"Don't think, duct tape," works good for this job. And I wouldn't try it yourself until I report back next week to let you know if it got hot enough (I'm hoping for 160F) without melting (because it's made out of styrofoam, duct tape, foam insulation, and reflective plastic insulation).
I've read things like, "for every 10 degree increase in temperature the epoxy composite will cure twice as fast", and also that the composite gets harder the faster you cure it. So I built myself a "heat box", which is a box full of heat.
This is a view of the inside of the heat box. What you are seeing is a reflective insulation that I got at a big box home improvement store; it's like two thin layers of aluminum sandwiching a 1/4" layer of bubble wrap. The bottom of the box is hardboard, the kind of thing you can buy perforated to hang tools from. In this case it's non-perforated; more like the kind of thing you might layer a workbench with. I'll be sliding the clamped-up guitar neck around on that, so I wanted something that wouldn't tear.The inside dimensions of the box are 48" long, about 14" high, and about 24" wide. Why? It's about the size of the material I had and could buy. The top of the box is 2" foam block insulation like you'd buy to insulate a basement, I suppose. I already had that. The sides are some cruddy styrofoam insulation from a kit full of 14" x 48" x 1" sheets - I would avoid that next time, because it crumbles. I put a layer of that on the hardboard floor of the heatbox, as well.
Note: you can sort of see how duct tape does not stick to styrofoam. It's really just serving as a binding around the outside. Fortunately, I bought some heavy-duty actual aluminum reflective tape (what I like to call "real" duct tape) to seal the inside corners. This stuff is great; hyper adhesive (almost annoyingly so) and strong in the long direction.
That's the front view, with the materials I'm going to use for a door on top of it: three layers of that reflective bubble wrap and two very junky hardboard sheets I laminated together. I figure I'll secure the door to the opening with a duct tape hinge of some kind and some mini bungee cords.
Finally we've got the "heat" part of the heat box. I've seen some trick setups on the internet involving water heater heating element controls with hysteresis whatnot optimization. I, on the other hand, am going to stick four incandescent light bulbs on this contraption, slam a meat thermometer through the top of the box, and turn the light bulbs on and off by means of a two prong plug. That's why I AM GOING TO CURE MY LAMINATE OUTDOORS IN THE DRIVEWAY, FAR AWAY FROM ANYTHING FLAMMABLE. You do what you want with your heat box; I'm scared of mine.
This is a flat, thin bar of plain soft steel like you'd make a strap out of to hang a garage door opener with. It's got holes drilled in it already, but I had to widen two of them to put the bulb fixtures in. The bulb fixtures are secured through these holes with brass lamp nuts, where are their own sort of beast. I will wire a two-prong extension cord to the black and white wires and secure the connections with wire nuts and electrical tape. I will fasten the steel bar to three pieces of 1" pine to hold it off the floor of the heat box and allow room for the lamp nuts and wiring.
Next weekend I fire this thing up, OUTSIDE IN THE DRIVEWAY. Wish me luck.
Materials list for the heat box:
- 2" x 48" x 24" blue hard foam insulation - had it already, leftover from an attic insulation job
- 11oz adhesive spray - $4.58
- 55yd all-purpose duct tape - $4.98
- 3/4 poly (styrofoam) pane kit - $13.70 (wouldn't use this again, in favor of blue hard foam)
- 2" x 50yd aluminum tape - $11.99
- 3/4" x 60ft blue electrical tape - $3.79
- 1-3/8" flat bar, slotted - $6.59 (this is the bar the bulb outlets bolt to)
- 7ft extension cord - $4.99 (will become the cord for the lamp setup)
- 2 weird dual lamp sockets - $5.98 + $5.98
- 2 brass lamp nuts to secure the lamp sockets to the flat bar
- 3 1" x 4" x 4" white pine segments - found in the basement
- wire nuts - already had them
TOTAL OUTLAY SO FAR: already $200. Oh my.
Again, the heat box is a one time capital expenditure. Its costs are spread out with each guitar you build.
ReplyDeleteI'm glad you resorted to the aluminum reflective tape. I was going to suggest that if I didn't see it here.
Still worried about the styrofoam. But you're doing it outside (smart man!) so if there's a catastrophic failure, the only thing you'll lose is the box (not the house).
One concern I have is the vapor ignition point. When the laminate is in curing process, the solvent is vaporizing. That vapor has a flash point (hopefully listed on the epoxy bottle). Since you're regulating temperature manually (pulling the plug), you're going to have to babysit this thing. I don't know what sort of time scale you're looking at here so I don't know how feasible that is. If there was some way to hook up a thermocouple to regulate the on/off switch, that would eliminate babysitting while maintaining safety.
Yes. That's why some people use water heater controllers. They pretty much handle that, plus the overshoot from hysteresis. I figured that would be yet another expense.
ReplyDeleteIf this thing flashes over, it shouldn't be a big deal because there's no pressure containment. But it shouldn't, because I've read about other folks using similar (hot filament) methods of heating.
Also I'm living on the edge.
Not being familiar with the process, I had to ask. :)
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