Lines Spectra or Dyneema ?
- Davis Cheek –Let’s talk about lines. Spectra or Dyneema ? Best overall strength and length? Stiff or not so stiff? Do you wax your lines? Is anybody using the Dyneema SK75 pre-stretched thin & stiff line? Is SK75 molecule alignment important to you?
- Wayne Carkeek – i thought spektra and dynema were just brand names for the same product ? Kevlar is the best , but dangerous as main lines
- John Jones – isnt kevlar banned from racing with ?? so no point in using that
- Davis Cheek – Well… As best as I figure, Spectra and Dyneema are the same animal. I believe it depends on the application that you use it for. We should be really calling it UHMWPE or humwipe or humpee. I’ll admit that humwipe or humpee is not as classy as Spectra or Dyneema but the fact is that’s the fiber! I like Spectra or Dyneema names better. 25m’s of Humpee just don’t sound right, does it? I just finished waxing all my Humwipes last week. Or should I say Humpee’s.
- Wikipedia says this; Dyneema and Spectra are gel spun through a spinneret to form oriented-strand synthetic fibers of UHMWPE, which have yield strengths as high as 2.4 GPa (350,000 psi) and specific gravity as low as 0.97 (for Dyneema SK75). High-strength steels have comparable yield strengths, and low-carbon steels have yield strengths much lower (around 0.5 GPa). Since steel has a specific gravity of roughly 7.8, this gives strength-to-weight ratios for these materials in a range from 8 to 15 times higher than steel. Strength-to-weight ratios for Dyneema are about 40% higher than for aramid.
UHMWPE fibers are used in armor, in particular, personal armor and on occasion as vehicle armor, cut-resistant gloves, bow strings, climbing equipment, fishing line, spear lines for spearguns, high-performance sails, suspension lines on sport parachutes and paragliders, rigging in yachting, kites, and kites lines for kites sports. Spectra is also used as a high-end wakeboard line.
For personal armor, the fibers are, in general, aligned and bonded into sheets, which are then layered at various angles to give the resulting composite material strength in all directions. Recently developed additions to the US Military’s Interceptor body armor, designed to offer arm and leg protection, are said to utilize a form of Spectra or Dyneema fabric. Dyneema provides puncture resistance to protective clothing in the sport of fencing.
Spun UHMWPE fibers excel as fishing line, as they have less stretch, are more abrasion-resistant, and are thinner than traditional monofilament line.
In climbing, cord and webbing made of combinations of UHMWPE and nylon yarn have gained popularity for their low weight and bulk, though, unlike their nylon counterparts, they exhibit very low elasticity, making them unsuitable for limiting forces in a fall. Also, low elasticity translates to low toughness. The fiber’s very high lubricity leads to poor knot-holding ability, and has led to the recommendation to use the triple fisherman’s knot rather than the traditional double fisherman’s knot in 6mm UHMWPE core cord to avoid a particular failure mechanism of the double fisherman’s, where first the sheath fails at the knot, then the core slips through.
Owing to its low density, ships’ hawsers and cables can be made from the fibre, and float on sea water. “Spectra Wires” as they are called in the towboat community are commonly used for face wires as a lighter alternative to steel wires.
It is used in skis and snowboards, often in combination with carbon fiber, reinforcing the fiberglass composite material, adding stiffness and improving its flex characteristics. The UHMWPE is often used as the base layer, which contacts the snow, and includes abrasives to absorb and retain wax.
It is also used in lifting applications for manufacturing low weight, and heavy duty lifting slings . Due to its extreme abrasion resistance it is also used as an excellent corner protection for synthetic lifting slings.
High-performance lines (such as backstays) for sailing and parasailing are made of UHMWPE, due to their low stretch, high strength, and low weight.
- Corey Jensen – Spectra is a long-chain polymer originally formulated and patented by Allied Signal (I believe) Dyneema is another not-quite as long-chain polymer developed overseas to avoid patent infringements. Kevlar is an aramid fiber from DuPont. Kevlar is very abrasive and breaks-down with exposure to UV. Spectra is lighter than Kevlar, no (or little) UV degradation, non-abrasive but it does have a very low melt point (161 degrees F) Both fibers, in a stabilized braid, have little or no elongation (stretch). As with most materials, the quality depends on many factors including the original extruded fiber source, quality of the braiding machines and quality-control at the mill.
- Wayne Carkeek – cheers Corey , very interesting, do you know the relative strength of kevlar vs spektra ? i thought Kevlar was about half the diameter for the same strength
- Corey Jensen – Diameter for round braid spectra is about the same as round braid kevlar. Flat braid appears narrower, but in use it vibrates under minimal tension and has a larger apparent profile. Strength is strength: ie 100# test cotton is the same strength as 100# steel. It is how they act under these loads that matters. Break strength and tensile strength are the two most valid measure. One measures a drop-load while the other measures elongation under tension. Another factor in kite use is the lower weight of spectra – .97 specific gravity – It floats! So the kite drags a thin line with less mass across the sky.
- Wayne Carkeek – kevlar tensile is about 3800 mpa and dynema can be as low as 1400 mpa so kevlar can be much thinner . I think the point is kevlar has better performance BUT it is banned in racing for main lines because is is so thin , strong and difficult to cut , all the qualities we want until its around someones neck. So dynema/spctra is currently the best compromise as long as its round 🙂