Planning to construct a good composite curing oven...request some feedback/input

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cblink.007

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So, looking ahead to our full scale build, we are researching the idea of constructing a curing oven. From what I have seen across the interwebs, I see this concept popping up:


Or this:


Seems straightforward enough...

Will something along the same concept, just bigger and plywood-reinforced do the job?

Size of the oven would be around 2m x 5m x 5m (preferred to accomodate and entire wing piece) and we have a 125000 BTU portable heater on hand. Desired cure temp of at least 180F if all possible; my parts will be vacuum bagged in a mold.

If any of you all out there have made and used a similar apparatus, I would like to know your experiences! How did you construct yours? Size? Heat source?

Again, we are merely planning at this stage of the game, and want to do as good as we can! Thank you much in advance, fam!
 

pictsidhe

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Umm, 125000Btu is an awful lot of heat. You'd have a hell of a time controlling that. A kiln controller from ebay and multiple metal room heaters or domestic fan oven parts would be how I'd do that. 180 might be ok with plywood, though I'd feel much better with a non flammable inner skin. Metal or cement board. 4” Glass wool for insulation on at least the top and sides.
I'm planning a 300F '6 children' sized oven with fan oven parts.

Unfortunately, aerated cement blocks don't seem to be available this side of the Atlantic. They are great for improvised ovens.
 

Hot Wings

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Unfortunately, aerated cement blocks don't seem to be available this side of the Atlantic.
They were at one time but I haven't seen any for a decade or more. Easy enough to make your own. Just add a bit of detergent to the Portland and whip it up. You can get down to around 6 pounds/ft^2 with not too much trouble. Add a little KCL (3-5%) to make it harden faster.

Always wanted to try a bit of aluminum radiator sealant rather than whipping in batches larger than lab size.
 

cblink.007

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Umm, 125000Btu is an awful lot of heat
We figured as such, but we found this heater with the hangar when we got it. Nobody claimed it, despite our (and airfield management's) efforts, so it is ours. Works good too. Heat lamps might not be enough on their own, would it?
 

pictsidhe

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You'd need a lot of heat lamps. I'd be worried about them heating surfaces past what you are measuring in box. Old metal room heaters are another option, or deplasticise new ones? Keep that monster heater for warming the hangar in winter!
 

wsimpso1

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On a hot day, wrapping it loosely in black visqueen and putting it outside can work pretty well too. I use Gougeon ProSet and Jan Gougeon recommended that technique to me personally for their resin. He thought that it worked best if you have completed all of the bonding of the assembly before doing this - it made for a structure that did not creep and change shape as much when heated.
 

TFF

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A friend built a 2ftx3ftx3ft with one heat lamp and it would go over 150F. It was reflective aluminized construction insulation.

The box you want is pretty big and will take a lot of insulation, but you will definitely need a manifold so the heat is not hot spotting a section. If you are pumping hot air in, it has to vent. Is this an electric heater or propane or kerosene? It kind of matters.
 

BoKu

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I use a 2'x4'x8' box made of foil-backed urethane insulating foam for my post-cure oven. The seams are glued with Liquid Nails and closed with aluminum furnace tape. A single 1kw hotplate gets it to about 140F in the winter with a nice shallow ramp. A second 1kw hotplate on an intermittent circuit boosts it to 170F. I use a couple cheap fans to circulate air inside the box and distribute the heat. All the electrical stuff came from the local Dollar General.
 

cblink.007

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Is this an electric heater or propane or kerosene?
The one we have is an electric. But we are looking at doing heat lamps instead. This heater, when on, is beyond stupid hot! I am pretty sure that even in a best case scenario, that kind of heat could do more harm than good!
 

Hephaestus

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Well 180f is 80c so less than boiling water... So easy enough, 5x5x3m is 15'x15'x10' ish

2x4 frame lined with 2" enerfoil (foil faced polyiso)? That's relatively cheap and light. No idea what to do on the floor but it'll be a huge heatsink so you'd want something there too. Even just the mylar/bubble wrap like they use on hot water tanks - at least it would reduce the heat loss there.

Then it's just a bunch of fans and heaters to make sure air turns over fairly strongly so you get even heating/curing.
 

pictsidhe

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They were at one time but I haven't seen any for a decade or more. Easy enough to make your own. Just add a bit of detergent to the Portland and whip it up. You can get down to around 6 pounds/ft^2 with not too much trouble. Add a little KCL (3-5%) to make it harden faster.

Always wanted to try a bit of aluminum radiator sealant rather than whipping in batches larger than lab size.
The European aerated concrete blocks are made by mixing aluminium powder with cement. Add water, and the cement eats the aluminium yielding hydrogen. Probably want to experiment with that outside...
 
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