"Waterproof" pack fabrics and other nonsense

[DaveC]

Kifaru's new use of Dimension Polyant fabric ("Xpac") has gotten a lot of attention, and a fair few of the answers to various questions and chatter generally has been misleading. I'll try to be as brief as possible in the following.

"Waterproof" fabrics

I'm not aware of anyone who uses a nonwaterproof fabric for the body of a backpack hunting pack. Kifaru is selling themselves short by claiming their new Xpac bags will be actually waterproof. Traditional pack fabrics are made waterproof by coating one side with polyurethane. Xpac is made waterproof by laminating a plastic film to one side. The Xpac laminate is (broadly speaking) heavier, more waterproof (200 psi), and more expensive than polyurethane coating. It is also more rigid/crinkly. The problem with the waterproof question is that the amount of PU applied to fabrics like Cordura varies widely. I've seen quality stuff (like that featured in every Kifaru product I've seen) with a thick glossy layer, and cheapo stuff with barely any at all. All of it is waterproof by one definition. The Cordura side pockets on the pack I took skiing today filling up with snow in the blizzard and when I emptied it 15 minutes ago were full of 2 inches of standing water, which was not leaking through the fabric.

What does become relevant is the PSI rating of that PU layer. I've had quality Cordura leak when it was on the bow of my packraft getting blasted by waves, when the pack was covered in wet snow for hours, and when a bloody bag of meat was sitting against, again for many hours. There is a case to be made that for many applications Cordura is often not waterproof enough, but it is waterproof, and saying otherwise is not really accurate by any meaningful standard. Plenty of people do not need the extra waterproofedness provided by Xpac, and for them they aren't getting much if anything by buying it.

Stone Glacier's use of Xpac is illustrative here.

It is sort of worth mentioning that in theory Xpac is more durable as a treatment than PU, insofar as PU eventually flakes off the fabric due to UV and abrasion. Quality PU takes a long time to do this, and Xpac hasn't been in wide use long enough to really provide a good test. (I've never heard of a confirmed case of XPac delaminating, and have made a few packs to really try to get it to fail in this way, but still.)

It is also worth mentioning that over the long term I've never owned a truly waterproof pack. Putting aside the whole stitching issue, long term use and abrasion will eventually put a bunch of tiny holes in your pack. Dig out an old bag which has seen good service, fill it with water, and see what happens. Kifaru is smart to use Cordura as an extra outer layer on the bottom and low sides of their Xpac bags, but in really wet conditions I would still put things like insulation and electronics in some kind of dry sack.

Face fabric is face fabric

Xpac is not a fabric, really, it is a laminate. If you have enough money Dimension Polyant will laminate whatever fabric you care to send them. You can get 500D Cordura Xpac, or the 210D Kifaru appears to be using, or a lunch of other stuff. Face fabrics perform the same no matter the waterproofing layer. In theory the XPac laminate increases tear and puncture strength, but in 200+D fabrics this is a moot point. For those who used it, the old Kuiu 160D Ultra pack fabric is a fair equivalent of VX21 when it comes to abrasion, i.e. it isn't that great.

It follows that face fabrics retain water the same, whatever laminate is underneath. All pack fabrics I can think of come treated with a DWR (same as your rain gear) and just like with your rain gear that DWR wears off very fast when exposed to dirt. In my experience new and unabraded pack fabrics don't retain too much water, and older fuzzed out fabrics retain plenty. I'd be all for a fabric with some sort of permanent external coating, but Arc'teryx is the only company I can think of who has done this (with PU). IMO water weight retention has much more to do with the foams and fabrics used on the harness elements of a pack than the main fabric or coating on it.

Ignore the following if your attention is waning

Xpac nomenclature is pretty simple. The number denotes the denier of the face fabric. X fabrics have the characteristic X/Diamond grid, between the face fabric and laminate. V fabrics have a white layer of fabric on the inside of the laminate.

I've always found the 2 Cordura face fabrics to perform best. X33 (330D Cordura) is widely available in multicam, and X50 (500D) in black multicam. The V fabric in the laminate makes the interior of dark colors easier to see inside, and otherwise doesn't seem to add anything. You need a headlamp to see to the bottom of a big bag made of X50. The X laminate is a liability, something I can say definitively now that I've had some plain 33 Xpac for the past few weeks. The X fibers create abrasion points. They also provide some branding for Dimension Polyant , but hopefully D-P will let that go as they get more market share.

 

[Rokwiia]

Given that all fabric/materials have some inherent limitation, what is your conclusion of which fabric offers the best protection from water?

 

[deadwolf]

Arc’teryx has been making waterproof backpacks for years


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[Hunter Sargent]

Dude, options are great. If you don't like it, stick with Cordura. If you are hunting in the NW or BC, the new materials are probably a great option.

 

[JP100]

Kifaru's new use of Dimension Polyant fabric ("Xpac") has gotten a lot of attention, and a fair few of the answers to various questions and chatter generally has been misleading. I'll try to be as brief as possible in the following.

"Waterproof" fabrics

I'm not aware of anyone who uses a nonwaterproof fabric for the body of a backpack hunting pack.

What does become relevant is the PSI rating of that PU layer. I've had quality Cordura leak when it was on the bow of my packraft getting blasted by waves, when the pack was covered in wet snow for hours, and when a bloody bag of meat was sitting against, again for many hours. There is a case to be made that for many applications Cordura is often not waterproof enough, but it is waterproof, .

are you trying to claim Cordura as a waterproof fabric?!?! because theres not a hope in hell it remotely is. and no one claims it to be! Not Cordura, and they make the stuff

I have a Argali from Kifaru and from day one it was by no means waterproof, not in rain, not with bloody meat, not in a river corssing. nor did anyone claim it be.

I have eberlstock packs, NOT water proof, Kuiu, NOT waterproof
Clients with Exo, NOT waterproof, Clients with SG NOT waterproof
Ive seen many packs, and none have been waterproof in rain, let alone river crossings ect

Cordura is water 'resistant' for sure, not not waterproof by anymeans.

x pac seems be an a real water proof fabric and with seam sealing should be nearly as good as a dry bag(depends on seam sealing and bag closure)

I have one of the Kifaru bags coming(hopefully very soon) and look forward to seeing if it is indeed waterproof.

 

[Bender]

Hello all, Bender here from Kifaru. Here's some of the reason why I made the new bags the way I did and the lowdown on the materials. Hang on, I tend to ramble.

The new Xpac bags are made from VX21-RS (210D Nylon Face w/ Polyester and Pu Lamination, 6.3 oz/yd^2) and 500d Ranger Green ( Solution dyed with a PU backing, 7.5oz/yd^2). This was the version of their 21 series they made to have a quieter quality than their typical Ripstop laminations. While it is still noisy while cold, it has a thicker face fabric than their VX07 line. We wanted to make a bag that would hold up better to the increasingly wet areas of the world as well as handle some abrasion. A non seam sealed bag made out of waterproof material is kind of counter intuitive because I train our sewers to stab a few thousand holes in every bag as the first thing they do. The thread will act as a wick to draw moisture past the Xpac and into the bag. Seam sealed (re: welded using radio waves) bags are very cool, but the equipment required is very expensive and specialized (and you have to simplify the design pretty drastically). To combat this i tried to make the design as simple as possible (less seams) and limit the amount of top stitching going through the Xpac. All of the bartacks and mid panel piercing are done on 500d fabric as it is generally tougher and resists tearing out better than Xpac. The only exception is the back panel of the packs, where I had to bartack a tab for water bladders. The reason it is Xpac back there is for the load shelf and to create a blood barrier. If you were to turn our new bags inside out and seam seal them with silicone diluted with mineral spirits (much like our shelters), you would get a pretty water proof bag that would hold up to most anything besides a good dunking. What we wanted to accomplish with this bag was a lightweight series of bags that have a higher abrasion resistance than our old KU like but were more water resistant than 500d. The Aquaguard zipper was chosen as waterproof (re: repelant, but still pretty waterproof) bags usually have limited access to keep the moisture out. If people would have to still use compactor bags because of the permeable zipper it would defeat the purpose as even our coated regular YKK zippers are susceptible to rain blasting between the teeth and zipper flaps can hinder access if not done correctly.

Let me know if that was clear as mud. If you guys have any questions about bag construction or materials feel free to contact me at [email protected].

TLDR: Xpac is lighter and gooder and waterproofer-er than 500d. But it's also noisy, less abrasion resistant and requires some sort of seam sealing to be fully waterproof. We tried to make something that would give our customers options while increasing capabilities through high tech materials and smarter production methods without having to buy equipment that costs a lot of money and has limited uses.

 

[Michiganhunter]

Hello all, Bender here from Kifaru. Here's some of the reason why I made the new bags the way I did and the lowdown on the materials. Hang on, I tend to ramble.

The new Xpac bags are made from VX21-RS (210D Nylon Face w/ Polyester and Pu Lamination, 6.3 oz/yd^2) and 500d Ranger Green ( Solution dyed with a PU backing, 7.5oz/yd^2). This was the version of their 21 series they made to have a quieter quality than their typical Ripstop laminations. While it is still noisy while cold, it has a thicker face fabric than their VX07 line We wanted to make a bag that would hold up better to the increasingly wet areas of the world as well as handle some abrasion. A non seam sealed bag made out of waterproof material is kind of counter intuitive because I train our sewers to stab a few thousand holes in every bag as the first thing they do. The thread will act as a wick to draw moisture past the Xpac and into the bag. Seam sealed (re: welded using radio waves) bags are very cool, but the equipment required is very expensive and specialized (and you have to simplify the design pretty drastically). To combat this i tried to make the design as simple as possible (less seams) and limit the amount of top stitching going through the Xpac. All of the bartacks and mid panel piercing are done on 500d fabric as it is generally tougher and resists tearing out better than Xpac. The only exception is the back panel of the packs, where I had to bartack a tab for water bladders. The reason it is Xpac back there is for the load shelf and to create a blood barrier. If you were to turn our new bags inside out and seam seal them with silicone diluted with mineral spirits (much like our shelters), you would get a pretty water proof bag that would hold up to most anything besides a good dunking. What we wanted to accomplish with this bag was a lightweight series of bags that have a higher abrasion resistance than our old KU like but were more water resistant than 500d. The Aquaguard zipper was chosen as waterproof (re: repelant, but still pretty waterproof) bags usually have limited access to keep the moisture out. If people would have to still use compactor bags because of the permeable zipper it would defeat the purpose as even our coated regular YKK zippers are susceptible to rain blasting between the teeth and zipper flaps can hinder access if not done correctly.

Let me know if that was clear as mud. If you guys have any questions about bag construction or materials feel free to contact me at [email protected].

TLDR: Xpac is lighter and gooder and waterproofer-er than 500d. But it's also noisy, less abrasion resistant and requires some sort of seam sealing to be fully waterproof. We tried to make something that would give our customers options while increasing capabilities through high tech materials and smarter production methods without having to buy equipment that costs a lot of money and has limited uses.

Thanks Bender

 

[Bender]

No problem. I should also add that yes, they do make cordura faced xpac and the cordura has the same ability to absorb some water. We decided that the VX-21 RS would be optimal for what we were trying to accomplish which was a lighter weight bag with weather resistant qualities. I really want to use some of the other Xpacs in the future with more durable face fabrics but this was the right fabric for what we wanted to accomplish. I should also add that all three of these bags have 500d reinforced bottoms and the grab handles have been reinforced much like the Crater and Cavern.

 

[Sverimerica]

Is there something I am missing or should have read that can give some sort of context to this?

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[Sverimerica]

Kifaru's new use of Dimension Polyant fabric ("Xpac") has gotten a lot of attention, and a fair few of the answers to various questions and chatter generally has been misleading. I'll try to be as brief as possible in the following.

"Waterproof" fabrics

I'm not aware of anyone who uses a nonwaterproof fabric for the body of a backpack hunting pack. Kifaru is selling themselves short by claiming their new Xpac bags will be actually waterproof. Traditional pack fabrics are made waterproof by coating one side with polyurethane. Xpac is made waterproof by laminating a plastic film to one side. The Xpac laminate is (broadly speaking) heavier, more waterproof (200 psi), and more expensive than polyurethane coating. It is also more rigid/crinkly. The problem with the waterproof question is that the amount of PU applied to fabrics like Cordura varies widely. I've seen quality stuff (like that featured in every Kifaru product I've seen) with a thick glossy layer, and cheapo stuff with barely any at all. All of it is waterproof by one definition. The Cordura side pockets on the pack I took skiing today filling up with snow in the blizzard and when I emptied it 15 minutes ago were full of 2 inches of standing water, which was not leaking through the fabric.

What does become relevant is the PSI rating of that PU layer. I've had quality Cordura leak when it was on the bow of my packraft getting blasted by waves, when the pack was covered in wet snow for hours, and when a bloody bag of meat was sitting against, again for many hours. There is a case to be made that for many applications Cordura is often not waterproof enough, but it is waterproof, and saying otherwise is not really accurate by any meaningful standard. Plenty of people do not need the extra waterproofedness provided by Xpac, and for them they aren't getting much if anything by buying it.

Stone Glacier's use of Xpac is illustrative here.

It is sort of worth mentioning that in theory Xpac is more durable as a treatment than PU, insofar as PU eventually flakes off the fabric due to UV and abrasion. Quality PU takes a long time to do this, and Xpac hasn't been in wide use long enough to really provide a good test. (I've never heard of a confirmed case of XPac delaminating, and have made a few packs to really try to get it to fail in this way, but still.)

It is also worth mentioning that over the long term I've never owned a truly waterproof pack. Putting aside the whole stitching issue, long term use and abrasion will eventually put a bunch of tiny holes in your pack. Dig out an old bag which has seen good service, fill it with water, and see what happens. Kifaru is smart to use Cordura as an extra outer layer on the bottom and low sides of their Xpac bags, but in really wet conditions I would still put things like insulation and electronics in some kind of dry sack.

Face fabric is face fabric

Xpac is not a fabric, really, it is a laminate. If you have enough money Dimension Polyant will laminate whatever fabric you care to send them. You can get 500D Cordura Xpac, or the 210D Kifaru appears to be using, or a lunch of other stuff. Face fabrics perform the same no matter the waterproofing layer. In theory the XPac laminate increases tear and puncture strength, but in 200+D fabrics this is a moot point. For those who used it, the old Kuiu 160D Ultra pack fabric is a fair equivalent of VX21 when it comes to abrasion, i.e. it isn't that great.

It follows that face fabrics retain water the same, whatever laminate is underneath. All pack fabrics I can think of come treated with a DWR (same as your rain gear) and just like with your rain gear that DWR wears off very fast when exposed to dirt. In my experience new and unabraded pack fabrics don't retain too much water, and older fuzzed out fabrics retain plenty. I'd be all for a fabric with some sort of permanent external coating, but Arc'teryx is the only company I can think of who has done this (with PU). IMO water weight retention has much more to do with the foams and fabrics used on the harness elements of a pack than the main fabric or coating on it.

Ignore the following if your attention is waning

Xpac nomenclature is pretty simple. The number denotes the denier of the face fabric. X fabrics have the characteristic X/Diamond grid, between the face fabric and laminate. V fabrics have a white layer of fabric on the inside of the laminate.

I've always found the 2 Cordura face fabrics to perform best. X33 (330D Cordura) is widely available in multicam, and X50 (500D) in black multicam. The V fabric in the laminate makes the interior of dark colors easier to see inside, and otherwise doesn't seem to add anything. You need a headlamp to see to the bottom of a big bag made of X50. The X laminate is a liability, something I can say definitively now that I've had some plain 33 Xpac for the past few weeks. The X fibers create abrasion points. They also provide some branding for Dimension Polyant , but hopefully D-P will let that go as they get more market share.

Just like your blog, this required a second read through. I enjoy the blog by the way.

You say, "There is a case to be made that for many applications Cordura is often not waterproof enough, but it is waterproof, and saying otherwise is not really accurate by any meaningful standard."

How are you defining waterproof? Your own definition would be helpful. It sounds like you are referring to what many consider to be water-resistant. I know you know the difference, (I follow your blog, as mentioned) and your post would make more sense if there was some context as to what you mean, rather than an article about fabric construction.

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[RockChucker30]

In my personal experience Cordura is not a waterproof fabric. It's a fabric with a good DWR that will wet out and soak through in rain.

X-Pac is waterproof. Seams are not.

A bit of advice on seam sealing Seek Outside packs. Our packs need to be seam sealed on the outside, not the inside. I've done extensive testing of waterproofing and water will still wick inside if the sealant is on the inside. Do a good job on the outside and you're good. There is a reason shingles are on the outside of your roof.

Worn upright in the rain, seam sealing usually isn't necessary with our packs. PNW, Southeast AK, jungle during rainy season, maybe, but usually not.

 

[DaveC]

...We wanted to make a bag that would hold up better to the increasingly wet areas of the world as well as handle some abrasion. A non seam sealed bag made out of waterproof material is kind of counter intuitive because I train our sewers to stab a few thousand holes in every bag as the first thing they do. The thread will act as a wick to draw moisture past the Xpac and into the bag. Seam sealed (re: welded using radio waves) bags are very cool, but the equipment required is very expensive and specialized (and you have to simplify the design pretty drastically). To combat this i tried to make the design as simple as possible (less seams) and limit the amount of top stitching going through the Xpac. All of the bartacks and mid panel piercing are done on 500d fabric as it is generally tougher and resists tearing out better than Xpac. The only exception is the back panel of the packs, where I had to bartack a tab for water bladders. The reason it is Xpac back there is for the load shelf and to create a blood barrier...

Good stuff Bender.

 

[DaveC]

You say, "There is a case to be made that for many applications Cordura is often not waterproof enough, but it is waterproof, and saying otherwise is not really accurate by any meaningful standard."

How are you defining waterproof? Your own definition would be helpful. It sounds like you are referring to what many consider to be water-resistant. I know you know the difference, (I follow your blog, as mentioned) and your post would make more sense if there was some context as to what you mean, rather than an article about fabric construction.

Most Cordura spec sheets have the 500D and 330D variations test at 350mm HH, which is roughly .6 psi. This means you can plug a tube with Cordura and fill that tube 13.77 inches tall with water and the fabric won't leak. Of course, with most Xpac fabrics you can make that same column 150 yards tall and that fabric still won't leak.

I prefer more waterproofing than Cordura now that I have such easy access to so many options, for the cases I mention above. But folks should be realistic about what sort of performance they need.

I know that in my own experience it takes quite a lot to get "traditional" PU coated fabrics to actually leak through the fabrics. I also know, as Bender highlights, that it doesn't take too much stitching into a bag to make Xpac leaky enough that you'd have a hard time making the case for a real world performance difference.

In short, if I were going to the West Coast of NZ, I'd take an Xpac bag for sure. Ditto for Alaska just about anytime, Montana any time between late Sept and June. For June-Sept in the Rockies and anytime in the American SW I'd take a PU fabric and not worry.

 

[Sverimerica]

Most Cordura spec sheets have the 500D and 330D variations test at 350mm HH, which is roughly .6 psi. This means you can plug a tube with Cordura and fill that tube 13.77 inches tall with water and the fabric won't leak. Of course, with most Xpac fabrics you can make that same column 150 yards tall and that fabric still won't leak.

I prefer more waterproofing than Cordura now that I have such easy access to so many options, for the cases I mention above. But folks should be realistic about what sort of performance they need.

I know that in my own experience it takes quite a lot to get "traditional" PU coated fabrics to actually leak through the fabrics. I also know, as Bender highlights, that it doesn't take too much stitching into a bag to make Xpac leaky enough that you'd have a hard time making the case for a real world performance difference.

In short, if I were going to the West Coast of NZ, I'd take an Xpac bag for sure. Ditto for Alaska just about anytime, Montana any time between late Sept and June. For June-Sept in the Rockies and anytime in the American SW I'd take a PU fabric and not worry.

I see. I appreciate the enlightenment. One thing I have noticed in comparing my kifaru vs stone glacier bags, both 500d cordura and both purchased used so hard to have a good basis for comparison, is that the Kifaru had more PU coating and was noticeably more water resistant, or water proof if you will, than the stone glacier. I use a pack cover now, which I never felt the need to with my kifaru.

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[Mike7]

This is interesting. I have wondered when Kifaru might consider covered or waterproof zippers. From testing on my old Timberline, over 90% of the water coming into the pack when walking through wet brush for days, came in not through the seams and not through the Cordura, but rather seemingly through the zippers. I also have had an inch of water sitting in Kifaru cordura hip pouches without any seam sealing done or added external DWR applied.

I can't say for sure, but I will bet that a good Cordura pack that has a thoughtful overall design (i.e. vertical zippers end under the lid edge, etc.), waterproof zippers, good DWR externally, and a drainage eyelet at the bottom of each compartment would perform excellent in very wet climates.

 

[mcseal2]

I haven't had to use the dry bag for my Exo 3500 yet, but since I'm going to AK this fall I bought it. It seems like a pretty decent idea and design, it buttons inside the main pocket and holds what needs to stay dry. It's a roll top design and might not keep everything dry if I submerge it in a river but should work for rain which is what I expect from it.

 

[MuleyFever]

Now if they would just make a bag in the middle from lighter Cordura

 

[JP100]

This is interesting. I have wondered when Kifaru might consider covered or waterproof zippers. From testing on my old Timberline, over 90% of the water coming into the pack when walking through wet brush for days, came in not through the seams and not through the Cordura, but rather seemingly through the zippers. I also have had an inch of water sitting in Kifaru cordura hip pouches without any seam sealing done or added external DWR applied.

I can't say for sure, but I will bet that a good Cordura pack that has a thoughtful overall design (i.e. vertical zippers end under the lid edge, etc.), waterproof zippers, good DWR externally, and a drainage eyelet at the bottom of each compartment would perform excellent in very wet climates.

I have a Kifaru Argali for this exact reason, and always prefer a large compartment to keep all gear together in one large dry bag/pack liner.

I can assure you even this style with no zippers and roll top, is NOT waterproof. Nor is it sold as/meant to be.

I think the Xpac, seam sealed will handle a fair bit, but I will still run my gear in a dry bag I think.

 

[JP100]

I should add, no offence to the guys here from the western USA and other 'dry' parts of the world, but unless you have been to a 'wet area' you dont really know what 'we'(guys in the wet) and talking about when we say wet.

The most recorded rain I have personally been in was 250mm++, thats over 10 inches, in around 6 hours. I emptied a rain gauge in the morning(which had around 100mm in it) and then returned later that day and emptied is and it was over flowing, and only holds 250mm.

In some parts of NZ that is not particularly unusual.

Just for perspective our rain fall records

1 hour- 109mm(4")
24 hours-682mm(26+")

1 year-18,442mm(726")

Obviously these are extremes, but does give some perspective. And alot of areas in the mountains have no records aswell.


I not saying 'we are tougher or you' or anything like that, but its just a very different set of circumstances that 'we' operate in. Things that seem good in theory(like floorless tents, and 'waterproof' Cordura) just dont work in the real world here.

Its great to see a company like Kirafu, who is based in a dry environment, go out of their way to make gear for those of us who are in the other environment.

I am really excited to see how one of these Xpac bags does handle things here.

 

[skaldugwas]

Kifaru's new use of Dimension Polyant fabric ("Xpac") has gotten a lot of attention, and a fair few of the answers to various questions and chatter generally has been misleading. I'll try to be as brief as possible in the following.

"Waterproof" fabrics

I'm not aware of anyone who uses a nonwaterproof fabric for the body of a backpack hunting pack. Kifaru is selling themselves short by claiming their new Xpac bags will be actually waterproof. Traditional pack fabrics are made waterproof by coating one side with polyurethane. Xpac is made waterproof by laminating a plastic film to one side. The Xpac laminate is (broadly speaking) heavier, more waterproof (200 psi), and more expensive than polyurethane coating. It is also more rigid/crinkly. The problem with the waterproof question is that the amount of PU applied to fabrics like Cordura varies widely. I've seen quality stuff (like that featured in every Kifaru product I've seen) with a thick glossy layer, and cheapo stuff with barely any at all. All of it is waterproof by one definition. The Cordura side pockets on the pack I took skiing today filling up with snow in the blizzard and when I emptied it 15 minutes ago were full of 2 inches of standing water, which was not leaking through the fabric.

What does become relevant is the PSI rating of that PU layer. I've had quality Cordura leak when it was on the bow of my packraft getting blasted by waves, when the pack was covered in wet snow for hours, and when a bloody bag of meat was sitting against, again for many hours. There is a case to be made that for many applications Cordura is often not waterproof enough, but it is waterproof, and saying otherwise is not really accurate by any meaningful standard. Plenty of people do not need the extra waterproofedness provided by Xpac, and for them they aren't getting much if anything by buying it.

Stone Glacier's use of Xpac is illustrative here.

It is sort of worth mentioning that in theory Xpac is more durable as a treatment than PU, insofar as PU eventually flakes off the fabric due to UV and abrasion. Quality PU takes a long time to do this, and Xpac hasn't been in wide use long enough to really provide a good test. (I've never heard of a confirmed case of XPac delaminating, and have made a few packs to really try to get it to fail in this way, but still.)

It is also worth mentioning that over the long term I've never owned a truly waterproof pack. Putting aside the whole stitching issue, long term use and abrasion will eventually put a bunch of tiny holes in your pack. Dig out an old bag which has seen good service, fill it with water, and see what happens. Kifaru is smart to use Cordura as an extra outer layer on the bottom and low sides of their Xpac bags, but in really wet conditions I would still put things like insulation and electronics in some kind of dry sack.

Face fabric is face fabric

Xpac is not a fabric, really, it is a laminate. If you have enough money Dimension Polyant will laminate whatever fabric you care to send them. You can get 500D Cordura Xpac, or the 210D Kifaru appears to be using, or a lunch of other stuff. Face fabrics perform the same no matter the waterproofing layer. In theory the XPac laminate increases tear and puncture strength, but in 200+D fabrics this is a moot point. For those who used it, the old Kuiu 160D Ultra pack fabric is a fair equivalent of VX21 when it comes to abrasion, i.e. it isn't that great.

It follows that face fabrics retain water the same, whatever laminate is underneath. All pack fabrics I can think of come treated with a DWR (same as your rain gear) and just like with your rain gear that DWR wears off very fast when exposed to dirt. In my experience new and unabraded pack fabrics don't retain too much water, and older fuzzed out fabrics retain plenty. I'd be all for a fabric with some sort of permanent external coating, but Arc'teryx is the only company I can think of who has done this (with PU). IMO water weight retention has much more to do with the foams and fabrics used on the harness elements of a pack than the main fabric or coating on it.

Ignore the following if your attention is waning

Xpac nomenclature is pretty simple. The number denotes the denier of the face fabric. X fabrics have the characteristic X/Diamond grid, between the face fabric and laminate. V fabrics have a white layer of fabric on the inside of the laminate.

I've always found the 2 Cordura face fabrics to perform best. X33 (330D Cordura) is widely available in multicam, and X50 (500D) in black multicam. The V fabric in the laminate makes the interior of dark colors easier to see inside, and otherwise doesn't seem to add anything. You need a headlamp to see to the bottom of a big bag made of X50. The X laminate is a liability, something I can say definitively now that I've had some plain 33 Xpac for the past few weeks. The X fibers create abrasion points. They also provide some branding for Dimension Polyant , but hopefully D-P will let that go as they get more market share.

I think you are confusing water resistant and water proof. There is a huge difference in semantics for that nomenclature. While I might agree kifaru’s cordura is water resistent I’d give it a solid hell no for waterproof based on my first hand experience.