frame sheet for Golite Pinnacle (or Jam)

Chris,

I'd be interested to hear how your heat forming experiments go. I tried "thermoforming" an ABS sheet in my oven over a wireframe "mold" covered in aluminum foil. It eventually worked out to something close to the shape, but the edges kept curling up, I think due to different thermal expansion on the top and bottom surfaces from uneven heating in the oven. This could be solved with a top and bottom mold, or using some other method to keep the plastic tight against the mold (legit thermoformers use vacuum molds).

Anyways, good luck, and I look forward to hearing about your results.

Cheers,
Andy

Coroplast. Although you'd be surprised at how well Walmart's blue CCF works.

Well I got the 1/16" hdpe, they messed up and sent me 1/8" instead of the 3/32" but thats ok because I wouldn't want any heavier then the 1/16"

The 1/16" can be heat formed but I don't think it is worth it. I messed around with a heat gun shaping small pieces and they just are to easy to bend back. This is fairly flexible stuff, yet I think still rigid enough alone to provide some support, especially with a foam pad.

10" x 20" x 1/16" 7 1/8 oz, 201g

10" x 20" x 1/16" with 8 2"(approx.) holes and corners rounded 5 7/8 oz, 167g

19" x 3/4" x 1/8" aluminum flat bar 2 3/4 oz, 75g

hdpe sheet with attached webbing sleeve and aluminum bar (complete) 9 5/8 oz, 274g

The reason for the 10×20 size is that is the size of my pad sleeve on my pack

I think this could certainly be lighted a fair amount, I will have to play with it.

And here are some pics

I think this will be nice for trips when packweight exceeds the 20-25lb range, although that doesn't happen very often.

very nice- looks like the bends came out good to me :)

where did you source the aluminum stay and nylon pouch?

I might have missed this, what pack are you using this in?

thanks

Thanks,

The aluminum is from a local metals supplier.

The nylon sleeve is just a lightweight 1 1/2" wide nylon webbing folded and sewn to the hdpe sheet with a velcro closure.

The pack I sized this for is actually a prototype for a pack I will be starting on very soon. I am waiting on some full spectra fabric from Dan Mchale (I couldn't resist). I am going to use the full spectra for the bottom and the shoulder straps, the other pack fabric will be a 500d cordura with dyneema gridstop. The extension collar, pad/framesheet sleeve, and zippered flap pocket to close pad sleeve will be 200d oxford.

Yep, heavy.

The prototype pack was made out of 500d cordura with an extra heavy coating (actual weight was 9oz sq/yd) The extension collar, pad/framesheet sleeve, and zippered flap pocket to close pad sleeve will be 200d oxford (same as prototype).

My pack weighs 22oz, 26oz with 4 sections of z-lite pad folded in half for back pad.

Weights do not include a hipbelt, one can be added though.

The final pack will weigh less with the lighter materials.
I can' wait to start on my pack.

Right now I am making a pack identical in size to my prototype for my sister, except hers will have a shorter torso and slightly shorter shoulder straps….and hers is being made out of X-pac.

quite a project!

I wouldn't have even guessed that the stay pouch was sewn- how difficult was that?

Mike,
The sewing of the webbing to the hdpe was easy…but… I cheated. I have a compound walking foot machine. That was sewn with a 92 bonded polyester thread.

I have developed quite an addiction to sewing, and making my gear.

so a needle and thimble is probably out then :)

Hi Chris, good stuff! Are you using an industrial machine? I just can't imagine an off the shelf walmart special being able to go through plastic sheeting like that. Also, does the arm on your sewing machine have a large clearance so that you can sew down the the middle of a hdpe sheet that wide across?

I haven't been able to figure out a way to sew a aluminum stay onto anything, mainly because of the clearance issues…so I've been reduced to duct taping the aluminum stay directly to plastic/foam. It worked very well for my jam2, but I'm always looking for a more professional/cleaner appearance. Oh and being able to removing the aluminum stay would be a perk :)

Oh, also, who's your source for hdpe sheeting and any tips as to how to cut?

Konrad, thanks
Yes I do have an industrial machine.

The frame sheet is only 10"wide, so no problem with the reach on the sewing machine arm.

I bought the hdpe sheet from professionalplastics.com, I will only order from them if I have to. Long story.

I would check out k-mac-plastics.net

hdpe cuts easily. table saw, jig saw, hole saw

Nice looking frame Chris!

Question – why webbing for the sleeve? Why not something lighter, like a 200D cordura?

Also – it looks like the aluminum stay is functioning only to provide the S-shape (and maintain it against horizontal deflection), but the plastic is what would carry vertical loads (i.e. directing forces to your hipbelt and away from your shoulders), assuming there is some kind of top flap over the frame in some kind of frame sleeve on the pack. I say that because the top of the aluminum stay is set lower and could only be compressed by the end of the webbing sleeve. I wonder if that is the most efficient use of weight for the purpose.

Either way, it looks great, and I think it's a great start.

Andy

Thanks Andrew, I appreciate feedback, and always welcome suggestions.

I used webbing because I had it on hand, I do think it would still need webbing on the ends just to guard against the stay abrading through. This is my first attempt at this.

My pack has a pad sleeve with a flap to secure the pad or pad/frame.

I am not sure if I fully understand your second question…
The webbing is sewn to within 3/4" top and bottom to the framesheet, once the stay is inserted and the velcro is closed, the hdpe sheet cannot be pulled away from the stay, the two become one the complete length of the stay. Yes, the stay does provide the S shape but also a substantial amount of stiffness.

The hdpe sheet by itself does add a fair amount of stiffness, more so then just a pad (in my case 4 sections of z-lite folded in half, so about 10"w x 20"h)…however with the stay added to the framesheet, force applied to the top of the sheet does not cause a deflection (bending/flexing) of the sheet/stay combo allowing far more transfer of weight to the hipbelt.

I hope I explained this well
Thanks

I made a board with aluminum stays and ensolite construction. You need to be good at statics for this to work or at least get a proper spread sheet made. Anyone you know that is good with CAD can do this for you too.

Ensolite construction is basically using filaments of kevlar that are dipped in an epoxy and wound around a frame at very specific angles under a very specific load. The lightest canoes in the world are made this way, as well as many other small boats. If you hated calculating vectors and all that stuff in physics then this ain't the project for you.

The actual manufacturing process though was designed for people to make boats in their living rooms with just hand tools. So once you get past the scary maths the rest is very straight forward.

I would at least cut some triangles/circles into the structure to help increase the efficiency. If using a board, you are better off with a thicker board that has holes cut into it than a thinner board of solid material. Just make sure you measure twice and cut once. Remember, a triangle is just a square cut in half.

that sounds like it's probably out of my league :), but curious what kind of weight you saw w/ your frame?

Chris,
I don't think I explained myself very clearly the first time. In order for a frame to transfer load from your shoulders to your hips, the frame must be loaded in compression (i.e. squeezed together from both ends). In the pack, the bottom of the frame sleeve and the top with whatever closure provide the compression force on the frame. The framesheet (especially a bent one) will also be loaded in the bending mode (keeping the S-shape and preventing things from poking your back). I was saying that based on your arrangement, the aluminum stay is not being loaded in compression – because the top flap of the frame pocket pulls down on the plastic only, but there's really no way for a significant amount of that downward force to be transferred to the aluminum bar. (The load path would have to go through the plastic, through the thread, through the webbing, and then be applied to the aluminum bar. Basically the webbing will stretch just a teeny bit and the aluminum will not be in compression). So the aluminum is just there preventing bending, while the plastic is both preventing bending and transferring load from shoulders to hips.

I don't doubt that the current frame sheet adds a lot of stiffness and comfort and carrying capacity to the pack. I'm just suggesting that you could lighten the frame while still achieving the essential function of increasing comfort.

This does raise the question, to which I don't have an answer, of what it is the frame needs to do to increase comfort: transfer load from shoulders to hips, maintain a nice S-shape against your back, prevent things from poking you? Surely the answer is some combination of these, but I don't know exactly what that combination is, and that is the key to really optimizing a pack frame for maximum function and minimum weight.

Troy – I'm really curious what this board looks like, what the CAD results were, what the load paths needed to be, etc. Can you share any of that?

Cheers,
Andy

Mike, I'm in the same boat – trying to add support to my GoLite Pinnacle for a trip in China. Like you, I expect to be carrying weight up to 40lbs, but I've been pleased with the support I've gained simply by using a folded-over sleeping pad (a Thermarest Prolite Plus). GoLite suggest 40lbs be the max carry weight in the pack with the stock pad, but after watching the video below (check it at about the 2 minute mark), I think a rudimentary frame sheet would be a very good idea. I'm currently thinking the corrugated plastic sheet I found at a local craft store will be sufficient, but I'm very interested to learn what you decide to go with. Please keep us posted!
Clod

Andy,
I understand better, thanks.

I can say in testing the frame sheet with and without the aluminum stay, the frame sheet resists compression and deflection with the stay in place ( at least with reasonable forces). With the bottom of the frame sheet on the ground, and pressure put on the top of the frame sheet it takes a fair amount of force to get the frame sheet to flex ( I am only pushing down on the center top, in line with the stay). The hdpe sheet and the stay when combined really do feel like one moulded piece. There is no perceivable independent movement between the two.

I do not have load lifters on my shoulder straps.

This trial at coming up with a frame sheet, frame sheet w/ stay is kind of pointless for me really as I have been extremely happy with just 4 sections of z-lite for a frame( placed in a sleeve with top closure to contain it) in my packs. I just wanted to see what I could come up with, maybe some trip I take will require me to carry way more weight than I want to.

Experiments are fun