Is Spinnaker waterproof?

First define what you mean by 'water-proof'.
Sheet steel is waterproof, and so is Cuban fibre cloth – up to a point. Most other fabrics will leak at some pressure – but that pressure varies wildly!

Cheers
PS: spinnaker fabric would normally be described here as not highly waterproof.

Okay, I concede the point. I debated whether or not to use that word actually. What I meant was, is the spinnaker fabric that can be obtained from sail manufacturers ready to use for tarp construction or should it be treated in some way to render it more resistant to the elements?

>spinnaker fabric that can be obtained from sail manufacturers ready to use for tarp construction or should it be treated in some way to render it more resistant to the elements

. . . which is a good question, and indeed the one you asked originally. (Don't mind Roger. Too many days away from the comforts of civilization have made him slightly cranky.) ;-)

I'd go to the font of wisdom on this subject. The folks at Gossamer Gear are the main purveyors of spinnaker-based shelters. I'm sure they wouldn't mind if you asked (especially if you're just working for yourself and not looking to muscle in on their territory).

I suspect that the answer is "no." High-performance sailing craft wouldn't perform so well if they were carrying a load of water soaked into their sails.

Also, I've had my One out on some pretty rainy nights. I've gotten some condensation but (in my honest appraisal, and I know the topic is controversial) no "drive-through" moisture. So whatever GG does or does not do to the cloth, it's pretty "water resistant."

Stargazer

P.S. Steven Colbert would say that spinnaker is "waterproofy."

Spinnaker, as is known by sailors, can be made of many kinds
of light cloth.

Cuben Fiber is a spinnaker fabric, IE used to make spinnaker
sails for racing boats.

The silicone coated kind comes in a few varieties with different weights of thread, weaving patterns, thicknesses
of coating etc.

Which varieties are used for the various backpacking shelters
are a bit of a trade secret. They vary in strength, weight
and waterproofness. Some can be easily torn by hand. Some
not so much.

Most have been highly calendared to reduce
stretch. This has its pro's and con's. It lessens the
need to re-tighten guy lines in the rain, but it
reduces the strength of the fabric and increases the chance
it will tear under load.

Silnylon (and there are varieties of this too) stretch
more and hence will distribute forces over a greater part
of the tarp, hence be stronger for a given weight.

The Spinnaker used in my Gossamer Gear SpinnShelter is waterproof, at least to the point of staying dry during 2 days where it rained a total of 7 inches on me. I know the Spinnaker sold by Thru Hiker is waterproof as well, but I don't think all Spinnaker would be waterproof enough for a shelter.

I just received a Spinn Shelter from GG yesterday, so during the short waiting time for shipment I scoured their website completely. Here is what they say about their Spinnaker and waterproofness, which implies–as others have pointed out–that not all Spinnaker is "waterproof."

From Gossamer Gear's FAQ:

I’ve heard spinnaker fabric is not water proof. What makes your fabric different?

We have gone to great lengths to find a fabric that is lighter than the conventional ultralight shelter fabric, silnylon, but that still offers the same weather protection. Our spinnaker fabric has a higher thread count than silnylon. Additionally, the fabric is coated using a long, precision coating knife, which ensures even coating on our fabric to .001 inch. With a higher thread count and virtually “perfect” coating applications, our spinn fabric achieves virtually zero porosity in field conditions. Spinnaker fabric currently available achieves rain protection to about 1 PSI, and can wet out fairly quickly. Our fabric withstood water pressure tests of 2 PSI, the same levels achieved by silnylon fabric. The savings of approximately .04 oz/sq. yd. over conventional silnylon is worth it, we think."

Looks like it's worthwhile to buy the stuff that's already coated. I won't accuse any reputable gear manufacturer of lying, but I suspect some are "modifying" the truth a little to make it sound as though their own proprietary fabric beats everything else. I don't doubt that they acquire high quality material, but it may be a matter of speculation how proprietary and "secret" their stuff really is. Thanks for the insight. Looks like you can buy silicone impregnated "spinnaker" from Prolite Gear for $19/yd. Does this sound like a decent deal?

Only if you think they are not lying.

"Looks like you can buy silicone impregnated "spinnaker" from Prolite Gear for $19/yd. Does this sound like a decent deal?"

For Spinnaker it's around the price. But at that price, I'd be considering 0.48oz/yd cuben fibre for only a few dollars more.

FYI – THe spinnaker from Prolite is the the same Spinnaker that GG uses.

"Looks like you can buy silicone impregnated "spinnaker" from Prolite Gear for $19/yd. Does this sound like a decent deal?"

That is about the standard price. I looked for cheaper fabric, but that is the price that I paid.

I don't know if it will stand up to hurricane-force rain, but for ordinary rain, it seems perfectly adequate.

Keep in mind that most of these fabrics are very thin and slippery. Before you commit it to the sewing machine, you probably want to experiment a little with thread, thread tension, methods of tacking it together, etc.

Many of us who are not in the fabric business do not own any big cutting table, so I used an extremely large unfolded cardboard box, maybe 4'x8'. I ended up cutting the fabric with a single-edge razor blade (for maximum sharpness). I tacked different pieces together with clear packing tape. I went through three or four different spools of thread until I found some that is strong and the right size to work with a very small machine needle.
–B.G.–

S-
Ordered several different brands last year of very light (represented as .6-.75 oz/sq yd, although weighed 1.1-1.2 oz/sq yd including coating) sail cloth from Kitebuilders in one yard lengths. Kitebuilders had a note on its site disclosing the weight differential. All of them were porous enough to blow through. The spintex sold by thru-hiker is not, although I have not tested it with a hose or in a tarp. Did not test further with these fabrics as they are also noisy, and do not make for a taut tent canopy for the reasons stated above by David Olsen. Did not know that they are weaker than silnylon, but David has much experience with them all, and is probably right about that also. With a difference of .2-.3 oz more per sq yd for silnylon, the added weight is 1-1.5 oz for a whole tent.
For me, that small weight penalty if offset by the other qualities of of best quality silnylon.

No yachty wants a wet sail – just too heavy. So modern spinnaker fabric is often treated with silicone to stop it absorbing water. The water just rolls off it. Fine.

But that does not mean the fabric is waterproof. A yachty doesn't care if water goes straight through the fabric (as long as air does not). So a fabric may be wonderfully water-shedding for a sail, and leak like a sieve in a tent.

Understand the difference.

Cheers

Roger,

See Talbot's post above. Again, I can confirm GG's claim from personal experience. It ain't a scientific study, but it's fair enough evidence for the claim that treated spinnaker cloth is resistance to soak-through at 2 PSI.

It seems to me that our requirements are far less demanding than a sailboat caught in a gale, but I could be wrong, of course. Both of us are speculating about the goals and performance of spinnaker in such situations.

Also, I would think that a sail soaked with water would be far less efficient than a sail not carrying the weight of H2O, even as it passes through. (In the scenario you suggest, it would indeed carry the weight as it passes through, since in a gale there would be continuous passage of the water through the measurable thickness of the sail.) It would be in the best interests of the efficiency of the boat to have "waterproofy" sails.

Of course, the question remains as to whether GG uses pre-treated spinnaker, presumably used in spinnaker sails, or whether they treat it themselves. They use the passive voice when they mention the silicone treatment, which leaves the question of whether the original poster should treat the cloth he buys an open question.

Stargazer

I don't see how Spinnaker (as sold by GG for example) would not be waterproof, as taken in the context of hiking and backpacking.

Any fabric is only waterproof to a certain pressure. Theoretically a lead box wouldn't be waterproof if you stood inside of it long enough for the water to erode a hole into it. You'd be there for a while, but it ultimately wouldn't be water "proof". Its all relative I guess.

"No yachty wants a wet sail – just too heavy. So modern spinnaker fabric is often treated with silicone to stop it absorbing water. The water just rolls off it. Fine.

But that does not mean the fabric is waterproof. A yachty doesn't care if water goes straight through the fabric (as long as air does not). So a fabric may be wonderfully water-shedding for a sail, and leak like a sieve in a tent.

Understand the difference."

Someone 'Sticky' this quickly. Great post Roger.

"I don't see how Spinnaker (as sold by GG for example) would not be waterproof, as taken in the context of hiking and backpacking.

Any fabric is only waterproof to a certain pressure. Theoretically a lead box wouldn't be waterproof if you stood inside of it long enough for the water to erode a hole into it. You'd be there for a while, but it ultimately wouldn't be water "proof". Its all relative I guess."

+1 —I like this.

Local air force survival instructors teach how to make
a tipi style shelter with UNcoated parachute cloth that
keeps out rain and snow.

One layer with a fire inside drives out the moisture.

Without a fire, two layers, set up so they don't touch each other, works too.

You can make most anything work and that which you can't
make work you can learn to live with. If your raincoat is
wet from the day before, put it on and start hiking, learn
to deal with being a bit wet.

If your idea of fun is to create things, and your style
of camping runs to minimalism, taking a tarp of
spinnaker can be shear luxury. Grandma G. used to dream
of such things.

There are probably *lots* of different types of spinnaker cloth out there. Some are probably not that great, but more than sufficient for someone who just wants the sail for puttering around on Lake Union when the weather's nice, and others are ultra-strong, ultra-light, and hydrophobic for the folks who will be pushing the limits of their yachts and aren't going to pack it in when the wind picks up — like the America's Cup race teams.

Given Cuben's price, I wouldn't expect it to be particularly popular in the casual yacht market.

As Roger said the only reason sailors use a silicon coating on sails is to make them lighter and more slippery. Those same silicon coated fabrics seem to be alot more water resistant than there urethane coated cousins.. Spinnaker coated with silicon is also alot quieter but a bear to work with. I personally would never waste my money on spinnaker. Its super expensive and easily tears. Silnylon or Cuben is the only way to go…

Hi Thomas

Yes, my measurements on a wide range of fabrics agrees with the estimate of 2 psi (13 kPa) for many spinnaker fabrics, and this is about the same as modern silnylon.

But is this enough for outdoors gear? I think not.

I recently tested some Chinese silicone/PU coated fabrics. They ran to about 10 psi (70 kPa). Now these are sufficiently waterproof! The old wet-look silnylon (no longer available) also tested to about 10 psi (70 kPa). Good stuff!

> our requirements are far less demanding than a sailboat caught in a gale,
I don't agree with ther implications here for several reasons. First, the tensile loads on a spinnaker are probably far greater than the loads on a tent or tarp. I'll go along with that OK. But a spinnaker has zero requirements for waterproofness, while we have significant requirements. A spinnaker has high requirements against water absorption, but that is not the same thing by a long shot.

My feeling is that modern silnylon and spinnaker fabrics are probably adequate for snow gear but are not adequate for rain gear (clothing and shelter), and certainly not for groundsheets.

Cheers

IMHO Spinnaker is not a type of fabric. It is an application for many different types of fabric. Whatever type you use, the water resistance will depend also, perhaps moreso, on the type of coating applied to the fabric. With nylon for example, a light silicon coating on 1.1 oz fabric provides a breathable, durable water resistant (DWR) coating that will bead and shed water, but that will leak like a sieve in a downpour. The double sided coating we are used to seeing on silnylon is more like waterproof. So is the coating on the spinnaker Thru-Hiker sells.

Roger, I hope the death of "wet-look" silnylon is greatly exaggerated. Maybe Down Under. Haven't ordered in a while, but I think Quest is still selling the same stuff that I have a basement full of. Recently ordered a sample set from a US supplier you mentioned, and it was indeed not the wet-look stuff. Quest is great about free samples, and maybe I should order some to see if you are right, and all has changed. Maybe folks using not so good stuff is part of the reason for all the "misting" posts we are seeing. The same issue would apply to spinnaker also, for those who prefer its stretch and UV resistance. The type and quality of the coating are at least as important to water resistance as the type of fabric.

Just wait until the sail industry starts using woven laminated spinnakers. I have inquired about having some made but they want you to buy 3-5 thousand yards at a time which isn't something I could afford…I have been thinking of doing it myself in short runs using a 1.1oz calendered ripstop laminated to a .5mil film… It is the perfect waterproof material. Plus the film would make it a little more stretch resistant.. I am officially taking pre-orders hahaha : )

I'm not a sailor by any means, but Thomas's point regarding the waterproofness of sails seems to make sense to me. Why would a sailor want a sail that would hold water when it could be treated? It would just make the sail heavier, no?

"My feeling is that modern silnylon and spinnaker fabrics are probably adequate for snow gear but are not adequate for rain gear (clothing and shelter), and certainly not for groundsheets."

Roger, if you don't mind me asking, do you just use cuben for these items (rain gear, shelter, and groundsheet) because you feel Spinnaker and silnylon are inadequate?

Sam

Could you please email me at roger@backpackinglight.com ?
(You don't have a PM address set up.)

Cheers