500d Cordura RSBTR 420 robic or or 210d Dyneema Gridstop for pack bottom ?????

500d Cordura is my choice. My wife recently sewed some 1000d with her no frills sewing machine.

“All thoughts are appreciated”

In that case, VX21 is strong enough by itself.  Sewing on a second layer will add needle holes that weaken the fabric and allow water to enter.  I don’t like taking any unnecessary steps.

If you were a rock climber or this was for a boy scout (both abusers of gear : ) then maybe a second layer of bottom would be reasonable.

But, like you said, the weight penalty is small because it’s such a small surface area…

Thanks Jerry.  I thought about the disadvantages and still would like the second layer.  Out east here we have lots of rocks to encounter even if you’re not a rock climber.  Sometimes (not frequently) you’re squeezing between them and dragging you pack along the way. Also, the concrete in parking lots is very abrasive and “helpful” people (boy scouts or their parents) who are loading up who don’t know any better will drag a pack across the concrete. I don’t think vx21 would survive many of those events.  I’ve had gear damaged in that manner in the past.

I’m very easy on my gear but I’m thinking about everything that it gets subjected to by everyone else.

Thanks. Cordura is a good choice (maybe the best for abrasion resistance).  I’m just wondering if either of the other two would be “good enough” considering that I’m putting a double bottom in it.  I have a sample of the RSBTR robic and its fairly robust.

What about X-pac X51? I’m happy with it for my pack bottom. It came highly recommended by folks on this forum.

My vote is for 420 Robic mostly because I’m curious.

I have no long term personal use with this material, though I can speak to using both 210 Dyneema Gridstop and 500 cordura on pack bottoms with tons of use.

The difference between a 210 denier nylon with dyneema ripstop and a 500 denier cordura weave weighs heavily toward the cordura being more robust for a pack bottom.

A 420 Denier pure Robic would likely bridge the gap, and depending on how tight the weave was, could be approaching the 500 Denier Cordura’s durability at a reduced weight.

But really, the 5-10g? you’re saving between these choices given the surface area of fabric we’re talking about is minimal.

What is the intended use for the pack?

General use backpacking.  I’m not an ultralighter but I have always adhered to lightweight principles.  So I pay attention to weight but if my pack weighs say over 30 pounds I don’t get wound up about it.  If my pack weighs 20-25 lbs on a weekend trip I consider that light enough.  The 5 or 10 g of weight difference between cordura 500 and robic 420 means nothing to me.  However, cordura is probably not as waterproof as the robic 420 and that is why I was leaning toward the robic.   True its a double bottom and the waterproofness is a secondary issue but its still an consideration since the corura would be lass waterproof AND heavier.  Robic would have to be in the same league with cordura abrasion wise in order to be my choice though and that essentially is why I posted this.

Of what you have listed I would got with 210d but really only because I like the hardier structure it provides.  I really like the looks of 420 robic but it is very flexible and I like a bit sturdier feeling pack bottom to give it some structure.  I love the robic for side pockets (see picture).

An option not listed would be vx42 since you are already using vx21

Lance H its a double bottom pack I’m making.  The other layer is VX21.  I see the flexibility as an asset in that application because it will be easy to work with.  VX21 with robic 420 is a fairly stiff combination.  I already planned to use the robic for the pockets due to its toughness/stability.  Using it on the bottom too simplifies things a bit on ordering fabric.

Any other thoughts?

I got one guy endorsing cordura 500d, one endorsing dyneema xgrid 210d, several endorsing something else (outside the confines of what was asked) and one telling me that I don’t need it.

500D cordura. You cannot go wrong with that as a pack bottom. I would think it would help with a little structure. Maybe go up the sides a little?

I am a huge fan of the 420 Robic offered from RSBTR.  In my opinion, it has a better abrasion resistance over the 500D Cordura based on my unscientific experiments consisting of rubbing samples against a brick wall, timing how how long it takes before the fabric wears through.

Green Pepper Alpine Ruck with 100% 420D Robic pack body and lid (and should strap tops, too).  This is an awesome fabric.

This more along the lines of the structure of the pack.  Is it necessary to have a double layer bottom.  Can a heavier duty bottom fabric be the only pack bottom, perhaps in a tub-like pattern?

I am working on the plans for an new pack and was planning to have a single layer bottom of a heavier material.  But it’s my first pack, so I’d love to hear why that might be a bad idea.

Thanks.  Thinking about that and VX42.  Rocywoods says that Vx42 is a 420d cordura .  If so, that would be plenty abrasion resistant for my needs.

@mando12,

Take a look at some of your favorite packs for influence.

In my opinion, the worst idea is to build a pack for the sake of some ideal that may or may not apply to you.  It will be your pack and no one else’s.

FWIW, I’ve owed a lot of packs….and have actually worn out a 500 cordura pack bottom [not easy]

If you really want to do it right use the Dyneema. Its pricey but you don’t need much. My 10 yr old McHale has a dyneema bottom and the cordura looks pretty bad right now….but the dyneema takes a licking and keeps on ticking.

Plus, varmints can’t chew through it.