Sailcloth and waterproofness

Referencing this link:

http://www.sailrite.com/Ripstop-Nylon-5oz-Red-60

Does "zero porosity" mean that it's waterproof?

If waterproof, what is the downside of using this stuff for a tarp? It weighs 1/2oz per yd...

Steadman

I have used some of this kind (kite fabric?). Not sure about longevity, but very strong, no sagging, no elasticity (got to use cat cuts).I think weight very near to cuben.
Waterproof, as far as I know, but different qualities: some have really good enduction, even contact with water, like for a ground cloth on soaked ground, nothing seeps through. Some, not that good.
Cons: the smallest puncture, even a pin hole, doesn't "self-seal like silnylon, does (a bit...)
Extremely noisy, and quite difficult to pack properly (a bit stiff, bulky...)
Some kite fabrics, like chikara, are very good for shelters, waterproof and not so noisy, lightweight and resistant, but on the "bulky" side too.
This shelter is one of them

That's sometimes referred to as "spinnaker cloth". The "zero porosity" part as more to do with wind than water. My sails most certainly get wet. I lay them out to dry...which they do very quickly...before storing them. Some spinnaker cloth is "crinkly" meaning it's slightly stiff and noisy.
It works great for kites.
Call Sailrite and ask for a swatch.

The kind of spinnaker cloth that Mountain Laurel Designs and Gossamer Gear use in their tarps is a special kind made specifically for tents and tarps. The regular kind used for sails is not sufficiently waterproof for a tarp or tent.

Lately this spinnaker variety has been very hard to find. MLD has given up using it altogether. GG is still using it but has had to send some batches back because they didn't meet standards. The alternative, cuben fiber, is far too pricey for most of us, so except for a few with deep pockets, it's back to good old silnylon.

Dryer

Good advice. I called and asked for a swatch, and will test.

Everyone, thanks for the info; I'm exploring options, and it's good to hear from so many experienced people.

Sincerely

Steadman

Ya know Mouse,that actually says a lot. I have found more uses for silnylon than any other light weight fabric for outdoor applications. It's super easy to seal, easy to repair/patch, easy to sew (once you learn), truly waterproof, very tough for it's weight, and reasonably priced. "good old silnylon" is right and shall be referred to as "GOS" from this day forward.

The only things it doesn't do well is...
1)breathe...horrible for clothing, except ponchos.
2)grip....some very slickery stuff, that "GOS".

Ok, I got my swatch, and did some more reading.

The literature over on backpacking lite seems to indicate that this stuff won't work well... if I'm comparing apples to apples over the course of several years.

However, I filled a jar, covered the top with the 4x4 inch piece of fabric, and I'm not really getting soak through. I mean, the sticker that sail-rite put on the middle of the swatch is slightly damp, but that's it - after over an hour. The volume inside the jar hasn't changed either (at least, not within my means of measuring it.

Anybody have another suggested means of testing waterproofness??

Steadman

Did it turn out to be the crinkly stuff? If so, over time, the finish wears out and its noisy.
How waterproof do you need it to be? I've got kayak dry suits made from coated nylon and GoreTex that withstand submersion.
My tarps are all made from coated nylon and silnylon and keep me plenty dry. If it sheds water and doesn't drip through, you're good to go.
Cotton canvas tents shed water fine, got wet, even dripped if you disturbed a wet tent with your finger during a downpour, but still kept us dry.

Dryer

It was crinkly, like paper. I just need it to be as waterproof as you'd expect silnylon to be... which you suggest it's not.

Given the expense I'm, as you and Oregon Mouse suggested, back to good old silnylon. Given what's available in silnylon tarps, I don't see a need to make my own...

Thanks much!!

Steadman

sailcloth is a generic term, not a specific fabric. Some sailcloth fabrics are extremely waterproof (mylar laminates for example which can be a bit crinkly) and some not so much.

If one is using silnylon as the measuring gauge, you can find plenty of sailcloth fabrics which are more waterproof than silnylon which is prone to misting in very heavy driving rains.

I own a spinnaker tent (Gossamer Gear Squall Classic) and a spinnaker tarp (GG Spinntwin) (both the special fabric made for tents). I haven't tested the tarp yet (waiting until bug season is over), but I've used the tent for several years in all sorts of weather--it works fine. The hype that says it doesn't stretch like silnylon is a bit inaccurate; it does stretch when wet but not as much as silnylon. Thanks to linelocks, though, I don't have to go out in the rain to tighten anything up. I've had no issues with misting, even in heavy rains or with a garden hose (with pressure nozzle) turned on it for almost an hour. To repeat, however, this is not the kind of spinnaker used in sails, and it is getting very hard to find.

I've used silnylon tents under similar circumstances (nasty weather and the garden hose under pressure) and have never had any misting. The tents were by Tarptent and Six Moon Designs. A lot depends on the quality of the silicone impregnation, as I understand it.

Quite a bit of spinnaker's crackly noise goes away after some use, and if the tent is pitched taut, the spinnaker is no noisier in wind than any other fabric.

The determination of the waterproofness of a fabric is normally done with a gizmo that puts it under measurable pressure. (As a non-engineer, that's about all I understand about it, sorry!)

I do have a few pieces in cuben fiber (a couple of dry bags), and like them--but there's no way I can afford a $500 tent in the stuff! My other concern with cuben is privacy-it's pretty transparent, so you can't depend on the tent to block the view when you're changing clothes! I did get a chance to look at a cuben tent earlier this year, and if I ever win the lottery....

I think I'm getting to a point of understanding...but I'm still confused.

Have I identified a point to do more testing, or a deadend?