New HMG Dirigo 2

Kevin –

Can you expand a bit on why your customers were so strongly in favour of the silnylon vs silpoly? Was there a practical reason, or was it just lack of confidence in a less familiar material?

Dan –

I’m personally not against silpoly per se for use on a foul weather shelter – I just have reservations about the specific options on the MYOG market.

So far as I know the only supplier offering a suitable lightweight silpoly is RSBTR. As I’ve said, no-one seems to use 20d in anything for a mountain tent (Black Diamond are using a 30d silpoly). Their 2nd gen 20d seems a good fabric with just enough HH, but is a bit light. The only other option is a rather heavy 40d  with their 1st gen coating at only 1500mm HH, which is going to be marginal in driving rain after weathering.  A 30d nylon 6.6 will be lighter with more than double the HH and is proven to do the job fine, so long as you design around the stretch. That’s really all I’m saying.

If you’re able to buy direct from the trade a 30d silpoly with an acceptable HH would probably be a good candidate, but it’s simply not available on the MYOG market.

“So far as I know the only supplier offering a suitable lightweight silpoly is RSBTR.”

dutchwaregear.com has 20d silpoly, a 1500mm and a 5300mm version. Dutch also offers a 15d .90 silpoly. I can’t attest to the quality though. I’ve only used their 20d silnylon and I didn’t like it quite as well as the RSBTR silnylon  https://dutchwaregear.com/product-category/myg/fabrics/waterproof/?fwp_paged=2

I’d love to see an olive green Durston X Mid made with a high grade 15d silnylon. It would be 2 oz lighter and probably just as strong.

Geoff

— The SIlpoly was from RSBTR , the use was Kodiak Island in the fall. The customers really sort of requested it, but we used it as a test .. as we are always testing and fall on Kodiak is a good test. I know it had larger and more prominent ember holes (hot tent specific). I think it was also more wispy. From my observance, as I had a test shelter, it was not as stout in wind. Granted these are larger shelters, and for smaller ones, maybe it does not matter as much. We did make one Eolus prototype out of it .. , really it seemed stretchier (which seems counter intuitive).

Kevin

Kevin

 …really it seemed stretchier (which seems counter intuitive)

Given that you normally use 30d silnylon, I’m guessing that the thicker thread of the nylon trumps the lower stretch of the 20d silpoly. I’m not convinced that 20d in anything is going to work well in nasty weather, as I suspect the panels will be prone to a lot of distortion when subjected to wind and/or snow load.

Something a lot of people do not fully appreciate is that the stretch they are seeing in a fabric is very often due more to the fabric weave than to the fibres themselves. This is especially so in the case of a stretch on the bias.

Cheers

Roger it seems to me that what you quoted Wacker as saying about silicone’s UV resistance has to do with the silicone coating itself rather than the yarns underneath.  From what I have read about fabrics (admittedly less than either you or Dan), silicone coatings and dyes only offer a moderate amount of UV resistance for nylon yarns.

I do appreciate that your blue tent has held up for many years – it really is a great tent.  I feel that you misunderstand Dan a bit though:

So much for UV degradation. (I am sure there has been some, but not quite as much as you are claiming.)

Dan is not saying that silnylon is an unfit material.  And the longevity of your blue tent does not disprove the that silnylon loses a % of its strength after a year or two of use.  It would seem to suggest, rather, that the tent is still strong enough even after losing that % of strength.  That is where Dan is coming from I think.  He is only saying that silpoly is strong enough not that silnylon becomes too weak.

On another note, Roger in your estimation is poly such an inelastic material that it is not good for foul weather (assuming good tent design without overly focused stress points)?  I am under the impression that poly does have a decent amount of stretch – less than nylon, but still a meaningful amount by numbers . . .

Dan I know you said material stretch was a big topic that you didn’t want to get into, but I am interested in what you have to say on the matter.

There are no clear answers here. Going from bulk polymer to spun fibre to woven fabric to coated fabric – it’s a bit of a maze with a near infinity of confounding factors. Really, you would need to actually test samples of the actual fabrics involved.

Yes, polyester does have some stretch – of course it does. But nylon, especially nylon 6,6, is stronger and more elastic. You don’t find polyester climbing ropes: they are all nylon.

All I can say with confidence is that nylon fabrics dyed in darker shades have enormous endurance in the field. My blue tent is 14 years old and going strong. My dark-coloured Taslan walking clothing – that’s an air-textured nylon, has endured decades of serious scrub-bashing. From limited experience with polyester clothing – it simply does not last as long. YMMV.

But it is a free world and you can make your gear out of any fabric you want. I look forward to seeing Donald Trump with a gold lamé tent – but he would need a couple of porters to carry it!

Cheers

Thanks for responding Roger.

All I can say with confidence is that nylon fabrics dyed in darker shades have enormous endurance in the field.

This does seem to be one sure thing.

It’s true that dynamic climbing ropes are not made of poly but this is because it does not stretch enough to cushion the fragile human body from the shock of falling.  Static poly climbing ropes can be made plenty strong.  As you said, it has more to do with the maze of factors going from bulk polymer to finished product more than it has to do with which material is chosen.

Perhaps where 20D nylon 6.6 is sufficient, 30D silpoly is needed, or something like that.  For 4 season used it seems entirely possible that 40D silpoly is plenty strong enough.

It does seem as if the industry is exploring this more and more so whatever the case is, I think we’ll find out soon.

Also, I read mention of a high tenacity polyester (25% stronger) made by Allied Signal (used to be Honeywell) designated IW70. This would seem to span the gap between nylon 6.6 and standard poly.

I look forward to the possibilities the future holds because neither silnylon not DCF are perfect fabrics. Some bias stretch is a really good property for tent design.

IW70: interesting, but I have never really worried about fabric strength. My concern is far more to do with elasticity: the ability of the tent fabric to absorb the impact of a gust of wind and to then snap back to the right shape.

Cheers

I see.  Now, you have much more experience with this stuff than me (stating the obvious, I know), and I have definitely heard you mention this before.  I don’t know if you’ve ever detailed why and I apologize if I have missed it.  Would you elaborate a bit on why that ability to deflect and snap back is important?  Couldn’t a tent simply hold it’s shape when made of a sufficiently strong material?  Is it that there is a need to reduce the impulse force on the poles and stakes?

@Peter

Actually, that is a good Q. Have a look at this photo:

That was in the morning after a night of wind and driving corn-snow. The corn-snow sounded like a machine gun. (The evening before had been quite delightful.) The wind was not steady: it came in gusts. When it hit the tent the fabric would stretch just a little and absorb the impact, then ‘snap back’ as soon as the gust had passed. To say the tent was being ‘hammered’ (all night) would not be an exaggeration. But we slept through most of that.

It is a bit like some of the philosophy behind Judo: you absorb your opponent’s attack and deflect it, rather than trying to brute-force your resistance. Nylon, and especially silnylon, is excellent at this.

Btw – those upright skis were not like that overnight! They were lying down right against the edge of the tent. I had just hauled them out and shaken them clean prior to striking the tent and leaving. Leaving was strictly by compass.

However, I do not rely entirely on the fabric for those conditions. Have a look at the next photo, where the blue line points.

Those are two ‘end guys’ going from the top of the pole arch to a distant good anchor. The guy ropes are ~2.5 mm Spectra/Dacron composite: they won’t break. They help the end-bell resist the wind. Belt and braces.

HTH
Cheers

The parable of The Oak and the Reed seems fitting here.

I’m not an engineer but I’ve spent years working professionally in fabrication. It seems wise to me to account for some “give” in systems rather than to have the hubris to design something that is immovable. Just my $.02.

Just asking again in case anybody can help. How have silnylon fabrics evolved in the last 7 years and have they improved substantially? Asking because the floor of my 2012 MLD inner failed spectacularly on my last hike.

Thanks

Z.

@rcaffin

Thanks Roger, again, for the thorough reply.  That makes sense to me.  Love the Judo analogy and gosh that red tent is a beauty.  The macpac is a classic but nothing seems to compare to yours.  I really love that tent.  It looks like it sheds wind extremely well and yet (because of those angles rather than curves) it looks quite roomy and comfortable.

One last (hopefully) question – If I look at the numbers for elasticity of nylon 6.6 and polyester (Dacron 52) I don’t see that much difference.  Certainly it is enough to make a difference over the length of a climbing rope when a climber falls.  But it doesn’t seem enough to allow a whole tent to deform in shape under wind load.  Isn’t it mostly what we call the bias stretch that allows this?  If so, does silpoly not have as much bias stretch for some reason?

@peripatetic

I don’t think that silnylon fabrics have evolved much in the past few years, but the quality being used by some manufacturers in the US is getting a bit better.

One thing you can do rather than buy a whole new tent, if it’s just your floor leaking, is to refresh the silicone coating on it.  This is one of the benefits of silicone waterproofing.

@Peter
I started with an Olympus, and developed on from there. Yes, 4 poles is stronger against off-axis winds.

Now, fabric evolution: an interesting subject. I spent 27 years associated with textile research, and towards the end there was some sentiment that research in fabrics was ‘finished’, that nothing new was possible. That proved to be spectacularly wrong!

The basic nylon 6,6 and polyester have not changed much, but the ability to spin ever finer threads continues apace. With the finer threads comes lighter fabrics, and the trend continues – albeit slowing down because you still need some strength after all. Diaphanous nighties are a different matter.

Where there has been a lot of evolution over the last decade in outdoors fabrics or so has been in the coatings. The original PU coating (which perished) has given away to silicone coatings and more recently to mixed silicone/TPU coatings. TPU is different from the old PU: it does not perish, and it has a higher hydrostatic head than silicone. But both work well.

Btw, do not make the mistake of thinking that ‘silicone’ is simple: there are probably over 1,000 variations on the structure of a silicone coating! Then you have several different ways of applying the coating.

As for the differences between nylon and polyester – both fibres have their supporters. Nylon has far greater stretch to break than PE and does not take a set as easily (ie does not wrinkle as much). On the other hand, it does absorb some water and stretch slightly (sag) when that happens. An unknown here is whether silicone-coated nylon is as bad as uncoated nylon for this sagging. I sometimes suspect not (field experience).

Cheers

Roger,
Thank you for the suggestion about micrographs. Have the camera, but possibly not the techie-ness to pull off and post digital images. But note that Stephen S added lower magnification micrographs to his post about Extrem Textil 20D silnylon while I have been away traveling and hiking:
https://backpackinglight.com/forums/topic/hh-test-of-extremtextil-20d-silnylon/

Appreciate your supporting your points with actual experience over substantial periods of time. We could use more of that. In my experience it beats what boils down to speculation. I got way overdosed on the latter staying in motels and too tired from driving to do much more than watch cable TV – CNN and the like.

Will do some admittedly crude tests on the Extrem Textil 20D silnylon with uncommonly high water resistance. But must be careful. The Epic Malibu formerly used by Black Diamond on tent canopies, leaked badly above 1500 HH on some of the tests you did a few years ago; yet when I put a hose nozzle directly up against it at high pressure, it leaked not a drop – suggesting that my amateur hose tests weren’t worth much.

Perhaps there are some folks out there who can provide some more helpful tests of the puncture, abrasion as well as tear resistance of the ET 20D. At very close to one oz/sq/yd (1.06), it might be a super tent fabric if the sag is moderate, and it is as durable as it is water resistant.  However, on inspection there was a lot of fraying along cut edges, which I’ve not seen on many sil or sil/PU coated nylons.  This was alarming in view of the fairly recent BPL post about the fabric unraveling from a lap felled seam.  Will resurrect that thread and post if I find anything that might be helpful.

@Sam

You can do an awful lot of experimenting at home without anyone being the wiser!

The bulge at 1,500 mm HH is almost alarming. When you get up to 3,000 mm HH, um …. Burst strength maybe? :)

Cheers

Roger,
Check out Stephen’s results for the Extrem Textil 20D water resistance: over 7900 mm/wc after simulated aging.  No bursting.

Hi Sam

URL for photos of the ET fabric at 7,900 mm HH? If you have it, please.

Cheers
Roger

Am sorry, Roger, but the testing was done by Stephen Seeber.  He did post micrographs of the fibers, shown in the link I posted above.  He doesn’t mention pix of fabric at drop point, and has been presenting his results much like Richard Nisley has done, with micrograph photos.  But you could PM him if you want to follow up.  His posts on the linked thread do describe the tests in excellent detail, which might be helpful (probably more to you than I, who was slow to grasp it all).

Thanks Sam.
Cheers

This may be the worst case of thread drift I’ve ever seen. Wasn’t this supposed to be about the HMG Dirigo?

Sigh, yes. But you cannot discuss any bit of very technical gear in total isolation. Fabric properties remain crucial to shelter performance (along with design of course).

Cheers

“Wasn’t this supposed to be about the HMG Dirigo?”

Yes.  IMO, the thread drifted only after it became apparent that the tent was subprime.  And Roger and some others always have interesting things to say – hence the drift.