Strength of .93 oz Membrane Silpoly vs 1.24 oz Silnylon

Thomas,

Thanks for the feedback. It’s a bummer but it certainly doesn’t scare me away. I’ve made a lot of stuff, just not anything as load bearing as this so it definitely requires a little more fine tuning than other projects. I.E. the offset, I actually did this intentionally and lined everything up with the stitch that makes the actual seam. I felt that it was the most load bearing since the flap of the French seam is just sewn down and doesn’t actually form the true center of the tarp. Logic might have been flawed a bit but that’s fine, I didn’t expect perfection. I’ve never seen, own, or handles a BPing tarp in person so every drop of knowledge I used to build this has come from here.

I feel like I should chime in. I also had a failure with a tent I was building. I had problems with the fabric tearing on the first and second test pitches. I forgave the first instance because my design was so bad and so many things needed fixing but the second time made me realize the fabric was not strong enough. It was membrane silpoly but I think it was the 4000 kind not the .93 osy type. I feel stupid for not learning more about the fabric before I ordered it . Sure could of used that chart back when I was planning this project last winter. Silnylon is looking better now. I am hoping to repurpose the fabric for a ground cloth. It was the need to find a replacement fabric that led me to this thread.

Some good info here.

Glad to see that others support my own thoughts about the patches needing not to be of a stiffer fabric . I’m attracted to James ideas of no reinforcement..  Has worked on mid edges for me.

Thomas thoughts on the ridgeline attachments are sound. That method is the one used  by Ray Jardine for his Tarps design.  It works really well. Solid.

But I’m guessing the fabric is the biggest problem really.

In my opinion, there is no way this particular fabric would hold up without reinforcements. However, in this case the reinforcement material was not suited for the job. The .93 Membrane needs them, they just need to be the same material so they stretch with the fabric. Of course at this point, it’s all theoretical.

“I’m attracted to James ideas of no reinforcement..  Has worked on mid edges for me.”

Same here – with 1.4 osy silnylon

with lighter fabric maybe you have to do reinforcements more carefully

maybe forget the 0.93 osy fabric and just use 1.4 osy?  It’ll last for years.  maybe 0.9 osy silnylon rather than silpoly?

I wonder if ripstopbytheroll.com has been accepted as a quality source of materials too quickly here.

While I appreciate all the advice I was given, I do want to address this before it unnecessarily tarnishes someone’s business and products. I knew the risks of using this material before I bought it. Yes, it’s disappointing, but RSBTR, sells materials, they don’t build tarps. If MLD were selling tarp kits, yea, we would expect the details to be spot on. However, a fabric vendor is trying to put kits together to enable customers to make their own stuff while also working to bring innovative fabrics to market. I actually pointed out my failure to Gen at Yama when I was working with him to order a Cirriform (yes I ordered one in cuben today, so not too upset :) ) and he said the same thing right away; I used too heavy a material for the reinforcements and didn’t cut the patches the same direction as the tarp. Spot on with everyone here. I would say if someone knew these details and had the expertise going in, this material would be just fine. Had I known all this, there might not have been an issue at all and RSBTR wouldn’t be questioned. I use materials from RSBTR for everything, booties, quilts, stuff sacks, pack covers, apex vests, etc. I have made a lot with no issues.

Off my soapbox now. Justification for this is that I don’t want to see a great and innovative vendor be scrutinized just because of a one off like this. I want options, and Dutch, DIY Gear Supply, Seattle, RSBTR, etc, none of them carry every single thing I want or need. I like to have options from many places. Hopefully you all feel the same.

An interesting discussion.  Lots of good ideas.  My thought on the defective area is too much concentrated stress.  I think a glued on curved reinforcing patch of similar fabric might help spread out the stress in that corner.  See my hand sketch.  I think some version of a curved reinforcement is what this fabric may need.

As mentioned earlier,  I too would salvage what you have by adding, glueing on a much larger and curved reinforcing gusset and try to spread out the stress.  I would probably have to sew also but would test without it first and see what it looks like.  I expect you could get some  use out of it.  Sorry about your trouble though.

I have sealed the stitching area on the existing reinforcement with silicone and it already seems much stronger. I was definitely planning on glueing another larger patch on but this raises a question…For the same reason I didn’t use circles in the first place since i didn’t know the answer to this, how do you manage to roll hem the circular reinforcement before applying it to the tarp? Or are you just cutting it with a hot knife and slapping it on? Will it not fray? I will be picking up mineral spirits tomorrow to get started so please let me know.

Hoosier, Like laying out any sheet goods, you really cannot role a hem around a circle. The easiest is to simply cut it and glue it down with silicone adhesive.  It is possible to slit the sheet carefully removing a small “V”. Basically simulating a curve with small linear sections.

You can hot knife it, but do not worry about a little fraying by just cutting it. Hot knifing can sometimes leave a small bead at the edge and may actually interfere with a good glue bond. The glue will take care of any fraying with just a razor or scissor.

T – Sorry to hear about your trouble with the seams. If it’s any consolation, thank you much for this thread, as it alerted me to the need to first perfect all seams with the Membrane fabric by creating test seams with scraps. If I can’t make little sample seams work, then will not proceed with the Membrane.

Another issue is the type of adhesive to use to bond before sewing. The simple PU or Sil distinction does not work for these newer hybrid coatings. Roger had a helpful post that mentioned the newer coatings. Have begun testing with sil glue, and am not satisfied. Will try Seam Grip, or a better non-foaming PU if found, to test for bonding.

One side of the Membrane is slightly shinier than the other, so I’ve been bonding shiny side to shiny side, and dull side to dull side, just in case there are differences in the coatings that will affect the bond with a particular adhesive.

The type of sewing thread, and machine used may also be factors here.

Whatever works best for both both adhesives and seams is what will be used. If not satisfied, a more expensive mini-ripstop nylon with a hybrid coating and taken from a S to S Escapist tarp will be used. Richard tested this with good results and posted them on the GEAR forum.

But I’d much rather use the Membrane 2000 with its far more economical price and higher water resistance if possible. (There is no significant weight difference – only around a tenth of an ounce/sq/yd lighter with the Membrane.)

You can do a rolled hem around a circle

The rolled portion has to have some folds to take up the extra material

Mark a line (circle) where you want the edge of the finished fabric to be.  Start at one place fold over twice, sew a few stitches.  Then go around the circle an inch or so and fold over twice, and then fiddle the in between fabric fold to use up the excess.  etc…

Silnylon doesn’t fray a lot so not real important to hem it.  Especially if you’re gluing it also

Good information here.  I’ll second the circular reinforcement patch, cut of the same material and in the same direction.  And I don’t bother to hem my reinforcements – silnylon and silpoly don’t fray enough to bother.  Just paint over the edge when you seam seal and you’ll be fine.

Also, as Hoosier noted, seams get stronger when you seam seal them, so I would avoid subjecting a tent to high winds before sealing the reinforcements.

As for the strength of the Membrane sil, that ‘mid that I had a failure with might actually find it’s way to gear swap one of these days.  Even though it’s the PU4000 coating it’s still got potential to be repaired (it mostly needs improved reinforcements).  I just need to find the time to fix it up.

I picked up spirits and a Brayer last night and got the circular patches applied. They’re curing at the moment. We will see…

Two pitches and the tarp is holding up like a champ. I don’t even see any wrinkles (like load dispersion?) at the tie out any longer. I’m going to take both it and my Cirriform tarp this weekend for two nights. There is a chance of rain so I want a backup just in case but I’m going to use this membrane tarp both nights if it doesn’t show any signs of tearing. Otherwise, I really think it’s solid as can be now. Thanks for all the help and advice! Btw, I did NOT sew the circular patch, only adhered it with non-diluted silicon. It shows no signs of separating from the tarp.

Also, this makes me want to build a new tarp just for fun now. It took me way too long to cut and hem 16 triangles for the first one. If all I have to do is cut 8 circles, cut them in half, then glue them on, I could have the next one done in a few hours. I think the permatex is a great match for the coating on the .93 membrane silpoly since it doesn’t have the PU coating. Running a fingernail along the step line, you can’t even feel the step, it’s like they’re now one piece of fabric.

thanks everyone for this great discussion! i’m working on a mid right now, made out of silpoly pu4000, and after reading up, will be using same-material circular glued reinforcements at all the tie outs.

Sounds like you did a good job re-doing the tie-outs. Thanks for posting the info. Hope it works out well! Bringing a backup tarp sounds smart

I bonded some 30d silnylon reinforcements to  a piece of 5′ X 8.2′  (same) fabric.

First I thoroughly cleaned the materials with odorless mineral spirits, then I coated BOTH the tarp and reinforcements with a thin layer of Permatex Flowable Silicone Windshield Sealant. Next I scraped the fabrics with a plastic putty knife to make sure the layers were as thin as possible. Then I stuck the pieces together. After that I placed  wax paper over the reinforcements,  followed by a roller.  Lastly I put heavy books on top and left them for 12 hours, then I pulled the books away and let cure for another 2 days.

Honestly, the bond looks so strong I don’t even think I’m going to sew the reinforcements. It’s just a cheap little solo tarp, so if it fails no big deal. I’ll leave it pitched in the yard for a few days, Good experiment.

Monte,

I followed these exact same steps to a T. The only thing I did different is I have two heavy steel plates with high density foam glued to them that I use to mold gun holsters. I threw a plate on each ridgeline tie out with a gallon of water on top of it. Very satisfied with the results. Although completely coating the patch was quite an endeavor being such thin material….It was a fun mod though and I think this tarp will last now.

Yes, coating the materials was challenging. The Permatex is quite sticky. I bought some 1″ wide disposable foam brushes from Walmart (25 cents each) and coated the fabrics over wax paper. Next time I’ll use Sam’s idea of 90% Isopropyl Alcohol to clean the tops of the reinforcements after I’ve rollered them. Would look neater and more professional because you’re bound to get some glue on top of the reinforcements through handling and rolling.

Used the tarp for two nights this weekend. It stormed both nights and it was awesome. My first time using a tarp and while I was cheating by using an inner, I loved it. The loss of head room honestly didn’t bother me at all compared to the benefits of the tarp. Ended up using trees both nights instead of poles for the ridgeline. Night two I was tinkering and tried a semi-raised side with the center lines a little lower. Kind of goofy, maybe pointless, but there was rain coming from that direction off the lake so I wanted decent storm proofing without giving up a view of the lake. Anyways, the tarp held up great with absolutely no issues after the “upgrades”. You should be able to see the circular ridgeline patches in the photos.

Night 1:

Night 2 pitch and from from under the long edge:

Adding a better pic of the reinforcement from beneath the tarp. Don’t mind my wet socks hanging to dry :)

Looks great Hoosier.  I have been doing some tie-outs testing with silpoly 1.1 PU 4000 and I think not stitching the perimeter of the reinforcement is key with this material.  I rather risk the chance of the reinforcement pealing off (maybe) than introducing a weak point thru the stitches. (Throught my testings the tie-outs  always failed at the seam).  Also I found circular reinforcements work better than triangular.   Glad to find out this findings are corroborated by your “fix”.  Cheers.

Looks awesome. You got through 2 nights of stormy weather, so the reinforcements must  be holding up for pretty good for now. I’m sold on the Permatex Flowable silicone.

I bought a new sewing machine over the weekend. Drove to Ocala and got a Janome My Style 100. Paid $250 for the machine and $50 more for a walking foot. Works fantastic.The foot really seems to help with the silnylon. I made a 5′ X 8′ solo tarp and now I’m going to make an emergency  solo tarp with either the .93 oz membrane silpoly or the 0.7 oz silnylon from Rockywoods. The 0.7 is expensive at $12.99 a yd, but at least I got practice on some cheap 30d silnylon first. The 0.7 silnylon is 10d whereas the .93 silpoly is 15d.

So I pose this question to the materials geeks out there: Which has more tear strength, the 0.7 oz silnylon or the .93 oz silpoly?

Overall strength of nylon vs poly is about 20-40% greater given equivalent weights. So, I would roughly estimate .7oz/yd silnylon to be roughly the same strength as .93oz/yd silpoly.

Some of the newer 1oz Robic fabrics are 1.5x stronger with 250% the tear strength than with standard nylon fabric. Using these would be *much* stronger.

You are talking old technology items, .7oz/yd and less (I believe they make/made some .54oz/yd stuff) is commonly called spinnaker cloth. It varies in coating density a LOT. GG used to make packs/tarps out of it about ten years ago.

The *minimum* strength for packs is(was) generally silnylon, though Robic has changed that somewhat. Spinnaker was too light for much over 15pounds. The minimum strength for small tarps(<9×11) was Spinnaker at around .68oz/yd (in an A-frame setup.) Larger tarps/ or different set-ups (lean-to) leave larger unsupported panels putting a lot of stress on the fabric. 10’x12′ for example was a good size for 1.1oz SilNylon Lean-to with 12’x16′ wanting 1.7oz/yd (based on my experience with these fabrics.)

As far as UV resistance goes, both are good at resisting UV damage, but poly is slightly better than nylon. I could not find numbers on the Robic stuff.