Executive Summary:
Sam Farrington sent me 6 premium tent fly material samples to analyze. The samples are listed in the order of increasing areal density.

According to ISO 811, materials with a hydrostatic head of more than 1,500mm H2O can be designated, in general, as rainproof.
By far the highest quality DIY material is sample 6. The tester only goes to 3514 mm H2O to prevent possible damage to the fabric. The test results showed the HH was in excess of the maximum possible HH test level even after 5,200 wet flex aging cycles (simulates about 2 weeks of wind and rain use; degradation normally levels off after about this level of stress). Later in the post detail section, the 20 mm field of view (FOV) clearly shows this fabric has the closest weave to minimize exfoliation of the coating.
Acceptable DIY performance, at a higher weight than 6 can be achieved with sample 1.
Products, versus DIY material, that will provide acceptable long term use include sample 3 (the Sea to Summit tarp) and sample 4 (the Terra Nova Tarp).
The most popular UL Backpacking cottage manufactures silnylon material, that I have previously tested, averages 1200 mm H2O when new.
Details
Sam described the samples that he sent me as follows:
1. -1.6 ozJsq/yd ripstop silnylon from Extrem Textil, represented to be 3500mm HH. It is the darker tan sample.

2. -1.16 ozJsq/yd ripstop silnylon from Extrem Textil, represented to be 1.06 ozJsq/yd and 2000mm HH. It is the lighter tan sample.

3. -1.05 ozJsq/yd mini ripstop nylon from Sea to Summit Escapist Tarp, represented to be 1200mm HH with sil/PU coating. It is the very light lime green sample.
4. -1.16 ozJsq/yd mini ripstop silnylon from Terra Noval Tarp One Tarp, represented to be 3000mm HH. It is the very dark green sample.
5. -1.45 ozJsq/yd ripstop silnylon from Lightheart Gear, represented to be 3000mm HH. It is the medium gray sample. This last one I am interested in knowing the HH about because it went into the floor of my tent.
6. – "1.1 oz Silpoly 2d Gen PU4000- Olive Drab," that Ripstop by the Roll has been selling. They spec it as 1.4 oz/sq/yd including the coat, and 4000mm HH.
I took micrographs of each sample in addition to measuring its thickness, areal density, initial hydrostatic head (HH) and aged hydrostatic head (HH):
1-1.6 ozJsq/yd ripstop silnylon from Extrem Textil, represented to be 3500mm HH.
I tested initial HH >3514 mm H2O, aged HH 1406 mm H2O, thickness .080mm, and areal density 1.62 oz/yd2.
20mm FOV

5mm FOV

2. -1.16 ozJsq/yd ripstop silnylon from Extrem Textil, represented to be 1.06 ozJsq/yd and 2000mm HH.
I tested initial HH 1406 mm H2O, aged HH 773 mm H2O, thickness .050mm, and areal density 1.17 oz/yd2.
20mm FOV

5mm FOV

3. -1.05 ozJsq/yd mini ripstop nylon from Sea to Summit Escapist Tarp, represented to be 1200mm HH with sil/PU coating. It is the very light lime green sample.
I tested initial HH >3515 mm H2O, aged HH 1406mm H2O, thickness .050mm, and areal density 1.17 oz/yd2.
20mm FOV

5mm FOV

4. -1.16 ozJsq/yd mini ripstop silnylon from Terra Nova Tarp One Tarp, represented to be 3000mm HH. It is the very dark green sample.
I tested initial HH >3515 mm H2O, aged HH 1757mm H2O, thickness .053mm, and areal density 1.14 oz/yd2.
20mm FOV

5mm FOV

5. -1.45 ozJsq/yd ripstop silnylon from Lightheart Gear, represented to be 3000mm HH. It is the medium gray sample.
I tested initial HH 2461 mm H2O, aged HH 984mm H2O, thickness .074mm, and areal density 1.40oz/yd2.
20mm FOV

5mm FOV

6. – "1.1 oz Silpoly 2d Gen PU4000- Olive Drab," that Ripstop by the Roll has been selling. They spec it as 1.4 oz/sq/yd including the coat, and 4000mm HH.
I tested initial HH >3515 mm H2O, aged HH >3514mm H2O, thickness .047mm, and areal density 1.40oz/yd2.
20.0mm FOV

5.0mm FOV


