Silnylon Strength and Bivy Sacks

**Firesong** · 03-17-2015, 14:43

First I want to say please no guessing on this one. Hoping I can get some
experience in play for this.

I am thinking of making a Bivy Sack and the bottom should be waterproof which means
using silnylon or a PU coated fabric.

Do you think a 1.1 Silnylon can withstand the abuse a bivy sack would endure for
normal use both in the winter and summer.

I have my concerns. The only reason I am considering this is due to the certain pattern
needed in camo that comes in 1.1 silnylon.

Thanks in advance
James

**punkisdead** · 03-17-2015, 14:51

Most bivy sacks I've seen have either silnylon or cuben floors and from what I hear most people don't use ground cloths with them, so I would say you're probably fine.

**sargevining** · 03-17-2015, 14:58

Epsilon would be a better choice, IMO. It is highly abrasion resistant and water resistant. The coating won't be as durable as sil would be vis a vis water resistance, but I think that the sil fabric would fail before the Epsilon coating would.

**ripstopbytheroll** · 03-17-2015, 19:37

Originally Posted by sargevining

Epsilon would be a better choice, IMO. It is highly abrasion resistant and water resistant. The coating won't be as durable as sil would be vis a vis water resistance, but I think that the sil fabric would fail before the Epsilon coating would.

Agreed epsilon is better durability wise, but when you're putting pressure on epsilon, or any fabric with just DWR, it effectively has no coating. Moisture will come straight through.

**Otter1** · 03-17-2015, 19:49

Add a polycryo groundsheet and no worries whatsoever.

**Boston** · 03-17-2015, 19:55

My only concern would be the hydrostatic head rating of the silnylon. A lot of the material we use for tarps wont have a high enough rating to prevent water seepage from the pressure your body will apply. You'll need a material with a heavier coating. I would talk to Dave Olsen over at Oware. He carries 30 and 70 denier sil with heavier coatings (0.3 and 0.5 oz/sqyrd respectively). He told me the 70D is rated at 3500mm, which may be good for a bivy bottom.

Durability wise you should be ok as long as you clear the area of sticks, etc. theres plenty of ground sheets and tent floors made of silnylon out there.

**Big Sweets** · 03-17-2015, 20:03

I would suggest a military surplus gore tex bivy. This is the same one I got and used on two trips before I started hanging.
http://www.amazon.com/gp/product/B00...?ie=UTF8&psc=1

**IRONFISH45** · 03-17-2015, 20:13

Originally Posted by punkisdead

Most bivy sacks I've seen have either silnylon or cuben floors and from what I hear most people don't use ground cloths with them, so I would say you're probably fine.

I built a bivy using Silnylon, I did not like how slippery the bottom was. One of my tents had a silnylon floor, it was wicked slick. In fact I would call it a design flaw.