Forum Index » Editor's Roundtable » MYOG: Backpack fabrics, features, and dimensions


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Ryan Jordan
(ryan) - BPL Staff - MLife

Locale: Greater Yellowstone
MYOG: Backpack fabrics, features, and dimensions on 07/30/2014 00:29:06 MDT Print View

Companion forum thread to:

MYOG: Backpack fabrics, features, and dimensions

Jon Holthaus
(t25hatch) - M
Great article on 07/30/2014 08:33:47 MDT Print View

This is a just a fantastic read. Thank you for your generosity of showcasing your experiences and successes with pack building. I have emulated some of your designs with a few minor changes, and I have to say I'm very satisfied with the results. The material comparision is far more in depth than your other writing on this topic. A number of the topics in this article have been discussed on different forums and blogs, however this is an all inclusive article that explains pack design and features very well.

Thank you for sharing your knowledge.

jerry adams
(retiredjerry) - MLife

Locale: Oregon and Washington
Re: MYOG: Backpack fabrics, features, and dimensions on 07/30/2014 09:06:56 MDT Print View

More excellent information about packs, thanks

But, you said circle provides 50% more volume than square with same circumference.

Presume that volume is proportional to area, since you're talking circles and squares.

Area of circle is circumference ^ 2 / (4 * pi)

Area of square is circumference ^ 2 / 16

Ratio is 4 / pi = 1.27

Circle provides 27% more area than square with same circumference

and in reality, all pack cross sections are some sort of flattened, circular shape, so differences aren't that important

yet your point is valid - it's hard to measure/compare volumes - I should just let your error slip by un-noticed : )

David Chenault
(DaveC) - BPL Staff - F

Locale: Crown of the Continent
Re: Re: MYOG: Backpack fabrics, features, and dimensions on 07/30/2014 09:48:29 MDT Print View

I will fully own that geometry is not my strength.

Roman Vazhnov
(joarr) - MLife

Locale: Russia
re on 07/30/2014 14:09:25 MDT Print View

Dave, thank you for the article! Have you seen Si\Si Cordura (210d, 420d) available anywhere?

Roman Vazhnov
(joarr) - MLife

Locale: Russia
pictures are missing on 07/31/2014 02:26:38 MDT Print View

"Examples above are the Paradox Unaweep at left, a two dimensional pocket, and the Gossamer Gear Gorilla at right, a three dimensional pocket."

Sam Haraldson
(sharalds) - MLife

Locale: Gallatin Range
MYOG: Backpack fabrics, features, and dimensions on 07/31/2014 08:31:52 MDT Print View

Regarding pack volume, the American Society for Testing and Materials (ASTM) test F2153 can be performed at home by filling your ruck with a known volume of small, plastic spheres (i.e. ping pong balls).

Pre-determine this "known volume" of ping pong balls by first filling a rectangular container with water, added one liter at a time marking the sides of the container in 1, 5, or 10 liter marks. Remove the water and then pour the spheres from your ruck into the rectangular container to see how many liters of spheres the ruck contained.

Backpacking Light built a system like this for accurately measuring the volumes of the Absaroka Backpacks sold here some years ago. You can see a photo of a similar method to this in one of the State of the Market Reports published here:
http://www.backpackinglight.com/cgi-bin/backpackinglight/lw_internal_frame_packs_part_1a.html

David Chenault
(DaveC) - BPL Staff - F

Locale: Crown of the Continent
Re: pictures are missing on 07/31/2014 09:09:28 MDT Print View

Oops, looks like a few things got left in when I cut this down a bit during final edit. Will see about fixing.

David Chenault
(DaveC) - BPL Staff - F

Locale: Crown of the Continent
Re: re on 07/31/2014 09:48:36 MDT Print View

I have not. It's seemed to me for a few years now that the obvious next step for heavier use fabrics is a 400ish denier plain or basket weave with some manner of impregnation on both sides. Some of the Arcteryx fabrics come close. Haven't seen anything like that for sale at retail.

Roman Vazhnov
(joarr) - MLife

Locale: Russia
materials on 07/31/2014 12:14:33 MDT Print View

What about woven dyneema fabric?
Some kind of it is available on aliexpress.com for example. Does anybody tried to make a MYOG pack out of it?

Bill Townsend
(Olmanwilly) - MLife

Locale: Midwest
Good work on 08/06/2014 14:06:55 MDT Print View

Tossing the flipside of your fabric weight argument out there: As you point out, at a yard or so of fabric- weight isn't the main thing to consider. But cost really shouldn't be either. An extra $10-$15 (assuming a final design) isn't a deal breaker, barely a factor really.

With that in mind-
Would you give the bump to a cuben hybrid in a 50d/cuben vs. VX 21?
Or a 150d CFH vs VX 42?

You make an excellent point regarding reinforcement, stitching etc. in favor of the heavier products. Ease of construction and clean lines are a big help as well. The lightest of light isn't worth it, but when speaking of the middle of the road between safe established trails and excessive abuse in a canyon- the fabrics above seem to be a good balance of weight/durability.

But what about your compelling arguments? Ease of construction, reinforcement, etc. Can you sew a CFH just like regular fabric?
Is the taping, crazy reinforcement and arduous technique solved with the addition of the face fabric?

I find the CFH compelling (Zpacks seems to as well)- I would appreciate more info/feedback/comparison from anyone on those aspects. It seems like this hybrid solves all the construction and field issues but I find little info from MYOG folks who've used it.

I greatly appreciate the feedback on the Dimension fabrics- that is hard to come by for sure!

Bit off topic- anyone have a source for that super stretchy mesh mentioned. Heavy I know- but handy to have a yard for little stuff here and there.


The circumference thing threw me off- it read more like a tubular body rather than the true four sided construction. Sorted it out as I caught up on the series, but from a construction standpoint you're building a rectangle. From a measurement standpoint- I understand using the circumference.

David Chenault
(DaveC) - BPL Staff - F

Locale: Crown of the Continent
Re: Good work on 08/07/2014 10:56:09 MDT Print View

Bill, I haven't used the 150D hybrid cuben long enough to really comment on durability. Given how easily I was able to put holes in that fabric (toting snowshoes wore through the face fabric in a day), I can't see any personal use I'd have for the 50D version. Honestly, comparing the 150D hybrid with X33 at effectively identical weights, it's hard to see what you're getting with the former, aside from more money spent. Theoretically the hybrid has a higher tear strength, but lower abrasion resistance, which in my experience is far more relevant.

The stitch hole elongation issue is an interesting one which merits further research. It seems plain that needle holes in cuben hybrid do not self heal at all, Dimension Polyant fabric do this as well, but to a much lesser extent (one assumes due to greater mass in the "normal" fabric portion). I've not experienced visible stitch hole growth in VX07, VX21, or VX42, this in normally sewn (ie not felled) seams joining side panels to back panels (which seem to experience the greatest torque). Contrast with the HMG packs. Every 3400 or 4400 pack I've personally seen which has seen significant use (eg >200 miles with 30 or more pounds) has easily visible stitch hole growth. Does this lead to longterm issues? I can't say, but it makes me hesitant to invest in hybrid cuben.

Bill Townsend
(Olmanwilly) - MLife

Locale: Midwest
Thanks on 08/07/2014 12:09:33 MDT Print View

Mainly- you're speaking in beefier terms than me- but I appreciate the worst case point of view in regards to abuse, and it does speak volumes to long term durability for less abused pursuits.

I build out of plain old 70d Sil. I don't strap on much more than the occasional odd item when a long resupply, libations, or luxury item comes along. In short- backpacking is my intended use- not the vehicle to pursue another sport. I'm off trail often, but not forced into wickedly devastating terrain or thorny brush crawls. There are little to no slot canyons, chimneys or ski's in my Midwestern future! Besides, us Midwestern boys are smart enough to climb the chimney first and then haul up our packs;)

I gave up on 30d because it was stupid light, hard to sew, and took too many reinforcements and fancy stitching. I can get a few hundred miles out of it- but the ounce switch to 70d was worth avoiding all the trouble.

Point being- I'd like to step up material quality now that designs are dialed in. You've done an excellent job addressing the DP fabrics. I was looking for a bit more of a UL perspective overall. VX07, VX21, or CFH50d are on my radar.

Other than a softer hand- even the 140d gridstop at $27/yd makes little sense financially- though you make an excellent point for it's use- I'd almost use a 70d sil there.

I suppose you are answering my question really- and the DP fabrics are the next step. A VX21 vs CFH50d- double weight/half cost is a pretty significant head to head. As you say- the 50d means little in that instance as a gauge.

Long story short- Seems like nobody is making that compelling argument for the Cuben I was hoping to hear. The drawbacks continue with Cuben it seems...
I was hoping that somebody would say the face fabric self heals, stabilizes the stitches, and solves the wear issues so dramatically that DP fabric is no longer worth looking at.

But seems as if that is not the case, and more and more folks like you are debunking the delam issue with DP leaving little, if anything to complain about.

VX-21 seems to be the answer for me. 6oz a yard is still a shockingly horrid weight to my UL sensibilities- but worth the waterproofness, ease of construction, etc. you point out. The VX-07 offers little advantage at $3 savings and an ounce lighter I can see.

Since you turned us on to their site- how about this stuff?http://www.cascadecraftworks.com/store/p7/X-Pac%E2%84%A2_X21_RC_54%22_Wide.html
4.4 ounces vs 6 is more my speed and not a bad hit versus the CF.

Excellent series- sorry to nitpick this item. Stepping up from sil to DP or CF is an investment in time and money I didn't want to make lightly, your timing is perfect!

I very much agree with your center stay concept, dimensions, and overall design philosophy very much. Easily one of, if not the best articles I have read on pack design overall.

Thanks

Bill Townsend
(Olmanwilly) - MLife

Locale: Midwest
missed one on 08/07/2014 12:14:47 MDT Print View

http://www.cascadecraftworks.com/store/p9/X-Pac%E2%84%A2_TX34_DWR_54%22_Wide_-_Black.html

how bout this guy- didn't see it my first time through.

David Chenault
(DaveC) - BPL Staff - F

Locale: Crown of the Continent
Re: Thanks on 08/07/2014 12:43:11 MDT Print View

Thanks Bill.

I think the X21 would be a fine choice for you. I've used X51 and X33, and aside from the former being dark inside there's little not to like compared to the VX series stuff. The X33 is suppler, quieter, lighter, and seems to have a tougher face fabric than VX21. If you've found 70D ripstop sufficient for your needs, you could probably do fine with TX07 (@ 3.2 oz/yard).

Edited by DaveC on 08/07/2014 12:44:07 MDT.

Ryan Smith
(ViolentGreen) - M

Locale: Southeast
Re: missed one on 08/07/2014 17:08:31 MDT Print View

Bill,

I've got some TX07 I could sell you really cheap if you want to try it out. Think I've only got $4-$5 per yard in it.

Ryan

David Drake
(DavidDrake) - F - M

Locale: North Idaho
Thanks on 08/07/2014 22:17:01 MDT Print View

Another excellent article, Dave. Makes me feel better about procrastinating on building my next pack--every MYOG piece you write gives me more to incorporate (or at least consider) for the design.

IIRC, you have often used commercial suspension components for your packs (hip belts, shoulder straps, etc). Does this mean won't be seeing an article focused on hip belt and shoulder strap design?

I ask because I've been nursing a pet theory (only partially tested, so far) that thick padding in belts and straps is a crutch to compensate for less than ideal fit. I suspect wider, thinner straps and belts, custom shaped to the actual contours of a particular user, will be more comfortable than thick padding.

David Chenault
(DaveC) - BPL Staff - F

Locale: Crown of the Continent
Re: Thanks on 08/08/2014 07:26:56 MDT Print View

Still not a fan of building hipbelts and shoulder straps if I don't have to. I do think you're correct that we often need a lot less padding than we think, so long as it's the right kind.

The next parts in this "series" would be suspension and harness design, but those are a lot more complex than this stuff. If I had 3k right now to spend on packs I might be ready to write that in 18 months.

Bill Townsend
(Olmanwilly) - MLife

Locale: Midwest
it's anoying to put a subject up here, lol on 08/08/2014 15:10:52 MDT Print View

@ ryan- thanks for the generous offer- PM sent

@ D.drake- FWIW- My experience in your theory.. not sure if this is wide/thin enough compared to where you are at now...

Shoulder straps can be reduced below 2" once they clear the tender parts of the shoulder and are on the collar bone to save weight, but I pretty well stick with a 2-3" starting width and taper to 1" or so starting around the old nipple area. I only use 1/4" foam. You can drop to 1/8" foam with lighter loads/perfect fit, but the weight savings wasn't there for me once food or any decent water carry piled on.

But- if weight transfer to waist, correct location etc. is there- the shoulder straps are only stopping the pack from tipping back- not really taking much weight.
Skip the mesh- that's the heaviest/most useless part IMO. sil nylon sleeves for the foam are fine. For the shoulder, all the fancy S curving and such is more trouble than benefit- but that's a personal call.

Haven't messed with it much but- assuming a basic frame- moving the shoulder straps up (increasing torso length)and wearing the straps so they came in at an angle across the chest would mean little if any weight on the shoulder- and little if any need for padding. You would need 99% load transfer to hips for this to work.

Waist-
standard for me is 4" wide with full width 1/4 foam, 3/4" buckle on 3/4 webbing at tip of belt only. I have a relatively good ghetto booty, so my bum holds up my pack well.

For curvy and/or hipless/assless folks- I have used a 5" wide belt, but with a strip of foam 1.5" wide on the outsides (2" no-foam in center) to make a lighter version of the conical hipbelts many folks like. A two buckle (or Osprey type) system is good for these. Seems to meet the needs of curves fairly well. A scaled down version- 3" OA with 1" foam top and bottom may work well too for the hipless and get better bite than a 3" straight foam would.

For a truly light pack... I took straps down to 1" wide, hip to 2" with 1/8" foam inside simple Sil-nylon sleeves. In the right places, with a 10lb load or less it works. This pack design pretty well needs a center stay- otherwise cut the hipbelt off and use a Rayway pack.

Over time though, anything less than 1/4" foam curls or deforms with use.

All that said- pretty well settled on 3/8" foam- single layer these days.

Bill Townsend
(Olmanwilly) - MLife

Locale: Midwest
next article on 08/08/2014 15:32:49 MDT Print View

Yes David, that's the point, lol.
I'm not interested in spending 3k or several months either. I'm too cheap, lazy and busy to buy a lousy yard of CF and DP to practice with and compare.

What may work a bit... With your heavier base fabric premise, a little detail, analysis, experience and even rampant speculation on how increasing the base material may reduce construction time, reinforcement, and even stitch requirements.

I know you touched on it briefly- but at the heavier weight fabrics are down to just reinforcement at the shoulder straps and grab loops?

How about the middle of the road stuff I asked about? Not having to back up/reinforce each connection is a bit of hidden weight saved, and obvious pain when building with light fabrics. I cut quite a bit out going from 30d to 70d, jumping to VX21... maybe a double layer with x-box stich to back the shoulders and that's it?

Looks like you are using a simple pass of stitching to join the panels, double row or down to single? straight stitch? Bottom line- does it even matter with that much material to grab- freedom from carefully selected stitches puts MYOG in easier reach.

Sorry- This heavier fabric thing, potentially cutting sewing work in half on the most time consuming item I can think of making is maybe a pretty sweet deal; and may come with little or no weight penalty really. More importantly, 3 ounces is worth not spending 8 hours overanalyzing and installing to properly tension/load a yard of fabric.