Topic

Tape to add strength to stitched Cuben Fiber?


Forum Posting

A Membership is required to post in the forums. Login or become a member to post in the member forums!

Home Forums Gear Forums Make Your Own Gear Tape to add strength to stitched Cuben Fiber?

  • This topic is empty.
Viewing 23 posts - 51 through 73 (of 73 total)
  • Author
    Posts
  • #1660246
    Sam Farrington
    BPL Member

    @scfhome

    Locale: Chocorua NH, USA

    Colin,
    See what you mean.
    Was thinking of bonding maybe 1" wide strips of cuben to the edges of both canopy pattern pieces before sewing them together with what is called a faux lap-felled seam (only laps on one side, but is much easier for me to sew).
    Then seal the seam with Seamgrip.
    The needle holes would always be at least 1/2" from the nearest unreinforced fabric. (Much bigger patches at corners and other stress points, of course.)
    Maybe even wider strips if .51 oz cuben is used.
    Would prefer to use the C2K.08, that is above .6 oz, and still reinforce with 1" wide strips. But don't know that I can obtain the beefier 2K shaded, which for me is a must.
    Much might depend on the adhesiveness and elasticity of the bonding agent.
    And I have no idea how vulnerable the cuben, even when reinforced, is to pressure from the thread at the needle holes. Have not tried to work with it as of yet.
    Thank you for your advice. More to think about.
    Sam

    #1660340
    David Olsen
    Spectator

    @oware

    Locale: Steptoe Butte

    It would seem (pun) that if bonding is causing failure
    right at the edge of the bond, then either bonding is an
    inappropriate method of attachment or is being done wrong.
    Perhaps a stretchy glue is needed, or a stretchy tape.
    Thread can be all kinds of stretchy so could be tailored (pun)
    to the fabric strength.

    #1660352
    Dustin Short
    BPL Member

    @upalachango

    David, the failures that people have been seeing (in testing mind you, not real world) is that at the bonded edge, the mylar delaminates from itself, exposing the spectra threads. The conclusion has been that the bonded seam (usually Hysol) is stronger than the intrinsic bond between the mylar layers.

    There's also the possibility that the bond edge is causing focal points of stress that lead the fabric to fail before the bond. I know hysol is flexible, but I don't know how much it stretches (and with a low stretch fabric like cuben how much a difference a stretch adhesive would make). I could see how using a weaker bond method could actually improve the overall strength in that it allows the cuben fabric to act more naturally than having a sharp disjunction in strength between face fabric and seams.

    #1660435
    Colin Krusor
    BPL Member

    @ckrusor

    Locale: Northwest US

    I don't think that a weaker or more stretchy adhesive would improve the strength of cuben seams. The glue layer is (ideally) a very thin film, so a more elastic glue wouldn't actually allow the seam to stretch.

    I think failures at cuben seams tend to occur at the edge of the overlap not because the adhesive type or adhesive process is inappropriate, but because the seam is one-sided.

    This is a guess about the mechanism: The mylar is somewhat stretchy (you can test this by pulling on a piece of cuben along the diagonal) but the spectra fibers are not. If you attach one edge of a piece of lycra to a table and pull on the other, you can see that points on the stretchy material that are nearest to your hands move the most with respect to the table. If you smeared something like honey on the table and pressed the stretchy material down, then pulled it again (not up, but down over the edge, or at a very low angle), the area of material nearest your hands would stretch first while the rest remained in immobile contact with the table. If you kept pulling (across the table, not up) a line of delamination would move away from you toward the attachment point, progressively freeing the stretchy fabric from the adhesive surface of the table. As you pull, the areas of the sticky bond that are beyond the delamination line are essentially unloaded. No pulling is felt by the fabric beyond that line. The fabric is just resting on the sticky table beyond the delamination line. A fabric with no stretch would distribute the load equally across the entire interlaminar surface, and every point on the fabric would move the same distance when tugged. The bond between the two surfaces fails first at the edge nearest you because the stretchiness of the fabric concentrates the interlaminar shear forces along a line perpendicular to the direction of pull.

    In the same way, the strain on the interlaminar bond between the mylar and the spectra in a piece of cuben is greatest at the edge of the seam overlap, where it is concentrated by the stretchiness of the mylar. The hysol bond pulls only on the mylar, and the mylar wants to move with respect to the underlying spectra, which doesn't stretch. At low loads, the interlaminar (mylar/spectra) bond is intact, and an appreciable fraction of the load transmitted through the hysol bond to a piece of cuben is borne by the spectra fibers (via the interlaminar bond). At a certain strain threshold, though, the bond between the stretchy mylar and the very slippery spectra fibers begins to fail within the area of seam overlap.

    When this happens, the spectra is no longer loaded (there is no bond to transmit the load to the spectra), so the large load that disrupted the interlaminar bond is suddenly borne only by the mylar. A tear immediately occurs in the film along a line where the tensile load is greatest. Due to the stretch in the mylar, as in the lycra analogy, the tensile load is greatest right at the edge of the hysol bond. When the mylar tears, the spectra fibers, which have already been freed of their attachment to the film, pull out.

    One way to improve the strength of bonded cuben seams, I think, is to bond both sides. Delamination and fiber pull-out are commonly (but not universally) observed modes of failure, and one can see just by peeling apart the edge of a new, untrimmed piece of cuben that the outer layers are not securely attached to the reinforcement. If we really want to bring the strength of the seam nearer to the strength of the reinforcement, we should be grabbing the laminate on both sides. This way, two interlaminar bonds and two plies of mylar must be broken (or the reinforcement, whichever happens first) in order to pull apart the seam.

    #1660451
    Rog Tallbloke
    BPL Member

    @tallbloke

    Locale: DON'T LOOK DOWN!!

    Colin, very smart thinking, thanks.

    #1660634
    Ike Mouser
    Member

    @isaac-mouser

    i have ct.2k.08 on the way, i will be making a tarp, waders, and shell mitts. Am i correct in assuming that the current recommended method for creating cuben gear is to use non-sewn hysol?

    #1660651
    Michael Davis
    Member

    @mad777

    Locale: South Florida

    Ike, I have been researching this topic also and have decided that the general consensus is not to sew cuben. That leaves two options, glue or tape, each having advantages & disadvantages.

    Glue requires clamping, which for a small piece is OK but could be problematic for large pieces. But, that gives you the ability to make adjustments after the pieces make contact.

    Tape doesn't get clamped. Once the two pieces touch, you're done. But, you get one chance, there is no room for error.

    #1660678
    Ike Mouser
    Member

    @isaac-mouser

    i dont have a clamp. would placing text books the a large container(10 gallon or more) of water on top of the books do the trick? im assuming the glue is hysol, do you have a product number? There are different types.

    If its hysol, how long should i leave it weighted?

    #1660769
    Steven Evans
    BPL Member

    @steve_evans

    Locale: Canada

    Ike,
    Books will be fine. Basically, you are trying to eliminate air bubbles and create a very thin bond line. I actually didn't even put weights on my stuffsack and tarp when I built them, but I would if I did it again.

    The Hysol number is U09-FL. Leave it weighted overnight if you can, but a few hours is probably fine aswell. Mix small amounts at a time as it is initially very easy to work with but starts to get tacky (making it hard to spread) fairly fast.

    #1660775
    Roger Caffin
    BPL Member

    @rcaffin

    Locale: Wollemi & Kosciusko NPs, Europe

    Colin's analysis seems right to me, but aren't we getting lost in the leaves here and not seeing the forest?

    Basically, what we are talking about here is, quite simply, pushing the Cuben fabric beyond its reasonable working load. Of course it is going to fail; so would any other fabric when overloaded. But that's not the end of it.

    Stepping back even further from the forest is needed. The forces needed to break Cuban like this are FAR beyond what you should expect to see with a reasonably made, reasonably pitched, tarp or tent, under reasonable conditions. If you want to camp on a ridge at 4,000 m in a howling storm, you should seriously consider a more robust tent! You should NOT be trying to design something which has a 10% margin of safety.

    You should also very seriously consider alternate occupations, but that's a matter for another thread!

    Cheers
    PS: and spinnakers do burst too, but all that means is you lose the race. Tough.

    #1660812
    Colin Krusor
    BPL Member

    @ckrusor

    Locale: Northwest US

    I think I agree with you in general, Roger, about the risk of sacrificing too much of one's safety margin to save a few ounces, but I also think you might be misclassifying the debate on these forums about cuben seams and tie-outs. I think all the talk about bonding vs. sewing and related topics is not necessarily indicative of a desire among posters to sacrifice any of their safety margin.

    Improving the strength of the seams in a shelter design is a good way to improve your safety margin. I think the discussion about cuben fabrication techniques and design considerations indicates that people DON'T want to push the limits of the material. They want strong seams and tie-outs because they want their cuben shelter to be robust, reliable, and safe.

    Cuben has shortcomings, but I'm not convinced at this point that cuben is an inherently unsafe shelter material (I don't know if you meant to argue that it is).

    #1660813
    Rog Tallbloke
    BPL Member

    @tallbloke

    Locale: DON'T LOOK DOWN!!

    Having seen a few photos of real life tent failures with cuben, I'd like to make sure I'm giving it the best possible chance by making the best possible seams and bonds.

    I don't like having to break camp in the middle of the night.

    My thanks to all the contributors here.

    #1660844
    drowning in spam
    Member

    @leaftye

    Locale: SoCal

    As I vaguely alluded to earlier, I think we're worrying too much about seam strength, although I could totally understand if the goal is to build a 4 season bomber shelter. When I'm more worried about is the longevity of the material(s). What happens to the cuben fiber, glue, and tapes after a few years out in the field?

    #1660865
    Ike Mouser
    Member

    @isaac-mouser

    Im not trying to push the limits, just trying to do it right the first time. I had to sell nearly all of my gear except what i absolutely need to buy cuben fiber. So im gonna do as much research as i can to do it right. Its not about pushing the limits, its about durability, using the money spent in a wise way, longevity, and safety.

    #1660934
    Colin Krusor
    BPL Member

    @ckrusor

    Locale: Northwest US

    Eugene, I wonder about that, too. I think long term environmental degradation will look very different for cuben than for coated nylon or polyester fabrics. A bonded cuben shelter would never fray or develop loose or unravelling seams like a sewn fabric shelter, and it should tolerate sunlight much better than nylon and at least as well as polyester fabrics. But it might get pinholes. And the bonding agents we use for cuben are all urethanes, which, as a general class of polymers, don't weather very well due to hydrolysis (unlike silicones, which last for decades outdoors). It will be interesting.

    #1660944
    Rog Tallbloke
    BPL Member

    @tallbloke

    Locale: DON'T LOOK DOWN!!

    "the bonding agents we use for cuben are all urethanes, which, as a general class of polymers, don't weather very well due to hydrolysis (unlike silicones, which last for decades outdoors)"

    Do the sailing guys share any knowledge? They have been gluing big sheets longer than anyone else I presume.

    Bearing in mind Roger's comment, has anyone tried a high modulus silicone to test yield strength on broad seams?

    #1661015
    Ike Mouser
    Member

    @isaac-mouser

    what about seam sealing cuben? If im making hysol sealed (nonsewn) waders, packliners, tarps, do i need to seam seal in addition to the gluing? Im thinking that especially in the case of the waders which will serve many purposes: as my gloves, laundry bag, stuff sack and possibly dirty bag for my filtration system, they will take alot of abuse, should they be sealed? If so, what works for seam sealing cuben?

    #1661023
    Colin Krusor
    BPL Member

    @ckrusor

    Locale: Northwest US

    Cuben is just fancy plastic film, and hysol is just urethane glue. When you smoosh them together there will be no way for water to get through.

    Cuben does seem to get pinholes after some creasing and abrasion, though. I wouldn't use it for a water storage container for that reason, and after a season of use this might cause your waders to leak a little. This has been reported in cuben dry bags by several visitors to these forums.

    #1661033
    Ike Mouser
    Member

    @isaac-mouser

    Im using the "bombproof" CT.2K.08(25.4 g msquare, .7oz). Maybw that will preveng some of these small abrasions.

    #1661039
    Dustin Short
    BPL Member

    @upalachango

    CT.2K.08 is by no means bombproof. It's just the best weight/performance ratio out there for specific applications (namely tarps and light use bags/packs). If you want a more bombproof cuben look at the 1.2oz and 1.5oz varieties. They have a much thicker mylar film and resist abrasion far more than CT.2K.08.

    Also if you're making waders, how are you protecting the bottoms? If it's just bare cuben, it'll get torn up after the first few dunking and then you have a pair of really expensive non breathable long johns…which aren't even that great as VBLs with the hole in the soles. I'd strongly recommend gluing some kind of felt (common in waders) or flipflop sole to the bottoms just to provide a bare minimum of protection.

    #1661040
    Dan @ Durston Gear
    BPL Member

    @dandydan

    Locale: Canadian Rockies

    CT2K.08 seems to fare the same as lighter weight variants with regards to developing pinholes. The biggest factor with the pinholes seems to be the thickness of the mylar layers, rather than the amount of spectra. CT2K.08 is a lot stronger than the lighter variants because it has a lot more spectra, but it still uses the same mylar layers. The last bit of the product code ('.08') refers to the thickness of the mylar.

    If you go heavier than 0.74oz cuben to 1.2oz cuben (CT3.5K.18) then you get a much thicker mylar layer (.18) that I doubt would ever develop pinholes under reasonable use. It would be cool to see cubic tech use this thicker mylar layer in conjunction with less spectra (ie. 2K) to create a material that's bomber strong like CT2K.08 and also bomber abrasion resistant. A theoretical CT2K.18 would weigh about 1.0oz/yd and would be perfect for groundsheets, durable clothing like rain pants but probably overkill for a tent flys, as they suffer very little abrasion.

    I wouldn't sweat pinholes too much for a tent canopy. Tents just don't suffer enough abrasion for this to be a concern. The only time I get pinholes is in the bottom of a cuben stuff sack that I use regularly around camp for a long time (ie. 1-2 years) and they are dragged around camp and set on rocks all the time. Even then, the pinholes are too small to see and if you used this material as a tent fly I bet it would still keep 100% of the water out. The pinholes are so small they only let water through if you actually fill up the stuff sack with a gallon or so of water, which is a ton of force.

    #1661047
    Ike Mouser
    Member

    @isaac-mouser

    I plan on using a pair of those featherlite/ultralight crocs(although they are not crocs, they are some other brand lighter than crocs but i cannot remember the brand-maybe someone can help me.) in conjunction with them. I would slip off my trail runners, slip them on, put on the crocs and cross. I think the waders will allow me to reduce the weight of my pack since they are so multipurpose. I thought about adding a felt/rubber layer, but there are disadvantages:

    felt:
    using it as a stuff sack with dirty felt on it would introduce all kinds of gunk into my pack as felt is a nice sponge for everything
    Cannot be used as shell gloves
    cannot be used in sleeping bag as VBL
    introduces more parts, meaning more places to fail

    rubber:
    cannot be used as shell gloves
    More parts, more places to fail

    penalty of not encorporating a bottom:
    a few oz in protection for the waders when crossing

    Does the multipurpose functionality of not encorporating a bottom material makeup for the penalty of carry crossing protection? Depends on the weight of the protection.

    #1661106
    Colin Krusor
    BPL Member

    @ckrusor

    Locale: Northwest US

    I know that Cubic Tech has experimented extensively (and produced in small batches) a much wider variety of products than they actually keep in inventory.

    Strong, hydrolysis-resistant, heat-sealable urethane films for lamination to fabrics are available in 0.3 mil thicknesses. A heat-sealable cuben product with urethane film and Vectran fibers could probably be made in the 1.5 – 2 oz range(CT1KV0.3?). Production time and tooling costs should be low because it wouldn't require any laminating adhesive, just heat and pressure (which CT already uses for standard cuben). It would be very puncture resistant and far more resistant to abrasion than conventional cuben of similar weight (although with lower tensile strength). It would be perfect for tent floors, inflatable sleeping pads, and other applications where toughness and puncture resistance are important (a sub-1-pound packraft?).

    Polyoxymethylene (Acetal, like Delrin), Polyetheretherketone (PEEK), and Polyphenylene Sulfide (PPS) films are commonplace. Cubic Tech may have tried them. They are much more expensive than mylar (particularly PEEK), but they offer interesting mechanical properties (like good toughness, which mylar lacks). Polyamide film (nylon film, used to make "mylar" balloons) would improve the puncture and abrasion resistance of cuben (and make it much easier to bond), but it could only be used for applications that offer protection from sunlight.

    I'm not suggesting nanotubes or something exotic. These materials are all ordinary(the "breathable" cuben is probably urethane film). I just think it would be fun if Cubic Tech kept small batches of alternative materials in inventory. It's a fantasy that comes to mind when I'm thinking about how to get around the abrasion and puncture resistance problem inherent to standard cuben.

Viewing 23 posts - 51 through 73 (of 73 total)
  • You must be logged in to reply to this topic.
Forum Posting

A Membership is required to post in the forums. Login or become a member to post in the member forums!

Get the Newsletter

Get our free Handbook and Receive our weekly newsletter to see what's new at Backpacking Light!

Gear Research & Discovery Tools


Loading...