Gerry Parent

Trevor,   Could you compress the file then try to upload that? The compression format may be accepted.

WAY to go Liz!  The perfect go-to present for that special someone that will last a lifetime.

Hi Joe,    Over the years there has been much study and refining of the J tube core that can't get much better in terms of complete combustion. Unless your chasing after half percents, making sure you burn dry wood, establish good draft, build it with low mass/ high heat resistant materials, keep an occasional eye on it while running etc. are going to be your best bets at making it as efficient as it was meant to be.

But don't take my word for it. Rocket science is all about experimenting for yourself. Playing with brick Legos in various fashions outside is fun and very educational so that you know from direct experience why the build ratios are as they are.

Hi Trevor,   Have you tried the "Attachments" tab below the text entry box when you go to reply to a post? Here you can "upload  a file" right below your message or add a link "Add from  URL" if you have your file saved on a separate internet site.

Below grade...gotcha Medrec.
The floor of the bell will not get that hot. In Peter van den Bergs ISA calculations, the floor is excluded because of this fact. It will also collect ash over time which will also add to the insulation value.
With that said, a few inches of stabilized perlite should suffice.

You will still get thermal bridging off the sides of the cement block walls as there is continuous cement from the inside to the outside in many places. Being at the bottom of the bell, temperatures are not that high so it would take a while before heat migrates outwards. Some of which is going into your floor so that's not too bad anyways. A thin layer of insulation on the outside of the bricks would be extra insurance for maximum heat retention but certainly not a show stopper.

Medrec Martin wrote:Quick question, how low from the floor can I get away putting the exhaust flu? I figured 2 - 3 inches but the lower the better. Even though this is an 8" system the flu is 10" and will shrink down to 8" (as it exits the masonry and enters the room) with the addition of the an inner liner of ceramic blanket through the wall and outside. Thanks.

Hi Medrec,   Scots is correct. Filling the brick holes with perlite is taking away at least half of your thermal mass and ability to store heat. It would be much better to fill with a sand/clay mix (and even stuff small rocks in there). The walls won't get overly warm so as long as you leave a gap between the blocks and the vinyl wall, you should be fine.

The exhaust entrance should be low as you mentioned. A small lip is helpful to allow ash buildup over time and not block the entrance.

Hi Robert,   External air has been discussed a fair amount here, having its pros and cons but typically favouring the cons. The best place I found that covers it well is here: the-outdoor-air-myth-exposed

In the RMH world, a chimney fan is only necessary (for some people) when you have poor draft at startup with a cold mass and want to give a little boost at the beginning of a burn, then turned off.
A bypass is a more low -tech solution that is hard to beat for its simplicity and reliability.

Hi Lew,   Not sure which DIY book your using but I see a few things that may be your problem. 1) Your heat riser is really short. I bet if you put a pipe to extend it at least a few feet, your stove should rocket a lot better. 2) That air flow device you mentioned is also important to make this L style rocket work properly. A simple plate that sits on the bottom of the feed tube (leaving about 1/4 of the pipes csa as an opening) is all that's needed.

Metal has a limited lifespan in the high temperatures experienced with a well functioning rocket stove. Great for certain areas but still often considered an expendable item that will need replacing, especially anywhere near the core.

Good luck, and let us know how it goes.

What a great build Solomon! Very clean and pleasing to the eye. Thank you for sharing.

The paper bag pots turned out to be a mold-fest so I replanted them again in proper containers.
Like yours, some are starting to pop up and looks to be about the same size.
In particular, it was those that already had some initial growth.
The root cuttings with no growth are still sleeping.