A tent’s ability to withstand heavy rain

Last year I had a Moment (SW-2011 ver) in a few hours of wind driven rain along the Colorado border and the fabric was fine. Only where my seam-sealing wasn't complete did I have a small leak (luckily I brought a sil repair mini tube of silicone). I don't think I've ever had a rain fly compromised. That said I'm looking at cuben for weight and bulk savings in a 3 season shelter. Still reading reviews as there are other trade-offs depending on the design.

I stayed dry under my Solomid XL during a recent 11 hour non stop record rain event. IMO you would have been fine in the Moment.

If almost no wind, can conditions be really 'bad'? Or just very wet? ;)

fabric wise, I think I'd choose almost new silnylon over a 25year+ old tent. (uv degradation? )

My 3 yr old Scarp has coped with many 12 hour+ rainy n windy nights without letting water through the fabric.

In your world, windy and wet define bad. In my world, 35F and wet are bad and can spell disaster in a hurry.

Whether or not the conditions were bad for you or anyone else, that doesn't impact what the tent sees. You had a hard rain, no wind, temperature wasn't an issue (for your tent). I would be confident in any shelter I have owned in those conditions, even my cuben fiber tarp that I used to use. If you want to check the storm worthiness of a tent I would have rain and wind or snow loading, not just rain. And I have seen what a moment can handle in snow. You would have had no problems with just a hard rain, unless you setup in a depression or had other site related issues.

Sounds like you have a perfect opportunity to set up both and find out!!

Wind is the challenge, snow next, then rain. Site selection is paramount, with protection from wind and ground water drainage being my concerns. There have berm many times that even a cheap tent was just fine, but I had a stream running under the tent.

Hammocks cure the running water up to 18" deep :) the big tarps with an open bottom make wind the issue.

For me, snow needs a tent built for that. Mids and heavier tents like Hillebergs and tunnels come to mind.

1) Any fabric designed as a tent fly, or a single skin in the case of those types of shelter, should minimally keep you dry. That is what they are designed for. I don't think Henry at TarpTent or others will compromise water resistance without informing you. The so-called Sub-Light are made of tyvec or similar. These *can* leak in your conditions but these are well known as doing so under heavy rains. I have had issues with 1.1oz fabric stretching (from many uses in windy conditions leading to *misting through*) and some minor issues with seams leaking on older tarps (where threads have elongated the thread holes and needed resealing.) But without a 30-40mph wind, I don't think this is a problem. Especially with a new tent, it should keep you dry, minimally. Note that 1.1oz fabric is generally covered both sides with silicone. Now the process can vary a lot. I would be inclined to use a heavier coating, like .4 or .5oz per yard, as opposed to some really cheap stuff that is only coated at .2oz per yard. I believe the fabric will be a bit stronger and it will hold up better in any winds, ie less stretching. I am sure the Tarptent people know more'n me, though and choose a good fabric since it is only one fabric. The biggest complaint I have heard is stretching in winds and heavy rains. I'm sure they have delt with these types of issues and can make recomendations.

2) Cuben is better? Well, that debate still goes on. If you can rely on a siliconized fabric to keep you dry, do you need more waterproofness? Seaming is still a problem with cuben. Adhesives creep over time. There is some evidence that repeated folding can weaken or cause leaks with cuben. So there is no single solution that works for the long haul and maintence can be impossible. If you are looking for SUL weights, then you are certainly very interested in cuben, despite it's astronomical price.

A good portion of a tent's weight is the stitching, stakes, cords, tape and attachments for them. This is the same with either CF or silnylon. It adds about 3-4oz ounces for any ul tent. If you take a cuban tarp weighing 6oz and add 4oz to it you have an 10oz shelter. Good. If you take a 12oz sil tarp and add 4 ounces to it you have a 1lb shelter (this is what my tarp weighs.) All I save is the 6oz in fabric. At a 9pound base weight, saving 6oz is not my biggest concern. And the durability goes down from 10 years to 5 years. My tarp cost me $54 to make(9ydx$7.) The same cuban fiber would have cost $225 (9ydx$25.) Or about 4 times as much. It lasts about half the time. Overall it is roughly 8times as expensive as silnylon for a 10 year tarp. It only saves about 1/3 of the total weight of the tarp. So, a lot depends on your packing system, your priorities, etc. I drool over cuben, but, I do not use it.

http://www.backpackinglight.com/cgi-bin/backpackinglight/forums/thread_display.html?forum_thread_id=69444
This thread will explain more about cuben.

http://www.backpackinglight.com/cgi-bin/backpackinglight/forums/thread_display.html?forum_thread_id=58096&disable_pagination=1
In this thread, Nick Beaudoin recomends sewing AND gluing. He is a sailmaker at North Sails. This series of notes pertains to cuben only and not silnylon.

or is 3M 9460 tape best?

it's supposed not to creep like some other tapes

if you glue, you have to wait for it to dry, weight it down,…

and then a row of stitches through the Cuben/tape/Cuben so it doesn't creep – but maybe that's "belt and suspenders" if you use 9460

"Cuben is better? Well, that debate still goes on."

Not to mention there are some reports now suggesting that cuben does not maintain resistance to UV exposure. Less than that of silnylon, weakening it and making it less waterproof.

The worst storm I every went through, 12 hours of heavy rain, wind and a lot of lightning, was in my Scarp 1. Stayed comfortable and dry the whole time.

3M 9485 is known as 'sailmakers seamstick'. Good permanent bond. The 9460 might be as good – don't know.

Cheers