HDPE framesheet for MYOG pack

[Jason Shaffer]

Hi all,
I’m hoping to source some HDPE plastic suitable for a framesheet, similar to what Granite Gear uses in the Vapor Trail. Is HDPE sheet relatively consistent in terms of flexibility / rigidity? In other words, if I bought an 1/8 sheet like this…
could I expect it to be of similar flexibility to the hdpe used by pack manufacturers?
Thanks!
-Jason

[EndoftheTrail]

Jason:

Sorry, but I know next to nothing about HDPE sheets. However, reading the Ebay auction, it sppears that each sheet weighs 3.5 lbs?!? Even using half (say 24 x 12 x 1/8), that’s still pretty heavy.

The auction also indicates that the sheets can be sawed! This really makes me wonder if the sheets GG uses are thinner?

[Jason Shaffer]

Hi Ben,
Thanks for your response. I too know little about the composition of HDPE. Just by feeling through the foam backpanel, I can tell the Granite Gear framesheet is somewhere in that range – I doubt it could be as thin as 1/16″.

As to the weight, I took that figure to mean the weight of the packaged shipment, or at least the figure on which the seller bases what he wants to charge for shipping. I can’t imagine how a 4 ft sq piece of plastic only 1/8″ thick could weigh that much all on its own, but maybe. Again, tho, I’m not sure WHAT to expect with general purpose hdpe, so any input is very much welcome!

[Michael Freyman]

I would have to agree … most shipping companies ship based on size of the package as well as weight.

[Daniel Roberts]

A 2′ square piece of 1/8″ HDPE will be almost exactly 2.5 lbs. Most people say it’s one of the easier plastics to mold and weld, but I don’t care for it too much. It seems to insulate heat really well or something, so the outside tends to become liquid before the inside becomes pliable. I’d consider abs for a pack frame. It’s rigid, but not brittle like acrylic, I find it easier to weld, and it isn’t affected by cold like most thermoplastics. I’ve got some HDPE (and abs) sheets out back, and I believe one is 1/8″. If it is and all you need is a 12×24, sheet I could send it to you for the cost of shipping. I’ve got gmail address and my name is whiteagle. Email me if you’re interested.

[EndoftheTrail]

Jason:

This may be of interest to you:

http://www.practicalbackpacking.com/forums/showthread.php?t=748

[Roger Caffin]

> In other words, if I bought an 1/8 sheet like this…
could I expect it to be of similar flexibility to the hdpe used by pack manufacturers?

You can expect that HDPE (High Density PolyEthylene) sheet from different suppliers to be very consistent. Of course, many ‘suppliers’ will be buying from a single factory.
Thickness? That’s up to you.

It is tough stuff.

Cheers

[Jason Shaffer]

Wow, thanks everyone! Sorry for the delay – just got back from a trip. Superb info, exactly what I was looking for. Tho its starting to look like this stuff is overkill for my purposes. I’ll definitely file this stuff under plans for a MYOG winter pack however. cheers!

[Dwight Shackelford]

I’m just about to experiment with some added frame material for my G4. I’m looking for something to tie load lifters too.

I tried it out today with 30 lbs in it. 20 was workable. 30 was a bit too much weight on my shoulders.

Just came from Orchard supply hardware with a length of aluminum bar (malleable, but heaviest of the options), a length of screen door framing (hollow rectangular tube, thin steel, very lightweight), and a length of 1/2″ pvc pipe. I’m thinking on going with the pvc first. Its springy and light, and, with a coupling, could possibly work for a fixed length tent pole. Nut sure though. Might not take too much downward pressure without bowing.

We’ll see.

Dwight

[Dwight Shackelford]

PVC pipe: 1.4oz per foot
4 ft minimum, 6 for rectangular frame, plus couplings.

Aluminum bar, 1/2″x1/8″: 1.75oz per foot
4 ft. total

Screen door framing: .75 oz per foot.
4 ft. total, plus something to cover the ends.

Seems like the aluminum would way much more than the pvc, but I guess not.

PVC: If I needed a square frame, it would be easy to construct with 90 degree ells. Can also take a hit and rebound, to a point.

Aluminum: Malleable and can be reformed and adjusted.

Screen frame: Lightest, but would be permanently kinked if it took a hit, and is only flexible up to a point. Ends would be sharp.

I think I’ll try the pvc first. I could feed it through the lashing loops on the back of the pack, and the sleeping pad should keep the lumps away from my back.

[Cameron Reed]

I am currently building my own backpack and planned to use the bottom of an old plastic laundry basket as a framesheet.
It may sound a bit ghetto, but I figure ‘if it works, I don’t care’

[Bill Fornshell]

Cameron,

Not so funny, I have used parts of plastic dish drainers for 2 different external frames. I haven’t posted any pictures of them yet.

One is for a heavy load and the other one is for lighter loads. I have named one of them the “Alpine Express”.

One is for a heavy load and the other one is for lighter loads. I have named one of them the “Alpine Express”.

The Alpine Express (current frame weight is 20.4oz) is a finished frame but I haven’t had time to make a pack bag for it yet.

[Sam Haraldson]

> I have used parts of plastic dish drainers for 2 different external frames

Bill are you referring to the external frame you built on one of your blogs? I think maybe there was a thread regarding it on the Yahoo MYOG Group as well. The breathabilty of that frame would be unbeatable in my opinion.

[Bill Fornshell]

Hi Sam,

I don’t think my “Dish Drain parts” external frame have been posted anywhere. I just finished the second one last week.

I will start a thread later today for them both.

[D G]

I’ve used coroplast (the stuff that political campaign signs are made from) for various projects. You can harvest these signs around election time.

It’s fairly light and stiff in the direction of the “grain”. It can also be stiffened by inserting rods into the internal tubes.

Dan

[Sam Haraldson]

> don’t think my “Dish Drain parts” external frame have been posted anywhere

There is no way I imagined this. However, I can’t find any of the blogs where I’d seen the pics. But I could swear it was your handiwork.

The pack was a relatively typical looking external frame, except for these spacers that held the pack away from the users back that looked like half-whiffle balls. As a matter of fact I think the prototypes were made with whiffle balls and then a more expensive material that had to be formed and pressed while heated.

Can anyone help me to remember what I’m thinking of? I’ve searched through a bunch of the Yahoo Makegear list looking for a reference and I’ve searched all over Ultra-Lite Skunk Works and 6 Banana but don’t see it. Grr!

[Benjamin Smith]

Sam,

That was indeed one of Bill’s packs. However, the materials were as you describe – the frame didn’t use a dishdrainer for parts that I recall.

Ben

[Sam Haraldson]

Thanks, Ben. I’m not going crazy just yet then. Perhaps Bill will be kind enough to refresh my memory (and maybe direct me to the blog where those photos live) and key me in on just what that material was.

[Benjamin Smith]

Hi Sam,

A quick Google search turns up:

http://ultraliteskunkworks.blogspot.com

Ben

[Bill Fornshell]

Try here:

Ultra-Light External Frame Pack

This is a lot of my first external frame stuff and I think it is also what Sam is talking about. Some of it is funny so if it makes you laugh it is OK, most of it also made me laugh.

I knew what I wanted but couldn’t find the right material. I then tried a lot of different stuff to prove to myself the idea would work and it was worth it to keep looking. These are the materials that will make you laugh but remember what I wanted to prove and where it was all heading.

I have been outside for the last few hours practicing hanging my new hammock and tarp and taking it down in the dark. I just came in a little while ago.

[Sam Haraldson]

Thanks, Bill – The pictures I was trying to remember were right here on BPL all along. I had been scouring through your other blogs, (Ultralight Skunk Works and 6 Banana Designs) as well as the Yahoo MYOG group!

Even if the stuff you start with makes you laugh it’s an important part of the inventive process. The early projects have certainly taught you good methodology for how to design and build prototypes, which pay off now that you’re working with expensive materials.

And Ben, thanks for the link but I know that one already ; ) What I meant in the earlier post was that I couldn’t find reference to this certain project within that blog.

[Author]

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