How to Improve this Silnylon Hydrostatic Head? Longevity? Effect on Weight?
Feb 4, 2016 at 3:37 am #3380074James MarcoBPL Member
@jamesdmarcoLocale: Finger Lakes
Thanks Richard. Yes, I do it by weight also. But, I have used close to 50:1 with many projects. But they did NOT last for more than 2-3 years.
Note that you *can* use white gas AKA Coleman fuel as a solvent. It evaporates off very fast to allow the silicone to dry properly on the tarp. (Still takes 24 hours to set properly.) Also with 20:1 mixes, I do both sides.
Thanks again.Feb 4, 2016 at 7:12 pm #3380254Ryan SmithBPL Member
@violentgreenLocale: East TN
“Unfortunately there is no other source in the US or internationally for the Multicam pattern on a 1.1 oz nylon base, that I am aware of.”
Just fyi – Dutchware recently started carrying a 30d Silnylon Multicam pattern fabric, but me thinks it’s from the same mill as RBTR.
RyanFeb 15, 2016 at 1:57 am #3382148James holdenBPL Member
I coated both microscope slides and 1′ square silnylon panels with a VERY LARGE combination of different solvents, concentrations, and silicones. After drying, I measured in the virgin HH and also the aged HH in 5,200 cycle wet flex increments for every combination.
The dilutions for solvents, were all by weight. It was simple to just put some silicone in a container of known weight. I then did the same with the solvent in another container of known weight to exactly match the mix ratio (I could pour back some solvent if I added too much to the 2nd empty container) and then slowly I added the proper amount of solvent to the silicone while stirring vigorously. Dilution ratios included 48:1, 12:1, 6:1, 3:1, 2:1, and 1:1. The higher dilution ratios all failed miserably during the first 5,200 wet flex aging cycle. 6:1 was highest dilution CA MS and GE Silicone ratio that would maintain > 1,500mm HH after wet flex aging on 5,200 iteration cycle (simulates a couple of weeks of wind and rain).
thats interesting richard as for years on BPL jim wood who did a whole bunch of test on sil recommended the a 5:1 ratio ….
Since I’ve been quoted here a couple of times, I thought I’d weigh in.
Having designed, built and used many silnylon shelters over the years, it’s my opinion that the degree to which misting occurs with standard weight (1.3oz) silnylon is partly a function of the fabric’s age and UV exposure history and but mostly related to how well the silicone coating is applied during the manufacturing process.
When new, some of the fabric samples I’ve used seemed to resist misting pretty well, while others have been horrible. Silnylon is one of those products that’s largely unbranded, so you never really know what you’re getting unless you buy products from companies that control the quality of their fabrics very carefully.
The good news, at least in my experience, is that the treatment discussed in my article and quoted in Ashley Brown’s post really does solve the problem, but with one caveat (see below).
About a year and a half ago, I hiked a portion of the AT and was subjected to several days of drenching rains. I was using a new tent prototype made from silnylon purchased from Outdoor Wilderness Fabrics (I’ve used silnylon from at least 6 or 7 sources for my projects).
The misting was awful in hard rains and my gear got quite wet. What I experienced was most certainly not condensation being knocked loose from the underside of the canopy, but instead, micro rain droplets that were being forced through the fabric.
By the way, if you’re ever in the same situation yourself, you can test the phenomenon simply. First wipe a section of your shelter canopy with a dry cloth to make sure there’s no condensation present, then hold a mirror near the fabric and watch the micro drops quickly accumulate on the shiny surface.
Likewise, if you have any doubt that silnylon leaks under minimal pressure, check out some of the photos in another of my articles.
Anyway, after returning from that trek, I coated the entire underside of the shelter with a 1:5 mix (silicone to mineral spirits) and the problem was solved. I’ve since tested the shelter in torrential rains for extended periods and there has been no misting whatsoever.
And now the caveat. With one of the silnylon samples I used on another project, the silicone impregnation was applied so lightly that the treatment coating wouldn’t stick very well. With this experience, I learned that not all silnylons are of equal quality, so YMMV. I should note, however, that with all of the other samples I’ve used, the treatment bonds very well.
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