Mark Persky

Jerry McIntire wrote:

Mark Persky wrote: I made a rocket stove hot tub and it takes about 2-3 hours to get ALL that water up to suitable temperature.  On the plus side, it’s sort of like compound interest, in that the first hour or so the temperature doesn’t rise much.  But as it warms and gets cycles back through the copper tubing buried within the cob, it’s fetter warmer and then hotter much faster.  I use a laser thermometer and estimate when to stop feeding the stove.  

Nice photo! How is the rocket heater set up/connected to the water in the tub? Is there another thread with information on your tub?

Thank you.   I am a total layperson so forgive any terminology I use that isn’t correct.

Basically I built the rocket stove around a coiled up length of copper tubing and connected the ends of the copper tubing to the side of the tub.
When I fill the tub, the water will make its way through the tubing and then I start the heating process.  As the water warms, it rises up through the copper tubing within the rocket stove and ultimately makes its into the tub.  This creates a siphon effect and draws colder water at the bottom of the tub into the lower portion of the copper tubing and INTO the rocket stove where THAT gets heated.  This is a continuous loop and the after gets warmer and warmer, hotter and hotter.

For a much better explanation and pictures of the entire build, here is a link:

https://www.instructables.com/Wood-fired-Rocket-Stove-Hot-Tub/

Ashley Cottonwood wrote:I'm wondering how a rocket design could help with some of the issues I had with my wood heated hot tub.

I bought a house that had one, it was made by the previous owners. It took all day to heat the hot tub, feeding it wood for hours. Once it we brought the water up to temperature, it was easy to 'over heat' and we would then end up adding cold water.

It was hard to hit the "sweet spot" for temperature and it took a lot of wood and a lot of time to heat up!

I made a rocket stove hot tub and it takes about 2-3 hours to get ALL that water up to suitable temperature.  On the plus side, it’s sort of like compound interest, in that the first hour or so the temperature doesn’t rise much.  But as it warms and gets cycles back through the copper tubing buried within the cob, it’s fetter warmer and then hotter much faster.  I use a laser thermometer and estimate when to stop feeding the stove.