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using a pocket rocket to heat a hottub  RSS feed

 
Joost Meijers
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Location: Delft, the Netherlands
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hi everyone,

I'm building a very low budget hot tub. So I decided I wanted to heat with a wood stove.

When I started looking on the internet I quickly found the concept of a rocket stove and after reading the book and looking around on this forum I tried to come up with a plan for a completely submersible rocket stove.
Then I read some more and realized I was completely out of my league I've never even built a traditional rocket mass heater so I discarded the plan.

Then I came across the Snorkel hot tubs this seemed like a very good design but now the problem was cost, this thing is made out of cast aluminum so way over budget.

In the end I thought of the pocket rocket (as described in rocket mass heaters by Ianto Evans) this seems to be a fairly efficient wood stove and it can be built for almost no money.
It is going to be quite a large hot tub so I was thinking about using a 55 gallon oil drum as the burn chamber, a 10" x 35" feedtube and a 6" x 80" flue exit

I only have 3 questions left:
1: Do the dimensions look about right to you?
2: Will a pocket rocket work at all when submerged? (the feedtube and flue exit will be above water level of course)
3: Will it still work when I make the exhaust come out of the side and make an extra "loop" around the oil drum underwater? (I will upload a drawing later today)

I realize I'm very new to this subject (in fact I started reading about it 2 days ago) so I hope i'm at least a little bit on the right track.

thanks in advance
woodstove.jpg
[Thumbnail for woodstove.jpg]
snorkel woodstove
 
Joost Meijers
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Location: Delft, the Netherlands
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I added some pictures, the first one is the alternative heat stove, there will be a chimney on top but for some reason I couldn't get it done with the drawing program...
The second one is a drawing of the complete hot tub with a traditional pocket rocket as heat source.
My father actually thought that this wouldn't be very efficient since the temperature inside the barrel would never be high enough to efficiently burn the wood.
What do you guys think?
heat-stove.JPG
[Thumbnail for heat-stove.JPG]
alternative wood stove
hottub-compleet.JPG
[Thumbnail for hottub-compleet.JPG]
complete hottub
 
Joost Meijers
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Location: Delft, the Netherlands
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okay, after thinking some more about it I thought that the temperature of the fire would indeed be to low.
So I'm thinking about lining the lower quarter of the barrel with thermal mass on the inside, this way I would get a high temperature at the fire and still conduct the heat to the water.
another idea I had was to put a stainless steel/copper coil on the inside of the barrel (starting low and going up) I hope I'll use more of the energy of the fire this way.
Let me know what you guys think

 
allen lumley
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Joost : check you this 'you tube video' / Instructables - www.youtube.com/watch?v=zhD-7pw2Pv0 , yes a more conventional pocket rocket will make a better heater but this is very doable ! Pyro - maticly yours - Allen L.
 
Chris Burge
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Location: Spokane, Washington
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Believe me, not only will the fire be just fine, but you could probably get away with a much smaller barrel--30, maybe smaller.

Many many years ago, I had a friend in Montana who had a hot tub in the woods. He would fill it from a nearby stream and heat it with a nifty little submersible woodstove. It was about as big as a 5 gal can, had a 4" chimney, a 2" air tube, a water-tight front door, and the whole thing slid up and down on a track. It was as simple as stacking a fire in the box, lighting it, shutting the door and lowering it into the tub. He couldn't even put a 'full' load in it or it would overheat the old-school 4-person cedar hot tub he was using it in. He said it was army surplus and that were smaller and larger versions in existence. In fact, I was at the local surplus store last month and saw a similar unit, but it was $500!
 
R Scott
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Location: Kansas Zone 6a
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I built such a thing as a stock tank heater for my livestock. Version 1 problems included:

-putting enough ballast in the bottom to sink it left most of the fire above the waterline.
-barrels don't last long in the stressed invironment of fire and water. I only got one year out of the outer barrel.

For V 2 this year I am searching for a 30 gallon tank. It will be set inside a 55 gallon barrel and sand filled in-between. This should put the heat lower and let the barrels last longer.
 
R Scott
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If you want to buy, this was the best deal I found: http://www.cowboyhottubs.com/frame_page/Products_and_Prices.htm

 
Miles North
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Joost Meijers wrote:okay, after thinking some more about it I thought that the temperature of the fire would indeed be to low.
So I'm thinking about lining the lower quarter of the barrel with thermal mass on the inside, this way I would get a high temperature at the fire and still conduct the heat to the water.
another idea I had was to put a stainless steel/copper coil on the inside of the barrel (starting low and going up) I hope I'll use more of the energy of the fire this way.
Let me know what you guys think



I am wondering if you made this hot tub and if so if you have any more specific plans (dos and donts) for a utter newby? Like the idea, live in alaska, have always wanted a hot tub, but haven't had the funds for a "real" one. Appreciate any insights you might have had in your building process. Thanks!!!
 
allen lumley
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Miles North : Did you ever work in a movie with Gary Cooper where he played Dusty Roads?
Look at my link above to a video from a contributor to Instructables, and available via U-Tube,
the people at 'Instructables 'are always a great resource, they also have a think for kids called Squid Lab !

Hope this helps ! BIG AL
 
Flick Johnston
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Location: Western Australia
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I believe in one of the DVDs they talk about this, Erica's suggestion was along the lines of sticking a pocket rocket into a solid mass. The solid mass contacts the water and acts to insulate the fire keeping it more efficient burning and also transferring the heat to the water. being a comfortable not to hot temperature you could also cuddle up to the mass like a regular RMH.

Might be worth a look, makes me wanna go back and watch the DVD again...
 
Julia Winter
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I would like to know if there is a way to improve the design of the stove that comes with a Snorkel Hot Tub. There's one for sale on CL for just $200.
 
Politics n. Poly "many" + ticks "blood sucking insects". Tiny ad:
Ernie and Erica Wisner's Rocket Mass Heater Everything Combo
https://permies.com/t/40993/digital-market/digital-market/Ernie-Erica-Wisner-Rocket-Mass
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