Tristan Vitali

paul wheaton wrote:what if we make a hole in the ground

Not sure how intensely the ground freezes over your way, but here on the east coast at similar latitude, filling a hole in the ground with hot water would be a losing battle from mid winter through early summer. Perhaps above-ground makes more sense in that context, and though I'm partial to the idea of a cob and rock tub, something along the lines of a cedar tub would reduce the need to fight thermal inertia of an outdoor mass in chilly weather.

William Bronson wrote: This is a great report Tristan!
I'd thought to use a parge of refractory cement, but this just works.
Considering clay with perlite failed, but clay over fiber did not, perhaps the fiber is making the difference.

The fiber definitely holds up well once coated - stiffens the surface and smooths it out for gas flow. I'm sure there's some loss of insulating with the slip coating filling up air spaces in the wool, so in future riser builds, I plan to increase the thickness with an extra 1/4 or 1/2 inch of wool to compensate.

I'm sure refractory cement would behave much the same way as clay slip, especially if you dillute and thin the cement into a more slip like consistency. Depending on the quality of the clay you have available, refractory cement might end up performing much better. My clay, straight from the ground, fires to a soft and crumbly pink (likely part of why the perlite riser crumbled so quickly). I can imagine a better quality clay or refractory cement would be an improvement for the laminar flow inside the heat riser, providing a much smoother / cleaner surface and would enhance the durability even more.

Tim Osborn wrote:...

It appears from the picture that you use 2 layers of 1" superwool. Is that correct  and if so, would you start with an 8" stove pipe to build a 6" riser? Would stainless steel stove pipe work for the outer layer of the core?

That's roughly what I have around the outside of my slipped version - 10 inch round galvanized hvac ducting around the outside of the riser while an 8 inch galvanized duct was used as a form on the inside. The interior of the riser is the metal killer, where pretty much nothing would stand up to the temperatures, but the outer wrap of the riser doesn't get nearly as hot. The Only "wear" I've noticed on the 10 inch ducting is the 3 or 4 inches at the top where some of it has become brittle and cracked over the many years of use (7 seasons already!). A good hot burn with dry beech and sugar maple will occasionally cause the top of the barrel to glow red, so I'm not surprised the gasses are hot enough to damage even the outer wrap a bit, but it hasn't seemed to interfere with its ability to hold things up and in place thus far :)  

I'd imagine that stainless steel, though, is financial overkill for that application with such cheaper alternatives available that would do the job just as well. Even wrapping with thick wire would probably suffice as long as it's on the outside of the riser and you account for the extreme temps likely near the top.

I can't wait to see what comes of this project, should everything work out. I *need* somewhere to soak my bones come winter, and plan to build a "hot tub" tub / shower into my roundwood timberframed cordword/cobwood cabin utilizing a RMH.

Hot water soaks are MANDATORY up here in the winter, even if only once every 3 or 4 weeks.

The BTUs needed for a good hot soak in 50+ gallons of water are somewhat enormous, plus the conundrum of transferring heat from a rocket to the water both safely and efficiently can be tricky - very interested in what sorts of ingenious solutions are worked out for this.

paul wheaton wrote:
straight cob

An idea:  take an 8 inch tube and wrap it with an inch of high temp wool.  Then wrap that with 3 inches of cob.  Once it is dry and hard, wrap that with an inch of high temp wool.  Slide out the tube.  This recipe could last decades.

My thinking on this is that only some high quality cob mixtures (really good firing clay, good sharp sand, etc) would withstand this treatment, and even then, would likely be quite crumbly. From my experience, using my "as found on-site" quality cob mix (a bit subpar by anyone's measure!), even the temperature of gasses reaching the bottom of the barrel cause the clay to fire and become unstable/crumbly without adding ash and grog to strengthen it. Perhaps taking that into account and building with this in mind, along with a thicker layer of insulation on the inside (2 inches wrap inside, 1/2 inch outside wrap) would improve the durability.

Also, as noted in the 5 minute riser thread, the laminar flow issues of fiber blanket directly exposed to the interior of the heat riser seem to call for a clay slip layer to add smoothness, reduce permeability and improve durability.

I think I just might have to rebuild myself a heat riser with this thinking. Only major issue I'm seeing is the thickness of this riser - 2" interior wrap, 3" cob, 1/2" exterior wrap...that's 5.5" of riser thickness. Too thick and we wont be able to fit a 55 gal drum over that thing! ;)

Perhaps we can call it the "forever riser"

Phil Stevens wrote:Mud's remark about them "getting wobbly" over time makes me wonder if I could prolong the lifespan by putting a skim coat of fireclay slip on the inner (and maybe outer) surface from time to time. Gonna try it and see. I replaced a clay and perlite riser last year with one of these and I really like the performance improvement.

As I think about it, the coating would also very likely improve the laminar flow of the superheated combustion gases in the riser by reducing the roughness of the wool. There's another motivation for trying it.

For what it's worth, I have this kind of setup in my main RMH. It's situated in the "sunroom", making it effectively "outdoors" along side the camper-trailer, so it gets run hot and heavy during our winters. A normal burn is 4 to 6 hours with frequent burns running 12 to 14 hours on the really cold nights.

I've had to replace the riser a few times on that 8" beast over the years - first try was a perlite/clay mix that crumbled after 2 seasons of use. That was replaced with ceramic fiber blanket between two sizes of hvac ducting - the interior ducting melted out and collapsed on itself after 1 season. I repeated this failure again due to time constraints and the "make do" mentality, knowing it would fail.

Realizing the conundrum I faced with such high temps for prolonged periods, I did the skim coat (about 1/8" layer of clay slip which quickly absorbed into the wool) on the interior, then rolled that around more hvac ducting as a form. After firing for a bit, the hvac ducting predictably collapsed and was pulled out leaving just the fiber blanket with slip coating. Haven't had trouble with it in 3 seasons so far. Still looks sturdy as I come out of that third burn season :)

Maybe rename it the 10 minute riser, as it takes a couple minutes to coat the wool, then a few more to pull the failed hvac ducting "form" out when it gives up. 10 minutes for 3 seasons of heavy use certainly ain't bad in my book!

Jenny Wright wrote:I'm really enjoying everyone's thoughts on this topic, whether I agree with everything or not! I thought this post was just going to be funny but thank you all for taking it seriously. I homeschool my children and think often about what things I need to teach them that are most important for their futures (and why I posted this in the homeschool forum.) This is one of my favorite discussion subjects. 🤗

Like some have said, it's more than we should expect from public schools to provide all these subjects, yet at the same time, as someone who spends the majority of my time educating my own kids at home, we can't expect parents to do it all themselves either, especially when those parents do not have the luxury and privilege of teaching their children 24/7.

I think the ideal learning situation, whether public, private or home-based, is when people are given the skills needed to learn (how to read, research, and mathematical sense), skills to communicate (through various forms like writing, speaking, and digital forms), and basic human skills of survival including community, kindness, and respect for self and others (because we can't forget that we are all humans together on this planet, not individual automatons in solitary bubbles). Then hopefully the individual can use these as a springboard to continue learning valuable things their whole life long.

I am writing this while eating my breakfast so I'm sure I don't have it all 100% figured out. 😂

Perhaps it's because the "state of the world" seems so desperate these days that we all take the question / premise so seriously. As I watch the "news" (you know, the little us permie types actually choose to take in), I can't help but think about what could be taught to the current school-aged generation(s) to avoid yet another repeat of these same mistakes. The ideas of self-reliance balanced with healthy community, critical thinking skills and creative problem solving, and better understanding of that all-important "needs vs wants" equation ... it's as though the majority of the world never really got these things.

So, is it even the place of "schools" to teach these things to our children? And how should these topics be approached? Through hands-on gardening and farming, or through theoretical and text book learning? Or is it the parents / guardians of the children that should be instilling these things into their children at home?

Where's the balance there?

I'd argue that it's the "job" of both the schools and the parents, and more. That the burden of the future falls on all of us, and the best way to teach is to do so by example. Teaching today really does seem to have become memorization and regurgitation, with very little if any emphasis on critical thinking and creative problem solving. It was happening long ago when I was young, but it's only gotten worse over time.

Where we sit now as a society, how well we can perform that task, and how we should go about it... that is another whole conversation, and a hot-button topic at that, which probably belongs in the cider press ;)  It certainly does seem these are discussions everyone today is itching to have, and the fact that so many of us out here are, in fact, living as "individual automatons in solitary bubbles" makes that a VERY difficult conversation (often involving capital letters, exclamation marks and lots of typos!).

Permaculture, though, direct from the big black book, is an exact fit to answer this dilemma - it magically covers all the key points. Perhaps summer PDCs offered for credit in middle / high school (grades 7 - 12) would make some sense ??

I take the question being asked to mean trees that are not pyrophilic, don't burn easily, and would help to reduce fire occurrence and severity in the system.

Conifers that are not fire-prone is quite a hat trick - don't think you'll find anything to fit the bill. Can't think of anything myself outside tamarack / larch, and those aren't evergreen anyway.

Your best bet would be to work with deciduous hardwoods. Most of the pioneer species like birch, poplar and alder will be more fire-prone as well, generating a lot of "fine fuels" as they colonize the landscapes, so you'd need to be looking at more quickly establishing stands of pinnacle species like oaks, chestnuts, walnuts, etc (using tree species I'm more familiar with - substitute with similar species for that region).

Looks like this isn't exceedingly far north - similar latitude to the northern great lakes region here in north america, plus some altitude due to the mountains. What sorts of winter low temperatures do you see in this region? negative 30 to negative 40*C sound about right? I'd imagine a dramatic temperature difference from place to place considering elevation changes, but a general average is good to have.

What's the annual precipitation? Are soils acid or alkaline on average?

A quick peek at google maps shows a lot of what appear to be agricultural fields in that area, mostly into the lowlands and valleys, spreading out into what appear to be "oak savanna" systems with grasslands and trees, then dense areas of conifers on the steeper mountain slopes.

What are the crops being grown on the farms? Were these farms more expansive in recent times and are being let run back to forest? If so, could this account for the preponderance of conifers? Do you know what the typical tree species were in the area before modern farming was introduced? What sorts of large mammals were in this area 1,000 to 3,000 years ago?

To reduce the risk of fire in a cool and humid climate like this, it really does come down to mainly the tree and plant species involved. Grasses and conifers will burn regularly, with both producing copious amounts of "fine fuels", while mixed hardwood stands will be far less likely to burn even in years that are drier than usual. From what I can see, we're not looking at a "British Columbia", "California-Colorado corridor" or a "New South Wales" type region here with extreme arid - this region looks much more like Ontario or Germany with some good sized mountains

Nancy Reading wrote:

Tristan Vitali wrote:
Another factor to consider is that the act of pollarding (and coppicing) tends to cause what are referred to as "adventitious sprouts", growth from dormant buds beneath the bark. These are less likely to be strongly bonded to the trunk or scaffolding branches, so the lower to the ground they are, the less likely they are to break off as they get to larger sizes necessary for firewood (especially during adverse weather like wind, ice and snow events). Also, should they break off, there is less exposure to disease through torn bark and split trunks.

This isn't an issue with pollarding when using it for things like growth control, leaf hay, etc, since you'd be doing it on a fairly tight rotation with small diameter branches, but it could quickly become an issue when attempting to grow out 4 inch diameter and greater firewood or timber.

I can't resist sharing this image with you. It's a tree I used to pass regularly in Solihull UK - a sweet chestnut that had been pollarded in the distant past, but probably not for 50  years or so now. (image cropped from source)

Gorgeous  Any ideas on the height at which it was pollarded? From my guesstimate, maybe like a 5 or 6 foot (1.5 to 2 meter) height cut, but I'm sort of terrible at judging measurements like that. I know your area gets enormous winds, too, so I do definitely stand corrected on this

This is the picture usually in my head when I think "pollard"


Then this for "coppice"


Maybe a bit of overlap between the two ?

Have you priced / would you consider shipping within the continental US? Up to now, we've have had ours delivered UPS by ebay purchases. Not sure what the actual shipping charge looks like as it's been included in total pricing.

You know you're a permie when you make your monthly shopping trip and realize the local market still has 50lb bags of locally grown potatoes in stock and your first thought is "we should grab another sack so we have more to plant come spring"

this with a foot or more of snow on the ground, negative teens in the forecast and 3 months to go (never mind the 3 more feet of snow) before planting season begins

You also know you're a permie when you find yourself holding your bladder during said shopping trip because you can't justify flushing all the precious nitrogen. Oh the things that go through our minds we never say out loud to "normies"