RBTR 7D Silnylon

Thanks for the heads up John! It is a little stronger according to specs at least: RBTR=Warp (1.6 lbF), Weft (3 lbF) vs Rockywoods=1.2 lbf in the Warp and 2.5 lbf in the Weft.  Just bought 7 yds to make my spouse and I the ultimate bomber, no stretch, winter/insulated, large square tarp (to do the mock “pyramid”, triangular, closed tent set up).

This thing will be a Frankenstein creation… bhwahahahahaha.  Reinforced with Kevlar cord at each guy out and 1.6 oz/yd2 Silpoly perimeter borders, a layer of IR reflective mylar core/middle, and the inner polycryo.  Light up a candle or two, and enjoy a nice light show and some extra warmth at relatively low weight.

Good news. I wish more colors were available. It’s $1.46 per yard higher than Rockywoods, but it’s probably a bit stronger. I’ve just never trusted  the strength of the.93 membrane silpoly

Currently and until Wednesday, it’s about 12 dollars a yard (so currently about 1.50 less per yard than Rockywood’s), which is why I bought 7 yds of same. Since my spouse will be using the tarp, and I’m more making it for her ultimately, she is pitching in some too.

John,
Thanks for the heads up on this fabric.  Given the two dark colors and the mini-ripstop, could it be the same fabric as the Rockywoods 7D, or significantly better as the specs indicate?  If so, will use it for an entire tent, except for a lighter colored inner ceiling with RBTR Monolite mesh double inner doors. Never had a problem with the gray on Tarptents, and the 7D will allow more light to come through. I think this may break the two pound barrier for a self-supporting framed solo tent, or ‘pop-up’ as Rober Caffin would say. He may like the all sil coat, and that the riptstop is only mini.

It could be the same base fabric as Rockywoods 7D but with a purely silicone coating instead of a silicone-PU coating. I don’t see Rockywoods advertising the Nylon 6.6 yarn though.

I think this fabric sounds good for a dome tent. That may be my eventual plan as well. I made a freestanding, double-walled 1-man + dog dome tent a few years ago using 30D thru-hiker silnylon for the fly, silpoly PU-4000 for the floor, and carbon fiber poles. Weighs 40 oz. With updated fabrics, that same design could probably be under 2 lbs. Why use Monolite for the mesh though? I’ve never had trouble with the 0.67 oz noseeum meshes.

John,
My experience with .8 and .9 oz noseeum meshes, not to mention .67 oz,  particularly polyester meshes, is that they quickly develop holes and tears. The tears also come to my eyes, as it is a bummer to put a lot of work into a tent, and then see the mesh pest barrier develop enough openings to welcome a throng of spiders (as actually happened to me once – spider bites actually can look like bullseyes, I discovered.)  And aside from patches, removing and replacing all the mesh is almost as big a job as resewing the whole tent. Please share your source for .67 oz mesh, and I’ll give it a try, but am not optimistic, having suffered for so long.

The monolite is only a few tenths of an oz/yd heavier, made of nylon not polyester, is very rugged, and should last the life of the tent made of 7-15D nylon. This would be a big change for me, and would keep me making tents. Otherwise, tent MYOG is just not worth the work for such a short useful life.

Further info is at this thread: https://backpackinglight.com/forums/topic/durable-mid-weight-mesh-from-rsbtr/

Hi Sam

I have used an extremely light tulle netting on my tents, lighter than ‘no-see-um’ stuff. Given the light weight, you would expect it to have a short life – but it has had a very long life in the field. One has to ask why.

Examining the netting very closely, and comparing it to ‘no-see-um’ netting, I can see one major difference. The no-see-um threads are very fine multi-filament ones; the tulle is made of quite coarse single filament ‘thread’, almost like very fine fishing line. The coarser filament seems to resist snagging much better.

It’s a thought. Buy a metre at your local fabric shop and test it.

Cheers

Hi John,
A little bit of math showed me that for an 8′ wide and 4′ high tent, with A-frame shaped doors front and back, both dimensions being reduced by the height of the bathtub floor wall and cant of the tent wall, the weight difference between the Monolite and .67 oz no-seeum netting is roughly an ounce. So I do not see the additional ounce as prohibitive in terms of tent weight, given the added durability of the Monolite mesh, and the resulting longer life of the tent.

Hi Roger,
I went on a tulle netting hunt several years ago, and ended up buying some .5 oz netting from Extrem Textil that seemed a bit flimsy for a tent. However, we do have a local sewing shop that has been great with maintaining my machines, and there is another sewing shop (“Vacman & Bobbin” hah-hah) about an hour away that I go to for the Mettler Metrosene Plus that sews much better for me than the Gutermann products. So will check with those stores for tulle. The chain sewing stores have always been a big disappointment, but can check with them on the next visit south toward the big cities. Oh how much the advent of online marketing and monopolies have cheapened the quality of just about everything here.

Should you happen to have a link to anyplace that sells the tulle that you mention by mail order. please post it if you can. And thanks for description of the tulle you use in your tents. That will be a great help in evaluating what I find in the stores.

Dear Folks,
Once again I have to eat my words, this time about the RBTR 7D. As some of you suggested, the charcoal gray was very dark, unlike the Rockywoods 7D gray, which is more like the lighter medium gray color on Tarptents.

The RBTR 7D also has a more silky quality than the RW 7D, and will therefore be more difficult for me to sew. No coating is visible on it, and it is quite slippery on both sides.

Before obtaining an HH test, I often use a “squeeze” test just to see if sending a swatch to someone with an HH tester is worth the trouble. Just make a ring using the thumb and forefinger, push the fabric into the ring to make a pocket, pour a bit of water into the pocket, and twist the top to seal the water in the pocket. The pressure formed by squeezing the pocket is nothing like the pressure created by an HH tester; but is much greater than puddling water in the fabric, and  you would not believe the number of purportedly waterproof fabrics touted on BPL that have exuded drops when subjected to a “squeeze” test. Happy to say that the RBTR 7D passed the squeeze test – no drops appeared. However, would anyone make a tent out of a gossamer silk-like fabric? Not sure about that.

Given the lighter color, greater body, and the excellent test results posted by Richard Nisley for the Rockywoods 7D, I think it would be better for a small tent fly to cover the ceiling portion of a tent, but not for a tent floor that is subjected to constant abrasion by occupants moving around in the tent. Richard’s post  (scroll down to 12/7/15)  is at:
https://backpackinglight.com/forums/topic/108230/

Hope this is helpful.

However, would anyone make a tent out of a gossamer silk-like fabric?
Perhaps. I note that silk fibres are supposed to be stronger than steel: ‘a given weight of spider silk is five times as strong as the same weight of steel’ according to Wikipedia.

There has been a lot of discussion about 7D fabric, but it is NOT clear to me what this means. You see, D or denier is often used to define the fibres which are twisted together to make the threads, and the lower the denier the smaller or finer the individual fibres. This says nothing about the thickness of the threads: you could have a fabric made of 0.5 mm thick threads while the threads themselves are made up from 5 denier fibres.

What the denier of the fibres does tell you is what is often called ‘handle’, or how soft the fabric seems to the hand. You could have two fabrics of equal weight (per square metre) and equal tear strength, but due to the different fibre deniers they could have really different handle. One could be stiff and the other could be soft.

So I guess the question over gossamer-soft fabric is whether the tent is for winter alpine use or for housing an Arabian harem…

Cheers

Sam, if the difference is only about an ounce, then it makes sense to use the Monolite. I think all the lighter no-seeum meshes are probably the same, but I’ve most recently purchased the 0.65 oz/sq-yd stuff from Quest, and it seems fairly robust.

My most-used MYOG tent has over 100 nights and it actually uses tulle mesh for part of the inner. Think it weighs about 0.25 or 0.35 oz/sq-yd (don’t remember). Purchased it at Jo-Ann’s. The only damage it has seen is when I installed some velcro on the tent – immediately created about 2 dozen snags, which I patched with more tulle. It looks a little silly, but has held up well. It has kept out all bugs, except for one night on a trip to Colorado where these tiny bugs were able to crawl through the tulle and bite me.

Thanks for reporting on your squeeze test. Sounds like it should be waterproof enough. I haven’t ordered any of the fabric yet – still need to weigh the benefits of a lighter tent with the 7D or no sagging with Silpoly.

Hi Roger,
Yes, denier (D) is a measure of the weight of the yarn use to make the fabric.
The fiber of the RBTR 7D is nylon. Not sure if our Arabian friends use only silk.

Yes, ‘denier’ can apply to both single fibres and to threads.

Fwiiw: a single silk fibre is about 1 D. So 7D fabric has some very thin threads.

Cheers

John,
Just my opinion, but don’t think polyester will perform well as low as 7D. I’ve used the ‘membrane’ for making scale models, and found that it will not even hold the fabric tightly on a scale model frame. As soon as the membrane is pinned tightly over the frame, it starts to separate at the pinholes along the warp or weft. RBTR says, ” We do not recommend use outside of relatively low-stress applications.”

The more robust and WP sil/poly from RBTR is 20D PU 4000, which is 1.4 oz/sq/yd, a weight comparable with 30D silnylons. Don’t see much weight savings there, compared to 7-15D fabric.

Like you, I’ve also weighed the nylon vs polyester in terms of the sagging factor of nylon when humidity rises and temp drops. Using some 15D nylon salvaged from StoS Escapist tarps, I found that the coatings, which are sil on one side and PU on the other, substantially reduce the sag factor. For this reason, and due to the greater strength of nylon generally, the choice was nylon with robust shock cord on the pull-outs, but only on the side that will be facing downwind, as Roger Caffin has often suggested. That of course only works on a tent where, like Roger’s tunnels, the entire canopy pulls taut just by tightening the pull-outs on one end of the tent.

But IMO the coatings on the sil/PU nylons also contribute greatly to sag resistance. Roger refers to these coatings as ‘TPU’, and his latest comment on them is is at:  https://backpackinglight.com/forums/topic/silnylon-tarp-fabric-deformation-seams/page/2/

But my opinion is based more on stretching fabrics in plastic embroidery frames, putting them outside for several weeks, and seeing how much sag develops.  It is interesting to see how much fabrics cycle back and forth between expansion and contraction as the weather changes.

Roger also suggests that stiffness of PU coatings will reduce the strength of a fabric; but also notes in the above link that the PU coatings on TPU fabrics are more flexible.  And on a number of occasions, he has suggested that tearing of a tent canopy due to wind and rain forces is very rare.  I agree with all his observations, and have chosen nylon, but with sil/PU coatings, over polyesters in order to obtain more strength for weight.  At the same time, agree with the concerns of many that the sag on some silnylons can be excessive.  But think that the sag can be greatly reduced.

I understand about threads, 7D and so on. But this differs greatly for the various densities of weaves, tightness of weave effects weight and thickness, for example. And hand or feel is often modified by the after treatments of a woven cloth…calendared, brushed, coated, etc. In general 7D, 0.71oz/yd fabric is really good weights. “Double” the strength is another matter. I make the average strength slightly more than 1.1oz/yd poly. Rather light for packs, et all, but good for a tarp or fly. It is close to the same weight as DCF 0.71, better in packability (volume) and abrasion resistance, but not as waterproof. Wow, it IS expensive. Weight goes down, price goes up.

Wow, it IS expensive. Weight goes down, price goes up.
Very true!
A factor not mentioned very often here at BPl is ‘TPI’, or Threads Per Inch’. Because the threads in a 7 D fabric are so much finer than the threads in a common 70 D fabric (state of the art 20 years ago!), you need many more of them per inch. That has serious implications for the design of the loom which weaves the fabric. In simple English: you need a very modern loom, and it will cost a fair bit more.

The set-up costs for 7D are also considerably higher than for 70 D, as you (normally) have to spool ALL the threads onto a big drum before weaving. And no, you can’t just buy such a loom from eBay or Amazon!

20 or 30 years ago some people were saying that Fabric Science had reached a stable end-of-the-road state. Ha! They were so wrong! As a former researcher in textile technology, I find it all fascinating.

Cheers

I was talking about the 1.1oz Silpoly that weighs 1.24 oz/sq-yd. The Membrane stuff seems rather fragile, and the PU4000 fabric has low tear strength – it is a good fabric for floors but would not recommend it for a canopy or tarp.

Membrane Silpoly is rather fragile, and that’s part of why I used it for the latter purpose:

I recently made a 1 ft2 mini tarp out of it, and tried to hang a 30 lb bucket of water from one of the guy outs, and soon as I let go of the handle, the main part of the fabric just ripped, near the guy out area. Wasn’t even close to holding 30lbs.

But the reinforced version of the Membrane Silpoly 1 ft2 mini tarp not only held the 30 lb bucket, but went to hold another 31 lbs without ripping. At that point, I had run out of weight.

In other words, these fragile UL materials can be greatly strengthened without much extra weight or cost.

The interesting thing to me is that I didn’t even use heavy duty thread to stabilize the cord to the tarp fabric, nor any special sewing technique.  The cord just got sewn over  a few times with straight lines.

I will be doing future testing with more weight, but I may do some zig zag sewing up and down the cord some, because I did note that the cord did start to slip after some 61 lbs was pulling on it.

I saw a note in the specs for at least one of the fabrics that was using a 10D warp and a 7D weft.  Of course this means a strange, angle for the bias. Care should be taken designing tents with this.

“The RBTR 7D also has a more silky quality than the RW 7D, and will therefore be more difficult for me to sew.”

Sam, have you tried using the iron on polyamide “no sew” bonding material to attach pieces before sewing?

I find it helps with sewing these gossamer type fabrics.  Sewing through this stuff does not cause problems for a sewing machine. It’s not like tape, it’s not sticky–it’s more like rubbery. There is some that does come with one side a bit sticky, but you can also get it with no sticky side.

It does not adhere permanently to silicone treated fabrics of course, but it adheres well enough temporarily to sew it.

‘Fusible bonding web’ on eBay.
Poor bond to the silicone side, probably much better to the PU side.

Cheers

Justin – for tricky seams I just use the standard basting tape from my local sewing shop.

Run your nail along the seam a couple of times and it holds just fine, even on silicone coatings.

Makes life a lot easier, especially for long flat felled seams. Weight is insignificant, and it probably helps keep the seam waterproof.

Thank you for the tip Geoff. I’m not sure I’ve seen basting tape before, but I will look into it.