Ultralight Titanium wood stove for hot tent set up

[Anonymous]

Can’t say this is an original idea as it was inspired by photos and general concept of a Seek Outside prototype, but at the same time, i didn’t know any details about that model. Anyways, not considering the pipe or bottom Ti, it weighs 4.6 oz.  Was a pretty easy and quick project.  The purpose of design is along the lines of the Seek Outside prototype, not for serious or long term heating like their larger box stoves, but for very light, quick, convenient heat for drying things out.  It would be for pretty small fires.  It’s very quick to set up unlike the Seek Outside box wood stove (which i have in the large version).

I’m thinking of lining the top of my Cuben MLD Solomid mid with a 54″ X 54″ piece of DP VS75 IR reflective material, using industrial strength velcro tabs and trying it out in it.  Between the air gap and IR reflective material, i’m thinking the cuben/dyneema material should be ok from the heat.   Obviously the solomid is not an ideal size for a stove/pipe-hot tent set up in the traditional type application.  But if you just want to dry stuff out temporarily while awake, it would work fine.

For the pipe, i’m thinking of using aluminum flashing since these will be small and not very hot fires.  In any case, i plan to line the first foot or to of the pipe with ceramic fiber paper.

This might be the first truly UL hot tent system?  The finishing touch will be adding some membrane silpoly to the bottom of the Solomid to close it up more.  Anyways, some pics below:

The left edge of the paper on the ruler is at 12 inches

With the hinged door over it

Hinged door open

Weight

[David Thomas]

Nice elegant design.  Very light weight.  I’m interested to hear how works in the field.

A bit of wisdom from generations of chimney builders:

“A chimney can be too narrow , too wide, or too short.  It can not be too tall.”

Too narrow and it constricts the flow of exhaust gases (and smokes up your tent).  Too wide (hard to imagine in a BP setting) and the heat of the fire gets diluted and doesn’t heat up the chimney enough for adequate draft.  Too short, and it doesn’t have enough length to develop enough draft (and put your tent fabric at risk because (1) sparks are so fully combusted and (2) they are released closer to your tent fabric).

If you can find small-diameter aluminum duct work, that will have most of the work done for you, compared to aluminum flashing.  You can snap it apart and nest one section in another.  The section have male-female ends that fit together securely without fasteners.  But the smallest size I commonly find is 3″ diameter.  Give that a try – it’s only a few dollars per section.

I’d also be cautious about using aluminum that close to a wood fire, even if you line it.  Aluminum + lining is likely as heavy as SS by itself.  It certainly is heavier and far less heat-tolerant than titanium for the first section or two.

[Anonymous]

Hi David, thanks for the encouraging comments and the suggestions.  I’m hoping that the shape helps to contribute to efficient draft combined with adequate length chimney piping.  Good idea about the Al duct work–i’ll definitely look into it.  I mentioned flashing just because i have some sitting around that i could use.  3 inch diameter would be perfect, since the top of the stove is roughly 3 inches diameter, which is based off my Seek Outside large box woodstove piping diameter. I could use my Ti piping that i already have, but it would be very long for use with my MLD cuben solomid (plus, i would like a backup chimney anyways).  It was designed to be used with a much larger Tipi tent, and is around 6 feet in length (not including height of the stove).

I’m also a bit wary/cautious about using Al piping, but i will test in the backyard a few times before taking it out backpacking. I wonder if anodizing it would help a bit in that regard?

I know small wood fires tend to range from 1000 to 1500 or so *F, so i would definitely be potentially pushing the limits.  I’m not sure about the ceramic fiber paper + Al piping weighing more than SS or not.  I haven’t handled CFP before, though i have some on order.  It’s supposedly pretty light weight.  Shouldn’t weigh too much if only the first foot or two is lined?

I’ve looked into SS shim and foil, and it’s surprisingly expensive, especially since you have to order it in semi-bulk from most places to get a decent price.

[James Marco]

Aluminum piping will be a problem. Unless you manage to insulate it well, it will anneal and loose temper. Wood gasses can reach as high as 900F so, you are right at that range (800F is needed to anneal Al.). Annealing will make the pipe very soft. Some combustion can reach well over 1500F and could melt an aluminum pipe, but I think I would worry more about it actually burning and forming oxides much like burning a can in an open fire. A soft and crumbly pipe will not even support a longer flue section above it and you could invite some rather disastrous consequences after a few uses. I would suggest sticking with Ti or steel.

Otherwise, a fairly good design, though I would caution about letting the fire area get larger than the stove.

 

[Richard Nisley]

In a Solomid, convection heat transfer will will go up and then rapidly out the vent. You want to optimize your mini-heater design for radiation heat transfer which will generally move at right angles to your cone’s shape to heat you. Thin sheet titanium typically will only provide an emissivity of about .5 at 800-1000F; fix “that” to achieve an optimal  Solomid small heater design.

[Anonymous]

Duly noted James.  I would love to make a Ti pipe for it, but Ti is dang expensive.  SS could be an option. But since i already have the Al and already ordered the ceramic fiber paper, might as well at least try it in my yard and see how it works or doesn’t.

Thank you for the feedback.

[Anonymous]

“In a Solomid, convection heat transfer will will go up and then rapidly out the vent.”

Even with the 54″ X 54″ DP VS75 IR reflective material being over the vent?  Otherwise, how would one optimize it along the lines you talked about?  Thank you.

[Richard Nisley]

<p style=”line-height: 18.9pt; margin: 0in 0in .2in 0in;”><span style=”font-size: 10.5pt; font-family: ‘Arial’,’sans-serif’; color: #333333;”>Justin,</span></p>
<p style=”line-height: 18.9pt; orphans: auto; text-align: start; widows: 1; -webkit-text-stroke-width: 0px; word-spacing: 0px; margin: 0in 0in .2in 0in;”><span style=”font-size: 10.5pt; font-family: ‘Arial’,’sans-serif’; color: #333333;”>The vent in your Cuben MLD Solomid mid will draft most convective transferred heat out into the night air. Your proposed reflective DP, added around the vent area, would be great for reflecting infrared radiation back to you only if there was a lot of it; the problem is that you will not have a lot of infrared radiation because of your stove material.</span></p>
<p style=”margin-top: 0in; line-height: 18.9pt; orphans: auto; text-align: start; widows: 1; -webkit-text-stroke-width: 0px; word-spacing: 0px;”><span style=”font-size: 10.5pt; font-family: ‘Arial’,’sans-serif’; color: #333333;”>There are a few titanium experts on the forum that might be able to help you regarding altering your titanium’s heaters emissivity if you specify the specific alloy you are using.</span></p>

[Richard Nisley]

<p style=”line-height: 18.9pt; margin: 0in 0in .2in 0in;”><span style=”font-size: 10.5pt; font-family: ‘Arial’,’sans-serif’; color: #333333;”>The above post said the following but it came out garbled and my edit button is greyed out preventing me from attempt to clean it up.</span></p>
Justin,

The vent in your Cuben MLD Solomid mid will draft most convective transferred heat out into the night air. Your proposed reflective DP, added around the vent area, would be great for reflecting infrared radiation back to you only if there was a lot of it; the problem is that you will not have a lot of infrared radiation because of your stove material.

There are a few titanium experts on the forum that might be able to help you regarding altering your titanium’s heaters emissivity if you specify the specific alloy you are using.
<p style=”line-height: 18.9pt; margin: 0in 0in .2in 0in;”></p>

[Anonymous]

Ok, thank you for the explanation, i understand better now what you were saying earlier.  Perhaps it would be too complex and heavy, but i wonder if there is a way to recycle that heat back into the tent sans the smoke?

I don’t know the specific alloy, but i bought the .005″ Ti foil from Titanium Goat.

[monkey]

I’m just not sure Solomid is suitable tent for this idea, its too small both in width and in height.

This winter we finally got the chance to use our Ti goat small wifi stove, with 7.5ft pipe, in a silnylon Supermid. It worked very well with two people and a dog, drying things quickly, and providing plenty of warmth. We were able to keep the tent’s doors closed when it rained and still run the stove. But, this is why I think it worked:

Due to the width of the tent, we could position the stove on the left towards the entrance just behind the centerpole (so slightly to the front/left but still close to the centre of the mid). This allowed plenty of space around the stove from the sides of the tent, and also from our mats/sleeping bags (which for the time when the stove was in operation, we piled on top of each other to form a sitting bench at the back of the tent).

Again due to the width of the tent, we had plenty of space on the front right to pile up the supply of wood. As it was rainy weather it was important to be able to store these inside. The supply had to be substantial, the stove is small so only small and short branches can be used, and those burn very very quickly (even the ticker ones which we needed a pruning saw to prepare).

Due to the height of the tent a good portion of the pipe was inside, and it helped heat up the tent (I think). The pipe is extremely hot, much hotter than the body of the stove. Still the body being square was useful as we successfully cooked on it, so I was able to leave my beloved ti-tri at home saving weight a little.

 

I just can’t imagine achieving any of this in a Solomid (I shudder to even think that it is a cuben solomid!….) The only way I can see it working, is to position the stove and the pipe outside the tent, so that the stovebox is about half-way into your vestibule. The doors will need to be kept open. Then in one corner of the tent you’ll be able to pile up the wood for burning, in the other corner you’ll have a sitting place for yourself. The input of heat will come from the feeding opening of the stove, which to improve the incoming warmth would probably make sense to keep open? It’s not going to be much, but better than none at all – just not sure how effective overall, to justify the trouble. Especially when it rains and doors needing to be kept open in Solomid?

 

[monkey]

Other than this difficulty I like the design, especially the simplicity of it (no screws to install the legs for one). Being able to roll the stove together with the pipe will also save space. However, it not having a flat surface rules out multi-use for cooking – which is an added weight of a separate cooking system.

[Anonymous]

Hi Monkey,

I would agree that it’s definitely not ideal.  A few thoughts related to your concerns:

1. It sounds like from what Richard was saying, that A LOT of the heat is going to be vented out the pipe to begin with (which makes for an inefficient design, but helps to keep it from getting too hot within the tent).

2.  A 54″ X 54″ durable, IR reflective material is going to be velcro’ed to the inside of the top of the tent, and with the combo of the air gap and the IR reflecting, it should help to protect the Cuben from getting overly hot.

3.  When i set up the Solomid, i use two fully extended poles in an inverted V, which gives me more space.

4.  I would use this before setting up all my stuff like sleeping pad, quilt, etc. Things can be selectively pulled out from the pack if they need to be dried.

5.  I’m adding some Membrane Silpoly to some of the sides of the Solomid, both to be able to close it up more and also effectively creating mini vestibules.  Wood can go in these extended, extra areas, and as it will be used more for quick, short fires just to dry stuff (and some distraction/entertainment during long, cold winter nights) and not any “long term comfort”, i won’t need a lot.

It does sound like i should reconsider using Al for the piping.  I’m going to look more into SS shim or foil.  Maybe someone from BPL can send me a 5′ long by 1′ wide piece for less than it would cost to order a larger roll?

I should mention that i have and have used a Seek Outside larger Tipi silnylon tent and large box wood Ti stove combo.  I’ve had that thing blaring with heat (much hotter than i’ll ever attempt to get this set up going). During those times, the box itself and the first foot or two of the pipe will become red hot.  This is why i think that if i use Al pipe and line the first couple feet with a heat resistant and insulating material, i may be able to get away with using Al.  But i may not be able to.

In any case, i will test it a couple times outside at home before taking it out backpacking.

[Anonymous]

Regarding the cooking thing, i would agree that it’s nice to have the double duty of being able to cook on the stove (i’ve done that on my Seek Outside large box woodstove), but unless it’s really cold and potential water sources are frozen (the latter is quite rare where i live), or i have to melt ice, i often go “no cook” anyways.  (my mainstay meals during cold, but not extremely so, winter trips are cashew clusters, smoked salmon, sheep or goat cheese, brown rice crackers, gluten free cookies, precooked dehydrated oatmeal and goat milk powder.  I’m one of those somewhat rare folks to whom food is more a fuel, then a sensual experience, and i don’t need variety, as i can detach myself towards food very well.  In regular day to day life, i eat A LOT of veggies, and it’s not based solely on taste and sensuality, but on mental ideals based on health and spiritual type principles).

If it’s cold enough that i have to bring a stove set up of some kind, there are very lightweight options that the heat from the woodstove/hot tent set up will faciliate, like a very light canister set up, even esbit, etc.

And if i still wanted to go no cook, i could still melt snow using this stove by hanging an Al (i would first burn and scrape out any lining) or SS bottle over it, or placing it very close to the opening.

[DAN-Y/FANCEE FEEST]

An educated guess,  you’ll need a minimum of 2″ diameter flue pipe.

 

I suggest preheating the pipe with a esbit cube to start the initial drafting or else smoke will fill your tent ;-) after a 5 min preheat, introduce your tinder and go from there.

 

An alternative, stack your tinder and twigs, place esbit on top and light.

Make a hardware cloth basket, vertical stack twigs inside of it, top light with esbit. The basket will mange your twigs from going too far off center.

 

http://www.bplite.com/viewtopic.php?f=2&t=4688

 

[Colin Krusor]

Ceramic fiber kiln paper uses an acrylic binder that burns off, leaving a pile of ceramic fiber dust. It is not reusable. In your application, it will crumble and fall into the fire. You could use woven ceramic fiber cloth, but this is much more expensive. Silica cloth is available from many sources, and alumina cloth is available from a few. The stuff is often on ebay.

You could reduce the temperature of the aluminum chimney a little by painting the outside with flat black stove paint. Bare aluminum has a pretty low emissivity, and it would loose more radiant heat with a high-emissivity surface treatment. This would also make it a better tent heater.

 

 

 

[Franco Darioli]

“i could still melt snow using this stove by hanging an Al (i would first burn and scrape out any lining) or SS bottle over it, or placing it very close to the opening.”
How do you melt snow inside a bottle ?

[monkey]

It sounds like from what Richard was saying, that A LOT of the heat is going to be vented out the pipe to begin with (which makes for an inefficient design, but helps to keep it from getting too hot within the tent).”

I think what Richard meant was that a lot of heat would go up and out through the *vent* on top of the mid. The pipe is supposed to have an up draft, I don’t think that its an inefficient design, its just the way stoves (any stoves) are supposed to work.

What provides warmth is the surfaces of the stove and the pipe when they radiate heat (that’s why the more surface you have inside, the greater the warmth). Titanium is about the worst material for this though, the best would be cast iron or welded steel or similar. But the latter weigh a tonne, so for ultralight purposes (and good durability) we go with ti. Which works absolutely fine I think, for brief tent heating/stuff drying/cheerful atmosphere purposes!

[Anonymous]

Hi Dan, thanks, good idea about the esbit preheat.

[Anonymous]

Well that’s certainly good to know about the ceramic fiber paper Colin, thank you for the heads up.  Now i know why it’s so cheap (thought it had more to do with the thinness originally).

Thank you for the other excellent suggestions–the painting thing had occurred to me.   Would it help to paint both sides, or is only the outside needed?   Sounds like i should try to do this with the titanium part too.

[Anonymous]

Franco, it would probably take a longish time.  Perhaps too long to be practical–don’t know, haven’t ever tried it. Overall, i definitely would lean to bringing a dedicated, very light weight stove system that being in a hot tent would help facilitate (and most likely an upright canister stove like the BRS one).

[Anonymous]

Hi Monkey, i thought it was a combination of that, (but more and) along with thin titanium having a lowish emissivity (and lower at higher temp apparently).  The stuff does look almost polished and semi-reflective.

So i thought part of what Richard was saying is that a lot of the IR spectrum of the heat will be reflected back into the stove and then up through the pipe (rather than being radiated through the stove/pipe).  What confirms this, is that i mentioned a couple of times that a largish piece of highly IR reflective material was going to be hung over the Solomid vent and good portion of the ceiling.  If Ti foil (and Al) was more emissive then the DP VS75 material would reflect that IR spectrum heat back into the tent rather than most of it being channeled out the pipe (you can think of it almost like light being reflected off and directed by shiny surfaces–except that heat, unlike light, naturally rises upwards).

It’s less of a conductivity thing than emissivity thing.  Thin titanium is actually pretty conductive, even though Ti is not considered a more thermally conductive metal.  But Ti actually has better conducivity than stainless steel at the same thickness.  SS is 16 with Ti being around 22 depending on the alloy at room temps (wheras Al’s conductivity is quite high at around 205, again depending on the alloy).

I just wasn’t aware that thin Ti foil has that low of an emmissivity, which apparently lowers at higher temps (rather, it’s better at reflecting that wavelength range of IR). It’s true that higher carbon steel is significantly more conductive than Ti, but the thinner the material gets, the less that matters, because a very thin, less conductive material is going to conduct heat more efficiently than a thicker, but more conductive material.  So like Ti foil vs a cast iron stove–if the Ti foil was very emmissive, the heat would just flow through that thin metal like water interrupted, whereas in the much thicker, but more conductive material cast iron, the thickness acts as a bit more of a barrier, insulating more.

My understanding of the above may be off, as i’m not educated or trained in any kind of physics.

[James Marco]

Justin, yeah, your understanding of the differing components is a bit off.

Conductance is simply passing energy from one molecule to the next. Aluminum and copper and gold all have very high conductivity. Infra Red (or IR) radiation is an energy wave. It can pass through a vacuum whereas conductance will not. Conductance (and convection, a specialized form of conductance regarding gasses and liquids, as opposed to solids) can cause heat to rise. But, IR radiation is like light or radio. It travels in a straight line until absorbed by some molecule.

Conduction/convection generally rely on some sort of molecular vibration. If we look at a simple model, a molecule will absorb some IR and start vibrating which is how things get warmer. Or, it can pick up this vibration from a neighboring molecule. Or, it can simply harmonize with a molecular frequency and release another photon of IR (sometimes more, sometimes less than what it absorbed.) Again, this is generally in a spherical release of the IR wave depending on which electrons are changing energy levels and exactly where they are in their orbits (not quite correct…but I will leave that.) The point being is that it ALSO spreads sideways! “Heat” in general will travel faster through aluminum AND disburse heat in a pan far quicker than Ti. By extension, heat not directly centered over the flame will also be transmitted through aluminum to whatever you are cooking in a pot, for example.

If you decide to build this, there are several substances that are very transparent to most IR radiation. A glass IR relief directly above the stove will allow a lot more IR out than a solid pipe. Better would be two 6″ windows directly above the stove about the first 16″. This will significantly reduce flue temps and above it and it may be possible to use the aluminum pipe. But, make sure you get fairly IR transparent glass. And, these will add about 8oz to the weight of the stove. (I think this was mentioned in one of the recent articles on a Winter Hot Tent where a simple Coleman Lantern globe was used.) Also, these should also allow much better the use of the piece of highly IR reflective material you mention. Ti will likely make this rather less effective as an IR reflector if there is little IR available (and work more if a second insulating wall, instead.)

Loosely fitting a “vent” relief over the stove will likely also help with flue gas removal from the tent. But, this also has the downside of drawing heat out, too. But this would also significantly reduce flue temps by allowing air to flow through the system, diluting the heat. Of course, this is mostly used with water heaters to prevent extreme flue overpressure during wind gusting. You might not want to do this unless you have trouble with the piping overheating/over drafting the fire.

[DAN-Y/FANCEE FEEST]

Just a visual reminder of the size of stove were concerned with ;-)

 

[Franco Darioli]

“Franco, it would probably take a longish time. Perhaps too long to be practical–don’t know, haven’t ever tried it”
Yes , I was just amusing myself visualising you trying to fill a bottle with snow to then melt…
but I suspect that it would only be amusing to folk that have melted snow in the first place.
Painting the chimney would add probably more weight than you think, maybe a spray such as Stove Bright (1200f) would help.

[Author]

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