Hi all,
I have beenreading here the past few night about Cuben bonding for the ridgeline on a tarp. It seems that Hysol is the preferred adhesive. Where is a source for this? How much do I need? ans any rough idea on cost?

After you bond the ridgeline, does this make it stiff to fit into the stuffsack? Thanks!

Zach-

Been doing the same research. Seems like the Loctite Hysol U-09FL is the way to go. I ended up buying a 20ml tube (double-barrel thing, the only size option) from H.S. Hughes, a chemical company with warehouses all over the place. Jamie said one tube was 20ml set was plenty for a tarp.

It was $28 with shipping, so not cheap.

Edit: My bad it's U-09, not UL-09 ...got that ultralight on the brain...

Edited by ctwnwood on 02/27/2012 17:23:57 MST.

http://www.amazon.com/Loctite-U-09FL-Urethane-Adhesive-Flexible/dp/B000WXL1UI
$18.93

Has a different name though. The one you bought is Hysol UL-09FL the one I posted is Hysol U-09FL. I wonder if it's the same. Google seemed to want to correct the first spelling to the second spelling.

seamstick basting tape is supposed to work

much easier than Hysol

Probably not quite a strong as Hysol

http://search.sailrite.com/?freeText=seamstick

The basting tape will hold, but it's not strong enough. Without sewing it after it will pull apart. I've had some stuff sacks that were just basting tape that didn't hold up. If you wanted sew free, I'd stick with hysol. It's a great place to start if you want to sew though.

Thanks all for the good comments here! How does a cuben tarp pack with a bonded ridgeline? Does this make a stiff spot to try to squeeze in a stuffsack?

Zack, I think, for many people, bonding with Hysol does result in a somewhat stiff seam, but it doesn't have to. If you want to improve your chances of achieving a very flat and flexible, nearly invisible seam, I would recommend three things:

1. Use Hysol U-09LV (the low-viscosity version, available from Fastenal), not Hysol U-09FL, and store the glue in the fridge. Since switching to the LV I have not gone back to the FL. The lower viscosity allows you to get a much thinner film of glue between the surfaces, and this gives a much flatter, more flexible finished seam. It also increases the apparent open time a bit because it takes longer to get unmanageably gummy. Storage in the fridge also increases the open time and improves the shelf life.

2. Use very, very little glue. A very small, threadlike bead of glue is plenty for a 1/2" to 1" wide simple overlap seam if you clamp it tightly. You can always go back and add a little more at the edge if you added too little, but you can't remove any if you used too much. Don't bother spreading the glue at all. just put the bead right down the middle of the surface to be glued, and press the two surfaces together.

3. Clamp! Clamp it very tightly. In my opinion, this is one of the most common mistakes that people seem to make with Hysol. There is no risk that you will force all the glue out of the seam. Use two boards at least the length of your seam (I use smooth, straight hardwood moulding). They should be at least two inches wide, to avoid a ridge of squeezed-out glue at the edge. Cut strips of LDPE painter's plastic and put them on top of and beneath the glued seam, between the seam and the wood. The plastic will be easy to peel away the next day. Buy a dozen or more (I sometimes use two dozen) 2" C-clamps from Harbor Freight or some other discount tool shop. Use these to clamp the boards together very tightly. Put the clamps as close together as you can. Leave the clamped seam in a warm place overnight. The bond will take about 48 hours to achieve full strength.

If you do these three things, you should be able to obtain an almost imperceptibly thin seam that hardly differs in flexibility from the surrounding material. If you don't clamp, or you add an excess of glue, you'll get a stiff lump, in my experience. I hope this helps.

Colin,
Thanks for the additional info.
? Have you ever tried using a roller, but without clamping with the U-09LV - results?
Thanks.

Samuel, I haven't tried a roller. I think you'd never achieve compression pressures as high with a roller as you get with tight C-clamps, though. And keeping the seam under pressure throughout curing allows the glue plenty of time to flow, which might facilitate a thinner and uniform film of adhesive. I'm only guessing. It might work well. A comparison would be interesting.

I once did an experiment with Hysol compression. I smeared a thin layer of Hysol U-09FL between strips of LDPE film, pressing it down thoroughly with my fingers. I clamped some of them, put heavy weights on others, and left a few others uncompressed. The next day I peeled away the LDPE and took the bits of thin Hysol film to work. I measured the thickness with a micrometer and looked at them under the microscope. The uncompressed samples were, on average, about twelve times the thickness of the clamped samples and seven times the thickness of the weighted samples. I initially attributed it to expulsion of excess glue in the compressed samples.

When I looked at them under the scope, though, I saw that the uncompressed sample was full of tiny bubbles. This may account for some of the difference in thickness. The compressed samples had no bubbles. Maybe Hysol produces a high-vapor-pressure product when curing. In any case, compression, either by heavy weights or clamps, seems to prevent the formation of bubbles (that otherwise might increase the thickness and stiffness of the glue layer).

If you do a search on this forum for tape, one of the posters works with cuben all day long at a sail maker shop. They use 3M 9485 tape, then sew. This might be what Joe at Zpacks sells, the roll I got from Joe didn't have the model number of the tape.

I've used 3M 9460 tape with success with stuff sacks. It has lower tack than the 9485 so is easier to work with. Time will tell if I would use it for the seam on a tarp.

Steve

Colin,
Thanks for the additional info. It clears up a lot.
Most Urethane glues bubble when they cure, which is fine for the right applications, but not for fabric-like materials.
So now I understand that it's the clamping that prevents this, not the type of Urethane. If I use the Hysol, which is likely, will clamp also. The next best thing I found is silicone glue, but I don't think it will be tough enough to keep stress on the cuben from pulling the stitch holes open over time.
Thanks again.

Edited by scfhome on 02/29/2012 00:26:02 MST.

When you clamp the ridge line, is this for a canternary? Is this difficult to get both curved pieces to lay flat and clamp? I annticipate that this may be a tad on the difficult side but not impossible. Thanks for all the good info here!!

Also do you need a special dispenser for the Hysol adhesive? or a regular caulking gun, or squirt out part A and B and mix? T

Zach, I dispense the Hysol by pushing the glue out of each tube with a dowel marked with gradations so I can get the same amount out of each one, usually. If I only need a very small amount, I draw it out in two small syringes. In either case, I mix it in a little plastic cup, suck the mixture up into a syringe, and squirt a very fine little bead onto the surface to be bonded.

I've done a couple of catenary ridgelines with cuben and Hysol. I'm just finished one on a Hexamid. I have tried two methods. Depending on the way the pieces are cut, they can be clamped stacked together, with the edge of one folded over the other, or a strip of cuben (or two) can be used to join them. There may be other ways that I haven't tried.

I think using a strip (or strips) to join them should be stronger, but stacking the pieces and folding an edge over is easier (and makes a lighter seam, I guess). I think Lightheart Gear cuben shelters use a bonded ridgeline strip. I made my hexamid ridgeline using two strips in three bonding operations: one panel to first strip, other panel to first strip, second strip to seam on opposite side. The cuben stretches just enough (in the bias direction) to clamp a catenary rideline without wrinkles in the seam. The wider the catenary seam, the more problematic wrinkling will be. This is one of my reasons for using two strips; it can be narrower for a given bonding area (and seam strength), since it involves bonding to both sides of the panels.

After bonding the cuben to cuben seams, we're still left with the challenge of sewing on the grosgrain pullouts. I've also seen examples of pullout stitching deforming the cuben needle holes under load. Has anyone tried bonding the grosgrain before stitching? This might take a small amount of the stress off the thread and stitching holes. Or would this add too much weight without adding much strength? Is an single extra layer of bonded cuben as a reinforcing gusset enough to beef up the fabrid under the grosgrain?

I agree that tie-outs remain a problem. Grommets and grosgrain are the only two common methods that I know of, and I don't think either of them are very well suited to cuben. This is an area that is in need of some innovation.

Some people use a bonded-down loop of cuben "webbing" made from a rolled up piece of cuben, and there was a thread here about a cuben pyramid that had clever mid-panel tie outs that included a little nylon tube to spread out the load. I don't see any non-grommet or non-grosgrain methods used very often, though.

I've never made grosgrain tie outs (I've always used the cuben loop method), so I don't know if bonding before sewing would work. A lot of adhesive can get into the grosgrain, so it might take a powerful sewing machine and a sturdy needle to sew it after bonding.

Edited by ckrusor on 03/02/2012 22:32:32 MST.