The chumby outputs about 2 watts on average. It does get quite warm while operating, to about 50 degrees C on the inside--unpleasant to touch but not to the point of injury. It was designed for the primary heat dissipation path to go through the screen and the bezel in anticipation of the body of the core unit being surrounded by an insulating material (such as polyfill). The screen is large enough so that the heat dissipation rate makes the screen feel warm to the touch, but not unpleasantly so. To be clear, the core temperature is higher than the screen due to the physics of the heat transfer processes inside the core module.
I should preface this next part with the statement that I am not an expert on the flammability of materials, so please use your own judgement to temper these guidelines, and you do use these suggestions at your own risk. As long as you use materials with a flash point well above the operating temperature of chumby, I think you should be okay. I am not an expert on fabrics and fills, but I would imagine that most clothes can tolerate that kind of temperature as it probably gets hotter than that inside a conventional clothes dryer.
The fabric currently surrounding the prototypes is nu-suede, and the plastic around the core unit is made out of TPE, an elastomer that is solvent resistant so you must sew to it. There will also be a limited number of TPU frames available in white. These have a much stiffer composition but they allow the use of glues and so forth for easier assembly.
This may all change by the time we go to production in Q107, but this will at least give you an idea of what we are thinking about right now, hopefully. It is my goal to make available on the chumby accessories site the "raw" frames for the soft parts so that crafters like you can more easily make a bag for chumby.
A final flat pattern should be showing up in about a week on the site, altho there is an early prototype flat pattern in the developer section, I believe.
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