Custom Molded Framesheet

[Robert Mak]

I was thinking of making a lightweight framesheet custom molded to my back for one of my packs. Any suggestions on what material would be good for that? I've heard of temperature activated moldable plastic but am unsure if it will work in outdoor conditions.

[Bill Fornshell]

Hi Robert,

I have used Thermoplastic (moldable plastic) parts on several backpack frames. This softens at around 155 degrees and then hardens when it goes back to room temp.

The down side of this material if you need a large piece is that it costs a lot.

[Denis Hazlewood]

I've seen threads in here using corrugated plastic sign material with thin wall brass tubing forced through the corrugations and then bent to suit your shape. Duct tape the edges to prevent abrasion of delicate pack fabric. You might be able to get the plastic free after the coming primary election.

I made a frame sheet for my Golite Trek. It was fabricated of CF cloth and cost a considerable bundle of bucks. Works great but too expensive.

[Robert Mak]

Thanks for the replies, guys. Yeah the plastic is a little expensive but seemed pretty nifty. The cardboard application wasn't something I thought of, though i guess it won't have lateral strength.

[Robert Mak]

Was wondering about CF fabric as I've never handled it before. How do you work with it? How would I mold into the right shape?

[Robert Mak]

ok i did a little reading. I guess you make a mold then put the fabric on it and apply some sort of resin or adhesive to set it.

[Joy Menze]

Sintra is a readily available PVC thermoplastic sheet good. I've usually used a heat gun to form it into many different shapes. An oven will do but it limits the size of the piece.

It can be welded to itself with PVC cement found at a hardware store. I like using the purple primer and use the blue colored cement (I'm less sensitive to its smell) where beauty isn't a factor. Otherwise I use the clear cement.

Holes can be tapped for bolts and even drywall screws are okay as mechanical fasteners.

1/8" is fairly flexible. But heat-shaped curving of the shape and edge will help to stiffen it. It comes thinner and thicker.

To get some cheaply – or for free – look for local plastics suppliers/fabricators and some shops that specialize in making displays. It's used alot for signage. The sizes needed for backpacking equipment is often unusable scrap at those places. Those same places also throw away scraps of polycarbonate (Lexan).

[Robert Mak]

Hey that sounds like a really good tip. Probably perfect for prototyping. It seems relatively inexpensive to try and easier to handle.

[Denis Hazlewood]

If your "cardboard" was in reference to my corrugated sign material, the material I meant was plastic. It seems that all of the recent political signs in my area are of a corrugated plastic. The structure is like the cardboard stuff with the two faces separated by a central corrugated layer, but it's all plastic. Check with a local sign shop and see if they stock the stuff. After elections you may be able to liberate some of the stuff from a neighborhood empty lot. Then check your local hardware store for thin wall brass tubing. There was some discussion of this process at BPL a year or two ago.

For the CF frameboard I made I made a mold of 2×4's cut to the shape of the aluminum stays for my (then) favorite internal frame pack. I laid a sheet of heavy pasteboard over this curve and stapled it into place. Then I coated it with melted wax (as mold release)and laid up several layers of CF cloth using WEST system epoxy. It worked great and my oldest son now carries the pack. Expensive though at about $90 for materials.

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