Cuben Mid Tent
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Aaron Robson
(quintessence)

Locale: Texas, California, BC
Cuben Mid Tent on 08/20/2010 02:20:02 MDT Print View

I've decided to set about making myself a replacement shelter for both my two-person Tarptent Double Rainbow and my solo tarp/bivy set-up. This decision was largely inspired by recent backpacking trips that left me less than happy with the protected area provided by my tarp and bivy – they kept me dry and free of bugs for the most part, but not in any manner of decent comfort.

My thinking (aided with input from the always helpful forum members here at BPL) lead me towards a mid-style tent. By making the tent myself, I can save a few $$$ over what I would get from any of the cottage manufacturers, and more importantly, have something that is designed to meet my exact specifications. Basically, I am hoping to design something that meets the following criteria:

- considerable weight-saving over the Double Rainbow (1150 grams)
- not too much heavier than my solo set-up (370 grams)
- bug and rain-proof enclosed space that will be cozy for two people, but ample for one
- simple enough design to not provide too many headaches in construction
- cost less that my current solo and two-person shelter values (about $400)

This thread is intended to be both a progress-update thread, where people can see how my shelter is progressing, but also a place where I can solicit opinions and ideas on design decisions.

My first major decision was what material to use for the shelter – I eventually settled on cuben fiber, after a little bit of deliberation, because it is only about twice the price of 1.1 oz sil-nylon, and is about half the weight. Furthermore, I actually think it is easier to work with than sil-nylon, as it doesn't stretch, making patterns easier to cut out, and bonding cuben allows for more precise seam tolerances and eliminates the need for seam-sealing. Having worked with it a few times before, I'm pretty comfortable using it – this decision is pretty much set in stone.

My next decision was the dimensions. I was less interested in the snow-handling abilities of a mid tent like the MLD Duomid, and more in wind-shedding properties, hence I decided to make the peak height a bit lower – 48” when pitched to the ground instead of 58”. With this lower height obviously comes less head room, which I decided to mitigate by using a hex- or tipi-style design. The sides of the tent will bow out, giving more room where it is more needed, and keeping the overall fabric demand down. For my 'tight for two, spacious for one' fit, I decided on a head and foot tent width of 44” (two sleeping mats plus a tiny bit extra). The mid-tent width was 16” wider on each side, for a total width of 76”. I'm pretty happy with these dimensions, after doing some CAD mock-ups and playing around with a few different dimensions. The following drawing shows the tent pitched at 6” above ground and at ground with 20” wide, 72” long and 12” high boxes representing slumbering backpackers inside.mid dimensions Though I'm pretty happy with the current dimensions, I would welcome any input people have here – experiences, opinions, etc.

We are now getting into design decisions I am much less certain of. I have though about putting catenary curves on some or all of the seams. Do people think this is needed and/or helpful with cuben fiber? I've never used them before, but I don't think they would be too hard to implement with CAD design.

As far as additional features go, I am planning on having two high vents, on on the door side, on opposite it that are protected by bug netting and closeable with velcro. I will have guy points on every corner, and in the middle of the two side panels. Not decided yet if I will make the guy points out of all-cuben fiber, or if I want to use Dyneema patches bonded to the cuben with tie-outs sewn to the patches.

Another big question mark I have is what to do with regards to the floor and bug netting. I basically see three options here. One, go floor-less (use a polycro groundsheet) and have bug netting attached around the perimeter of the tent that is long enough to keep the mosquitos at bay. Two, put in a cuben bathtub floor and attach bug netting from the perimeter of the tent to the top of the bathtub. Three, put in the same cuben bathtub and bug netting, but also add netting behind the two door panels and a zipper so that it would be possible to open both the shelter doors in nicer weather for ventilation and views and still have a bug-proof space. The second option is the lightest, the third the most comfortable and versatile, and the first the easiest to design. What are people's opinions here? I'm a little concerned about using cuben as a tent floor – anyone with relevant experience?

Finally, as I don't use trekking poles, I need a good mid-pole. I've looked at most of the tent-specific pole offerings and have been largely unsatisfied – most are designed to bend (to accommodate the bent-hoop design of most tents) which is exactly what I don't want, or are heavier than I think they should be. I've looked at a number of carbon fiber tube suppliers, and a 0.5” diameter, 0.03” wall thickness wrapped carbon tube looks the best bet (from here: http://www.rockwestcomposites.com/index.php?p_resource=items&p_itc_pk=1). I'd use small sections of 0.5” inner diameter tube for the ferrules, and find some decent end caps for the top and bottom.


The preceding discussion pretty much sums up where I am with the project. Still working on getting my pattern finalized, and figuring out how best to do the vents, tie outs, zippers, bug-netting and floor. Any input would be much appreciated. I'll be sure to update this thread as the construction moves along.

Edited by quintessence on 08/20/2010 02:23:07 MDT.

Erick Panger
(eggs) - MLife

Locale: Mid Life
center pole option on 08/20/2010 07:19:13 MDT Print View

http://seekoutside.com/accesories.html

I've ordered one of these from Kevin for my Shangri-la 3

Since I don't have it yet can't say much about it. You might consider it.

Also one other source for Carbon poles is

http://www.graphitestore.com

Steven Evans
(Steve_Evans) - MLife

Locale: Canada
Re: Cuben Mid Tent on 08/20/2010 08:07:42 MDT Print View

Looking forward to see this progressing. I "sort of" built a smaller version of what you are after except instead of a center pole, I went with a pole on each side and a strut in between and no floor or bug net. Here's a link

http://www.suluk46.com/RandD%20-%20RD14%20ALL-WET.html

I'm a fan of floorless shelters because it's easier to cook, clean, and for me just more versatile (not to mention easier to build) and I just hop in a bug bivy in the evenings. that said, I have a Refuge X with netting around the perimeter and a few vents - love it for heavy bug season. If I were putting in a floor, I'd use cuben and it would hold up aswell as a silnylon floor, as long as I was using it. Others might disagree with me.

I've never done a catenary curve before, but cuben doesn't stretch (as you mentioned) so it might not make much of a difference, I'm not sure.

Pole: I remember reading somewhere that one of the cottage manufacturers is working on a UL mid pole (was it gossamer gear?)...anyway, check into it as it may be worth waiting. I think Kevin is developing it so it will not doubt be light as a feather.

Keep us posted!!!

David Chenault
(DaveC) - BPL Staff - F

Locale: Crown of the Continent
shelter on 08/20/2010 10:43:46 MDT Print View

Hats off for tackling such an ambitious project. I thought about making a mid last fall, then decided to let MLD do the work for me.

Like Steven, I've become a big fan of floorless shelters for use in anything but high bug season. I also like the idea of being able to open the door and still have big protection, as bug season seems to coincide with hot weather and I can't sleep well if it's hot and muggy inside. I vote for the full inner tent.

It seems like with two people you're cutting the head and foot space rather close, given that the walls will slope quite a bit at the ends. If you're working with cuben, it seems like it'd be worth it to make things a bit bigger so you and your partner will be able to relax in style out of the rain and bugs.

One thing I really like about the MLD mids is the largish dyneema patch inside the apex. I can use a branch or paddle as the center pole without worry of puncture. Depending on where you hike you might be able to at least occasionally leave the pole home and scavange a center pole at each camp.

I look forward to seeing the finished product!

Michael Ray
(topshot) - MLife

Locale: Midwest
Re: Cuben Mid Tent on 08/20/2010 11:31:18 MDT Print View

I think you'll get some good ideas for floor, netting and pole from this thread.

I, too, think you're cutting the length a bit close. Even though I'm just 5'9", if your mid was pitched to the ground my bag and head would almost certainly touch the cuben. Granted, I'm a side sleeper and thus use an inflatable. Perhaps you don't roll around and have really measured how much vertical space you take.

I look forward to following your project. I'm thinking of doing something similar in a different material.

Rakesh Malik
(Tamerlin)

Locale: Cascadia
Re: shelter on 08/20/2010 11:32:51 MDT Print View

For that matter, since it's not that high, hang the apex from a branch or something. :)

I've seen only a few shelters so far using Cuben floors, but I don't have any experience with them yet. It might be worth to poke the Hyperlight Mountain Gear folks (or their customers :)) and find out what they have to say about it. In their literature they say that they're using a heavier grade of Cuben for the floors, which from their description seems like it's comparable to what Joe Valesko is using for his packs (1.5 oz per square yard).

I'm with you regarding the bug thing, also. When camping on a toasty and buggy evening, I found it worked nicely to have a lot of ventilation (high A-frame pitch) to let breeze keep me cool while the bug shelter kept the skeeters away.

With a lower and more breeze-proof pitch, the bug shelter added a surprising amount of warmth when I was camping in chillier weather, so the only quandary is how to dodge the bugs in order to cook with a bug shelter, so I might see about making/commissioning a bug net so that I can have a bug-free place to cook and/or reload my film holders. Though reloading film holders I can do inside the bug shelter, that does't require too much space, and doesn't involve things like heat that could damage the bug shelter's floor.

Lawson Kline
(Mountainfitter) - M

Locale: LawsonEquipment.com
Currently in testing on 08/20/2010 23:19:17 MDT Print View

I built a version of what your looking to build a few months back and its currently in testing. If you have any questions regarding design or construction to aid you in your project please let me know.

Mountainfitter paklight cuben fiber ctf3 mid

John Kays
(johnk) - M

Locale: SoCal
http://seekoutside.com/accesories.html on 08/21/2010 10:56:41 MDT Print View

Xed out

Edited by johnk on 08/21/2010 16:36:22 MDT.

drowning in spam
(leaftye) - F

Locale: SoCal
Re: http://seekoutside.com/accesories.html on 08/21/2010 11:13:53 MDT Print View

Those prices are expensive compared to what other large pyramids/tipi's? I know of a Chinese one that's significantly cheaper. Tigoat is priced about the same. Oware is a couple hundred less expensive, but it also slightly smaller and doesn't come with a pole, much less a carbon pole.

Lawson Kline
(Mountainfitter) - M

Locale: LawsonEquipment.com
cuben floor on 08/21/2010 11:41:40 MDT Print View

I am not sure it makes sense to ever use a cuben floor. A 30d silnylon or PU coated material would weigh the exact same, last longer and cost about 1/6 as much. If your a ground sheet kind of guy then there is absolutely no point in either of these lightweight floor materials. I would go with a good quality 70d Urethane Coated Nylon at 2.5oz. When you add up the 1.5oz cuben or silnylon and then your 1.8oz Tyvek ground sheet your at 3.3oz for a floor that just cost you an arm and a leg. Just my two cents

drowning in spam
(leaftye) - F

Locale: SoCal
Re: cuben floor on 08/21/2010 11:48:00 MDT Print View

Why use 1.5 ounce cuben if a ground sheet will be used anyway? Nevermind that I'd use a polycro ground sheet beneath cuben, it's a lighter weight of cuben that I'd want to use, especially if I was going to put tyvek beneath it. Also, I believe Big Sky uses .51 ounce cuben as their floors in their cuben tents. That setup would result in about 2 ounces a yard with tyvek. I thought tyvek was lighter though...

Lawson Kline
(Mountainfitter) - M

Locale: LawsonEquipment.com
Big Sky on 08/21/2010 13:02:35 MDT Print View

Their new cuben version looks like it would blow down in a rainstorm so it doesn't surprise me they use a cuben floor.

Fred eric
(Fre49) - MLife

Locale: France, vallée de la Loire
floorless on 08/21/2010 13:09:55 MDT Print View

My first lightweight shelter was a double rainbow.
But as Steven and David, i now use only floorless shelter, with if necessary a bug bivy or a headnet according to what is expected.

If a bug bivy isnt necessary i dont always use a groundcloth, if the expected weather is mild i prefer using a 3mm evazote full length ( 54g) under my neoair to protect it.

I find it much more practical to be able to go under my shelter with my shoes on and my clothes dripping water without caring about my shelter floor when its raining :)

drowning in spam
(leaftye) - F

Locale: SoCal
Re: Big Sky on 08/21/2010 13:31:27 MDT Print View

I'll agree with you that the Mirage 2 they had at the OR show didn't look good, but the 2 cuben tents they had at ADZPCTKO looked good. Wait, that's beside the point.

What are we looking for in a floor? Water resistance. Abrasion resistance. Puncture resistance. Strength, at least for free standing tents. I don't know how cuben does at abrasion resistance, but it does well at the other two. There are a few people here with cuben bivies. Maybe we should ask them how their cuben is holding up. Also, cuben has the benefit of being easily fixed with tape, which is a big part of the reason why I'd be willing to risk using it for a floor, and even a thinner 0.51 ounce version. The weight savings certainly make it worth the risk too. It would save 0.2 ounces per square yard for whatever nanoseeum it replaces. Abrasion should pretty much be taken care of by polycro that I already use with my Hexamid, so there's nothing left but weigh less.

Edited by leaftye on 08/21/2010 13:40:38 MDT.

Dan Durston
(dandydan) - M

Locale: Cascadia
Cuben on 08/21/2010 20:11:43 MDT Print View

For floors I prefer a PU coated 30D nylon. I imagine it's heavier than silnylon but it's also not slippery and it's more waterproof for a minor weight difference.

I believe the main issue with a cuben floor is abrasion resistance. If you're going to use a bomber ground sheet then it's not an issue and you can use quite a light variation of cuben (ie. 0.75oz), but if you want to use the tent without a groundsheet then you need something more durable if you want it to last. 1.5oz cuben (CT5K.18) uses a thicker mylar layer than 0.75oz cuben (CT2K.08) because the last part of the code (ie. .08) refers to the mylar layer. Maybe the .08 is the thickness is millmeters? I haven't tried 1.5oz cuben as a floor material, but I imagine I would prefer it to silnylon because it's not so slippery and it's more waterproof, but I'm not sure it would last as long. The next heavier variation (CT5FC.5) appears to use a mylar layer that is 3x as thick as 1.5oz cuben so it would likely be quite robust, but at 2.16oz/yd it's getting pretty heavy. I'm not sure what 70 denier nylon is, but it probably isn't much more than that.

Edited by dandydan on 08/21/2010 20:23:46 MDT.

Aaron Robson
(quintessence)

Locale: Texas, California, BC
good stuff on 08/21/2010 23:47:59 MDT Print View

Thanks for the replies and discussion everyone.

I'm definitely going to look around at different center pole options, perhaps ask GG and/or Kevin about their upcoming pole as well. I want to do some proper structural analysis on it to see what diameter/wall thickness is going to give the best strength/weight for this application. I am curious as to how some of these manufacturers get a continuously adjustable pole from these carbon fiber sections that will still take a good vertical load.

@Steven: I did see your thread about your W.E.T. shelter - it looked really nice. I did quite a bit of thinking about how to possibly get the center pole out of the way, but, as I don't have the 'free' weight of hiking poles, I couldn't figure anything out that didn't come with a significant weight penalty from poles.

@David: I'm definitely looking to put some sort of Dyneema patch in the peak of the tent. Does Dyneema X bond well to cuben? I really try and avoid sewing cuben.


As to the length questions - I messed up in my original post. The box in the length-wise diagram is 80" not 72", so there's more room that you might have thought. I'm going to do a mock-up out of paper before I do anything with cuben, so if things seem tight I'll make some alterations.


The floor vs. floorless discussion is pretty interesting. Dan made the point I was going to make - with a cuben floor, it is really the mylar film durability which is the question. And I really don't have any experience with this. Going to have to ask around, I guess. Adding a polycro groundsheet (tyvek or anything else would be way heavier) kind of seems redundant, as if you are going that route, you might as well just skip the floor and only use a groundsheet. Perhaps the best solution is to use a polycro groundsheet and come up with some way to be able to temporarily hook it to the walls of the shelter if necessary to provide a bit of a bathtub.

Steven Evans
(Steve_Evans) - MLife

Locale: Canada
Re: good stuff on 08/22/2010 09:12:19 MDT Print View

Another option would be to just use netting for the entire floor like Joe at Z-packs does on his hexamid. I actually like the way it can create a draping bathtub floor and appears pretty easy to implement in a shelter.

drowning in spam
(leaftye) - F

Locale: SoCal
Re: good stuff on 08/22/2010 09:37:54 MDT Print View

I don't believe the mylar would be all that abrasion resistant, but remember that even if you wear out one side of mylar, there's still spectra in the middle and then another layer of mylar.

I suppose only using a polycro groundsheet would be the way to go if you were willing to give up a separate floor altogether. I would still want it for two reasons. It prolongs the life of an expensive floor and because I can pack it separately when it's used on wet ground.

I do use polycro with the nanoseeum floor of my Hexamid. Switching to a .51 oz/yd cuben floor would save weight, even with the redundant polycro ground sheet.

Kevin Egelhoff
(kegelhoff) - F

Locale: Southern Cal
Ultralight tent poles. on 08/23/2010 21:49:03 MDT Print View

On the tent poles, contact Grant at Gossamer Gear. He has some new parts that make a super light yet stiff pole that was designed specifically for Mids and shelters. He doesn't show them on his web site yet but has been filling some orders.

drowning in spam
(leaftye) - F

Locale: SoCal
Re: Ultralight tent poles. on 08/23/2010 21:54:59 MDT Print View

Kevin, are those the ones you had a hand in? Did you post pictures of them?