in line with the tent helped reduce this problem by pulling the poles against each other.

[ROBERT TANGEN]

Re: "On the subject of the relative stormworthiness of domes vs tunnels, this article and the video it contains graphically demonstrate the point about tunnels deforming to shed the wind while geodesics just get blown away."

I have a question. I am not an expert, and I do not know the answer to the question, but why do videos of Everest's South Col (about 26,000 feet and a natural wind tunnel) show ONLY Buckminster Fuller-type geodesic domes such as the VE25, and ZERO tunnel tents?

[Rog Tallbloke]

The VE25 is twice the weight of my Peapod, with slightly more innertent floor area, though more useable height for sitting in.

Geodesics start to make more sense weightwise for bigger tents designed for more people. Their hexagonal shape sheds the wind equally from any direction, and with plenty of snow built up around the skirt on the fly, they are rock solid. So for everest expeditions, they have the edge on the ledge.

For wet moorlands and mountains though, poor peg grip and an unyeiding skeleton on a tall design with steep lower sides can combine to work against stability in high winds.

In these circumstances, a tunnel pitched tail to the wind is a better proposition weight for weight. The very light geodesics and semi geodesics such as the TNF Tadpole are vulnerable to storm force winds in my opinion, because the extra pole lenth can get distorted into shapes that snap them.

[Lynn Tramper]

>a tunnel pitched tail to the wind is a better proposition weight for weight

Yes, it still comes down to weight rather than strength. On Everest they have sherpas to carry whatever their little hearts desire (and can afford), in which case a heavier geodesic is wonderful to sit around in and wait out a storm. For ULers, by definition weight becomes at least as important as strength, so tunnels are a good compromise.

My Tadpole was the sturdiest little tent I ever owned. I would call it virtually bombproof really. This in spite of the flat roof which collected water and snow (the tent could handle the weight) and that is was claustrophobic! Oh yeah, and it flew like a kite if you didn't anchor it down 100% Of course, it's nearly 20 years old now, and I don't know if they are as sturdy as they used to be…

There was a women here in NZ who was killed a couple of years ago in strom winds. I think she was sleeping in a dome tent that was caught in a gust and rolled her to her death. At least a tunnel tent is more likely to collapse before you get blown away.

[Roger Caffin]

Hi Robert

On a more technical note, we distinguish (rather roughly) between 'domes' and 'geodesics' by counting the number of poles. A dome may have 2 -3 poles, while a geodesic often has 5 – 7 poles – and these are often made from larger diameter tubes as well. You can imagine the increased strength coming from all the extra poles! And, of course, the increased weight.

The other half of the story is as others have indicated: porters to carry the loads and having space for larger numbers of people.

But we are Ulers!

Cheers

[Ross Bleakney]

I think that is the key.
"a geodesic often has 5 – 7 poles."
Exactly. The funny thing is, even at 7 poles, a tent maker has too few poles. If you look at "real" geodesic domes (e. g. http://www.desertdomes.com/domecalc.html) the simplest design, a 1V, has 11 poles. But this design is not ideal. A better design would at least a 2V, with its thirty five poles. As you get more poles, you increase strength. A geodesic dome gets stronger as it gets bigger. That's why building really big domes (Epcot, etc.) make a lot of sense. Fuller even envisioned huge domes (http://en.wikipedia.org/wiki/Cloud_nine_(Tensegrity_sphere)) which could float in the air.

The other thing I remember Fuller saying is that right now (in our time) tensile strength is much stronger than compression strength. Ultralighters know this well. Modern advances in (carbon fiber) poles haven't kept up with the strength of cords. Poles are just too heavy. Which is why, as you have said, it only makes sense if you are building a really big tent.

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