[Stoves] Accidental TLUD technique discovery

[neiltm at uwclub.net]

There have been days of rain here in the SE of England, and my outdoor 
wood, consisting at the moment mainly of Hazel coppiced two or three 
years ago for runner bean poles, but now too weak and snappy to be 
re-used, but ideal easy fuel for the (ebay/amazon) Chinese wood gas camp 
stoves, has been getting progressively wetter as the softening (rotten) 
fibres cease to be able to repell water as well as more freshly or 
quickly dried or seasoned wood.

So this morning, despite having loaded the stove yesterday for this 
morning's breakfast, and kept the stove indoors, the wood simply hadn't 
dried out well enough to sustain the pyrolitic front once the top 
ignition layer of well dried fuel had been exhausted.  This is an old 
learned lesson, that there is no use, beyond a subtle difference at least 
in stratifying a TLUD in the hope that it will be going well enough by 
the time it reaches a lower layer to cope with meeting wet wood.  There 
is an extent to which you can get away with it, but it's too easy to 
miscalculate, although it does have the potential if you can manage it 
for a strong boiling flame to turn itself into a simmer flame at the 
point where you want that.

Rather than tip the whole smoky mess out into a tin and put the lid on 
it, I hoped that it might not be too far off and might sustain if I just 
put more dry tinder and candle wax gratings on top, as is often the case 
with a failed start.  Three times I did this.  It did not want to burn 
that damp wood.  Still I didn't bail out, but instead contented myself 
with feeding the top with thin dry wood, and cooked on that, continuing 
refuelling as I went, just as you would if continuing the burn of a TLUD 
batch AFTER it had all pyrolised because you still want a fire.  In other 
words this morning I worked this in reverse, refuelling from the outset 
as slowly, the batch burned right down by the end of the cooking.

It was immediately apparent that this way round had several advantages 
over the more expected batch burn, then refuel to extend.

The fire was a much steadier middling heat level throughout the cook, 
which was better suited to what I was cooking.

The fire was easier to sustain for the length of time and amount of the  
cooking, needing less rather than more tending as the batch burned down.

The problem of sustaining a fire in these stoves after the batch has 
burned are twofold:

Firstly ash builds up and chokes the primary air requiring riddling, 
(there are no lower on the side primary air holes).  Secondly, unless the 
lumps of wood are large, so much small char builds up with only the base 
ignited, that no amount of riddling will permit refuelling without smoke. 
 If the fuel is large, the char is burning vigorously with its own blue 
flame, but this results in the refuelled fire losing its base eventually. 
 Refuelling works great for a while, but then unless refuelling is 
sustained at quite a high rate, the base of the fire simply disappears, 
leaving insufficient embers to ignite new fuel.  However, even with these 
vigorous stoves maxing out on primary air, not even trying to design for 
a soot free fire, it is possible to add too much fuel and start to make 
smoke, something that the cleaner burning 1:6 air ratio stoves suffer 
from to a much greater extent.  In general though it is the greater 
forgiveness of lack of fine tuning and fuel fussiness that is the 
strength of these stoves, and why IMO they are so much better in camping 
situations, where adaptability to whatever fuel is available is key.

But my persistence this morning resulted in discovering a different way 
of using these stoves that worked well, once I adapted to continuing the 
refuelling from the outset, and which I can easily adapt to doing by not 
initially filling the stove right to the top.

There is a clear advantage, in camping type situations at least, but 
possibly elsewhere such as refugee camps maybe where there might be a 
problem of sufficient dry wood, to know that there is a good way of 
utilising a batch loading of wetter wood, by lighting and refuelling a 
conventional fire on top of it with dry wood until it will sustain the 
rest of the batch, or perhaps with decreasing feeding of dry wood 
depending on how wet the wood is, or strength of flame wanted.

There is also an advantage in gaining greater heat control, and the 
primary air supply will remain more constant with reloading at the start 
of the burn rather than at the end.  The wet wood batch sitting 
underneath the dryer wood fire acts as a buffer, a stabiliser of the 
small fire on top in a way that simply lighting a small fire straight 
onto the grate does not.  This must be because there is a stable, but 
slow pyrolytic front constantly at the base of it.

I'm not advocating this as a generalised preferred way of using TLUD's, 
merely sharing, for me at least, a newly discovered versatility that 
definitely has worthwhile application in some circumstances, but in 
general does perhaps show that some TLUD designs that have or can permit 
less restricted primary air can be highly versatile and adaptable stoves, 
capable of utilising in the same physical stove a very wide variety and 
condition of fuel, and being controllable through fuel 
modification/selection rather than, or in addition to stove damping.  

I can't help but conjecture that where an end user has spent their 
lifetime daily tending a three stone fire, they will have such a wealth 
of experience with fire and fuels that they can bring to maximise the 
potential in a TLUD, that if that TLUD permits greater versatility 
through permitting at least a maximum possible of primary air, then this 
surely might be one key to continued adoption of a stove, that it permits 
wide adaptation and uses the lifetime empirically gained knowledge of how 
to use fire that the user brings to it.  If on the other hand it's design 
is too specialised, and cannot adapt, its future will be the more 
dependent on the supply of a consistent and affordable fuel that it works 
well with.

I'm guessing that when Paal Wendelbo used to say 'start with the fuel and 
build the stove around that', what he was mostly doing was adjusting the 
size/proportions of his Peko Pe stove and primary/secondary air ratios to 
most suit the fuel he found?  Good principle where the fuel and cooking 
needs are more of a constant, but the Chinese camp stoves, as with the 
similar Bush Buddy stoves and derivatives (like the Solo range) with wire 
grates, maximising the primary air, encourages an endless learning curve 
that teaches the user how to get just what they want from them.  It 
teaches you no less about biomass, different woods, their condition and 
preparation, and fire making, than an open fire does.

There is real satisfaction in that, just as I've just been reading about 
traditional hay making with a hand scythe delivers, despite back breaking 
labour, a profound happiness and contentment.  Another unquantifiable 
dimension to contend with, LOL.

Maybe that sort of unsuspected intangible is why Bangladesh once came top 
of an early 'world happiness survey' in the 90s, despite great poverty 
and loss of life in natural disasters.  I can easily afford to cook 
breakfast on natural gas in our centrally heated kitchen, but something 
that gives me a satisfaction I find hard to resist, drives me out even on 
frosty mornings, to cook it on a simple wood stove instead.

But here is what we are intended to aspire to in the affluent west:

http://www.telegraph.co.uk/technology/2016/10/12/man-spends-11-hours-tryin
g-to-make-cup-of-tea-with-wi-fi-kettle/

Tears rolling down cheeks!  A candidate for the Darwin awards perhaps?

I don't think so.  I'll stick with my eccentricity!

Neil Taylor