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Auto-controlled Epoxy Hot-box Upgrade


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First of all, I'm a bit of a control freak... :rolleyes:

I built my epoxy hot-box as a large unit (on wheels!) with three compartments.

 open_hotbox.thumb.jpg.7bb54ef519ddff6793eb2c2dbe7b7244.jpg closed_hotbox.thumb.jpg.f70e9b440d3771c77fade5be68dcb563.jpg

The top compartment has its own door, and holds the dispensing bottles (I use capped sauce bottles, and measure on a digital scale) and the containers holding flox, microballoons, etc. I figure keeping the micro or flox warm as well would not drop the temperature of the mix, ensuring lower viscosity and lighter micro mixes. Small difference, perhaps, but I have space, so why not?

The compartment below that is open to the hot compartment above (holes in opposite corners of the top shelf) that is large enough to hold 20kg of resin and 5kg of hardener so that the 'bulk' epoxy is kept warm to avoid crystallization issues over winter.

The final compartment at the bottom is not open to the heated area above, but is still insulated. I now keep containers of a different resin and hardener in here (fast hardener, and a resin more suitable for sanding). While not kept as warm as the compartments above, the insulation will still protect it from the daily extremes of temperature in my current uninsulated workshop.

The top of the unit happens to be ideally sized to hold an open set of Aerocanard plans!

I installed an incandescent light bulb as a heat source, per the traditional method, at the top of the right-rear of the MIDDLE compartment. Above it is a hole, approx 2"x3". There is a hold the same size in the opposite corner of the shelf. This creates a gentle convection, keeping the air in the top compartment warm, and the middle compartment almost as warm. It should also reduce the 'hot-spot' next to the heat source, which also has a shield between it and the epoxy containers.

I wired the light bulb to a temperature controller mounted in the front of the unit. I got this off Ebay quite inexpensively . It is a little awkward to wire, but not too difficult. It switches the light OFF once the selected temperature is reached, and turns it back ON once the temperature drops 1deg below the selected temperature. The temperature probe hangs from the top of the topmost compartment. Thus the epoxy bottles are kept within 1 or 2 degrees of the temperature I want at all times, all year round.

The downside is the light bulb gets cycled on and off every 20 minutes or so, and will blow after only 2 - 3 months. This didn't bother me particularly, the blubs are inexpensive. But now incandescent bulbs are getting harder to find!

I looked at the reptile heaters that have been suggested. They could work, but cost a bit more than I wanted to spend, or would not easily fit where I need it to.

I found and purchased this 100w ceramic heater, also on Ebay . It is almost the perfect size to mount under the hole in the top shelf, where the light bulb once was. It works great, and hopefully will be far more durable than a light bulb (not that it is impossible to build a durable incandescent bulb, but then you would never buy new ones!). It has been operating for about a week, and works at least as well as the light blub did before.

Note that the linked parts a 220v. If you decide to create a similar setup, be sure to get one matching the voltage supply in your country! ;)

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Aerocanard (modified) SN:ACPB-0226 (Chapter 8)

Canardspeed.com (my build log and more; usually lags behind actual progress)
Flight simulator (X-plane) flight model master: X-Aerodynamics


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