West of Virihaure - the shelter

During my hike north and west of the Virihaure I used a brand new shelter. A homemade combination of innertent/bugtent and rain fly. Cuben fiber was the main ingredient and the weight was astonishingly low.  So, how did I make it and how did it work?

By Jörgen Johansson

The construction was simple, I have used it before in a silnylon shelter that I made in 2004. It became my shelter for a 500 kilometer three week hike from Hemavan to Nikkaluokta, through some of the most spectacular parts of the Swedish mountain range.

The silnylon shelter made in 2004. Here in nice-weather-mode with elongated poles and plenty of space for ventilation around the bottom of the fly. Inside the ripstop combination of innertent and bivy (tight like a bivy from thighs and downward, spacious as a tent around the upper body).
Since then I have used a number of commercial shelters, but actually none that I have felt as confident about in really windy weather.
The shelter is basically a ridge tent employing two poles, one at each end and one longer than the other. It is a variant of my very first tent bought in 1969, a Fjällräven G66.
My original G66 on the West Coast Trail, Vancouver Island.
This tent-model is till used in the Golite Shangrila 1. I have wintered snowstorms in the original model from Fjällräven, not to mention numerous other instances of rough weather in many places so I know that the construction is very storm proof, providing the material stands up.

So it has been growing on me to see how light a tent like this I could make. And given the positive experiences many others have had with Cuben fiber this seemed the place to go. Calculations showed a tent like what I had in mind could be pretty light...

Said and done; I read up a bit and found that some sources advocated both taping, gluing and sewing for joining pieces of Cuben. Sometimes all three at the same time. The nearest source of Cuben was http://www.extremtextil.de/ and they also had a tape for the material. It also turned out they had Cuben that was "light olive-brown" which really sounded nice compared to the usual Gladpak. Unfortunately they were just 0,4 meters short of what I needed when I ordered, so I resigned to being "the man from Glad". Seing no reason for anthing else I ordered the lightest Cuben they had at 21 grams/sqm, which was pretty close to half the weight of the silnylon I had used in 2004.
First night out on the mountain
While practising working with Cuben I made a pair of rain pants for my son, which I have written about elsewhere. I found out that it was fairly easy to work with the tape. You take sections of 200-300 mm or you will just end up in a tangle like Donald Duck. That is really all there is to it. The impression of the tape is that it really bonds securely and it showed no tendency of failing anywhere on the first trip.

Cutting the Cuben with my regular silnylon cutting method (soldering iron and a steel ruler on the stainless kitchen bench) turned out to work very well. I was also impressed by the resiliency and apparent strenght of the Cuben. It gives the impression of being even more durable than silnylon which gave me renewed confidence in the shelter I was building.

I had planned to both sew and tape the seams, but sewing through the gluey mess of the tape proved difficult. The needle got all covered in sticky film and the stitching was failing. Since the seams felt very solid only taped I just sewed the seams in some places where the strain would be greatest, i.e the tops where the poles went through and around the perimeter of the reinforcement patches. The bottom seam around the lower perimeter of the tent was just that; a seam. I just folded it and sewed. That was all very easy. More tedious was cutting small pieces of tape to cover the triangles of ripstop nylon I used at stress points to reinforce. In retrospect maybe sturdier Cuben would have been better for this and glue would have been faster.

Some details:

Showing the taped and sewn triangular reinforcement patch for the guyline. One of the green polyester bands I used for loops came off the last night. Has never happended to me before, inspite of sewing a lot of loops like that. Shoddy work.
The zipper was just taped in place and a reinforcment patch was added. A seam across the zipper there acted as a stopper.
Reinforcements and a grommet plus attachment of top line. There should have been an extra patch cordura on the inside, which I forgot. Could have become something I would have regretted...
Inside view of the pole at the low end.
Inner-tent or bug-tent with Cuben bottom, black ripstop sides for wind-protection and the rest noseeum-mesh. Note the small 'window' of mesh with a velcro-fastened flap of ripstop on the inside to give me a view while lying down. There was plenty of space to cook beside my bed with the fly completely closed. Something I appreciated since mornings and evenings where cold.
The innertent in action on the tundra. Pads and sleeping bag are sticking out of the lower part. The weather was too cold for insects, but since it was so cold I used the innertent anyway for added warmth. For a straight fall trip when absence of all bugs would have been a certainty I would have skipped the innertent completely and brought a warmer sleeping bag.
The biggest failure was that the grommet at the high end of the tent was coming loose on the last evening. I taped it best as I could with duct tape; no passer-by would have been impressed. The tape did not stick very well, which it is supposed to do on Cuben (but not on silnylon). My guess is that it was too cold. I tied the cord securely around the pole on the inside and pulled it through the hole. This might have held up in bad weather. Luckily the wind that night (as well as all nights) was modest.
The grommet at the low end was reasonably OK, but I used the same method and attached the line to the pole on the inside. This grommet failure makes it pretty evident that version 1.1 of my shelter would not have stood up to a storm. In fact I had no hard winds (per definition over 13,9 m/s or 50 km/h) as far as I could judge (no wind-meter but an allergy towards people using the word 'storm' when their hair ruffles).
To sum it all up my shelter worked reasonably well. Obiviously I will have to look at another way of attaching poles and lines. I am thinking of some sort of cross-grain 'harness' on the inside. Next season...

I had not succeded in measuring all the parts well, which made it a bit difficult to get good tension all over the fabric when pitching. This was mostly due to some brain-failure on my part which made the tent end up a bit smaller than planned. Especially the high end triangular space that passes as fore-tent. I also had some problems with the ridge line, which took a bit of fiddling to keep it from sagging, which usually is not a problem with the tarptents I have made. I'll have to see what I can do about that. The innertent needs a few centimeters extra cloth at the lower end, it was a bit tight around my butt when laying on the side.

Conclusion: A very feasible and light tarptent solution that in competent hands would have been very wind-resistant as well. I just hope someone reading this will make one lacking the aforementioned weaknesses and then go find some nice and really hard winds. Send me a Youtube-link of what ensues.

You are all wondering about the weights. Well the tarptent/fly weighs 165 grams and the bug-tent weighs 160 grams. To this I added 110 grams of tent pegs. I use a mixture of 10-12 gram 'regular pegs and 6-7 gram titanium. Twelve pegs in all plus two 1-2 gram Terra Novas for the upper corners of the bug-tent.

A simple sketch of the tent, with measurements can be found here.
Comments in Swedish on the Utsidan Do-it-yourself forum here.
Comments in English below.

10 comments:

Nielsen Brown said...

Jörgen, this is very interesting, as you know I am planning to revisit Lapland in 2011 and one of my shelter options was the GG Spinnshelter. However, now you have got me wondering whether I could make a Cuben version. As I will be there in bug season I will need a bug shelter, I very much like what you have made and it would seem that it would be a good practice run for a MYOG Shelter.
For cutting cuben (or silnylon) I was able to purchase an electric hot knife, I expect that it would work. I will need to look at your measurements and also BPL.com catenary curve guide thanks for this very useful article. You have given me a lot to think about.

Mark Roberts said...

It looks like a great shelter. I especially like the inner design, giving a roomy upper and a little viewing window. The side entry zipper is also a good idea.

What was your error in the calculations (the brain-failure)? Was it something to do with the catenary curve?

Unfortunately I am utterly unskilled when it comes to making things like this, so I admire your achievement immensely.

Jörgen Johansson said...

Thanks for the positive comments.
A hot knife should work very well, I suppose. I just use a soldering iron/pen since I have one anyway.
I'll try and scan a drawing giving the measurements in a couple of days or so.
The mistake was that I had all the measurements for the 2 triangular pieces that join to form the front end. I then did not realise that one of the angles was not 90 degrees before cutting it from the roll of fabric. This meant that I had to shorten the lengt of the front 'pointy' end foretent considerably. Same mistake at the rear end, although it did not have the same impact. You can see the difference in profile between the Cuben and the G66 Vancouver Island photos.
However, the space in the front end was quite enough for my gear(I do not have much)so it might have been an improvement. What I do not know is if the front end is too upright and does not shed a very strong head wind as well as I know the old version does.
When I made the shelter in 2004 I thought about catenary curves, but failed to measure such a curve on the ridgeline of the old tent. The photo above still gives an impression of one though. I probably made a mistake somewhere.
I have not used catenary curves in any shelter I have made. My personal feeling is that it is a bit of over-engineering. I am sure that it is based on fact and that a tent pitched in a store or on somebodys lawn will get a tighter pitch and ridgeline with a catenary curve. But I have never had any problems without catenary curves when it comes to pitching on the naturally uneven ground you encounter in the field. So I have simply left it to the people with a special interest and not felt it was worth the bother to learn, measure and especially join catenary cut fabrics. But that is just me.

Joe Newton said...

That's a really simple, very light, clean looking shelter Jörgen! I'm sure the issues with the grommets will be revised on version 1.2!

As Maz stated, I like the idea of side entry zip.

Jörgen Johansson said...

Joe,
The side entry adds immense comfort, even more comfortable is a second zip at the low end, so you can flip up the whole side and have breakfast in the sun. I used that on another sil-nylon tent that can be seen here http://www.fjaderlatt.se/2010/07/summer-days-of-dreaming-cuben-and-proof.html#more
That tent is on the first and third photo.
Version 1.2 :-)

Gustav Boström said...

Thanks for sharing Jörgen! I was really curious about this one.The total weight is really truly amazing. I have some questions:

1.Do I read you correct in that you just taped, and not sewed, most seams? I would have thought that you would first sew normally and then apply the seam tape.
2. What did the fabric and tape cost?

Jörgen Johansson said...

Gustav,
Yes, the weight impressed me as well.
Correct, I taped all seams that join separate pieces of fabric. It is a double-sided tape and not a seam sealing tape that you use in rain gear.
I bought 6 meters of fabric at 27,90 Euro, total 167,40 Euro and one roll of tape (I have plenty left) of 55 m costing 23,90 Euro. Cuben is expensive compared to silnylon.

Anonymous said...

I really love your tent and would be very pleased if you could publish measurements of your tent and innertent etc. b/c I would like to make something myself. I read somewhere that it would be wise to put the (dark yellow) cell foam mat under a cuben fibre floor as protection for the cuben fibre (abrasion is cuben's weak point).I would also try to make a 'keeper'of some sorts to put the handles of my walking poles into and reinforce these places, perhaps by glueing the reinforcements??? Have a look at www.Suluk46.com with a lot of information on Cuben fibre. Kind regards, Marianne

Jörgen Johansson said...

Marianne,
Yeah, I have made a rough sketch and it will be on the web as soon as I figure out how :-)
I have used cell foam underneath ripstop nylon bivy bags/innertents before. But I find it easier to have it inside.
I also have to be candid about the fact that having breaks or punctures in any tent floor is no big deal to me. So I feel the same about extra footprints for tents as I do about double fabrics in trousers: If it ain't broke, don't fix it.
Should I have a puncture or a hole in a tent floor (which as far as I can remember never has happened in spite of quite a few tent nights)it is easy to patch with some tape and a needle and thread if need be. I have had holes in tents, so I have practised. When you come home after the trip you can make a better repair.
Yes, a sleeve for the handles of the poles is a good idea. I have used it and found that actually having the points going through the fabric has made for a more stable tent in high winds. But that is probably just a matter of finding a good sleeve solution. I will consider this.
Suluk46 has lots of interesting stuff on Cuben, that was one site that I used to educate myself a bit. Also a film showing how tear resistant Cuben is.

Jörgen Johansson said...

Using a predecessor to CAD a k a paper and pen, I have know made a simple sketch of the tarptent including measurements available at http://www.nui.se/tmp/Cuben_tent.pdf

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