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bemental
05-09-2015, 18:49
I've seen a few tents that have cuben bottoms to eliminate the need for a groundcloth due to cuben's waterproof nature.

I'm looking at purchasing the super light bivy from MLD (http://www.mountainlaureldesigns.com/shop/product_info.php?cPath=22&products_id=30) with the cuben bottom, but I'm concerned about the durability of the fabric. I typically sleep with my x-lite inside my current bivy, but it's made of Gortex and I haven't had any problems with holes yet. I'm a rough sleeper who tosses and turns all night, and can only imagine what that's going to do to the bottom of a cuben bivy.


The super light bottom is .75 cuben. They also have a Silnylon option as well.


Any thoughts?

MuddyWaters
05-09-2015, 19:32
I have read unfavorable things about 0.74 cuben as a groundcloth.

I camped near a woman one afternoon on JMT. We both pitched our shelters to ride out a rain squall. She had a 0.74 cuben groundsheet for her hexamid solo+. She had water come thru her floor and stuff got wet.

So i believe it is not sufficient for use on ground alone.

Put another groundsheet under it, and im sure its fine.

Lyle
05-09-2015, 19:48
If I were you I would get some polycryo from Gossamer Gear, 2 pk for $9.95. While not indestructible, it is amazingly tough and weighs only 1.6 oz. I've been using this for years, and am very satisfied. Place this underneath your bivy and I will bet you double your protection. Just for full disclosure, I'm one of the hikers who always uses a ground sheet underneath my tent, even if it is floored. Just seems to make complete sense to me to add the protection of a $5 and 1.6 oz item when I'm using a $300 dollar tent. Much easier to replace an abraded ground sheet then it is to replace a tent floor.

http://gossamergear.com/polycryo-ground-cloth-medium.html

The problem I see with using a ground sheet underneath a bivy (with no tarp) is water running off the bivy and staying on top of the ground cloth, thus trapping it right underneath you - not good with any floor material. Would be counter productive. That may make everything I said above wrong. Perhaps try it out, if it does develop leaks, add the polycryo inside the bivy - might work.

bemental
05-09-2015, 21:02
I'd like to avoid an additional groundcloth if possible.

What do we think about the Silnylon option instead? Tough enough?

-----

My readings have also come across various 'sources' stating the strength and longevity of 'newer cuben' as such:

"Cuben fiber is sensitive to abrasion. However the latest versions of multi-biased Cuben Fiber in the .75 weight category ***are vastly stronger than any other fabric on the market***. The weaknesses tend to be how Cuben is bonded, as in how panels are joined in a tarp or tent. It can be sewn together but the more high end gear seems to favor chemically bonded seams. This has the advantege of no stiching to leak or require seam sealing.
Mountain Laurel Designs even boastes a 100% record of Cuben fiber seam integrity when bonded instead of sewn.

As for abrasion resistance comanies Like Mountain Laurel Designs, Lightheart gear, and Bear Paw Wilderness Designs are making bivy sacks and even groundsheets out of the newest versions of Cuben Fiber."
(http://www.highsierratopix.com/community/viewtopic.php?f=15&t=5877)


Tough decision really, since I've never owned a piece of cuben, or Silnylon gear before.

MuddyWaters
05-09-2015, 21:53
There are reports out there from people that have had pine needles penetrate 0.74 cuben floors of tents like the SMD skyscape X.

Zpacks will make a 0.74 groundcloth or tent floor, but they dont offer it standard anymore, you have to ask. There is a reason for that.

bemental
05-09-2015, 21:57
There are reports out there from people that have had pine needles penetrate 0.74 cuben floors of tents like the SMD skyscape X.

Zpacks will make a 0.74 groundcloth or tent floor, but they dont offer it standard anymore, you have to ask. There is a reason for that.

Thanks Muddy, now that you mention it the MLD cuben option, while not a special order, is not standard either.

If I'm not mistaken, isn't Silnylon known for absorbing a bit of water, especially when under pressure (sitting/kneeling/LYING on it)?

Starchild
05-10-2015, 05:55
I have the z-pack cuban floor, IDK what weight it is, but it did survive the thru + more. With that said it did get punctured in 2 places, easily and perminatly sealed with cuban tape. That last part seems to be a big plus for CF, if it does get a hole it is easily field repairable even duct tape would work.

But cuban does start to break down, I have not had this on my tent yet, but on stuff sacks. The strands lose their laminate coating and just run as a series of very strong threads. A small section of this could be taped, but in the case of the stuff sacks it's usedful life is up as that is starting to happen everywhere. Such wear seems to happen based on use, not time.

HeartFire
05-10-2015, 07:36
As for abrasion resistance comanies Like Mountain Laurel Designs, Lightheart gear, and Bear Paw Wilderness Designs are making bivy sacks and even groundsheets out of the newest versions of Cuben Fiber."
(http://www.highsierratopix.com/community/viewtopic.php?f=15&t=5877)


Tough decision really, since I've never owned a piece of cuben, or Silnylon gear before.
I (LightHeart Gear) Do not make Bivy's and I no longer make any cuben fiber tents. As far as seaming the fabric goes, sewn seams are just fine as long as they get taped. There are 2 different components to the cuben fiber - the dyneema threads and the mylar laminate. The threads are what gives it strength, The 'bias" cuben just has threads laid in at 90* angles and 45* angles, that cuts down on the stretch from the angles. Holes from sewing go through the mylar layers, when the fabric is stretched setting up a tent, tarp etc, pulling on it will open those holes since it's not a woven material, you poke holes in plastic. If you tape over those holes, the seam integrity is just fine DEPENDING

HeartFire
05-10-2015, 07:39
oops, hit enter to fast.
DEPENDING on the tape you use, same goes with bonding seams, it depends on the bonding agent used. Some hold better than others. you can't always bond seams - when I made tents of cuben fiber, often I had 3 layers - 2 cuben and one mesh being joined - you caont bond mesh to the cuben, it has to be sewn. I never had problems with the cuben tent seams if they were taped.

All that being said, I no longer work with cuben, I've had bad fabric that delaminated quickly, it's just too expensive and I don't like working with the bonding agents - toxic chemicals.

bemental
05-10-2015, 07:52
I have the z-pack cuban floor, IDK what weight it is, but it did survive the thru + more. With that said it did get punctured in 2 places, easily and perminatly sealed with cuban tape. That last part seems to be a big plus for CF, if it does get a hole it is easily field repairable even duct tape would work.

But cuban does start to break down, I have not had this on my tent yet, but on stuff sacks. The strands lose their laminate coating and just run as a series of very strong threads. A small section of this could be taped, but in the case of the stuff sacks it's usedful life is up as that is starting to happen everywhere. Such wear seems to happen based on use, not time.

I'm starting to get the same feeling about a cuben ground cloth/bivy bottom that I did with my air mattress that ended up tearing a week into my thru. "Good initiative, bad judgement".

I want something that is tough enough to not have to tape, or worry about having to tape, especially if I plan on not having to use a ground cloth underneath it.

Thanks for the input.


oops, hit enter to fast.
DEPENDING on the tape you use, same goes with bonding seams, it depends on the bonding agent used. Some hold better than others. you can't always bond seams - when I made tents of cuben fiber, often I had 3 layers - 2 cuben and one mesh being joined - you caont bond mesh to the cuben, it has to be sewn. I never had problems with the cuben tent seams if they were taped.

All that being said, I no longer work with cuben, I've had bad fabric that delaminated quickly, it's just too expensive and I don't like working with the bonding agents - toxic chemicals.

And thank YOU, both for the information, and for being so accessible to the masses. We appreciate that (and your work!).