Questions About 10 Denier vs. 30 Denier

[Jerry Adams]

yeah, that makes sense, tighter weave is more waterproof

and maybe it’s the large denier fabric like 1000D that has problems making it waterproof

maybe not much difference between 10D and 30D.  Tight weave will make them waterproof enough with a good coating.  Test results will be interesting

 

[Sam Farrington]

After pondering Jerry’s posts, and Dan Durston’s about polyester, I thought it was about time to take a closer look at membrane silpolys from RBTR.  The ones I have were from around 2015-2016, and were marketed as membrane silpoly PU 2000, and also as membrane silpoly PU 4000 with a heavier polyurethane or PU coating.

At that time, when I pinned them up on model frames, the tear strength was so weak that the pins could not hold them in place due to tearing.

More recently, I opted for a lighter tent with some bias stretch, but that would keep the canopy taut in weather that turns silnylon limp and saggy.  DCF has no stretch at all, so I did not want that.  Reading about Jerry’s silpoly tent, I learned that he is using the lightest silpoly, woven with 15 denier thread, and still dubbed “membrane” by RBTR.   He had some issues with the bias stretch, but reported no failures from tearing.

And I thought the bias stretch could be addressed by tent design.  Some even feel that woven fabrics’ bias stretch is a good thing because it absorbs the force of wind, rain, and mishaps.  Am not sure about beak-shaped vestibules, but could see no reason why bias stretch could not be an advantage if a fabric were tightened over a frame with a partial dome shape, a feature that also provides added interior space compared to the A-frame designs that predominate.

So it was time to compare the old membrane with the new, and I was pleasantly surprised that the material actually had some reasonable resistance to tearing, unlike the old stuff with tear strength that was virtually nil.  Simply poked a ball-end straight pin through the fabric and tried to move it sideways in different directions.  Unlike the older fabrics that simply split apart, it resisted splitting in the same way that most woven tent fabrics do.

Don’t know whether it was the PU coats or the quality of fiber or weave that hampered the older material, but this one works well enough to survive for a while.  So designed a tent with a partial fly that covered only the ceiling over the floor area, the part of the tent that also is most often protected by insect netting doors.  The partial fly is basically a long rectangle with no frills, so if the newer membrane does wear out, it will be a simple and inexpensive matter to make a new fly.  The fly will also be easier to install in high winds.

Whether a stouter ripstop silpoly will be needed for the tent’s vestibules is another question.  So opted for sewing the vestibules to the inner tent.  The smaller fly covers most of the tent, and saves considerable weight, enough to add a short ridgepole to beef up the tent frame.

The new membrane also appears to be quite waterproof, but opting for some HH testing should be a good idea.  So 15 denier is my outcome with “10 denier vs 30 denier,” and we’ll see how it does.

[Roger Caffin]

the tear strength was so weak that the pins could not hold them in place due to tearing.
I am now guessing. I suspect that the old fabric was light polyester coated with thick PU of the old sort. It is well-known that the old PU coating made the fabric quite weak. That is why I like a silicone coating: it actually increases the fabric tear strength.

Cheers

[Sam Farrington]

Roger: agreed.

Please note that RBTR states that the silcoats on its fabrics, unless labeled PU, are a blend of polyurethane and silicone.  I had thought the two were like oil and water, but perhaps not.  In any event, the silcoats stretch with the fabric, and must be sealed with silicone based sealers as one would expect.

 

 

 

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