SilNylon Stretch Factor

**oldgringo** · 09-23-2010, 18:03

Properly speaking, plastic is a property, not a material, but it has been widely (mis)used to identify a wide range of materials, some weak, some strong. As G stated, there is most likely considerable variation in the strength of various "plastic" fittings. I have broken one D ring, and so have a permanent bias against them. If I must use anything, I opt for stainless steel split rings.

**Barefoot Child** · 09-23-2010, 18:06

Thank you Acer for that answer about bias direction. I do own at least one diamond shaped tarp.
Why would it be important for diamond tarps?

**warbonnetguy** · 09-23-2010, 18:11

bias is 45 degrees rather then down the length of the roll (warp) or directly side to side (weft or fill). it stretches on the bias because none of the threads run in that direction.

i find if i stretch a silnylon tarp very tight to begin with moisture won't cause it to sag, it will loosen some, but not sag. a 3/4" plastic ring will hold over 100# if i recall (some materials are stronger than others, some rings are thicker than others)

i assume by "balanced" he's talking about fabrics where there is roughly the same number of threads running both warp vs fill, such a fabric would also have a similar strength in both directions.

generally 1.3 silnylon is pretty strong for tarps. different methods for doing corner attachment points would certainly effect strength, generally the more stitches you can spread out the guyline force over, the stronger the pull tab will be

**Barefoot Child** · 09-23-2010, 18:12

If plastic is a property and not a material, would it be more correct to ask a manufacturer of seemingly "plastic" parts to actually say what "material" the part is made from?

And by knowing this bit of information could someone then do reasearch to find out the failure threshold of said certain material?

**oldgringo** · 09-23-2010, 18:17

Originally Posted by Barefoot Child

If plastic is a property and not a material, would it be more correct to ask a manufacturer of seemingly "plastic" parts to actually say what "material" the part is made from?

And by knowing this bit of information could someone then do reasearch to find out the failure threshold of said certain material?

Probably, but it would take an engineer to work through all of that, and a very determined, patient saint to ferret out the info to start with...I'll bet the bulk of it is made in China.

**TiredFeet** · 09-23-2010, 18:33

As for the S-biner strength. All of the Nite Ize Figure 9s and S-biners we have have a max load laser etched on the side. I have read that manufacturers use a 25% factor to compute working load. If Nite Ize uses that factor, then the breaking strength is 4x the max load etched on the s-biner.

**jeepcachr** · 09-23-2010, 19:05

Is all sylnylon assumed to be the same? Is there only 1 type/weight of sylnylon?

**Barefoot Child** · 09-23-2010, 20:25

Thank you Brandon,
I too have found it to be that if I stretch my silnylon tarps tight, that with moisture they may sag a little but any stretching is minimal. Therefore I don't take out the slack in the tieouts since it will return to it's original condition when the tarp drys out (my tieouts are made from 2.2mm Dynaglide and don't seem to absorb any moisture).

I was wondering if anyone else has observed this phenomenon.

By that I mean that in the morning the tensioners have gotten shorter thereby taking up the slack caused by a tieout that got looser because the tarp sag or stretched a little, but later when the tarp has had time to dry the tensioners are longer and the slack in the tieouts is gone. This is easily observed if the tarp is set up in the same location and not moved to a different campsite.

**nacra533** · 09-23-2010, 22:07

Originally Posted by Barefoot Child

And since I am only concerned about silnylon I would prefer to not get geeky.
Please don't take me wrong... but at this time I only have tarps made from silnylon, and that is why I asked about silnylon specifically. I would like this discussion to stay centered on silnylon and not have to weed through all of the other types of material information.

Spinn ul is ripstop nylon. Sil is ripstop nylon. The difference is weight so the chart and info apply to sil. Sil is spinnaker cloth.

You asked about stretch. This chart describes elongation at different loads in different directions. The shape of the curve should apply to all ripstop nylons. Obviously, the heavier the fabric, the more load it takes to stretch it.

**nacra533** · 09-23-2010, 22:22

Originally Posted by jeepcachr

Is all sylnylon assumed to be the same? Is there only 1 type/weight of sylnylon?

Typically, when the term sil is used, most are referring to 1.1 oz ripstop nylon impregnated with silicone. This coating takes the weight to about 1.3 oz.

There are other weights but usually called something else. For example, Spinn UL is a .75 oz material but basically the same thing.