Interesting, I just started a thread about this yesterday. (:
I have between 20 and 30 metres of flourescent pink polyester sheathed dyneema kite bridle thread in the post on its way to me. Its diameter is 1mm and it has a breaking strength of about 100kg (or, slightly more than my own weight).
When I get it I'm going to replace the thick-but-invisible beige lines on my tent with them. We had a couple of kids run and fall over them at one busy site on the coast near here last year.
I got mine from a kite shop in the Midlands. I'd tell you which, but I just bought all the 1mm dyneema he had left - a quick Google search will render plenty. He tells me that the pink is the most visible against grass.
I got it polyester sheathed. You can get it bare, but Dyneema is slippy as owt, and won't hold a knot by itself. The sheath is a 12 strand braid (I think), which is why I went for bridle line rather than kite line (the bridle, in case you don't follow kiting, is the string setup that tethers the points on the kite spars to your line(s)).
Dyneema is basically inelastic, meaning that the tent will have to flex differently. I'll be seeing if thats an issue. It's stronger than Kevlar per weight, so in a fierce wind it could mean that either the tent goes boing or the line comes away from the ground. My plan is to use a Midshipman's Hitch, also known as a Taughtline Hitch, because the cord is so thin that the sliders wouldn't stay put. I do hope that link works...
Anyway, I'll definitely be reporting back here how it appears, although if it's not here by this weekend than it's unlikely that I can take it out camping for a few weekends. I'll definitely subject it to some abuse around the flat, though!
i have been kiting for 10 years now and have lots and lots of kite line,kite line can be exspenive to buy. If anyone would like sume let me no i have 100 of meters of it at a breaking strength of 360kg
I now have 30 metres or so of 100kg bridle line. It's so thin! The scissors hate it, and it's stronger than me when it comes to breaking strength. The weather's all drizzly, so I'm not taking a tent out today, but I plan to start fitting the new (pink with yellow flecks) lines to the outer this weekend.
Quick update. When cutting sheathed Dyneema, the Dyneema and the sheath both fray quickly. Easily remedied with a lighter? Sort of. Dyneema melts first, but oddly enough not enough to bind, and frays again. You need to heat it up so that it melts into a little blob, which pushes the sheath out.
It never binds to the sheath, either, meaning the sheath can easily retract, although a good knot seems to help.
I'm fixing the lines to the flysheet with figure-eight loops (aka "Flemish bowline" - a common climbing knot). The adjustable stake knot might have to be changed from the Midshipman's Hitch (linked above) to this interesting knot, because the M's Hitch seems to be able to slip with the thin bridle lines.
I was wondering about this over the weekend. Dyneema has a bit of a reputation for cutting other materials, and even itself, and I wondered if it might cut through the guying points on the tent, especially as there's little stretch, so the wind loading is likely to make the action of guyline on guying point all the more pronounced (more 'snappy').
It might be an idea to tie a loop of normal guyline cord to the guying point, and then tie the Dyneema to this. This could then be easily replaced if the Dyneema does cut it; replacing the guying point would be much more difficult.
The Dyneema in question is sheathed, meaning it would need to cut through its own polyester sheath first. This line is designed to be tied to itself and to kite spars in the sort of winds that keep kites up - and then to be tied to your kite line, which might not be Dyneema. Being cut through isn't a desirable trait for bridle line.
I'm confident that it won't damage the tent, and even more confident that if it was going to I'd spot the fraying sheath first (especially as I'd be looking at it regularly).
Oh yeah - an additional property of Dyneema is its low melting temperature. If something's wearing, the friction is likely to damage the Dyneema long before polyester. This is what leads to Dyneema's reputation for cutting itself. If you have (unsheathed) Dyneema kite lines and get your lines crossed with somebody flying with Dacron or something, the Dacron will tend to cut right through the Dyneema with the friction.
I have to say that I'm really chuffed with these guy lines. They stay taught, and never sag when wet. They stood up to some gust winds, holding the tent more or less rigid. The give in the tent poles was enough to let the tent as a whole deform during a gust.
At no point was there any sign that the Dyneema lines might cut into the tent's guying points. They are braided lines, not cheesewire.
Being braided, they do hold knots beautifully. The Midshipman's Hitch was the perfect knot in this situation - it allowed me to tighten or loosen the lines at will.
Before I struck the tent, I wound up the lines into coils and bound them like miniature climbing ropes. They were tiny like this, and striking the tent and packing the fly away was made much easier.
Not sure how much weight was saved, but it was basically whatever the old lines weighed. The Dyneema lines have negligible weight, and don't budge my spring scale at all.
Visibility was incredible. These flourescent 2mm lines were more visible than the beige 6mm invisible tripwires that came with the tent. I chose that colour on the advice of the kitemaker who sold me the line - he uses the same colour when he needs marker lines that show up on grassy kite fields. It was a good choice - my camera almost refused to believe such a pink existed, so the photos had to be rebalanced a little, but they were far more visible to the naked eye.
I bought the line from Free Spirit Kites in Wolverhampton. This guy will happily take telephone orders in the late evening (his hours are 9am-9pm) on any day of the week, and is also happy to talk about his stock in detail. Definitely recommended by this customer.
My speculation on whether Dyneema might cut other fibres was the result of incorrectly recalling a discussion on the choice of materials for making up cordelettes for climbing. A number of candidates were proposed and tested, including Spectra and Spectra-A. The former is linearised polythene (as is Dyneema), and the latter uses aramid (Kevlar) fibres. It is the aramid fibres that have a reputation (based on experiment) for cutting other fibres. The cutting isn't an action of friction; it's the action of a very fine, very strong fibre (a cheesewire, if you like) being pulled through a weaker fibre in the composite fibre bundle that makes up the cord.
Apologies for my failing memory; I only raised it as a word of caution to prevent damage to your tent had I been correct, which is why I suggested a precautionary approach to start with. Glad to hear you're pleased with the outcome.
Cool. Dyneema's very low melting point tends to make it vulnerable to friction - ask any kiter whose expensive Dyneema lines were severed by somebody else's nylon.
The braided sheath is essential, which is why I went for bridle line. Normal Dyneema kite lines are only sheathed at the very ends, so that you can actually tie them. Dyneema alone has a very low friction coefficient, and tends to slip out of its own knots, so you'd have trouble making it taught or even keeping it attached to the tent. Additionally, the sheath is often brightly coloured - although I could have paid a quarter of what I did for the same strength of line, but sheathed in black. That coul dhave interesting military applications, but isn't exactly a safety feature.
A day after we pitched, a caravan rally moved in. One of my Dyneema lines was tripped over, and then driven over an hour later. It was fine, although my tent went a funny shape as the 4x4 pickup went over the line!
Perhaps I should have mentioned that - should somebody drive over your Dyneema, the tent's going to get a hefty yank.
They're very expensive! I got 30m of sheathed line for a tenner. Remember to look for bridle line, as it's sheathed. Normal flying lines are naked dyneema.
