More silpoly from Tarptent

Here is an archived page from late last year: https://web.archive.org/web/20210616131108/https://www.tarptent.com/product/stratospire-2/#tab-id-2

Looks like the new 20d silpoly fly is about 0.8 ounces lighter than the most recent version of the 30d silnylon fly.

New color looks great. Silpoly fly appears to have a few wrinkles. Polyester is stiffer than nylon, so less forgiving in pitching. Compared to silnylon, silpoly is probably a bit harder to get a perfectly taut pitch, but the panels should stretch and deflect less under wind loads. And that latter difference will be magnified when the flys are wet.

The only times I’ve really disliked silnylon flies are when the wind and rain arrive simultaneously. The rain and sudden drop in temp relaxes the fabric, loosening the pitch, then the wind plays havoc on it. With a single-pole mid this is not a big deal cuz one can raise the pole a bit to take the slack out of the fabric, but this isn’t as easy with more complex dual-pole geometries. The other time is packing up a wet or damp fly – the weight gain can be pretty big. Silpoly should eliminate both problems.

Kudos to Tarptent for sourcing this new fabric. I think it’s probably pretty great stuff. Judging from the weight of the fly, it must be about the same, or a little heavier, than the 30d silpoly sold by Extreme Textile. As I’ve written before, that fabric appears identical to the 30d silnylon used by Locus Gear – the weave is identical, as is the feel of the coating in hand.

The guys over on trek-lite.com are saying the fly weight went from 731 g to 697 g. So if that’s correct a 1.2 oz decrease.

Yes, same silpoly (now in green) as we introduced in the Preamble.  We really like this stuff as the key reason we didn’t jump on earlier bandwagons was excessive bias stretch which makes for too much movement in wind. This stuff has comparable bias stretch to our stiffest flavor of silnylon and when fully tensioned in the StratoSpire makes for very nice performance.

-H

Well done, Henry!

How is bias stretch reduction achieved in a woven fabric?

Nice.

> How is bias stretch reduction achieved in a woven fabric?

Coating aside, tighter grids have less ability to deform.

Thanks, Henry.

BTW, does your new silpoly Stratospire exhibit reduced panel deflection under wind loads than the silnylon version did? If so, do you have a ballpark quantification (e.g. ~10% reduction)?

We haven’t measured it quantitately but after watching it in wind and hand stressing it I can say it’s somewhere in the “equal to better” range. When wet it’s certainly in the better range if you haven’t already retightened the silnylon version.

Many thanks, Henry.

Nice looking update.

The fabric sounds like an improvement. The silpolys that I’ve used before in the 15- 20D range (with the notable exception of the 30D from ET mentioned above) were all a little  too stretchy in the wind. It’s interesting to hear that the grid weave makes as much difference as the coatings.

If I remember correctly, Henry mentioned earlier that the new 20D silpoly was coated on both sides with pure silicone, not blended with PU or PEU as many recent fabrics are (eg. those from RBTR or the fabric used in the X-Mids).

Looking over the TT website, it seems unless I’m mistaken that the SS2 page doesn’t mention that the new 20D silpoly is sil/sil. This would be a useful thing to mention, if it is indeed true, highlighting the superiority of the new fabric.

> Looking over the TT website, it seems unless I’m mistaken that the SS2 page doesn’t mention that the new 20D silpoly is sil/sil. This would be a useful thing to mention, if it is indeed true, highlighting the superiority of the new fabric.

Thanks for catching that. We’ve amended the description.

-H

this is great to see. ive never had an issue with silnylon except for the sag and the water-weight, and this seems to address both without the bulk and cost of dcf. i would like to see them do a silpoly motrail as it is their lightest, simplest singlewall 2p shelter and, more importantly, budget friendly.

From this thread, it sounds like the use of ANY PU in a fabric coating is a big negative.  Mention it because Paraglider fabric has a very thin coating of PU, usually but not always on both sides, and is used more to reduce elasticity and porosity than for waterproofing.   Yet people regularly spend a lot of airtime depending on the paragliders made of the fabric; so can’t imagine it being less than quite strong.

It would be helpful to know more about the shortcomings of PU, especially when it is not used as the primary ingredient in silicone coatings, and/or is used very thinly.  I posted several years ago about PU/Sil “blends” from RBTR; but only because I found one or two references to blends after pouring through their website.  Much of the references were to ‘sil/PU’ or the like and were unclear about composition.  Did note that RBTR silpoly has significantly less bias stretch than silnylon; but that could be from the polyester vs the nylon.  I think we need to know more about the composition of the coatings on these fabrics and the effects of the use of polyurethane, which has been used for eons.  Also there are new and different compositions of polyurethane these days.  Any thoughts?

it sounds like the use of ANY PU in a fabric coating is a big negative.
PU is quite ‘stiff’, and when it bonds to the fabric it makes all the load in a tear concentrate on just one thread at a time.
Silicone is more flexible, and it will spread the tear load across many threads. Same fabric, but different tear strength.

Paraglider fabric has a very thin coating of PU,
People who design wings do not want fabric stretch: it changes the wing shape.
To be sure, people hang off those paragliders, but the loading is limited (one body weight) and relatively static. Contrast this with what a tent can cop on a high saddle in a storm!

The reason for ‘sil/PU’ was so that they could tape the PU side with a conventional (and cheap) sealing tape.

Cheers

“Contrast this with what a tent can cop on a high saddle in a storm!”

Thanks, Roger.  Understand and agree on most points, but am not sure how to compare a fabric supporting a flyer to a fabric sheltering a hiker in a blow.  Don’t have the testing gear to compare the strength of the paraglider with silpoly.  So as I’ve mentioned, am first going to see how a very thin layer of Permatex sil sealer does to boost the WP of the paraglider.  Maybe another boondoggle, but we’ll see.

Data on different strength measures of the Paraglider can be obtained from older copies of the Extrem Textil website.  However, RBTR is not so forward with such data for their own reasons, I’m sure.  There is always the RBTR 20D silpoly at 1.25 osy, but it is a bit heavier.

Did have some luck with harvesting a Yama silpoly flat tarp before they sold out.  1.08 osy.  It is very WP, but on the dark side.  Have in mind a floor.  And very expensive for just a few yards of material.  Probably not helpful for most who build their own.

Please note that the sil/PU “blend” silpoly from RBTR requires a sil sealer, or so they say.  But sil/poly less than 20D has HH tested well below WP by Steve Seeber, as has the Dutchware. Some of the Sea to Summit sil/PU is all PU on one side, and sil on the other as you suggest.  Guess you never know for sure what you’ve got until you see what sticks to each side of a fabric sample.

So am probably looking at simple tests of the paraglider and RBTR 20D, and even the nylon Sea to Summit, to see how they hold their shape in the wet.  Am trying to get away from nylon, but simple tests on those embroidery hoops I was crowing about are easy enough.  Have found that sil/nylon just does not perform well in the wet if trying to tailor it over a framework that depends in part on the fabric to hold the shape of the structure.

Appreciate your insights.  More food for thought.

P.S.  You mentioned that you looked at Icarex, but rejected it.  Could you expand (no pun intended) on that a bit.  Thanks.

not sure how to compare a fabric supporting a flyer to a fabric sheltering a hiker in a blow.
A paraglider will not be getting a hammering or buffeting. Well, it shouldn’t! You are meant to be gliding smoothly and gently through the air.

see how a very thin layer of Permatex sil sealer does to boost the WP of the paraglider.
My gut feeling is that it will do nothing. If the PU is on and bonded to the fabric, it will determine the tear strength.

the sil/PU “blend” silpoly from RBTR requires a sil sealer, or so they say.
I am told that one can mix PU with silicone, but I was not told why one would.

But sil/poly less than 20D has HH tested well below WP by Steve Seeber, as has the Dutchware.
The coating is too thin. Made that way for lightness I guess, in pursuit of XUL rather than function.
Probably works fine if what you want to keep off is mist and dew rather than storm.

Some of the Sea to Summit sil/PU is all PU on one side, and sil on the other as you suggest. Guess you never know for sure what you’ve got until you see what sticks to each side of a fabric sample.
In hindsight, I do not know why they tried that idea either.
I use ordinary sticky tape for that test.

Cheers

Roger,  the PU on paraglider fabric appears to be thin enough to maintain tear strength.  But as noted on another thread, when I added a thin layer of Gear Aid Tent Sure on both sides, the tear strength was lost, and I could easily tear it by hand.  So ordered a beefier fabric, with a finer ripstop, but still under an oz/sq/yd.   We’ll see if your prognostications apply to that one.

As for Sea to Summit, they state:  “[T]he 15 Denier Ultra-Sil is a siliconized nylon fabric with a polyurethane (PU) inner coating for mild waterproofing … it has a 1200mm hydrostatic head.”  My concern is not with the HH, but with the effect of moisture on the nylon for the reasons stated earlier.

And it can get pretty choppy up there in the air.  Ever since I got caught in a light plane with a pilot who could not land it despite repeated attempts, I often succumb to white knuckle fever.  Fortunately, it turned our that the pilot was a trainee, and the real pilot was there to take over the controls.   I like both feet on the ground, so remain a hiker, not a climber.

On a more relevant note, hope the silpolies being used by TarpTent can handle the big blows.  With the advent of DCF and silpoly tents, it does appear the the elasticity of nylon is not essential to durability in storms.  Rather, the design of the shelters appears to be the key.

Now you can add the Protrail to Tarptent’s polyester lineup. Notch next?

https://www.tarptent.com/product/protrail/

Now you can add the Protrail to Tarptent’s polyester lineup. Notch next?

https://www.tarptent.com/product/protrail/

Is there any weight savings going to Silpoly over Silnylon?

Or is it just a performance thing?