Kevin Riley

Having just built a great stove out of firebrick, I'm not in a huge hurry, but I'm thinking my next stove will also be cast core. I found your post, Troy, after I watched this video:

https://www.youtube.com/watch?v=7ANMXGrxgnE

I'm hoping to ride on the coattails of your question, soaking up suggestions. The criteria I'm filtering ideas with, are as follows:
1) Very Durable, especially in feed tube area
2) Insulative (keep the heat concentrated in the burn tunnel for optimal combustion)
3) The more eco-conscious and locally available the materials, the better
4) Cost effective

If it doesn't meat those criteria, I would be tempted to stick with firebrick.

Jeremy/Others,

Jeremy claims that a larger heat riser diameter will boost the rocketry. This concept has my head reeling, trying to think like fire and flow like gas. Suppose our entire J-tube system with 55 gallon barrel was built with 6" flue pipe, with the only exception being a larger insulated heat riser (maybe 8-10 inches). Is that better than 6" all the way through?

Wait, there's more... Do these also effect the thrust?:
- The height of the exit flue (7)?
- Or the space above and around the heat riser (4) & (5)?

Ultimately, we'd love to be able to have the feed tube be taller than average in order to stack some wood up for a prolonged burn after leaving the greenhouse for the night. Seems that if we could get enough thrust, we could raise the height of the feed tube (1)?

It doesn't seem possible to have too much thrust because it would be fairly easy to choke/damper it as needed somewhere along the way. Hmmm, that makes me wonder... where would the ideal location be for a damper in order to fine tune the burn of a very rockety stove?

Thanks,
Kevin