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Post by portlandpizzaboy on Mar 17, 2017 15:52:56 GMT -8
I just finished building my cedar hot tub and would love to get the wood fired heater built.
I need some help from seasoned builders.
I have seen commercial products (http://cowboyhottubs.com/) that are essentially submerged J tube rocket stoves. What i hear is that they heat the water twice as quickly the "wrap copper tubing around the chimney" system.
I assume that by submerging the rocket stove, heat is robbed in the wrong place which cools the stove and creates smoke.
Any thoughts on the cleanest burning, quickest way to heat water?
I am inclined to use a 6" tube with the wood loading area being 3' deep, the horizontal 2' over and the chimney will be 5' tall. It will be submerged almost 3' into the water.
Thanks for your help and expertise. John
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Post by pinhead on Mar 23, 2017 7:19:03 GMT -8
A J-tube with a 3-foot feed absolutely won't work. Especially when stealing heat from the riser and burn tunnel.
For a proper rocket to even BE a rocket, you must not extract heat until AFTER the heat riser.
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Post by Donkey on Apr 6, 2017 16:49:17 GMT -8
I've been mulling this one.. My thought is to build a metal bell that goes inside of the tub and route the exhaust from a J-tube (or better yet a BatchRocket) into it.
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Post by SteveStuff on Apr 7, 2017 16:32:19 GMT -8
Wondering if the "submerged rocket" is HEAVILY insulated... in which case, it MIGHT work.
Im still thinking a separate stove next to it with efficient heat transfer would be better but....
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Post by pigbuttons on Apr 7, 2017 20:52:10 GMT -8
I spent some time in Japan and had a lot of experiences traveling around the country. One place I stayed was with a relatively poor family that still had an old fashioned ofuro ( soaking tub ). It was a wooden tub that had about 25 to 30 gallons of water in it, a sheet steel skirt that lifted it about 10" above the floor, a thin steel plate below the wooden floor of the tub, and a 4" black chimney that came through the floor, through the water and then through the roof of the shed where bathing was done. The entire heat transfer was through the floor and the chimney into the water. It was coal fired, used a lump of coal about the size of a softball, and could heat that much water in about 90 minutes to 104*F, it had a wooden lid on it to keep the heat in.
When getting in the tub one had to be very careful not to touch the chimney stack as it would burn skin on contact. It was much easier for them at 5' 4" and shorter, for me at 6' 1" not so easy.
Just some background data to think about.
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mudder
Junior Member
Posts: 50
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Post by mudder on Apr 8, 2017 5:31:25 GMT -8
not a seasoned builder by any means, just an opinion.
i think i would go with a pump and external heater system, instead of the heater submerged in the tub. your rocket "say" cook stove or "heated bench" next to it could also be the heater when needed. seen examples of coiled tube in the barrel or tanks over the riser in a bell heaters.
again this is just speculation on my part.
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Post by drooster on Apr 10, 2017 12:01:07 GMT -8
...One place I stayed was with a relatively poor family that still had an old fashioned ofuro ( soaking tub ). It was a wooden tub that had about 25 to 30 gallons of water in it, a sheet steel skirt that lifted it about 10" above the floor, a thin steel plate below the wooden floor of the tub, and a 4" black chimney that came through the floor, ... I'd love to see some photos of that setup, or a more thorough description Pigbuttons. How was the coal burn chamber made? How high did the chimney extend above the ceiling? How was the coal fire started?
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Post by pigbuttons on Apr 11, 2017 21:49:14 GMT -8
No photos, sorry, that was nearly 40 years ago. The tub was thick staves like a whiskey barrel, oval shaped, with the chimney at one end.
No burn chamber, and I looked closely. Just the open area under the tub with the steel bottom to the tub which was the top of the burn area and the skirt to keep it closed in to prevent drafts that might steal heat. Just above where the coal was placed was the chimney with a cone hanging about half way down between the concrete floor and the bottom of the tub, so about 4" worth of height and the cone had about a 45* angle. So most of the heat went straight up the pipe which was about eight feet tall all together, sticking out of the single skin metal roof about 2 feet or less. I was there in the winter and the bathing area was unheated, cold, cold, cold. In Japan, you wash outside the tub, then rinse, then climb into the tub to soak. The whole family used the same bath water and I, being an honorable guest, was allowed to go second after the man of the house had finished. It was not for the faint of heart as it was probably only 35* in the bathing area, but I had to make sure I was well washed before getting in the tub to soak.
The fire was started with a handful of pine kindling stacked teepee style against one side of the lump of coal. The skirt had a round hole with a makeshift door over it, the hole being about 10" in diameter so you could put the coal in and light the fire.
Coal is significantly hotter and it smolders more than it burns, so once lit it looks like a hot piece of charcoal that won't go out.
I hope that helps.
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Post by drooster on Apr 12, 2017 9:04:48 GMT -8
Thanks a lot! : that is exactly understood. It sounds like a nice project ... maybe one day
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