myog mountaineering cuben tunnel tent?

[Roger Caffin]

Hi Pierre

In my opinion … you need to reinforce the key bits of fabric and sewing properly.

In the image here you will see what I mean.

The thick red lines are a layer of Cuben fibre which has been folded over to protect the seam in the fly itself. The sewing (thick blue line) in this line of stitching is CRITICAL to the whole tent. It must be strong, and it must be reinforced. I use Rasant 70 thread here.

You will also see that the sewing on the pole sleeve is protected in the same way: the pole sleeve fabric has a reinforcing strip over the top.

This is probably a bit over the top for a summer-use tent for sheltered situations – but you did say you are building a tunnel for the mountains.

Cheers

[Pierre Descoteaux]

This diagram helps me a lot. Thank you Roger. I wasn't doing the folds the proper way. I'll test this out tonight. In the mean time, I am hanging 40lbs off of my 3'' long sleeve sewed to the fly and underneath reinforcement strip. It's been doing well with 30lbs. But the way your are folding the fabric to reinforce it made me think that I can improve on my technique. I'll this later.
I plan on using Rasant 75 and 120 depending on the areas but I've only been using Gutermann Tera so far. Rasant was a pain to get being in Canada.

For the inner, I'm planing to use Argon 67. Anyone has experience with this material for an inner?
Floor; the silnylon from LightHeartGear or from Thru-Hiker (tested).
Cheers
Pierre

[Roger Caffin]

Hi Pierre

> This diagram helps me a lot.
There's a cost of course: we want photos of the finished gear!

> Rasant was a pain to get being in Canada.
I know – but it is really good stuff! Buy in bulk.

Cheers

[Pierre Descoteaux]

I just tested Roger's technique for the sleeve attachment and… The reinforcing tape under the fly (on top in my testing) started to peel of almost instantly at 20lbs of load. I'll let it overnight to see where it gets. (This is because I DID NOT PUT ENOUGH TENSION ON THE SEAM BEFORE APPLYING THE TAPE!!! Roger's sleeve works great when you do it right!!
My own sleeve rig broke off at 40lbs just at the junction of the reinforcing cuben tape but not for the sleeve I was testing. I'll have to retry this one with new fabric strips.

Here is a pic from my attempt at Roger's technique.

Cheers
Pierre

[Adam Kilpatrick]

The reinforcing tape is coming away here, but is that actually a problem? I'm guessing that the rest of it will actually be quite strong. If this seam needs to be sealed, then maybe tape should go on the other side, two lines of tape over the top of the stitching there (one on each side). Or put the tape down first then stitch through it. Minimal holes aren't going to leak that much in this case.

[Roger Caffin]

Interesting, but I wonder …

Was the seam under tension when the tape was applied? I suspect it was not. In which case, yes, the tape bond will likely fail, and in a peel mode. But that is the tape bond which is failing, not the seam construction.

This really asks the question 'what is the tape meant to be doing'? If it is meant to be reinforcing the join, then clearly that is not working. But the seam was not designed for tape to be used that way. On the other hand, if the tape is meant to be waterproofing the seam, then I think it was just applied incorrectly. The seam needs to be fully stretched out before the tape is applied. This a known problem with taping complex 3D Cuben Fibre seams. You could proof the seam in other ways too.

You should note that the tension at the seam across the line of stitching is far higher than the 20 lb of load you mention. You would need to do the maths after measuring the fabric angles, but if the included angle is 140 degrees (guessing from the photo), then the tension in the fabric or across the sewing is more like 20/cos(70)=58 lb. That is extremely high for a seam in a tent!

Incidentally, the two lines of stitching holding the sleeve to the Cuben are rather close together. Me, I would prefer to separate them a bit more when dealing with Cuben – or with slinylon, for that matter.

More testing!

Cheers

[James Marco]

Yeah, I agree with Roger. But I believe that the forces applied approach infinite across the tent fly as it pulls down on the fabric. Even if you apply the tape under tension, as was suggested, it will try to pull itself apart as the tension is removed and the cuben springs back to the rest position. Hence, every set-up and tear-down of the tent will eventually, probably in a few uses, cause the tape to loosen. I have a couple suggestions:
1) Use a heavy sleeve. You can likely do this with 2.4oz cuben.
2) Tape will not work in peel without reinforcement.
3) Tension on the tent will offset tension on the sleeve. This means they will work together. Usually, a distributed loading will be stronger than single point loading.
4) Three or four stitches are needed for strength in severe wind.

This is not an engineered static load joint. Rather it is a dynamic load joint. The more wind, the more tension on the tent body. The more tension on the poles/sleve. The joint will ofset the extreme load deformation causing the tape to peel loose inside. The heavy cuben fabric should resist any catastrophic pole collapse, but you will always have this item present, poles are just so strong. The tape should provide any sealing at the seam, and, reinforce the joint, too. The stitching will reinforce the joint without all the pressure being applied to one row of stitches. This will much reduce hole elongation in the tent body. This will likely not test really well under your rig. You need the tent fabric under dynamic tension as you increase the load. This happens naturally in a wind, though.

Nick Bedouin had some to say on this subject here: http://www.backpackinglight.com/cgi-bin/backpackinglight/forums/thread_display.html?forum_thread_id=58096&disable_pagination=1

[Pierre Descoteaux]

Roger, your seam has not moved at all overnight. I'll take it down and see how I can better apply the tape to it or to a new testing strip if needed. But I do think that James is right for the forces applied on that tape. (From a climbing perspective anyways) Also, that row of stitch does not got thru the cuben. It is part of the double layered sleeve.

James, thank you for the links. The info sent by Cubic Tech does say that a straight stitch is best. But here is what they say: ''Optional stitch: If necessary, stitching may be added to the seam to improve the peel strength. Be aware that stitching may reduce the strength of the seam because of the perforations. The stitch may also reduce the water-tightness of the laminate; a liquid adhesive such as Seam Grip® may be applied over the stitch to cure this. A straight stitch is recommended, 6-8 stitches per inch, 16 or 18-gauge needle, Nylon 69 thread. Stitch no closer than 1/4-inch from the edge of the laminate.''

Now, I must admit that I like my simpler sleeve attachment. Am I wrong in thinking that by keeping the cylindrical part of my fly (not talking about the ends) one long piece of cuben (from one end to the other) I minimise the chances of failure/issues? There would be less puncture holes to lessen the strength of the laminate. Much less sewing so less holes.

In any case, I received all my cuben supplies Yesterday, I'll be able to do the testing on exactly the cuben that will be used for my project. By the way emailing Cubic Tech to get info and order was a charm, I wish Fibraplex was as easy to get in touch with. They suck with email so far…

Cheers

[Roger Caffin]

Hi Pierre

> how I can better apply the tape to it or to a new testing strip if needed.
I wonder … if the seam holds just fine anyhow, do you actually need the tape? Or would some other sort of seam sealing work better and weigh less – and be easier to apply? Just wondering.

> keeping the cylindrical part of my fly … one long piece of cuben … I minimise the
> chances of failure/issues?
Don't know.
If the seams are a weak point, then clearly yes. But at least on sylnylon I have never found the seams to be 'weak'.
By having the seams I was able to have a more profiled shape, with the middle a bit higher. It gave us a bit more room inside.

Cheers

[edvin mellergård]

>> how I can better apply the tape to it or to a new testing strip if needed.
>I wonder … if the seam holds just fine anyhow, do you actually need the tape? Or would some other sort of seam sealing work better and weigh less – and be easier to apply? Just wondering.

Not sure if you seen it already Pierre but most(all?) tapes lose alot of strength in the cold. Do a search, plento of info about it in some previous threads. As for sealing how about either seamseal it from the outside with silicone or inside with some of the various glues suitable for cuben?

Seamsealing it with glue/silicone instead of glueing a piece of cuben over the seam would have the added benefit that you could incorporate the attachments for the inner directly in the seams for the pole sleeves

>> keeping the cylindrical part of my fly … one long piece of cuben … I minimise thechances of failure/issues?
>Don't know.
If the seams are a weak point, then clearly yes. But at least on sylnylon I have never found the seams to be 'weak'.
By having the seams I was able to have a more profiled shape, with the middle a bit higher. It gave us a bit more room inside.

With Cuben I would try and eliminate as many seams as possible, if you dont plan on shaping the cylindric part of the tent I would definitely try and go with just one piece of cuben

[Jerry Adams]

"tapes lose alot of strength in the cold"

I keep going back and forth on making a Cuben tent

that Argon silnylon at 0.7 oz/yd2 sounds better

except they're out of stock

[Roger Caffin]

As Edvin wrote:

> Seamsealing it with glue/silicone instead of glueing a piece of cuben over the seam
> would have the added benefit that you could incorporate the attachments for the inner
> directly in the seams for the pole sleeves
Very definitely agree!

Cheers

[Pierre Descoteaux]

True enough, my seam sealing tape might not be needed. it did nothing to Roger's seam technique. It is made for the cold dough. It will (according to the manufacturer) still adhere at -10C's. Meaning you can place it for repairs at -10C's. Will it hold in colder temps? I do not know. But I have faith in a Canadian company making winter tape the right way.

If (big if still) I go with my seam free cylindre I was planing using the ''Stick on Mitten Hooks'' from Zpacks to hold the inner. Well if they hold in the cold that is!

Also, the tape sold by Cubic Tech is supposed to not have the cold issue.

I have made a version of my technique with the CT2K.18 with an underlayer of CT2K.08/PSA tape and top sewed sleeve with a ''protective'' fold. To test tomorrow night. This is, other than the color, exactly what I'm hoping to use for the final tent. If it works, the only main seams would be at the ''cone ends''

I have placed the tape (needed or not) with more tension on the inner fold on Roger's seam which I'm testing overnight.

Profiled shape: I will keep it as simple as possible. It will be a simple half cylinder with 60ish deg ends. All 4 poles will have the same length. No confusion possible at setup.

Roger, Edvin, would you mind if I sent you my sketchup file? I bet you can find issues faster than me…

Argon Silnylon: It would still have the sagging issues I dislike so much! Bear in mind that I've been using an old leaky Stephenson 3RS for the last 15 years.

Cheers
Pierre

[Roger Caffin]

Hi Pierre

> Roger, Edvin, would you mind if I sent you my sketchup file?
I don't mind, but my BPL email account is currently disfunctional. It logged me out before I went walking, and I can't remember the password for it! I will have to wait until Ryan J gets back late next week to sort it out.

> Argon Silnylon: It would still have the stretching issues I dislike so much!
Why? I'm curious, because I think the fabric stretch is essential to absorb wind blasts. It adds toughness.

Cheers

[James Couch]

Pierre,

Have you considered using internal poles instead of external poles/sleeves. Something along the line of some of the Garuda tents out of Seattle or the Bibler. With internal poles you get completely way from sleeves all together. I would think it might well be the best setup for a cuben fabric tent.

[edvin mellergård]

>Roger, Edvin, would you mind if I sent you my sketchup file? I bet you can find issues faster than me…

Happy to take a look! You can send me a mail at edvin.mellergard at hotmail dot com

[Pierre Descoteaux]

''Argon Silnylon: It would still have the stretching issues I dislike so much!
Why? I'm curious, because I think the fabric stretch is essential to absorb wind blasts. It adds toughness.''

I should have said: ''sagging''. I know you love the stretching/forgiving part of silnylon. And that is partly why I'd like to use it for the sleeves. But you did raise a concern with regards to mixing silnylon (stretchy) with cuben (no stretch).

By the way, re-applying the tape with much more tension solved the peeling issue. But it might not be needed at all as you suggested. Your srtip is now under a 30# load till tonight. But to me, the real test for your technique will be to weight the seam in a way that tries to open it. The CT2K.18 ends would be tensioned but not the sleeve. I'm eager to compare this result to my simple strips. But for now, I have to stick with the ''sleeve'' testing.
Cheers

[Roger Caffin]

> But you did raise a concern with regards to mixing silnylon (stretchy) with cuben (no stretch).
I had a think about this. I don't think having a stretchy silnylon sleeve on a Cuben fly would have to be bad in any way. The fairly small amount of stretch would just equalise the tension on the Cuben, imho.

> the real test for your technique will be to weight the seam in a way that tries to open it.
Very interesting question there.
I THINK … that the tension along the roof will be much higher than the sideways tension from the poles sleeves. Certainly, when I pitch one of my tunnels, I do put a fair bit of tension along the length, very deliberately. This is done at the corners at ground level. But because the poles are designed to put no more than about 1% stretch along the pole sleeve, there is not a lot of sideways tension.
If the wind starts to blow from the side the sideways tension goes up of course, but even so I suspect that the lengthwise tension remains greater.

Cheers

[Rog Tallbloke]

This thread has inspired me to do something with the 5 yards of 0.74oz Cuben I've had sitting in my gear cupboard, apologies for crashing in with a question.

Roger C: What weight of carbon fibre poles would you recommend for a 'Laser Ultra' style mountain tent (slightly scaled up for my 6'8" height)?

I'm looking at some roll type 6mmx4mm 500mm long pieces on ebay and wondering if they are adequate for a 3m pole with elbows. There are some 8mmx6mm available too.

Thanks

[Roger Caffin]

Hi Rog

I use 2D-wrap arrow shafts equivalent to the Victory Archery VForce 400, seen here:
http://www.victoryarchery.com/vforce

Inside diam = 0.245" (6.22 mm): this slips neatly over 1/4" SS tubing and elbows from Easton and Yunan. OD = 0.295" (7.51 mm) – well, it works fine for me.

Actually, I got mine from a local archery shop as low-cost Brand-X Chinese equivalents. They seem to be just as strong though. I would NOT be surprised if Victory actually bought theirs from the same supplier. Beware of Carbon Express: some of their shafts are just pultruded fibregalss with a dusting of CF on the outside. They SPLIT fast.

Note that there is a technical difference between 2D-wrap and rolled fabric: the latter is not as strong but may be a little more flexible. Avoid anything pultruded at all costs.

6 x 4 mm sounds far too weak to me. Get up on the moors in bad weather … no … But 8 x 6 would be fine.

Cheers

[Rog Tallbloke]

Thanks for the advice Roger, I'll consult my archery friend to source some good quality 2D shafts. I am torn between straight sections with elbows and a stressed curve. Maybe I'll go for a hybrid solution with a single elbow at the top.

[Roger Caffin]

Hi Rog

> I am torn between straight sections with elbows and a stressed curve. Maybe I'll go
> for a hybrid solution with a single elbow at the top.
I doubt you can bend CF tubing tight enough for a real tunnel design, and the 'Laser Ultra' is about as bad for that (it's almost a tunnel). In fact, I think you need to pre-curve even aluminium tubing for one of those. I tried using a straight Al pole like that on a tunnel but had an 'unfortunate experience'.

I have made tunnels with a single elbow at the top. That works, but the head room is much less than with 3 elbows. Do NOT try 2 elbows: the flat top is very bad news under rain or snow.

Cheers

[James Marco]

"In fact, I think you need to pre-curve even aluminium tubing for one of those. I tried using a straight Al pole like that on a tunnel but had an 'unfortunate experience'."
Roger, Exped uses straight aluminum poles for the Serius/Aeries series. They have been in use for over 10 years. They are about 10mm or so.

[Rog Tallbloke]

Roger C: "I doubt you can bend CF tubing tight enough for a real tunnel design"

Fibreplex seems to manage it. This image is from Doug Johnson's BPL article

.

Anyway, the company supplies 145* elbows, so using three for an included angle of 105* using 4 of their 31.5" sections would give a free width at the pole feet of 80.55" (allowing for the additional length the elbows provide. Pulling that in to 72" for a generous porch space plus sleeping room for two would put a bit of outward stress into the pole to resist wind and leave me with a generous 46" of headroom at the apex sloping down to a windcheating 20" at the secondary pole.

Too tall! I hear you cry, but then people have been telling me that since I was 15. ;-)

[Pierre Descoteaux]

Alright then, it is settled that I'll use silnylon for my sleeves.

My sleeve technique and Roger's held 24hrs with a load of 40#. This was not a problem.

I'm so far unable to test either sleeve while pulling in the other direction (ie: simulating tension along the roof) since the cuben strips slips with a 30# load. They held fine at 20#. I'll have to figure a way to better use my clamps.

Poles:
Is it possible to find Yunan Scandium poles in the 9mm range?
Anyone has experience with the Fliegfix 9.2mm carbon fibre poles? (Don't get excited since they are not available at the moment.)
Cheers

[Author]

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