Is it a big difference between the the two? Im not even really sure what it means. I noticed the superfly is 2000mm 30d. Im looking at fabric from ripstop by the roll and it says it is 1500mm and 20d. Is that a big deal?
Is it a big difference between the the two? Im not even really sure what it means. I noticed the superfly is 2000mm 30d. Im looking at fabric from ripstop by the roll and it says it is 1500mm and 20d. Is that a big deal?
Those are Hydrostatic Pressure Ratings. That is, the amount of water pressure applied before the water penetrates the fabric. The 20D fabric is lighter weight and I use it as side panels with a 30D top piece.
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How about this question instead - Will 1500mm be waterproof enough for my type of shelter and in my area? If so, that extra 500mm has no consequence except for making a heavier tarp generally. In my opinion, 1500mm is fine for a steep sided shelter like a tarp especially given that you will be in tree cover.
Ryan
agreed really no noticeable difference between 1500 and 2000. as a more extreme example the HH (hydrostatic head) of an MSR Hubba tent is something like 1200 and it seems US tents have lower HH ratings than tents made by European manufacturers. I have a Vango Halo 200 (UK made tent) which has a HH of 5000. European manufacturers seem to play on our fears that we need materials that are much more waterproof as apparently our rain is more wet and our wind stronger than yours
but that doesn't stop many many Europeans buying US made tents/tarps etc including an absolute sh-t load of Hubba's... and funnily enough even our super wet rain doesn't make your products leak
point of my long winded story is don't worry about 1500 or 2000, you'll stay dry.
All the gear and no idea.....
There is no universal standard for what hydrostatic head pressure is considered waterproof, as it varies based on condition's.
I have seen standard's that classify a material as waterproof if it it's minimum HH is 800mm. Others state 1000mm, or 1500mm.
A Sea to Summit article states a heavy, wind driven rain (what wind speed, I don't know) can penetrate 2000mm.
Tyvek is ~1300mm and I have had an umbrella made from it mist in a heavy KY rainstorm.
That said, in hammock you're generally in tree cover, which provides a wind break, and can serve to break up the rain drop's. A fabric that might mist when set up out in the open, may be ok for a hammock set up because of this.
Many sil provider's wont advertise, or wont know their HH rating. RSBTR has his material tested and advertises it, which is great.
You can also judge by the coating weight. Generally more will provide a better result. Oware told me his 70D sil coated fabric with a 0.5oz/sqyrd coating is rated to ~5000mm. He didn't know for his lighter material's, but the 1.1 sil 2nd's I got from him were about 1.5 oz/sqyrd - for about a 0.4 oz/sqyard coating. This fabric has a significantly visible, and tactile difference when compared to other silnylon's I've used (RSBTR, Noah Lamport). The coating is much heavier.
I imagine the weave, and thread count will also impact the rating (tighter weave may be better).
There is a ton of variables that account for how waterproof the fabric is - coating type, how the coating is applied, yarn count and density, how the yarns are woven, how the fabric is being loaded (stretched), how old the fabric is, how the ripstop is woven, etc, ect...
The last big factor is how it is tested - there are several test standards available, all of which have their pluses and minuses. Not to mention the fact that Boston had mentioned - what is the minimum required? Some of it is marketing, some of it is actual good science.
I had done my Master's thesis work on a bunch of this work, feel free to take a look for yourself - http://outdoorequipmentsupplier.com/Thesis_web.pdf.
All in all, I personally feel that a 1500mm rating is pretty darn acceptable (and then some) - once you start getting real world conditions where you get enough permeation through the fabric to start to cause moisture problems with that type of coating, you're going to have much bigger problems (i.e. very heavy winds).
Lots of good info in this thread. I'll risk a bit of layman's experience. Seems to me that when it's all that rainy and windy, you're getting a lot of air moisture (humidity) on everything under your rainfly, no matter how waterproof the rainfly is. So, fixating on the rainfly might give a false sense of security from all wetness.
Even so, I do want my rainfly as waterproof as reasonable, of course.
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