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Simon Johansson
(simjoh) - F
Feedback on my 2 man cuben tent design on 04/27/2013 12:59:32 MDT Print View

Hi everyone I've been on this forum for a while getting inspiration to get my backpack a litte less heavy. So far I've made a 600g sleepingpag that has been testet down to -10 degrees celsius a light weight backpack for ski mountaineering. Both project has been successful in my opinion. I' might post them here some day.

My next project is a cuben fibre tent for two persons. I plan to have it under 500g. The fly will be made of cuben with weight 25g/m^2 and the floor with cuben 50g/m^2. The inner tent will be made of some light netting and will be sewn to a strip of cupen which is taped on the fly.
The design so far is shown in the pictures below.ISO view

In this image you see the main design. I've not bothered to sketch all the tieouts and reinforcements. I plan to put a zipper at the front seam. What more that is not in the picture is that i plan to have a guideline in the middle of the large panel in order to get a good pitch and some more room inside.

I did a quick mockup of the tent today in the yellow ripstop inner tent material. Unfortunatly i didn't have enough fabric for the entire tent so I only sewn the area where me and mu buddy will sleep. The pitch was quite good but since the fabric is a little stretchy I have to make the ridge line with a catenery cut and maybe put some cat on all the seams. My cell died when i was about to take a photo. But will pitch it again tomorrow.

I've read some threads about cat cuts and some people say that since cuben doesn't stretch so much, there is no need for a cat cut.
I also know that since cubent doesn't stretch one has to be really careful when cutting the cuben to get as perfect pieces as possible. However the there will always be some difference from the model. I therefor consider to do a slightly cat cut on all my seams and at bottom line of the fly to be able to pitch it better. Am I totally lost here? Maybe one inch on all shorter and 3 inches along the long line.

Another thing that i wonder about is if i should bond the pieces with 3M tape or hysol. From what i've read these methods are strong enough and I will not have to sew. I live in a quite small rental apartment and don't have any clamps is hysol still possible without making a mess of my whole apartment?

Here are oictures of a side and front view with dimension.
Side view
Front view

Please shine some light on all my questions or give me some other good advices. I know that plenty of you've made somthing smilar.
And Sorry for my english. I'm not a native english...

/Simon

Edited by simjoh on 04/27/2013 13:00:38 MDT.

Mark Dijkstra
(Markacd) - F
feedback on 04/28/2013 05:49:43 MDT Print View

Your design seems pretty small for 2 people. I don't know what kind of trips you'll be using this tent for, but especially for a longer trip you might want something bigger. Right now your usable height is probably around 85 cm in the peak. And that's in the middle! Above your mattress it's even less. You won't be able to sit up on your bed. I would also make the inner a little longer. You're taller when lying down and your sleeping bag adds even more length. With an inner of 220cm you won't have to worry about touching the fabric with your head or feet. Also, 82cm at the foot end is very narrow. 2 tapered mats will barely fit next to eachother there. I hope you're close friends with your hiking compagnon ;). For one person who can put his mat in the middle this tent is fine, but for 2 I would make it bigger. You're using cuben, so the weight penalty isn't even that high.

I have no experience with cuben, so I can't help you with that.

Simon Johansson
(simjoh) - F
Thank you mark for you feedback on 04/28/2013 06:53:11 MDT Print View

The height of the tent will be flexible. This is in the lowest setup when there is some wind. A normal good day I plan to set it about20cm higher.
You´re absolutely right with the argument about space to weight when working with cuben. So I might do my tent a little longer and wider at the foot end which would nearly cost nothing extra since there are quite a waste of material at the moment.
The size at the head end is pretty much optimizes. The cuben comes in one width and I'm using it all for each side panel except for 4 cm that is seem allowance.

I've read Stephen Bateman thread 5.5oz Cuben tarp with carbon tieouts (http://www.backpackinglight.com/cgi-bin/backpackinglight/forums/thread_display.html?forum_thread_id=75909) and I think i will try something similar for reinforcement and tie-outs. He also did a cat cut. Do you think that his values are for this tent as well? Maybe tweek them a little since my tent is higher and longer.

c. c.
(chemicalcraig) - F
cuben tent on 04/28/2013 11:02:42 MDT Print View

Nice design. Might be a tight squeeze for two, but should work. I used hysol/clamping for my tarp and it can be a bit messy if you've never tried it before. Very strong seam. I've also taped some stuff sacks and that too seems very strong. The thing you have to remember is cuben is very strong in shear (layers sliding over top of one another) but very weak in peel. Take care in designing any stress points that have a tangential stress component.

What software did you use?

Simon Johansson
(simjoh) - F
Thank you c.c on 04/28/2013 13:12:07 MDT Print View

Thank your your input according to stress points. I'will think twice before doing the final cuben version. I do appreciate your info about the hysol so I think i will go for the 3M 9460 or 9485. Neither of these are easy to get in sweden so i think i take what i can find.

I used the free Google sketchup (SU). I think it is a pretty good program once you get used to it. A real cad program like UGS NX and catia is much more powerful but once getting used to SU it is quite good. But I think it is quite annoying that you can change the dimensions afterwards. It more like a free modeling program like alias. But I'm a real new to this program so there might be some functions i've missed.

Eric Blumensaadt
(Danepacker) - MLife

Locale: Mojave Desert
a "weather door" on 05/03/2013 23:32:48 MDT Print View

To keep from kicking yourself after you have made it plan to have an overhang for the door so WHEN OPENED it does not let rain come directly in on the floor, as so many tents do (like most 2 pole wedge tents, for example).

A shielded entrance is a must for good design. A nice vestibule for pack and shoe storage is also a plus.

Otherwise it looks like a nice A-frame tent.

P.S. (Check out some Tarptent designs that use only hiking poles for support. Since you are not making it for sale you can use any of Henry's ideas in your own tent.)

Edited by Danepacker on 05/03/2013 23:35:19 MDT.

Eric Blumensaadt
(Danepacker) - MLife

Locale: Mojave Desert
Your ski mountaineering pack on 05/03/2013 23:40:27 MDT Print View

Simon,

I am a ski patroller (EMT on skis) and a backcountry skier. I'd like to see some photos of the pack you made.

I modified a large (5 Liter) Camelbak camoflaged hunting pack for backcountry skiing to carry emergency overnight and avalanche gear.
But it weighs 2.5 kilos. :o(

Sumi Wada
(DetroitTigerFan) - F

Locale: Ann Arbor
Re: Feedback on my 2 man cuben tent design on 05/05/2013 23:00:53 MDT Print View

The dimensions of your design are very close to a basic 2-person silnylon tarp I made using Henry Shire's DIY original tarptent directions (www.tarptent.com/projects/tarpdesign.html). I've used it with two people -- two SMALL people -- and it's very snug. And that was when we were using a prolite and a zlite for pads. I basically only used it on trips when we expected to cowboy camp most of the time.

On the last trip that we used it, we had one really rainy night when we were squeezed under there for 12 hours... that's what convinced me to buy a cuben Trailstar.

Simon Johansson
(simjoh) - F
Thanks sumi and eric on 05/13/2013 12:20:26 MDT Print View

Thank you for your inputs to this project. I think i will have the door at the front or maybe at the middle of the triangular front pieces e.g. not at the seam close to the netting. I showed the quick mockup to my girlfriend and she thought it was roomy enough. But as other mentioned before i might to it a little longer and also make the vestibule a little bigger.

Eric: The pack will be shown in another forum thread later tonight.

Sumi Wada
(DetroitTigerFan) - F

Locale: Ann Arbor
Re: Thanks sumi and eric on 05/13/2013 12:53:04 MDT Print View

Just to clarify, we had issues with the headroom, which is a function of width, not length. The sides on a ridgeline (A-frame) design are sloped and, for two people to be comfortable side-by-side, you need a surprising amount of extra width to allow for the unusable space along the sides. And if you're using air mattresses (e.g. Neoairs) which are thicker, they will put you that much closer to the sides.

You might try stringing up a bedsheet between two chairs at the height and width of your design, slide your pads under it side by side and make sure you can both fit under it without feeling claustraphobic. If one of you has wide shoulders and is a side-sleeper on an air-mattress, you may have problems...