Bushwalk Australia

Hi all,

I thought I should finally have a crack at a Cuben Fiber tarp and have been playing around with tie out options.

For the reinforcement patches I ordered in a small amount of a pressure sensitive adhesive film from a Sail cloth shop in Sydney who I already deal with. They didn't have what I was after so I just got some PSA clear film which is used as a covering material on film sails. I was a bit dubious but it seems to work ok. They do have a taffeta and Polyeter X-Ply PSA which I wanted initially, and I assume would be a little stronger.

The thing I like about the clear film is once it's stuck on it's almost invisible but still seems to give it good strength. I used 1/2 inch grosgrain, with the cuben fibre sandwiched between the grosgrain, and a lineloc3 for my practice piece and tried to break it but couldn't. The film seems to add strength and prevent any elongation of the needle holes. It actually feels rock solid which surprised me. Though once I do the tarp I will know for sure in the long term.

I am not sure of the weight of the film, I have not weighed it yet (Edit: I just weighed the tie out patches. Each patch adds about 2 grams). What weight fabric/material reinforcement have other people used?

I had some lightweight coated nylon ripstop pack cloth (about 115 g/m2) sitting in my box of stuff so I used that. I sewed a piece of the nylon to a piece of the 18 g/m2 cuben I was using and then taped that to the tent. These pieces totaled 12.1g for my tent, but I don't think that included the weight of the adhesive tape. I would estimate that the tape added another 5 or 6 grams bringing the total up to about 18g. That was spread over 9 patches (corners and sides), so probably about 2g per patch on average, give or take.

I remember kind of obsessing about the seemingly heavy pack cloth I was using out of fear my tie outs would fail.

Yours look really nice. Did you do a test pull on one?

Yeah between my wife and I, we tried to destroy it and it never moved. No elongation of stitch holes. I will do more of a destruction test later on. It feels rock solid though and I think it would hold in most wind conditions - hopefully. Dutch is sending me over some CT3.5K.18 Cuben Fiber to try out as reinforcement so I will compare the two but this stuff is certainly easy to apply just peel the backing off and stick it down.

My tieouts are cuben with a cuben reinforcement patch, always surprises me when we comes through a nasty,
blustery storm unscathed....relatively speaking....my fingernails are noticeably shorter & my eyes are always bloodshot from lack of sleep.
Yours look good Simon.

Good to hear yours is still going strong ofuros.

I don't know whether to stick with this clear film or I can go a 3.3oz polyester PSA or the CT3.5k.18??? Too many options.

It sounds like the adhesive film could be a winner and sandwiching the cuben between the two ends of the grosgrain is an excellent technique. I don't think the backpacking community has spent enough time investigating the sailmakers techniques and specialist materials. It seems to me that the main issue with tie outs is minimising the localised high stress point loading where thread passes through fabric. If using cuben as the re-enforcing one technique is to orient the fibres in the patch at 45 degrees to the fibres in the main piece.

An idea I have been pondering is using double sided tape/adhesive to adhere the grosgrain to the cuben to spread the load a bit better. This is not to replace the stitching but may reduce the point loading.

As an aside, while Cuben has such light weight and non stretch properties it is interesting to see sil-nylons now coming down in weight for use in tents. 15 and 20 denier are now quite common and 10 denier is the new benchmark now that Hilleberg is starting to use it (26gsm) which is the equivalent weight of CT2K.08 (25.3gsm) which several manufacturers (SMD, MLD etc) use as their standard. It seems that we will soon be choosing tent fly fabric for its performance characteristics (stretch or no stretch) rather than weight.

Hi Mark,
If you want to try out some of this adhesive film let me know and I will send some to you. It certainly seems to do what it should.

I didn't know Hilleberg were using 10d sil. Is that a polyester or nylon? I have used a 15d silnylon but I didn't like the amount of stretch.

There is also some silicone coated polyester on the market which supposedly has less stretch.

I just tried a sample of PSA backed 3.3oz polyester as reinforcement. Brief testing seems to indicate that is equally as strong as the clear film whilst being lighter, and having a more natural soft hand.



Having performed some unscientific repetitive destructive shock testing to the tie outs, the failure point seems to be just above where the reinforcement patch ends with the laminate and fibres showing significant distortion.

OK That's probably because there is no gradual phase out of the reinforcing and all the load is being taken by the small transition points.
Try a much smaller first triangle ending just above the webbing and see if that helps
S
I have read that when making sails that the correct way to sew on the patches is to have the fabric all oriented in exactly the same way.

A bartack on the edge seam may also help as may over-sewing with a repeated zig-zag stitch
Mind you that's sewing technique I'm not familiar with the PSA method so my advice may not be relevant

Hey mate,

I think it is as a result of what you say but it's consistent with the effects of the same testing I have done on silnylon. The shock testing is not necessarily consistent though with the forces applied in the real world. It's a small square of fabric so the force is concentrated, there is no give in the system at all, the test basically involved one end being tied off to an immovable object and me pulling relatively hard repeatedly on the cord of the tie out.

Personally I would be happy taking this out and using it. I just like to see where the potential weak points in the system are.

Most reinforcing methods will work in the field particularly if they are bonded and optionally sewn (not just sewn). Pretty much every article I have read on cuben tie outs (bpl, suluk46 etc) suggest that the issue is not the strength of the tie out but the way stresses are passed to the main layer of cuben. I believe the best reinforcement patches are the ones with radiating fingers (google sail reinforcement) but these would be a pain to make and use a lot of material. To get the best out of them you also need to consider the stress lines in your design and orient the fingers to suit. I think a quarter round patch is likely to perform a little better compared to the triangle due to spreading the stresses a bit more widely and the idea of using different sized patches radiating out from the corner as suggested by Moondog is a common practice in sailmaking as well. The other benefit the quarter round patch may give is creating a bit more distance from the sewing on the grosgrain and the edge of the reinforcement.

Hilleberg's 10D sil-nylon can be found at http://docs.hilleberg.net/news/Hilleber ... r-Enan.pdf . While polyester has lower stretch properties I suspect at that low denier the extra strength of nylon 6,6 is a factor in the choice of fabric. It is notable that Hilleberg only uses a sil-polyester in their heaviest fabric using a 75D fibre (http://www.hilleberg.com/home/tent_info ... rength.php).

Thanks Mark - my original, clear film, patch was a quarter round patch. Due to the nature of my samples with the PSA polyester it was just easier for me to cut it square but for my tarp I will go with round and I think I will use the polyester.

I am pretty sure Ofuros used radiating fingers in his design.

There has been a lightweight silicone coated polyester just released in the USA for the DIYers but the strength in the field is an unknown.